Vegetable Production Guide

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Insect Control

This section was updated - 05 May 2017


These small, soft-bodied, black, winged or wingless insects are found clustered on tassels, upper leaves and silks. Large numbers on silks and under husks may make ears unmarketable on the fresh market. A very heavy infestation, particularly in late plantings, may result in incompletely filled cobs.

If large numbers of aphids are present at tassel emergence or closer to harvest, control is necessary.


White, ribbed round eggs are laid by the moths on exposed fresh silk. Eggs hatch in approximately 1 week, and the caterpillars crawl down the silk into the cob, where they feed for 2 to 4 weeks. There are two to three generations per year. The caterpillars vary in colour from greenish to brownish and are marked with light and dark stripes.


Note: To protect bees, do not move them within foraging distance of the treated field until at least 36 hours after spraying. See “Bee Poisoning,” .

Kill the newly emerged larvae on the silk before they enter the cob. Treat, when eggs first observed, with one of the products listed in Table 2, Corn Insect Control.


Full grown larvae are up to 2.5 cm long, olive green with a pale head and a lightly striped body. There are three pairs of legs at the head end and three pairs of fleshy legs at the rear. They move with a looping action.


Loopers will be controlled when Lannate or Sevin are applied for corn earworm control.


Wireworms are yellowish-brown, shiny, slender, hard-bodied worms 5 to 25 mm long which bore into corn seeds and seedlings and destroy them. In heavy infestations they will feed on established plants and greatly reduce the yield.


Poncho (clothianidin) and Cruiser (thiamethoxam) are registered as a seed treatments. For use in commercial seed treatment facilities only. Not for use on farm seed treatment applicators used at planting.

See Pest Management section, Wireworms, of this guide. If wireworms are present see Table 2 (Corn Insect Control) for control options.

Seed-corn Maggot

Small, legless cream-coloured maggots attack germinating seeds.


Use seed treated with diazinon, Cruiser (thiamethoxam) or Poncho (clothianidin).

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