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

Yellow Jackets in the Landscape

Yellow jackets are social wasps and are well equipped to defend a nest when disturbed. They almost always nest in the ground. They really don't dig, so they depend on preexisting holes or loose organic matter that they can remove. In the landscape, container-planted material where the peat moss has decomposed, mulch piles, voids under sidewalks and rotting landscape timbers, and even places where stumps or logs were buried in the yard during new home construction are common locations. The rarely seen nests are quite similar to the paper hornet nests that are sometimes seen in trees, but on a smaller scale.

Yellow jackets can actually be considered beneficial because they eat a lot of other insects. They may even help indicate scale infestations if they are seen scouting plants for honeydew. However, a nest in the wrong place may need to be treated. The best control is usually an aerosol can of "hornet and wasp killer" sprayed directly into the hole in late evening. The product must be delivered inside the nest or it will not be effective. While pouring gasoline down the hole is tried and true, it is illegal, dangerous, and will ruin the soil making it hard to grow anything in that spot for a while. Nest populations start from a single queen every spring and build through July. When enough individuals are present, a disturbed nest will respond in defense. For more information, see Residential, Structural and Community Pests Insect Note No. 15 at http://www.ces.ncsu.edu/depts/ent/notes/Urban/horn-yj.htm.

From: Steve Bambara, Extension Entomologist

Japanese Beetles Have Arrived

On Wednesday, June 16, we caught the first Japanese beetles of the year on the North Carolina State University campus in Raleigh. Last year Japanese beetles were not very abundant here so it will be interesting to see what this year brings. As most people know, Japanese beetles emerge once per year to feast on a variety of ornamental and crop plants. Their favorite ornamental hosts include roses, rosaceous trees and shrubs such as crab apple, crape myrtle, and linden. Beetles aggregate on plants in response to plant volatiles (smells) and pheromones from other beetles. This aggregation can result in rapid defoliation of trees and shrubs. It also means that one plant can be severely damaged while nearby plants are just nibbled on.

Japanese beetle traps do not offer any protection to landscape plants and may actually attract more beetles on to your property, so hang them in your neighbor’s yard! Likewise, treating a lawn for Japanese beetles grubs will not reduce defoliation of plants on that property since beetles fly in from great distances. Long-term protection for landscape and nursery plants can be achieved a neonicotinoid insecticide such as imidacloprid (e.g., Merit, Marathon II) or acetamiprid (Tri-Star). A new product with extremely low vertebrate toxicity but good efficacy for a number of pests including Japanese beetles is Acelepryn (chlorantraniliprole). For more information on the biology and management of adult Japanese beetles in nurseries and landscapes, consult Ornamentals and Turf Insect Information Note No. 147 at http://www.ces.ncsu.edu/depts/ent/notes/O&T/flowers/note147/note147.html.

From: Steve Frank, Extension Entomologist