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Doc #84 — Pest and Weed Management Without Imported Chemicals

Integrated Pest and Weed Control for New Zealand Agriculture Under Permanent Trade Isolation

Phase: 2–4 (chemical stocks deplete Phase 1–2; non-chemical methods critical from Phase 2; ongoing management indefinitely) | Feasibility: [A] Established (all core strategies use existing NZ capability, knowledge, and materials)

Unreliable — not for operational use. Produced by AI under human direction and editorial review. This document contains errors of fact, judgment, and emphasis and has not been peer-reviewed. See About the Recovery Library for methodology and limitations. © 2026 Recoverable Foundation. Licensed under CC BY-ND 4.0. This disclaimer must be included in any reproduction or redistribution.

EXECUTIVE SUMMARY

New Zealand agriculture depends heavily on imported pesticides, herbicides, fungicides, and animal pest control products. NZ imports approximately NZ$700–900 million worth of crop protection chemicals annually, with virtually no domestic synthesis of active ingredients.1 Post-event, existing stocks of agrichemicals in the distribution chain — at merchant stores, on farms, and in regional depots — represent approximately 1–3 seasons of supply at pre-event application rates, depending on the product. Some specialist chemicals (certain fungicides, nematicides) may run out sooner; bulk herbicides like glyphosate may last longer due to large stocks typically held in-country.2 By Years 2–5, most imported chemical pest and weed control is unavailable.

This is a serious but manageable problem. NZ agriculture existed before synthetic pesticides — they were not widely available until the 1940s–1960s — and many of the non-chemical pest management methods described in this document were standard NZ farming practice within living memory.3 The transition is not to an unknown system; it is to an older one, adapted with modern ecological understanding.

The honest assessment: Crop losses to pests and weeds will increase. Pre-event NZ agriculture loses approximately 10–20% of potential production to pests, diseases, and weeds despite intensive chemical control.4 Without synthetic chemicals, losses will rise to perhaps 20–40%, depending on the crop, region, and management quality. This is a significant productivity reduction that compounds the losses from nuclear winter (Doc #74, Doc #75) and reduced fertiliser availability (Doc #80). But it does not threaten NZ’s ability to feed its population — it reduces the margin and requires more labour.

What changes: The mindset shifts from eradication to management. Pre-event agriculture treats pests and weeds as problems to eliminate. Post-event agriculture must accept higher pest and weed levels, manage rather than eradicate, and recognise that some organisms classified as pests have productive uses — possums produce fur and meat, rabbits produce meat, gorse fixes nitrogen, blackberry produces food.

Key honest uncertainties: How quickly existing chemical stocks actually deplete (depends on rationing discipline and stockpile levels at the time of the event). Whether biological control agents already established in NZ continue to function under nuclear winter conditions. Whether pest pressure increases or decreases under cooler temperatures (some pests are suppressed by cold; others may benefit from weakened crops and reduced predator populations).

Contents

First month:

  1. Inventory all agrichemical stocks nationally under the emergency stockpile framework (Doc #1). Include manufacturer and distributor warehouses, merchant stores, and on-farm stocks. Prioritise identifying stocks of copper-based fungicides, sulfur, and pyrethrum-based insecticides — these are the chemicals with the longest useful life under local production.
  2. Implement agrichemical rationing. Restrict remaining synthetic pesticides and herbicides to highest-value uses: seed treatment for emergency crops (Doc #76), disease control in critical food crops, and animal health applications. Cease all amenity use (domestic gardens, roadsides, parks).
  3. Issue guidance to all farmers: begin transitioning to non-chemical pest and weed management. This is advisory, not punitive — farmers need information and support, not additional regulation during a crisis.

First season (months 1–6):

  1. Distribute practical guidance on biological, mechanical, and cultural pest control methods (Sections 3–5 of this document). Through existing agricultural extension networks (DairyNZ, Beef + Lamb NZ, HortNZ field staff), MPI regional offices, and community agricultural advisers.
  2. Establish pyrethrum plantings. Source chrysanthemum seed (Tanacetum cinerariifolium) from existing NZ botanical collections and seed banks and begin propagation for insecticide production (Section 6.2).
  3. Begin local Bordeaux mixture production in wine-growing and horticultural regions where copper sulfate and lime are accessible (Section 6.1).
  4. Coordinate rabbit and possum control with food harvest programme (Doc #82). Reframe pest control as food and fur production.

Years 1–3:

  1. Scale up locally producible pest control agents: Bordeaux mixture, sulfur dusting, pyrethrum extract, nicotine extract, soap sprays (Section 6).
  2. Establish regional pest monitoring networks. Farmers and agricultural advisers report pest and disease outbreaks through a coordinated system, enabling targeted response rather than blanket spraying.
  3. Train agricultural workforce in integrated pest management (IPM) principles. Many farmers have limited experience with non-chemical methods. Training through field days, demonstration farms, and extension programmes is essential.

Years 3–5:

  1. Achieve self-sufficient pest control from NZ-produced materials. Pyrethrum crops established, copper-based fungicide production routine (dependent on sulfuric acid production — Doc #113), sulfur supply from geothermal sources established (requires mining, transport, and processing infrastructure at Taupo Volcanic Zone sites — Doc #80).
  2. Revise crop variety recommendations based on observed pest and disease resistance under NZ recovery conditions. Prioritise resistant varieties in the seed programme (Doc #77).

ECONOMIC JUSTIFICATION

Labour cost of non-chemical pest and weed management

Non-chemical methods are more labour-intensive than chemical methods. The additional labour required per hectare depends on the crop and methods used:

  • Hand weeding and cultivation: Approximately 50–200 person-hours per hectare per season for vegetable and grain crops, compared to 2–5 person-hours per hectare for herbicide application.5 This is the largest labour increase.
  • Trapping and shooting (rabbits, possums): Approximately 5–20 person-hours per hectare per season in areas with significant pest pressure, but this labour produces food and fur as a co-benefit (Doc #82).
  • Biological and cultural methods (crop rotation, resistant varieties, timing): Minimal additional labour once systems are established, though they require knowledge and planning.

Total additional agricultural labour for pest and weed management nationally: Roughly 5,000–15,000 additional person-years per year compared to pre-event chemical-based systems. This estimate is approximate and depends heavily on which crops are grown and where.

Comparison with the alternative

The alternative to increased pest and weed management labour is higher crop losses. If weeds are not controlled by non-chemical means, crop yields decline by an additional 15–30% beyond the losses from nuclear winter and reduced fertiliser.6 On NZ’s emergency cropping area of approximately 200,000–400,000 hectares (Doc #76), this represents roughly 100,000–300,000 tonnes of lost food production per year — enough to feed 500,000–1,500,000 people. The labour invested in non-chemical pest and weed control prevents this loss and is among the highest-return labour allocations available.

