Trap Crops and Emergence Cycles

When sufficient space allows for it consider inter-planting trap crops. Although not much study has been given to this, trap crops are the food of choice for offending insects. Trap crops draw insects away from the plants you value. Once infested predatory insects can be purchased and released on to the trap crops where the predators will devour the offenders. This method can be a win/win, affording protection for your food crop while introducing predators that stay around, reproduce, and work your garden for you as long as a food source is available to them. Here are a few examples of how trap crops work. 

Dill and borage will draw hornworms away from your tomatoes. Harlequin bugs love mustard, and green beans attract Mexican bean beetles. Flea beetles and Colorado potato beetles dearly love eggplant. Pale colored zinnias and commercial marigold hybrids afford a banquet for Japanese beetles. Arugula will draw flea beetles away from eggplant. If predatory insects aren’t available or affordable, destroy the trap crop once it becomes infested. 

I have little doubt that we could add many possibilities to this list. But as we consider ways to outsmart insects I should also mention emergence cycles. 

Specific insects emerge at specific times in the growing season. By knowing when this occurs precautions can be taken. Insects simply won’t stick around if there is nothing to eat. This is where growing your starts indoors under lights becomes extremely valuable. You can hold off planting while insects are emerging but your plants continue to grow and mature. The timing of insect emergence is sensitive to the weather. Consequently predicting precise dates remains elusive. But the windows of opportunity are reasonably well known. I will include an example of Eastern Tennessee where the climate zone range extends from 5 to 7 depending on the holler in which you might be gardening. The rule of thumb is to wait two to four weeks after insects emerge to set out your plants. Emergence cycles are extremely local and therefore the information must be obtained from your local Cooperative Extension or Department of Agriculture.



Most beetles in April and early May.

Squash bugs emerge about May 1.

Cabbage loopers emerge about April 1.

Squash vine borers emerge in late June. One method of deterring them is to wrap the stems in nylon stocking, Continue wrapping as the stem grows and mound up the soil as you go. Don’t forget to mulch heavily.


Including a wealth of flowering plants and herbs tremendously improves the biological control of insects even if these insectary plants aren’t blooming. A list of basic companion or insectary plants can be found near the beginning of this blog, entitled Shopping for Companion Plants. I consider them the bare essentials. Soon I will post articles about beneficial/predatory insects, butterflies, and hummingbirds that vastly expand the initial basic list of companion plants.

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