Extension Educator, Horticulture
To quote the famous philosopher and baseball legend Yogi Berra: "you can observe a lot just by watching". It's time to slow down and stare at your evergreens especially at the top of arborvitae, juniper and spruce and at any brown areas. If you look closely you may just 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. In the next week 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), 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 checklist for July.
Remove any stagnant water to avoid mosquito problems. Consider flowerpots, gutters and birdbaths. Use Bti (Bacillus thuringiensis israelensis) sold as Mosquito Dunks or Mosquito Preventer in rain barrels or other standing water.
Don't let weeds go to seed. "A year of seeding equals 7 years weeding." Mowing off or collecting young flower heads before they set seed can help to lessen weed seed production.
Continue removing spent flowers on ornamentals. If petunias look leggy, trim back to 6-8 inches then water and fertilize for renewed growth.
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.
Divide bearded iris -mid July to the end of August when the clump becomes crowded and fewer flowers are produced each year.
Treat for lawn grubs depending on product and past pest history. Adult female beetles prefer laying eggs in moist soil such as well-watered lawns. 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 branches. Prune off infested branches or use Btk products such as Dipel or Thuricide.
Pull up garlic bulbs when the tops start to yellow and dry. Do not wait until the leaves are completely dry or storage life may be shortened.
Scout for tomato hornworm on tomatoes and peppers. Remove by handpicking. I usually just pinch off the leaf they are munching. Then use your favorite squishing technique. Btk products such as Dipel are also effective but not nearly as entertaining.
Make a habit of looking closely at your plants to monitor for insects and diseases. Early management is best. Check with your local U of I Extension office for information. UI Extension's websites are also a great resource http://web.extension.uiuc.edu/state/hort.html
Thanks to the many Master Gardeners and garden fanatics who made the 2011 Garden Walk a great success. Also huge thanks to the garden owners that opened their garden gates to the community.