Pest animals as resources

Reframing pest animals as resources changes the economic calculation. Annually, managed harvest of pest species produces:7

Species Estimated harvest Food value Other value
Possums 2–3 million animals 2,000–6,000 t meat 2–3 million pelts (clothing, insulation — Doc #36)
Rabbits (Canterbury/Otago) 1–5 million animals 500–5,000 t meat Fur, skins
Wild goats 50,000–200,000 animals 1,000–6,000 t meat Hides; live capture for dairy

This production partially offsets the cost of pest management labour and provides protein and materials that have independent value.

1. KEY AGRICULTURAL PESTS IN NZ

1.1 Insect pests

Grass grub (Costelytra zealandica): NZ’s most damaging pasture insect pest. Larvae feed on grass roots, causing pasture dieback and bare patches, particularly in Canterbury, Otago, Manawatu, and Waikato. Damage is worst in autumn and spring. Pre-event control relies on the insecticide diazinon, which will not be available post-event. Grass grub populations cycle naturally with a period of approximately 5–10 years, driven by fungal and bacterial diseases that build up at high larval densities.8 Under non-chemical management, these natural cycles continue — peak damage is higher, but populations collapse naturally once density-dependent diseases take hold.

Porina caterpillar (Wiseana spp.): Larvae feed on grass at the soil surface, particularly in wetter regions (Taranaki, Southland, West Coast). Damage can reduce pasture production by 20–40% in affected areas during outbreak years.9 Natural control agents include parasitic wasps and fungal pathogens.

Diamondback moth (Plutella xylostella): The most damaging pest of brassica crops (cabbage, kale, broccoli, turnips) in NZ. Pre-event, controlled by synthetic insecticides. Biological control through the parasitoid wasp Diadegma semiclausum is partially effective and already established in NZ.10

Aphids (multiple species): Affect a wide range of crops. Transmit plant viruses. Controlled pre-event by neonicotinoid and organophosphate insecticides. Natural enemies — ladybirds, lacewings, hoverfly larvae, parasitoid wasps — provide partial but inconsistent control.11

White butterfly (Pieris rapae): Caterpillars damage brassica crops. Pre-event, the introduced parasitoid wasp Cotesia rubecula provides substantial biological control.12 Post-event, this biocontrol should continue functioning without intervention.

1.2 Animal pests

Rabbits (Oryctolagus cuniculus): In Canterbury, Otago, Marlborough, and parts of Hawke’s Bay, rabbit populations periodically reach plague densities of 40–80 per hectare, causing severe pasture and crop damage.13 Pre-event control uses a combination of 1080 poison, pindone poison, and rabbit haemorrhagic disease virus (RHDV/calicivirus). Post-event, poisons become unavailable as stocks deplete, but RHDV and myxomatosis continue circulating naturally. Management shifts to trapping, shooting, ferreting, and harvest for food (Doc #82).

Brushtail possums (Trichosurus vulpecula): Approximately 20–30 million animals nationally. Damage pasture, crops, and native forest. Transmit bovine tuberculosis to cattle and deer herds. Pre-event control relies heavily on 1080 (sodium fluoroacetate) aerially distributed. Post-event, 1080 stocks will deplete — NZ has a single domestic 1080 manufacturer (Orillion, Whanganui), but the precursor sodium fluoroacetate is imported.14 Management shifts entirely to trapping, shooting, and harvest for food and fur (Doc #82).

Rats (Rattus spp.): Damage stored grain, food stores, and crops. Carry leptospirosis. Post-event, rat control relies on trapping and farm cats and dogs, plus secure grain storage infrastructure (Doc #78).

Wild goats (Capra aegagrus hircus): Approximately 100,000–300,000 nationally, primarily in hill country. Damage pasture and native bush. Managed through harvest for food, hides, and live capture for dairy use (Doc #82).15

1.3 Diseases

Facial eczema: Caused by the fungus Pithomyces chartarum, which grows on dead pasture litter in warm, humid conditions and produces the toxin sporidesmin. Sporidesmin causes severe liver damage in sheep and cattle. Facial eczema is NZ’s most economically important livestock disease, costing an estimated NZ$200–300 million per year pre-event.16 Pre-event prevention uses zinc supplementation (zinc oxide orally or through water supply) and fungicide spraying of pastures. Post-event, zinc oxide stocks deplete within 1–3 years. Zinc is not readily producible domestically in sufficient quantities (NZ has no zinc smelting capacity). Management shifts to: grazing management (avoid high-risk pastures in late summer/autumn), use of tolerant livestock breeds (some Romney and Friesian lines have genetic resistance), and monitoring spore counts to guide management decisions.17

Psa (Pseudomonas syringae pv. actinidiae): A bacterial disease that causes severe damage to kiwifruit. Pre-event, managed through copper-based sprays and orchard management. Post-event, copper-based sprays can be produced locally (Section 6.1), and kiwifruit cultivation can continue with adapted management — though kiwifruit is a lower priority crop than staple foods under recovery conditions.

2. KEY AGRICULTURAL WEEDS IN NZ

NZ’s worst agricultural weeds are almost all introduced species that thrive in modified landscapes. Under post-event conditions, weed pressure on productive land increases as herbicide use declines, but several of these weeds have useful properties that reframe their presence.

Gorse (Ulex europaeus): NZ’s most widespread and recognised weed. Colonises cleared land rapidly. Fixes atmospheric nitrogen through root nodule bacteria — approximately 100–200 kg N/ha/year on established gorse stands.18 This nitrogen-fixing capacity is genuinely valuable on degraded land. Gorse is also excellent firewood, provides livestock shelter, and was historically used as stock feed (young shoots are palatable to cattle and goats). Management: controlled grazing by goats (which eat gorse readily), mechanical clearing for cropping, and acceptance on non-productive land where its nitrogen fixation improves soil.

Blackberry (Rubus fruticosus agg.): Invasive and difficult to control mechanically. Produces abundant, nutritious fruit (January–March). Under post-event conditions, blackberry’s food value rises substantially. Management: harvest fruit, control spread through grazing (goats, cattle), and mechanical cutting where it encroaches on productive land. Eradication is neither achievable nor necessarily desirable.

Ragwort (Jacobaea vulgaris): Toxic to cattle and horses (contains pyrrolizidine alkaloids that cause chronic liver damage). Sheep tolerate ragwort better than cattle and are used for biological control through preferential grazing.19 The ragwort flea beetle (Longitarsus jacobaeae), introduced as a biocontrol agent, is established throughout NZ and suppresses ragwort populations in many areas. Post-event, management relies on grazing management (sheep preferentially on ragwort-affected pastures), maintaining flea beetle populations, and hand-pulling on high-value land.

Nodding thistle (Carduus nutans): A problem in pasture, particularly in drier eastern regions. The crown weevil (Rhinocyllus conicus) and receptacle weevil (Trichosirocalus horridus), both introduced biocontrol agents, are established in NZ and provide partial control.20 Additional management: mowing before seed set, hand-grubbing in small infestations.

