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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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Types of Garden Enemies
