The Homeowners Column

The Homeowners Column

July pest updates

Photo of Sandra Mason

Sandra Mason
State Master Gardener Coordinator

To quote the famous philosopher and baseball legend Yogi Berra: "you can observe a lot just by watching". July is the perfect time to observe your landscape. Heat and sweat may make us slow down; however, many insects rev up their engines in mid-summer.

It's time to grab a lemonade and stare at your evergreens, especially at the top of arborvitae, juniper and spruce and at any brown areas. If you watch closely you may see the swaying movements of bagworm caterpillars with their one half to one inch long cone-shaped bags on their tail ends. As the caterpillars eat and grow, their bags get larger. They continue to cover the bags with bits of leaves from whatever plant they are feeding.

As long as they are still moving, insecticide sprays can be effective. By the time we hit mid-August or so they will quit moving then picking the bags off is your only management option. Insecticide options for bagworms include Btk, Bacillus thuringiensis kurstaki, (sold as Dipel, Thuricide, Safer Caterpillar Killer and others), spinosad (sold as Conserve and some Ferti-lome products), or cyfluthrin (sold as some Bayer products). Read and follow all label directions. Because caterpillars often start feeding at the top of the tree, sprays need to reach the top to provide complete control.

A week or so after applying insecticide sprays repeat your evergreen stare technique. Any caterpillars still feeding after spraying show green leaves at the top of the bags and their caterpillar heads are still visible; therefore, a second application may be necessary.

Timing is everything in knife throwing and gardening so here is your watch list for July.

Remove any stagnant water to avoid mosquito breeding. Consider flowerpots, gutters and birdbaths. Use Bti (Bacillus thuringiensis israelensis) sold as Mosquito Dunks or Mosquito Preventer in rain barrels or other standing water.

It's the "haves" and the "have-nots" with Japanese beetles. Some areas of the state have reported very few while the northwestern and north central report high numbers. If you are one of the "lucky" ones, continue control of Japanese beetles on roses and many other plants. Collecting beetles in the morning by shaking branches over jars of soapy water can help with small infestations. Insecticide sprays including carbaryl (Sevin), cyfluthrin and permethrin can be effective. Traps can result in more damage if used in heavily infested areas.

Lawn grubs have also been spotty so you may not need to treat unless you've had a history of grub problems. Check out University of Illinois Extension Home, Yard and Garden Pest newsletter for more in-depth discussion. Adult female beetles prefer laying eggs in moist soil such as well-watered lawns; therefore unwatered lawns are less likely to be damaged. Some products such as imidacloprid sold as Merit and halofenozide sold as GrubEx need to be applied in July in order to be active when the grubs start feeding in August.

Scout for fall webworm nest building near ends of tree branches. Prune off infested branches or use Btk products such as Dipel or Thuricide.

Scout for tomato hornworm on tomatoes and peppers. Remove by handpicking. I usually just pinch off the leaf they are munching. Then use my favorite squishing technique. Btk products such as Dipel are also effective but not nearly as entertaining.

Keep a look out for the new pest of raspberries, grapes and other thin skinned fruit, spotted wing Drosophila. Unfortunately this fruit fly does not wait for rotting fruit but attacks fruit before harvest. Infested fruits "melt down" from larval feeding and fungal rots in just a few days. Check out

Make a habit of looking closely at your plants to monitor for insects. Check your local UI Extension office for information as well as our website

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