Californian thistle (Cirsium arvense): A deep-rooted perennial that is extremely difficult to control by any method. Spreads vegetatively from root fragments. Pre-event, controlled with persistent herbicides (clopyralid, MCPA). Post-event, management options are limited: regular mowing or topping to prevent seed set, intensive cultivation to exhaust root reserves (requires 2–3 years of repeated cultivation), and competitive pasture management. Californian thistle increases under reduced management, and farmers should accept higher levels than pre-event while focusing control effort on highest-value land.21

Old man’s beard (Clematis vitalba): A climbing vine that smothers native bush margins and shelter belts. Not primarily an agricultural weed but damages farm shelter belts and forest edges. Mechanical control (cutting stems at ground level) is effective but labour-intensive. Not a priority for agricultural labour allocation.

3. BIOLOGICAL CONTROL

NZ has a long history of deliberate biological control introductions, many of which are already established and functioning without ongoing management. These continue to operate post-event.

3.1 Established biocontrol agents in NZ

Target pest/weed Biocontrol agent Status Effectiveness
Rabbits Rabbit haemorrhagic disease virus (RHDV) Established since 1997 Suppresses populations 60–90% in some areas; less effective in wet/cool regions22
Rabbits Myxomatosis Present but limited effectiveness in NZ (wet climate reduces transmission) Moderate23
Ragwort Ragwort flea beetle (Longitarsus jacobaeae) Widespread Good — substantially reduces ragwort in many areas24
Nodding thistle Crown weevil (Rhinocyllus conicus) Widespread Moderate — reduces seed production25
White butterfly Parasitoid wasp (Cotesia rubecula) Established Good — significantly reduces white butterfly populations26
Diamondback moth Parasitoid wasp (Diadegma semiclausum) Established Moderate — effectiveness varies with conditions27
Clover root weevil Parasitoid wasp (Microctonus aethiopoides) Established since 2006 Good — reduces clover root weevil by 25–50%28

These agents require no chemical inputs, no maintenance, and no ongoing human intervention. They are the most robust form of pest control available under isolation conditions.

3.2 Encouraging natural predators

General predator encouragement reduces pest populations across the board:

  • Native and introduced birds: Morepork (ruru), kōtare (kingfisher), kāhu (harrier hawk), and introduced species like starlings and magpies consume large numbers of insects, including grass grub adults and pasture caterpillars. Ruru are also significant nocturnal predators of rats and mice; they require dense native or exotic cover with hollow trees or dense canopy for roosting, and their populations are suppressed by deforestation.29 Restoring native bush corridors between productive land and existing forest increases ruru populations in adjacent agricultural areas, providing ongoing rodent control. Maintaining hedgerows, shelter belts, and nesting habitat supports predator populations generally.
  • Native bush as weed and pest suppression: Dense native understorey (māhoe, kāpuka, native ferns) suppresses germination of introduced weed species. Gorse and blackberry colonise disturbed, open ground; where intact native bush occupies riparian margins and slope breaks, their spread is limited.30 Maintaining bush corridors on non-productive land (margins, gullies, steep slopes) is a long-term pest and weed management investment.
  • Parasitoid wasps: Multiple species of tiny wasps parasitise aphids, caterpillars, and other crop pests. Flowering plants (particularly umbellifers — carrots, parsnip, fennel — and buckwheat) provide nectar that sustains adult parasitoids. Planting strips of flowering species alongside crop fields increases parasitoid activity.31
  • Predatory insects: Ladybirds, lacewings, and ground beetles consume aphids and caterpillars. These are suppressed by broad-spectrum insecticides — the cessation of insecticide use post-event should increase their populations over 2–3 seasons.

4. MECHANICAL AND PHYSICAL PEST CONTROL

4.1 Animal pest control

Trapping: Kill traps (Timms traps, DOC series traps), leg-hold traps, and snares are effective for possums, rats, and stoats. NZ has tens of thousands of traps deployed for existing pest control programmes, and additional traps can be manufactured by blacksmiths from mild steel (Doc #92). Trapping is the primary post-event possum and rat control method.32 When manufactured traps become scarce, traditional Māori snare and noose trap designs using harakeke fibre rope (Doc #100) and supple native timber provide a practical fallback.33 Trap placement knowledge held by iwi hunters – understanding of mammal movement patterns, territorial behaviour, and seasonal activity along runs and crossing points – improves trap-take rates substantially and should be drawn on for possum, rat, and rabbit trapping programmes.

Shooting: Effective for rabbits, possums, wild goats, and feral pigs. Constrained by ammunition supply (Doc #82 addresses ammunition conservation). Prioritise shooting for species that are difficult to trap (rabbits in open country, wild goats in hill country).

Ferreting: Using domesticated ferrets to drive rabbits from burrows into nets. An established and efficient NZ rabbit control method that uses no ammunition. Existing ferret populations and expertise are concentrated in Canterbury and Otago.34

Fencing: Rabbit-proof netting fences protect high-value crop areas. Labour-intensive to install but effective. Netting can be manufactured from wire (Doc #105). Standard rabbit netting (1050 mm, 40 mm mesh) buried 150 mm below ground prevents rabbit access to enclosed areas.

4.2 Weed control

Hand weeding and grubbing: Labour-intensive but effective for low-density infestations. Most practical for gardens, small crop fields, and spot treatment of scattered weeds in pasture. A person can hand-weed approximately 100–500 m² per hour depending on weed density and soil conditions.35

Cultivation: Ploughing, discing, and harrowing kill annual weeds effectively and suppress perennials by exhausting root reserves over repeated cultivations. Mechanical cultivation using tractor-drawn implements continues as long as fuel is available; horse-drawn implements become relevant as fuel depletes (Doc #74).

Mowing and topping: Prevents weed seed production and weakens perennials over time. Does not eliminate perennial weeds (they regrow) but manages their spread and competition with pasture.

Mulching: Suppresses weed germination by blocking light. Effective in gardens and orchards. Mulch materials include straw, wood chips, seaweed, newspaper, and cardboard. Application rate of approximately 10–15 cm depth provides season-long weed suppression in vegetable gardens.36

Flame weeding: Passing a flame briefly over weed seedlings kills them without cultivating the soil (which brings new weed seeds to the surface). Requires a gas burner — LPG-fuelled flame weeders are used commercially in NZ organic farming. As LPG depletes, flame weeding can use wood gas or biogas where these are produced (Doc #56, Doc #57). Most effective on small-seeded annual weeds in their seedling stage.37

5. CULTURAL PEST AND WEED MANAGEMENT

Cultural methods — changes to farming practice that reduce pest and weed pressure — are the foundation of post-event pest management. They cost little except knowledge and planning.

5.1 Crop rotation

Growing the same crop repeatedly in the same field allows pest and disease populations to build up in the soil. Rotation breaks these cycles. A minimum 3–4 year rotation (Section 2.4 of Doc #80) is essential for disease management as well as fertility. Specific rotation benefits:

  • Brassica crops (cabbage, turnips) should not follow brassicas for at least 2–3 years — club root (Plasmodiophora brassicae) persists in soil for 7+ years but declines without a host.38
  • Potato crops should not follow potatoes for at least 3 years — potato blight (Phytophthora infestans) and parasitic nematodes build up under continuous potatoes.
  • Cereal crops benefit from a break of at least 1–2 years to reduce take-all disease (Gaeumannomyces tritici).

