Powdery Mildew on Squash and Other Cucurbits

Powdery mildew is a common disease of cucurbits under field and greenhouse conditions in most areas of the world. Yields are reduced because of a decrease in the size or number of fruit, or a shortened harvest period. Premature senescence of infected leaves can result in lower market quality because fruit become sunburned or ripen prematurely or incompletely.

Symptoms are white, powdery fungal growth developing on both leaf surfaces, petioles, and stems. Symptoms usually develop first on crown leaves, on shaded lower leaves, and on leaf undersurfaces. Yellow spots may form on upper leaf surfaces opposite powdery mildew colonies. Older plants are affected first. Infected leaves usually wither and die. Plants may senesce prematurely.

Control - Fungicides should be applied every 7-10 days beginning early in disease development following detection through an IPM scouting program. Inspect plants weekly beginning in July and after fruit initiation (when plants become more susceptible). Examine upper and under surfaces of five older leaves at ten separate sites or until symptoms are found. Initiate a weekly spray program when symptoms are found.

Genetic resistance is used extensively as a control measure in cucumber and melon, and is being incorporated into other cucurbit crops. Yield potential should be considered when selecting varieties because some resistant summer squash varieties produce less fruit than susceptible varieties that have not been treated with fungicides. Resistant varieties of pumpkin and winter squash are under development. Successive cucurbit plantings should be physically separated because older plants can serve as a source of conidia.

Information for this article was taken from the fact sheet, "Powdery Mildew of Cucurbits" Cooperative Extension, New York State, Cornell University.

Forestry Newsletter

To better serve Woodland Owners in NC, NCSU Extension Forestry has created a new listserv “Woodland Owners Update”. This service updates you directly through email on woodland owner events throughout the state. We also inform you on current and new publications as they come out. Informed landowners make the right decisions about their woodlands and we are dedicated to providing NC woodland owners the best information available. If you would like to join Woodland Owners Update, please visit our website

http://www.ces.ncsu.edu/forestry/resources/woodland_owner_update.php

Fall Webworms

It seems early, but fall webworms have hatched their early season brood. This is the less abundant race of fall webworm that develops in mid-summer and defies their common name. The web starts at the branch tips and becomes enlarged to encompass fresh, green leaves until the web may become two to three feet long. This is more noticeable with the later season race. Because fall webworm damage accrues over the summer, they usually cause little long-term health damage to the trees they defoliate. At any one location, the populations of fall webworms wax and wane so that they are conspicuous and damaging for a year or two and then the populations seem to thin.

Webworms feed on over 600 types of trees, shrubs and other plants. In North Carolina they are most often reported on pecans, persimmons, sourwoods and willows. Small trees infested with several broods of caterpillars may be entirely enclosed in webs. After feeding for four or five weeks, the caterpillars crawl down, spin cocoons and pupate in mulch or soil.

Fall webworms can be managed by pulling down the webs and destroying the caterpillars if the webs are within reach by a pole. If the webs are within reach of a sprayer, several insecticides can be sprayed for control. Only spray foliage adjacent to the web. Insecticides work best when the caterpillars are young, so it is best to treat as soon as the webs are first noticed. A product containing Bacillus thuringiensis or carbaryl is appropriate for homeowner use, while commercial applicators can use B.t. (e.g., Dipel), Conserve, Talstar or one of several other options. View a QuickTime movie clip about fall webworms at http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note07/fallwebworm.mov. For more information about fall webworms, see Ornamentals and Turf Insect Information Note No. 46 available on the “web” at http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note46/note46.html.

From: Steve Bambara, Extension Entomologist