No. 12/July 26, 2016

Cherry Leaf Spot on Cherry and Plum Trees
Cherry leaf spot is a fungus that can infect production and ornamental cherry and plum trees. Symptoms start to develop in early summer as small, round, purple spots on the upper surface of older leaves. Eventually, the spots turn reddish brown, and they may coalesce to form larger, irregular dead areas on the leaf. Leaf tissue near the older spots turns yellow, and the leaves start to die and fall from the tree by mid-summer.

Oak Wilt
The plant clinic has received several questions on Oak Wilt and recommended control strategies. Oak wilt is a devastating fungal disease that essentially plugs up the vascular system and disrupts the water and nutrient flow within oak trees. The disease progresses rapidly, killing mature trees in the red oak group within one season.

Japanese Beetle
Japanese beetle adults are numerous throughout Illinois. Damage has been reported on linden, crabapple, and various other trees and shrubs. Heavy feeding is likely to continue until about mid-August.

White Grubs
Large numbers of Japanese beetle adults along with sporadic rainfall makes it necessary to treat preventatively for white grubs in irrigated turf in some areas of the state. Much of southern and central Illinois continue to be dry, creating conditions where white grub damage is likely in irrigated turf. Much of the rest of Illinois has had sufficient rainfall that non-irrigated turf is generally green and attractive to egg-laying Japanese beetle and masked chafers.

Syrphid Flies
Large numbers of syrphid, or flower, flies are being seen. They are small flies, usually 1/4 inch or shorter, with yellow and black or brown bands on the abdomen. They hover around your arms when you have been perspiring and land to lap up the sweat. This hovering also gives them the name of hover flies. They are called flower flies because they are commonly found on flowers, pollinating as they move from flower to flower. They are called syrphid flies because they are in the fly family Syrphidae.