5.2 Resistant varieties

Plant breeding for pest and disease resistance is one of the most cost-effective long-term pest management strategies. NZ’s seed programme (Doc #77) should prioritise:

  • Facial eczema-tolerant livestock: Romney and Friesian lines with demonstrated genetic tolerance exist and should be preferentially retained during destocking (Doc #74).39
  • Psa-tolerant kiwifruit cultivars: Gold3 (SunGold) was developed specifically for Psa tolerance and should replace susceptible varieties where kiwifruit is grown.
  • Grass grub-tolerant pasture species: Tall fescue and cocksfoot are less palatable to grass grub larvae than ryegrass and suffer less damage.40

5.3 Timing of planting and grazing

Synchronising planting and grazing to avoid peak pest periods reduces damage without chemical inputs:

  • Grass grub: Damage is worst in autumn and winter when larvae are actively feeding on roots. Autumn-sown crops on land with high grass grub populations are at greatest risk. Spring sowing avoids the worst damage period.
  • Diamondback moth: Peak populations occur in summer. Early-season brassica crops that mature before peak moth populations suffer less damage.
  • Facial eczema: Risk is highest in late summer and autumn when spore counts peak. Grazing management that avoids high-risk pastures during this period — moving livestock to safer, shorter pastures or supplementary feed — reduces exposure.41

5.4 Toxic plant awareness on unfamiliar land

Post-event, livestock may be moved to unfamiliar land including areas near regenerating native bush margins. Several native NZ species are toxic to livestock: tutu (Coriaria arborea), karaka (Corynocarpus laevigatus), ngaio (Myoporum laetum), and poroporo (Solanum laciniatum).42 As farmers lose familiarity with native plant identification, poisoning risk increases. Surveying and marking toxic plant concentrations on farms near native bush is a practical, low-cost preventive measure; Māori botanical knowledge holders can assist with identification in areas where conventional farming has reduced familiarity with native flora.

6. LOCALLY PRODUCIBLE PEST CONTROL AGENTS

Several effective pest control substances can be manufactured from NZ materials. None match the efficacy of modern synthetic chemicals. Modern systemic fungicides achieve 80–95% disease suppression; Bordeaux mixture achieves 50–70% and is protectant only (not curative). Synthetic insecticides (neonicotinoids, organophosphates) provide 7–21 days of residual activity; pyrethrum degrades within 24–48 hours, requiring frequent reapplication. Soap sprays require direct contact and have no residual activity at all. These performance gaps mean higher crop losses, more frequent applications, and greater labour input per hectare — but all these agents provide meaningful control and have long histories of agricultural use.43

7.1 Bordeaux mixture (copper-based fungicide)

Bordeaux mixture is a combination of copper sulfate and hydrated lime, used as a fungicide for over 150 years worldwide. It controls downy mildew, late blight (potatoes, tomatoes), leaf curl, and a range of fungal diseases.44

Ingredients: - Copper sulfate (CuSO₄): Produced by dissolving copper in dilute sulfuric acid. This requires: (a) a functioning sulfuric acid production capability (Doc #113), which itself depends on sulfur supply from geothermal sources or pyrite roasting, and furnace infrastructure; (b) copper feedstock from electrical infrastructure recycling (copper wire, cable), plumbing scrap, and eventually from limited NZ copper mineral deposits; (c) acid-resistant vessels (glass, ceramic, or lead-lined) for the reaction. Bordeaux mixture production cannot begin until sulfuric acid production is operational. - Hydrated lime (Ca(OH)₂): Produced by slaking burnt limestone with water. Lime is domestically abundant (Doc #80).

Preparation: Dissolve 1 kg copper sulfate in 50 litres of water. In a separate container, mix 1 kg hydrated lime in 50 litres of water. Slowly add the copper sulfate solution to the lime solution while stirring. The result is a blue suspension to be applied as a spray.45

Application: Spray on foliage before disease onset. Reapply after heavy rain. Effective on grapes, potatoes, tomatoes, stonefruit, and other susceptible crops.

Limitations: Bordeaux mixture is a protectant only — it must be applied before disease onset and cannot cure existing infections, unlike modern systemic fungicides that move within plant tissue and can treat established infections. Copper accumulates in soil with repeated application and can become toxic to plants and soil organisms at high levels. Application rates should be tracked and soil copper monitored over years. Not effective against all fungal diseases. Requires reapplication after heavy rain (no systemic action).

7.2 Pyrethrum (insecticide)

Pyrethrum is a natural insecticide extracted from the dried flower heads of Tanacetum cinerariifolium (Dalmatian chrysanthemum). It is a broad-spectrum contact insecticide effective against aphids, caterpillars, beetles, and many other insect pests. It degrades rapidly in sunlight — typically within 24–48 hours — meaning it has low environmental persistence.46

Growing in NZ: T. cinerariifolium grows well in NZ’s temperate climate. It is a perennial herb that thrives in well-drained soil in full sun. Seeds are available from NZ botanical collections and some specialist seed suppliers. Plants take 1–2 years to reach full flower production. A planting of approximately 1 hectare can produce 1–2 tonnes of dried flower heads per year, yielding roughly 10–20 kg of crude pyrethrin extract.47

Extraction: Dry flower heads thoroughly, then grind to a fine powder. The powder itself can be dusted directly onto plants as an insecticide. For a liquid spray, steep 100 g of dried flower powder in 1 litre of warm water with a small amount of soap (as an emulsifier — Doc #37) for 12–24 hours, then strain and dilute 1:10 with water before spraying.48

Limitations: Pyrethrum kills beneficial insects as well as pests — it is not selective. Use should be targeted and timed to minimise impact on pollinators (apply in evening when bees are inactive). Supply is limited by the area planted and takes 1–2 years to establish. Pyrethrum is the highest-priority locally producible insecticide and deserves early planting investment.

7.3 Sulfur (fungicide and miticide)

Elemental sulfur dusted or sprayed on crops controls powdery mildew, certain rust diseases, and mites. NZ has geothermal sulfur deposits in the Taupo Volcanic Zone — sulfur was commercially mined from White Island (Whakaari) and Rotorua-area deposits historically.49

Application: Finely ground sulfur dusted onto foliage (5–15 kg/ha) or mixed with water and a wetting agent for spray application.50 Most effective above 15°C — under nuclear winter conditions, efficacy may be reduced during cooler periods.

Limitations: Sulfur can damage some crop varieties (sulfur-sensitive grape and apple cultivars). Do not apply within 2 weeks of oil-based sprays (causes phytotoxicity). Supply depends on developing geothermal sulfur extraction infrastructure.

7.4 Nicotine extract (insecticide)

Nicotine is a potent insecticide extracted from tobacco leaves (Nicotiana tabacum). Tobacco is not widely grown in NZ but can be cultivated — small-scale tobacco growing occurs in the Nelson/Marlborough region, and the plant grows in most of the North Island and warmer South Island areas.51

Extraction: Soak 500 g of fresh or dried tobacco leaves in 4 litres of water for 24–48 hours. Strain. Add a small amount of soap as a wetting agent. Dilute to approximately 20 litres and apply as a spray.

