Saturday, September 5, 2009

Landscape - Current Pests

The following are some current pest problems in Delaware landscapes.

Septoria leafspot is one of several common diseases showing up now on flowering dogwood (Cornus florida) and silky dogwood (Cornus amomum). Some trees have numerous small angular spots on the lower branches that look like small dogwood anthracnose spots. It is too late for any chemical control.

This time of year we often see an increase of anthracnose on oak, maple and walnut. On oak and maple, look for large brown spots that follow the veins and some round spots as well. This late in the season no control is necessary. On walnut, the spots are irregular in shape, numerous and can cause premature defoliation. Again it is too late in the season for any control and the fungus does little to harm the health of the trees.

Puss caterpillars and other stinging caterpillars are actively feeding. Puss caterpillars have been found on Ilex and Acer.

Ground nesting wasps, yellowjackets, and hornets are active and becoming more of a nuisance as we approach fall.

Slime molds have been appearing on lawns especially after recent rains. Slime molds produce a gray growth over the blades of turf that give it a dark appearance from a distance. What you see is the reproductive stage of this primitive fungus. It is not harmful to turf and can be removed by cutting the grass. These are related to the slime molds that appear in mulched beds as white, pinkish red, and yellow blobs often referred to as the “dog vomit fungus”.

Information from the current issue of the Ornamentals Hotline newsletter from the University of Delaware Cooperative Extension.

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