ds of one that contains 25 per cent of DDT.
Make three applications, the first about 30 days before the first nut is
due to drop, and the second and third after intervals of 12 days. Unless
the entire bur, especially that portion near the stem end where most of
the feeding punctures are made, +is thoroughly covered+ with a film of
DDT, the weevils may feed without being affected by the insecticide. In
handling DDT, one should use the same care as with such well-known
poisons as lead arsenate, Paris green, calcium arsenate, and nicotine.

* * * * *

Mr. Gravatt: I might say that Mr. Van Leeuwen has used only a small
section of our experimental orchard, and right near-by would be large
sections not used. The weevils are not killed quickly by the DDT, they
are somewhat resistant, and so we think quite a number of weevils come
over and deposit eggs before they are killed by this DDT, because they
don't lose any time getting to work on the nuts. He hopes to have much
better results where the entire orchard is sprayed. This year we
sprayed our entire orchard twice, and it is a real pleasure to go out
there now and gather up nuts and not be eating weevils when we do eat
them.

President Davidson: Well, Mr. Gravatt will now give us a talk on
Diseases Affecting the Success of Tree Crop Plantings, and I am sure we
all are on our toes to hear about that. Mr. Gravatt.

Mr. Gravatt: I only ask a few minutes to show a few slides.

(Slides shown.)

Diseases Affecting the Success of Tree Crop Plantings

G. F. GRAVATT and DONALD C. STOUT

Division of Forest Pathology, Plant Industry Station, Beltsville,
Maryland.

Mass plantings of many trees of the same kind frequently result in an
increase in the severity of insect pests and diseases. Leaf diseases,
for instance, spread quickly through such plantings when weather
conditions favor growth of the causal organisms. Plants on sites
unfavorable to a specific tree species also are responsible for disease
increases. Chinese chestnuts grown on a site where they are subject to
early-fall and late-spring frosts will fail. Not only will crops be
reduced by the killing of buds or blooms, but the twigs, or even whole
trees, may be killed by freezing. The blight fungus develops rapidly on
such injured trees and may mislead people into thinking that the blight
fungus is the primary cause of the killing.

Still another factor that determines the damag