Caution: Nicotine is toxic to humans and other mammals. Handle with gloves; do not ingest or allow prolonged skin contact. It is acutely more toxic than most synthetic insecticides. Use only where pyrethrum or other options are insufficient, and only by trained applicators. Nicotine also kills beneficial insects and is toxic to bees.

7.5 Soap sprays (insecticide)

Dilute soap solutions kill soft-bodied insects (aphids, whitefly, mealybug, mites) by disrupting their waxy cuticle, causing desiccation. Soap is producible from NZ tallow and wood ash lye (Doc #37).

Preparation: Dissolve approximately 10–20 g of plain soap (not detergent) per litre of water. Apply as a spray directly onto infested foliage, ensuring coverage of undersides of leaves where pests cluster.

Limitations: Soap sprays require direct contact — they have no residual activity. Multiple applications may be needed. Some plants are sensitive to soap (test on a small area first). Effective only against soft-bodied insects; ineffective against caterpillars, beetles, and most larger pests.

7. WEED MANAGEMENT WITHOUT HERBICIDE

8.1 Accepting a higher weed baseline

Post-event NZ agriculture must accept weed levels that would be considered unacceptable under pre-event conditions. Some weeds in pasture — docks, dandelions, plantain — are edible by livestock, nutritious, and not seriously competitive at moderate densities.52 The labour cost of achieving pre-event weed-free standards without herbicide is prohibitive. Management focuses on preventing weeds from dominating, not eliminating them.

8.2 Grazing management for weed control

Livestock grazing is the primary weed management tool on pastoral land:

  • Goats eat gorse, blackberry, thistles, and many broadleaf weeds that sheep and cattle avoid. Strategic grazing of goat herds through weedy areas is the most effective non-chemical gorse and blackberry control available. Feral goats can be live-captured and deployed for this purpose (Doc #82).53
  • Sheep are effective at controlling ragwort (they tolerate the alkaloids better than cattle) and maintaining short, competitive pasture that suppresses weed establishment.54
  • Cattle are less selective grazers and control rank pasture that shades out low-growing weeds.
  • Mixed grazing — running sheep and cattle (or goats) together or in sequence — provides the most comprehensive weed control through complementary grazing preferences.

8.3 Weed value reframing

Several species classified as weeds under pre-event conditions have productive value:

  • Gorse: Fixes nitrogen (100–200 kg N/ha/year), provides shelter, and is a fuel source.55 On non-productive land, gorse improves soil for eventual conversion to pasture or cropping.
  • Blackberry: Produces 2–5 tonnes of fruit per hectare of established bush (season: January–March).56 Under food scarcity, this is a meaningful caloric and vitamin contribution. Blackberry fruit is high in vitamin C.
  • Dandelion: Leaves are edible (for humans and livestock), roots serve as a coffee substitute, and the plant provides early-season nectar for pollinators.
  • Plantain (Plantago lanceolata): Now deliberately planted in NZ pastures for its drought tolerance, mineral content, and livestock health benefits (contains bioactive compounds that reduce methane and improve animal performance). Pre-event, it was considered a weed.57

CRITICAL UNCERTAINTIES

Uncertainty Range Impact
Agrichemical stocks at event 1–3 seasons of supply at pre-event rates Determines transition timeline to non-chemical methods
Nuclear winter effect on pest populations Some pests suppressed by cold; others favoured by stressed crops Net pest pressure under nuclear winter is unknown
Biocontrol agent efficacy under nuclear winter Cooler temperatures may slow insect biocontrol agents Key agents (RHDV for rabbits, flea beetle for ragwort) may be temperature-sensitive
Facial eczema severity under nuclear winter Cooler autumn temperatures may reduce fungal spore counts Could reduce NZ’s most costly livestock disease — a rare positive of cooling
Copper availability for Bordeaux mixture Depends on copper recycling from electrical infrastructure Copper supply constrains the most important locally producible fungicide
Pyrethrum establishment timeline 1–2 years to first harvest from seed Insecticide gap between chemical stock depletion and pyrethrum production
Labour availability for hand weeding Competes with other agricultural labour demands Non-chemical weed control fails if labour is not allocated

CROSS-REFERENCES

Document Relationship
Doc #1 — National Emergency Stockpile Strategy Framework for agrichemical requisition and rationing
Doc #36 — Clothing and Footwear Possum fur from pest harvest for clothing production
Doc #37 — Soap Production Soap for insecticidal soap sprays
Doc #56 — Wood Gasification Gas supply for flame weeding equipment
Doc #74 — Pastoral Farming Under Nuclear Winter Companion doc — pasture pest and weed context, destocking and grazing management
Doc #76 — Emergency Crops Crop protection needs; pest control as determinant of crop yields
Doc #77 — Seed Preservation and Distribution Resistant varieties; pyrethrum seed sourcing
Doc #78 — Food Preservation Stored product pest management (rats, insects in grain stores)
Doc #80 — Soil Fertility Management Crop rotation for pest/disease management; gorse nitrogen fixation
Doc #82 — Hunting and Wild Harvest Pest animals as food and material resources; trapping and shooting methods
Doc #92 — Blacksmithing and Forge Work Manufacture of traps and pest control hardware
Doc #100 — Harakeke Fiber Harakeke cordage for traditional trap construction; Section 6.3
Doc #105 — Wire and Fencing Rabbit-proof fencing; snare wire
Doc #113 — Sulfuric Acid Production Required for copper sulfate manufacture (Bordeaux mixture)
Doc #160 — Heritage Skills Preservation and Transmission Partnership framework and institutional structure for engaging iwi environmental knowledge (§4.5–4.7); kaitiakitanga resource management principles

  1. NZ agrichemical imports from Stats NZ trade data. NZ imports approximately NZ$700–900 million of pesticides and related products annually, with no significant domestic synthesis of active ingredients. Major suppliers include Bayer, Syngenta, BASF, Corteva, and Nufarm. See: NZ Environmental Protection Authority, “Hazardous Substances in NZ” reports; Stats NZ overseas merchandise trade data. https://www.stats.govt.nz/↩︎

  2. Agrichemical stock levels in-country: NZ typically holds 1–3 months of supply in the commercial distribution chain (manufacturer warehouses, merchant stores, on-farm). Stocks fluctuate seasonally — highest before spring application season, lowest in late summer. The actual volume at any given time is uncertain. Source: industry estimates; exact figures are commercially sensitive.↩︎

  3. NZ agriculture before synthetic pesticides: Brooking, T. and Pawson, E. (eds.) (2011), Seeds of Empire: The Environmental Transformation of New Zealand, I.B. Tauris. Synthetic pesticide use in NZ agriculture expanded dramatically from the 1940s–1960s. Before this, pest and weed management relied on methods described in this document — biological control, mechanical methods, cultural practices, and locally available materials.↩︎

