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Scouting Report 7/1/98

Lacebugs are present on sycamores and oaks. These insects cause whitish stippling on the upper leaf surface and black specks on the lower surface. Fully grown lacebugs are about 1/8 inch long and whitish to clear, with brown to black markings. The even smaller nymphs are somewhat clear with blackish markings. Both nymphs and adults will be on the leaf undersides next to the veins. The damage rarely warrants control.

Spirea aphids are present on the stem tips of spirea. The same aphid commonly attacks crabapple branch tips and associated leaves, so be watchful for them. On spirea, these aphids may build to huge numbers. They can be controlled with a variety of synthetic pyrethroids and other insecticides. Spraying with insecticidal soap or summer spray oil will greatly reduce their numbers and be less damaging to natural enemies that are present. On crabapple, they usually do not need to be controlled unless the sticky honeydew that they produce becomes a problem on parked cars or sidewalks.

Peach tree borer moths are being caught in increasing numbers at The Morton Arboretum. To protect flowering cherry and purpleleaf plum, we recommend spraying the base of the trunk with chlorpyrifos (Dursban) or lindane about two weeks after peak moth trap catches.

Solitary oak leafminer damage is appearing in northern Illinois. This insect is most noticeable in northern Illinois, where it causes aesthetic damage to burr, white, and other oaks. Control is achieved by spraying the foliage with acephate (Orthene) when damage first appears.

Periodical cicada damage is very noticeable through much of the southern two-thirds of Illinois. On oaks and many other tree species, the outer six to eight leaves of scattered twigs have turned brown due to cicada eggs laid in the stems. There is little to be done or that could have been done to prevent this damage. The leaves or branch tips will soon drop. Next year, the tips of the branches will have more twigs and leaves due to lateral bud break, but there should be no lasting ill effect on the tree.

Author: Phil Nixon and staff at The Morton Arboretum


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