Insect Behaviour and Plant Health — Dr Tom Dykstra

Insects are attracted to unhealthy plants, not healthy ones. Raising plant health (measured via Brix) above a threshold eliminates insect damage without pesticides. Based on Dr Tom Dykstra’s research and Regenerative Agriculture podcast, reported in Direct Driller Issue 6.

Core Finding

“Insects are only attracted to unhealthy plants.”

  • Plants with Brix levels of 12 or higher experience virtually no serious insect damage
  • Most crops score Brix 4–8 (productive but susceptible to disease and damage)
  • Brix 14+ indicates a genuinely healthy plant
  • The consequence: if healthy plants don’t attract insects, they don’t need pesticides

[Source: dd-issue-06, 2026-04-11]

How Insects Smell — Insect Olfaction

  • Insects have highly tuned receptors detecting suitable food over distances of a mile or more
  • They have poor digestive systems → seek food that is deteriorating (the bad apple principle)
  • Signal comes from both antenna and palps
  • After 10+ years of research, by November 2016 Dykstra’s lab decoded the mechanism: insects smell wavelengths, not just chemical “lock and key” receptors

Key Attractants

  • Ethanol: a universal odorant advertising plants as unhealthy — many stressed plants release alcohols
  • Nitrates and ammonium: indirectly attractive to certain insects — as N application increases, plants advertise stress, becoming more susceptible
  • Detection distances for insect signalling compounds are “extraordinarily great”

Brix Is Not Static

  • Brix levels vary with weather conditions
  • Plants lower their defences shortly before a storm → insects become increasingly active and feed
  • This explains why insect damage can appear suddenly in specific fields

[Source: dd-issue-06, 2026-04-11]

Implications for Farming

  • Pesticides create a vicious cycle: they damage soil microbes → weaker plants → lower Brix → more insect attraction → more pesticide needed
  • Soil microbes feed nutrients to plants and their population is reduced by fungicides, insecticides, and mechanical damage
  • Soil without microbial action becomes fluffy and easily eroded
  • Raising Brix scores comes from soil biology, not spray applications

Practical Steps (Dykstra’s Recommendations)

  1. Experimental fallow: leave 5 acres per 1,000 on high ground (no pesticide run-off); let weeds grow; spray sugar solution at 5 lbs/acre to feed soil microbes; plant cover crops to speed pesticide residue breakdown
  2. Focus on building soil health to raise Brix rather than treating symptoms
  3. Higher Brix crops have greater flavour and longer shelf life — benefits translate to market value

[Source: dd-issue-06, 2026-04-11]

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