  4. Crop losses to pests and weeds: Oerke, E.C. (2006), “Crop losses to pests,” Journal of Agricultural Science, 144, 31–43. Global average crop losses to pests, diseases, and weeds are approximately 30–40% of potential production even with chemical control. The 10–20% NZ figure reflects NZ’s generally favourable pest environment compared to tropical regions. Without chemical control, losses typically increase by 10–20 percentage points, depending on the crop.↩︎

  5. Hand weeding labour requirements: Approximate figures based on organic farming practice. Actual rates vary enormously with weed species, density, soil conditions (wet soil makes weeding easier), and worker experience. See: Mohler, C.L. (2001), “Mechanical management of weeds,” in Liebman, M. et al. (eds.), Ecological Management of Agricultural Weeds, Cambridge University Press.↩︎

  6. Crop losses to pests and weeds: Oerke, E.C. (2006), “Crop losses to pests,” Journal of Agricultural Science, 144, 31–43. Global average crop losses to pests, diseases, and weeds are approximately 30–40% of potential production even with chemical control. The 10–20% NZ figure reflects NZ’s generally favourable pest environment compared to tropical regions. Without chemical control, losses typically increase by 10–20 percentage points, depending on the crop.↩︎

  7. Pest animal harvest estimates: Derived from Doc #82 sustainable harvest calculations and population data from NZ DOC and regional council estimates. These are order-of-magnitude figures.↩︎

  8. Grass grub biology and control: Jackson, T.A. et al. (2012), “Use of Serratia entomophila for the management of New Zealand grass grub,” in Use of Microbes for Control and Eradication of Invasive Arthropods, Springer. Also: East, R. et al. (1981), “Pasture pests of the North Island of New Zealand,” NZ Journal of Agricultural Research, 24, 285–292. Natural population cycling of grass grub is well-documented, driven by Amber disease (Serratia entomophila) and other pathogens.↩︎

  9. Porina caterpillar: Barratt, B.I.P. et al. (1990), “Porina and other stem and root feeding larvae,” in Pasture Pests, AgResearch. Damage estimates of 20–40% pasture production loss during outbreak years in affected regions.↩︎

  10. Diamondback moth biocontrol: Cameron, P.J. and Walker, G.P. (2002), “Field evaluation of Cotesia rubecula (Hymenoptera: Braconidae) for biological control of diamondback moth,” NZ Journal of Crop and Horticultural Science, 30, 235–247. Also: Talekar, N.S. and Shelton, A.M. (1993), “Biology, ecology, and management of the diamondback moth,” Annual Review of Entomology, 38, 275–301.↩︎

  11. Aphid natural enemies: Wratten, S.D. et al. (1998), “Conservation biological control of aphids in New Zealand,” in Conservation Biological Control, Academic Press. NZ has a substantial community of aphid natural enemies, but their effectiveness varies with habitat management and pesticide use.↩︎

  12. White butterfly biocontrol: Cameron, P.J. et al. (2006), “Progress in biological control of Pieridae (Lepidoptera) in New Zealand,” in Proceedings of the 2nd International Symposium on Biological Control of Arthropods. Cotesia rubecula has been highly effective since its establishment.↩︎

  13. Rabbit biology and control in NZ: Norbury, G. and Reddiex, B. (2005), “European rabbit,” in The Handbook of New Zealand Mammals, 2nd ed., Oxford University Press. RHDV effectiveness varies by region — less effective in wet, cool areas where the virus persists poorly in the environment. Myxomatosis is present in NZ but less effective than in Australia. Plague densities of 40–80 rabbits/ha documented in Canterbury and Otago.↩︎

  14. Possum control and 1080: Eason, C.T. et al. (2011), “Toxic bait and bait stations for possum and rat control,” NZ Journal of Ecology, 35, 38–44. Orillion (formerly Animal Control Products) in Whanganui is NZ’s sole 1080 manufacturer, but relies on imported sodium fluoroacetate precursors. Without imports, 1080 production ceases once precursor stocks are exhausted (likely within 1–2 years).↩︎

  15. Feral goats: Parkes, J.P. (2005), “Feral goat,” in The Handbook of New Zealand Mammals, 2nd ed., Oxford University Press. Population estimates range from 100,000 to 300,000, down from historical peaks of over 1 million due to DOC control programmes.↩︎

  16. Facial eczema: di Menna, M.E. et al. (2009), “Facial eczema in New Zealand — a review,” NZ Veterinary Journal, 57, 155–166. Economic impact estimated at NZ$200–300 million per year including subclinical losses. The disease is most severe in Waikato, Bay of Plenty, and northern regions where late-summer conditions favour Pithomyces chartarum growth.↩︎

  17. Facial eczema resistance breeding: Morris, C.A. et al. (2004), “Genetic studies of tolerance to facial eczema in Romney sheep,” NZ Journal of Agricultural Research, 47, 231–240. Genetically tolerant lines have been developed through selective breeding and represent a key long-term management strategy.↩︎

  18. Gorse nitrogen fixation: Egunjobi, J.K. (1969), “An evaluation of gorse as a nitrogen-fixing plant in a New Zealand forest ecosystem,” NZ Journal of Science, 12, 53–60. Also: Magesan, G.N. et al. (2012), “Nitrogen cycling in gorse land in New Zealand,” Nutrient Cycling in Agroecosystems, 93, 285–294. Fixation rates of 100–200 kg N/ha/year are comparable to well-managed clover pasture.↩︎

  19. Ragwort biocontrol and sheep grazing: Wardle, D.A. et al. (1995), “The ecology of ragwort in New Zealand,” NZ Journal of Ecology, 19, 43–56. Sheep tolerate the pyrrolizidine alkaloids in ragwort better than cattle, though chronic exposure at high levels still causes liver damage. The ragwort flea beetle (Longitarsus jacobaeae) was introduced in 1983 and is now the most effective ragwort control agent.↩︎

  20. Thistle biocontrol: Shea, K. et al. (2005), “The biology of invasive organisms: Nodding thistle,” in NZ Journal of Ecology, 29, 179–190. The crown weevil reduces seed production by 50–80% in areas where it is well established.↩︎

  21. Californian thistle management: Bourdôt, G.W. and Kelly, D. (1986), “Californian thistle in New Zealand,” NZ Journal of Ecology, 9, 151–160. Among the most difficult weeds to control without herbicides. Repeated cultivation over 2–3 years can exhaust root reserves but requires land to be out of production during that period.↩︎

  22. Rabbit biology and control in NZ: Norbury, G. and Reddiex, B. (2005), “European rabbit,” in The Handbook of New Zealand Mammals, 2nd ed., Oxford University Press. RHDV effectiveness varies by region — less effective in wet, cool areas where the virus persists poorly in the environment. Myxomatosis is present in NZ but less effective than in Australia. Plague densities of 40–80 rabbits/ha documented in Canterbury and Otago.↩︎

  23. Rabbit biology and control in NZ: Norbury, G. and Reddiex, B. (2005), “European rabbit,” in The Handbook of New Zealand Mammals, 2nd ed., Oxford University Press. RHDV effectiveness varies by region — less effective in wet, cool areas where the virus persists poorly in the environment. Myxomatosis is present in NZ but less effective than in Australia. Plague densities of 40–80 rabbits/ha documented in Canterbury and Otago.↩︎

