Fall Steps to Reducing garden insects

By: Kelly Feehan, Extension Educator, kfeehan2@unl.edu

 As the vegetable garden season nears its end, frustration with insect damage may still be fresh in gardeners mind.  A common question asked is if anything can be done during fall to reduce insect damage next season.

One thing NOT to do during fall is apply an insecticide to soil or plant debris. Over the years, I’ve been asked if spraying the soil will kill insects. While some insects do spend the winter in soil, plant damage cannot be controlled this way.

When using any pest management practice, be sure it is targeting the correct pest at the right time. Positively identify the cause of plant damage. If it is a harmful insect, most vegetable insects are managed when present on the plant during the growing season, whether the control method is hand-picking or a pesticide.

 An important fall practice is sanitation which is removing or tilling under plant debris. Residue left in the garden can harbor insects and diseases. Be sure to also discard fallen fruit as it drops to the ground throughout the season. Manage nearby weeds as some garden pests overwinter in weedy areas.

Sanitation is a good practice to use in vegetable gardens where the majority of plants are annuals and removed or tilled under each year. It is best to deal with plant residue soon after harvest or once the plant begins to die. This reduces the number of insects that may move into soil for winter.

In perennial flower gardens, there is now a focus on leaving plant residue over winter to conserve nesting pollinators. If a plant had a serious pest this past season, it would be best to remove top growth. If not, wait until next spring or leave 12 to 15 inches of plant stems to aid pollinators.

While fall tillage can kill some insects, excessive tilling with a rototiller damages soil structure. An alternative is to hand remove plant residue, then rake the area smooth. Turning the surface area over with a shovel may expose insects to the elements.

 Maintaining good soil structure leads to healthier plants better able to resist or handle insect damage. If you have not incorporated organic matter, like compost, in some time, fall is a good time to do this. Hand spading organic matter to incorporate it is less harmful to soil structure than rototilling.

Some insect eggs or pupae may overwinter on equipment like tomato cages. Clean and sanitize garden tools and structures. Wash off soil and plant debris, then sanitize with a 10 percent bleach solution and dry items before storing. Sanitizing is targeted at disease pathogens.  

 Crop rotation remains an important practice for minimizing pest damage. If you do not have a garden plan on paper, create one now while this year’s plant locations are fresh in mind. Next season, avoid planting the same vegetable or vegetables from the same family in the same locations.

 Make note of plant varieties that had a pest problem and avoid these next year if feasible. If you recall when insect damage showed up, make note of that. For example, with bean leaf beetles, if you planted in succession, which succession had the most damage and could this one be avoided next year?

 Insect management is aimed at reducing unacceptable damage to plants while conserving beneficial insects. The loss of beneficial insects can lead to increased pest populations and plant damage over time.

 This winter, take time to learn more about garden insects you deal with. If and when they need to be managed, and best methods to use that help conserve beneficial insects are some things to learn.