Diseases and Pests

Disease of the Month: Cherry Leaf Spot Weed of the Month: Crane Fly

by Heather Prince

Disease of the Month: Cherry Leaf Spot

Cherry leaf spot (Blumeriella jaapii) is popping up on ornamental and fruit cherries in Illinois. Symptoms typically appear in early to midsummer, beginning as small reddish/purple spots on the upper leaf surface. Eventually the spots turn brown and may merge together. The centers then drop out giving the leaves a shot-hole appearance before turning yellow and dropping. On tart cherries, the yellow leaves drop readily, while on sweet cherries, yellow leaves are Blumeriella jaapiiretained. This fungal disease can significantly affect the fruit production of cherries and cause debilitating stress on ornamental varieties.

Treatment:

Apply fungicides to highly susceptible trees or trees that were severely affected in previous years. Fungicides containing chlorothalonil, chlorothalonil + thiopanate-methyl, copper + mancozeb, mancozeb, myclobutanil, propiconazole, and pyraclostrobin + boscalid are labeled for use against this disease. Plan applications to begin in spring at petal fall, with a second application 10 days to two weeks later. If symptoms continue to develop, later applications in summer may be required. Wet and humid summers acerbate the disease. Since the fungal pathogen survives the winter on fallen leaves; rake and remove leaves in the autumn to help reduce infection the following year.

Pest of the Month: Crane Fly

Crane fly (Family Tipulidae) adults resemble oversized mosquitoes with slender bodies and very long legs. The adults appear during the summer and spend their time mating and laying eggs. They do not Tipulidae feed. The eggs hatch in the fall and the insect overwinters as larvae. The larvae begin eating turfgrass shoots, roots, and crowns in spring, achieving their full size by early summer.

Treatment:

Crane fly larval feeding is usually a nuisance. However, large larvae populations can cause thinning and substantial bare patches in the lawn. Turf injury is usually seen in late spring when larvae are near their full size. On golf courses, crane fly larvae injury can be mistaken for black cutworm injury. Apply a soap flush to the turfgrass to bring the larvae to the surface of the turfgrass for identification. Mix one tablespoon of dish soap with two gallons of water and pour evenly with a watering can. If you are not sure what kind of larvae you have, they can be submitted to the UIUC Plant Clinic for identification.

Crane flies thrive in damp areas, so for cultural control avoid watering in wet conditions and improve drainage in damp areas. Reducing moisture will make the area less attractive to and kill larvae. Regular mowing and fertilizing to keep lawn health reduces the presence of thin or bare areas where adults prefer to lay eggs. You can also add the nematode Steinernema feltiae to reduce populations of crane fly larvae. Insecticide options for control include carbaryl, chlorantraniliprole, clothianidin, and imidacloprid. Read the label and follow directions as some insecticides are applied in fall and some in spring.

Additional resources:

University of Illinois Extension Service https://web.extension.illinois.edu/state/ horticulture/index.php 217-333-0519 The Morton Arboretum http://www.mortonarb.org/Plant Clinic: http://www.mortonarb.org/trees-plants/ tree-and-plant-advice/ 630-719-2424 Chicago Botanic Garden Plant Information Service: https://www.chicagobotanic.org/ plantinfoservice 847-835-0972