BLOOMINGTON, Ill. — University of Illinois Extension Master Gardeners in Livingston, McLean & Woodford Counties have been busy during their scheduled help desk hours this summer. Speaking within their communities, they have come to hear that many gardeners have been plagued with numerous, unwanted garden visitors. University of Illinois Extension Horticulture Educator, Kelly Allsup, wants to share a few of their findings and let you know how to handle these visitors.
When the phone rings, it is usually a discussion on the large populations of Japanese beetles to the sudden infestation of blister beetles in the tomato patch. Another call happens to be about the caterpillars that are eating the oak leaves or the concern about the large menacing wasps flying around the house known as cicada killers.
Kelly Allsup says helping gardeners find the silver bullet for the Japanese beetle is a difficult task because controlling the larvae that live in the ground for ten months of the year does not ensure the adults will not decimate your apple trees. Gardeners must have a plan as soon as they see the first beetle to prevent the large populations.
Allsup says, “blister beetles have flown under the radar in my five-year appointment as horticulture educator until this year. They have come out in droves to eat on our veggies.” “Be careful when picking them off the plants as they will cause blisters with their spray,” states Allsup. Other sources indicate they are only a temporary problem.
Small caterpillars skeletonizing the leaves are also consuming oaks. The leaf looks white from the caterpillars eating the mesophyll layer of the leaf. Entomologist, Phil Nixon, says this is just an aesthetic issue, and no control is warranted.
Cicada killers (Sphecius speciosus) are on the prowl, and there have been many inquiries about them at the Master Gardener plant clinics.
Cicada killers are solitary wasps with yellow banding on their abdomens. They appear in late July and early August and resemble large, black hornets. These insects are considered beneficial because they help control the annual cicada (Tibicen spp.) population. However, the excavating and burrowing that they do in open, dry ground when constructing their nests; can be a nuisance for gardeners and homeowners.
Cicada killers are usually non-aggressive, although the male may investigate a person who invades its territory to determine that it is not another male cicada killer. Males are unable to sting. The females can sting but do so only when handled or disturbed because they lack the instinct to guard their nest as the honeybee does.
The singing of the annual cicadas causes the adult wasps to come above ground out of hibernation. On their search for annual cicadas, they will stop and drink nectar and water from gardens. Once the female cicada killer has found and paralyzed a cicada, she will carry it back to her underground nest. She places the cicada in a nest cell, lays her eggs on it and seals up the cell. The larvae hatch in a few days and begin to feed upon the cicada before they form a cocoon to pupate for the winter and early spring.
For gardeners concerned about the safety of children or pets, University of Illinois Extension suggests planting ground covers and grass to prevent bare spots, adding mulch, and using irrigation to deter nesting. An application of a carbamate-based chemical product to the nest will kill cicada killer adults and their larvae, but killing this beneficial insect is discouraged.
For more information on garden pests, please visit us at web.extension.illinois.edu/lmw/hort.html, and make sure to check in with Master Gardeners during their scheduled help desk hours. For schedules and additional questions, please contact Kelly Allsup, Extension unit educator, Horticulture-Livingston, McLean, and Woodford Unit at (309) 663-8306 or email her at firstname.lastname@example.org.
— Kelly Allsup
Extension Educator, Horticulture
University of Illinois Extension
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