Types of Garden Enemies
Fig. 15
Control. Potato varieties Kennebec, Sebago, and Essex are resistant. There is a spray-warning service telling farmers and home gardeners when blight is imminent. Spraying with bordeaux mixture or other copper spray early in the season sometimes stunts tomatoes or prevents fruit setting. Dithane, or Parzate, is satisfactory, and for small gardens there are special dusts containing copper. In experimental work Manzate and Phygon XL have given good results on tomatoes.

BORERS
Borers are chewing insects working in wood or herbaceous stems. They are usually larvae of beetles, grubs, or of moths, caterpillars. Trees that are newly set, or weakened by drought, starvation, winter injury, or defoliation by leaf-eating insects are predisposed to borer attack. Sawdust coming out of holes in the trunk is a sign that borers are actively at work. ASH BORER (Podosesia syrtngae fraxint). A close relative of the lilac borer, but limited to ash and mountain-ash.

BRONZE BIRCH BORER (Agrilus anxius).
This is one of the chief reasons why white or paper birches are so short-lived. Upper branches turn brown, starting at the tips, and may be somewhat swollen or ridged, with small holes in the bark. The inner bark is full of burrows, packed with sawdust. The grubs are white, slender, with a brown enlargement just back of the head, 3/4 inch long. They winter in sapwood, pupate in spring, and emerge in May, June, or July as greenish-bronze beetles, 1/4 to 1/2 inch long, with blunt heads and pointed bodies. They lay eggs in bark crevices.

Control. Keep birches growing vigorously with proper food and water; wrap newly transplanted trees; cut out and burn infested parts before April 1st. Spray 2 or 3 times with DDT, starting in late May or early June.

CARPENTERWORM (Prionoxystus robiniae).
Common on oak, often destructive to elm, locust, poplar, willow, ash, and other shade trees. There are very large burrows in the wood, with sap colored dark, and sawdust coming out through the bark. The borers are white caterpillars, 1 to 2 inches long, with dark-brown head and tubercles over the body. The moth, gray with dark and light mottling, and a 3-inch wingspread, comes out of a pupal case left hanging at the mouth of the burrow.

Control. The borers can be killed by injecting a tablespoon of carbon bisulfide into each burrow, closing the hole with mud or putty. Spraying trunks with DDT is sometimes practical.

COLUMBINE BORER (Papaipema purpurijascia).
A salmon-colored caterpillar, 11/2 inches long, works in stems and fleshy roots of colum- bine. Eggs are laid on ground around the plant by a reddish-brown moth. Scraping the soil to kill eggs and spraying or dusting with DDT is recommended.




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