  24. Ragwort biocontrol and sheep grazing: Wardle, D.A. et al. (1995), “The ecology of ragwort in New Zealand,” NZ Journal of Ecology, 19, 43–56. Sheep tolerate the pyrrolizidine alkaloids in ragwort better than cattle, though chronic exposure at high levels still causes liver damage. The ragwort flea beetle (Longitarsus jacobaeae) was introduced in 1983 and is now the most effective ragwort control agent.↩︎

  25. Thistle biocontrol: Shea, K. et al. (2005), “The biology of invasive organisms: Nodding thistle,” in NZ Journal of Ecology, 29, 179–190. The crown weevil reduces seed production by 50–80% in areas where it is well established.↩︎

  26. White butterfly biocontrol: Cameron, P.J. et al. (2006), “Progress in biological control of Pieridae (Lepidoptera) in New Zealand,” in Proceedings of the 2nd International Symposium on Biological Control of Arthropods. Cotesia rubecula has been highly effective since its establishment.↩︎

  27. Diamondback moth biocontrol: Cameron, P.J. and Walker, G.P. (2002), “Field evaluation of Cotesia rubecula (Hymenoptera: Braconidae) for biological control of diamondback moth,” NZ Journal of Crop and Horticultural Science, 30, 235–247. Also: Talekar, N.S. and Shelton, A.M. (1993), “Biology, ecology, and management of the diamondback moth,” Annual Review of Entomology, 38, 275–301.↩︎

  28. Clover root weevil biocontrol: Gerard, P.J. et al. (2011), “Establishment of the parasitoid Microctonus aethiopoides for the biological control of clover root weevil,” NZ Plant Protection, 64, 23–27. The biocontrol agent has reduced clover root weevil populations by 25–50% in established areas.↩︎

  29. Native bush and pest suppression: Clout, M. and Gaze, P. (1984), “Effects of plantation forestry on birds in New Zealand,” Journal of Applied Ecology, 21, 795–815. Also: Ruscoe, W.A. et al. (2004), “The effects of pest control on native bird density and productivity on offshore islands,” NZ Journal of Ecology, 28, 59–69. The relationship between native cover, ruru (morepork) population density, and rodent pressure is documented in DOC island restoration work: where native forest cover is maintained and rats are controlled, native predator populations recover and provide ongoing rodent suppression. See also: King, C.M. (ed.) (2005), The Handbook of New Zealand Mammals, 2nd ed., Oxford University Press, chapter on rats and their predators.↩︎

  30. Native bush and pest suppression: Clout, M. and Gaze, P. (1984), “Effects of plantation forestry on birds in New Zealand,” Journal of Applied Ecology, 21, 795–815. Also: Ruscoe, W.A. et al. (2004), “The effects of pest control on native bird density and productivity on offshore islands,” NZ Journal of Ecology, 28, 59–69. The relationship between native cover, ruru (morepork) population density, and rodent pressure is documented in DOC island restoration work: where native forest cover is maintained and rats are controlled, native predator populations recover and provide ongoing rodent suppression. See also: King, C.M. (ed.) (2005), The Handbook of New Zealand Mammals, 2nd ed., Oxford University Press, chapter on rats and their predators.↩︎

  31. Conservation biological control: Wratten, S.D. et al. (2012), “Pollinator-friendly management does not increase the diversity of natural enemies in agricultural landscapes,” Biological Control, 62, 145–150. Flowering strips and companion planting to support beneficial insects are well-studied practices with demonstrated effectiveness in NZ conditions.↩︎

  32. Possum control and 1080: Eason, C.T. et al. (2011), “Toxic bait and bait stations for possum and rat control,” NZ Journal of Ecology, 35, 38–44. Orillion (formerly Animal Control Products) in Whanganui is NZ’s sole 1080 manufacturer, but relies on imported sodium fluoroacetate precursors. Without imports, 1080 production ceases once precursor stocks are exhausted (likely within 1–2 years).↩︎

  33. Traditional Māori trapping methods: Best, E. (1942), Forest Lore of the Maori, Dominion Museum Bulletin, Sections 4–6 describe traditional trapping systems for birds and mammals in detail. While the original targets (native birds for food) differ from post-event pest species, the trap construction principles, snare materials, and placement knowledge translate directly. Traditional snare and noose designs have been reproduced and tested in DOC trap trials for stoat and rat control. See also: Anderson, A. (1998), The Welcome of Strangers, Otago University Press, on pre-European resource exploitation systems.↩︎

  34. Rabbit biology and control in NZ: Norbury, G. and Reddiex, B. (2005), “European rabbit,” in The Handbook of New Zealand Mammals, 2nd ed., Oxford University Press. RHDV effectiveness varies by region — less effective in wet, cool areas where the virus persists poorly in the environment. Myxomatosis is present in NZ but less effective than in Australia. Plague densities of 40–80 rabbits/ha documented in Canterbury and Otago.↩︎

  35. Hand weeding labour requirements: Approximate figures based on organic farming practice. Actual rates vary enormously with weed species, density, soil conditions (wet soil makes weeding easier), and worker experience. See: Mohler, C.L. (2001), “Mechanical management of weeds,” in Liebman, M. et al. (eds.), Ecological Management of Agricultural Weeds, Cambridge University Press.↩︎

  36. Mulch depth for weed suppression: Chalker-Scott, L. (2007), “Impact of mulches on landscape plants and the environment — a review,” Journal of Environmental Horticulture, 25(4), 239–249. Organic mulches at 7.5–15 cm depth suppress most annual weed germination for a growing season, with thicker applications needed for aggressive perennial weeds.↩︎

  37. Flame weeding: Ascard, J. (1995), “Effects of flame weeding on weed species at different developmental stages,” Weed Research, 35, 397–411. Flame weeding is most effective on broadleaf annual weeds at the seedling stage (cotyledon to 4-leaf stage); larger weeds and grasses are more resistant. The technique has been used commercially in NZ organic vegetable production.↩︎

  38. Club root: Donald, E.C. and Porter, I.J. (2009), “Integrated control of clubroot,” Journal of Plant Growth Regulation, 28, 289–303. Plasmodiophora brassicae resting spores can persist in soil for 15–20 years, though populations decline significantly after 3–5 years without brassica hosts.↩︎

  39. Facial eczema resistance breeding: Morris, C.A. et al. (2004), “Genetic studies of tolerance to facial eczema in Romney sheep,” NZ Journal of Agricultural Research, 47, 231–240. Genetically tolerant lines have been developed through selective breeding and represent a key long-term management strategy.↩︎

  40. Grass grub biology and control: Jackson, T.A. et al. (2012), “Use of Serratia entomophila for the management of New Zealand grass grub,” in Use of Microbes for Control and Eradication of Invasive Arthropods, Springer. Also: East, R. et al. (1981), “Pasture pests of the North Island of New Zealand,” NZ Journal of Agricultural Research, 24, 285–292. Natural population cycling of grass grub is well-documented, driven by Amber disease (Serratia entomophila) and other pathogens.↩︎

  41. Facial eczema: di Menna, M.E. et al. (2009), “Facial eczema in New Zealand — a review,” NZ Veterinary Journal, 57, 155–166. Economic impact estimated at NZ$200–300 million per year including subclinical losses. The disease is most severe in Waikato, Bay of Plenty, and northern regions where late-summer conditions favour Pithomyces chartarum growth.↩︎

  42. Māori knowledge of NZ flora including toxic plants: Connor, H.E. (1977), The Poisonous Plants in New Zealand, NZ DSIR Bulletin 99 — the authoritative reference on NZ plant toxicity to livestock and humans. Traditional Māori plant knowledge is documented in: Crowe, A. (1997), A Field Guide to the Native Edible Plants of New Zealand, Viking; and Brooker, S.G., Cambie, R.C., and Cooper, R.C. (1981), New Zealand Medicinal Plants, Heinemann. The taxonomy of native plants supporting beneficial insects is addressed in: Wratten, S.D. et al. (1998), “Conservation biological control of aphids in New Zealand,” in Conservation Biological Control, Academic Press, which includes habitat assessments for native flowering plants as beneficials support.↩︎

  43. Performance comparisons between synthetic and locally producible pest control agents: Modern systemic fungicide efficacy data from Oerke, E.C. (2006), “Crop losses to pests,” Journal of Agricultural Science, 144, 31–43. Bordeaux mixture efficacy of 50–70% disease suppression documented in Lamichhane, J.R. et al. (2018), “Thirteen decades of antimicrobial copper compounds applied in agriculture,” Agronomy for Sustainable Development, 38, 28. Neonicotinoid residual activity periods from Jeschke, P. et al. (2011), “Overview of the status and global strategy for neonicotinoids,” Journal of Agricultural and Food Chemistry, 59, 2897–2908. Pyrethrum degradation rate from Casida and Quistad (1995), see [^25].↩︎

  44. Bordeaux mixture: Lamichhane, J.R. et al. (2018), “Thirteen decades of antimicrobial copper compounds applied in agriculture,” Agronomy for Sustainable Development, 38, 28. First used in 1885 in French vineyards. Remains one of the most effective and widely used fungicides in organic agriculture globally.↩︎

  45. Bordeaux mixture: Lamichhane, J.R. et al. (2018), “Thirteen decades of antimicrobial copper compounds applied in agriculture,” Agronomy for Sustainable Development, 38, 28. First used in 1885 in French vineyards. Remains one of the most effective and widely used fungicides in organic agriculture globally.↩︎

  46. Pyrethrum: Casida, J.E. and Quistad, G.B. (1995), Pyrethrum Flowers: Production, Chemistry, Toxicology, and Uses, Oxford University Press. Tanacetum cinerariifolium is the commercial pyrethrum species. Pyrethrin content of dried flowers is typically 1–2% by weight. The insecticide degrades rapidly in sunlight (UV), giving it very low environmental persistence.↩︎

  47. Pyrethrum: Casida, J.E. and Quistad, G.B. (1995), Pyrethrum Flowers: Production, Chemistry, Toxicology, and Uses, Oxford University Press. Tanacetum cinerariifolium is the commercial pyrethrum species. Pyrethrin content of dried flowers is typically 1–2% by weight. The insecticide degrades rapidly in sunlight (UV), giving it very low environmental persistence.↩︎

  48. Pyrethrum: Casida, J.E. and Quistad, G.B. (1995), Pyrethrum Flowers: Production, Chemistry, Toxicology, and Uses, Oxford University Press. Tanacetum cinerariifolium is the commercial pyrethrum species. Pyrethrin content of dried flowers is typically 1–2% by weight. The insecticide degrades rapidly in sunlight (UV), giving it very low environmental persistence.↩︎

  49. NZ geothermal sulfur: Hedenquist, J.W. and Henley, R.W. (1985), cited in Doc #80 footnotes. White Island (Whakaari) was commercially mined for sulfur from 1885 to 1914, when operations ceased after a lahar killed all 12 workers. Rotorua-area geothermal deposits also contain recoverable sulfur.↩︎

  50. Sulfur application rates for fungal disease control: Based on standard organic agriculture practice. See: Tweedy, B.G. (1981), “Inorganic sulfur as a fungicide,” Residue Reviews, 78, 43–68. Application rates of 5–15 kg/ha are typical for powdery mildew control; exact rates depend on crop, disease pressure, and formulation (wettable sulfur vs. dusting sulfur).↩︎

  51. Tobacco growing in NZ: Tobacco was grown commercially in NZ (primarily Nelson/Motueka) from the 1890s until the 1990s, when the last NZ tobacco factory closed. The climate in northern NZ is suitable for tobacco cultivation, and small-scale growing occurs. See: McLintock, A.H. (ed.) (1966), An Encyclopaedia of New Zealand, entry on tobacco.↩︎

  52. Pastoral weed tolerance: Popay, I. and Field, R. (1996), “Grazing animals as weed control agents,” Weed Technology, 10, 217–231. Many broadleaf “weeds” in pasture are palatable to livestock and contribute to dietary diversity and mineral nutrition. The economic threshold for weed control in pasture is higher than commonly practiced under chemical management.↩︎

  53. Feral goats: Parkes, J.P. (2005), “Feral goat,” in The Handbook of New Zealand Mammals, 2nd ed., Oxford University Press. Population estimates range from 100,000 to 300,000, down from historical peaks of over 1 million due to DOC control programmes.↩︎

  54. Ragwort biocontrol and sheep grazing: Wardle, D.A. et al. (1995), “The ecology of ragwort in New Zealand,” NZ Journal of Ecology, 19, 43–56. Sheep tolerate the pyrrolizidine alkaloids in ragwort better than cattle, though chronic exposure at high levels still causes liver damage. The ragwort flea beetle (Longitarsus jacobaeae) was introduced in 1983 and is now the most effective ragwort control agent.↩︎

  55. Gorse nitrogen fixation: Egunjobi, J.K. (1969), “An evaluation of gorse as a nitrogen-fixing plant in a New Zealand forest ecosystem,” NZ Journal of Science, 12, 53–60. Also: Magesan, G.N. et al. (2012), “Nitrogen cycling in gorse land in New Zealand,” Nutrient Cycling in Agroecosystems, 93, 285–294. Fixation rates of 100–200 kg N/ha/year are comparable to well-managed clover pasture.↩︎

  56. Blackberry fruit production: Estimated from productive wild blackberry stands in NZ. Dense, established blackberry bush typically produces 2–5 kg of fruit per linear metre of bush margin per season. Total production from NZ’s widespread blackberry infestations is difficult to estimate but potentially substantial.↩︎

  57. Plantain as pasture species: Judson, H.G. and Edwards, G.R. (2016), “Evaluation of plantain (Plantago lanceolata) as a pasture species for New Zealand dairy systems,” NZ Journal of Agricultural Research, 59, 141–155. Once considered a weed, narrow-leaved plantain is now commercially sown in NZ pastures for drought tolerance, mineral content, and livestock health benefits.↩︎

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