Report on the Agricultural Experiment Stations, 1952 Page: 64

64 REPORT ON EXPERIMENT STATIONS, 1952
State Station and yields were increased 3 to 51/2 tons per acre. Fertilizing
the cabbage increased yields substantially, but when no insecticides
were used the fertilization increased the bursting of the
heads. The beneficial effects of the insecticides were evident regardless
of the amount of fertilizer used. This effect of the insecticides is
believed to be brought about by maintaining uninjured and complete
leaf areas. Not only were the leaves stronger and more resistant
to physical stresses that cause bursting, but they also had a greater
transpiring surface which kept internal moisture fluctuations to a
minimum.
Border Spraying Controls Melon Flies
At the Hawaii station spraying border vegetation adjacent to, but
outside of, crop areas with DDT was found to be an effective control
for the melon fly, which is a severe pest of such crops as tomatoes, cucumber,
and melons in the Hawaiian Islands. Border spraying was
developed after a detailed study of the habits of the flies in and around
infested fields had revealed that practically all flies found on tomato
plants were females ready to lay eggs. Males, immature females,
and gravid (egg-laying) females are commonly found in large numbers
on certain plants such as corn or natural growth of plants like
Crotolaria, pigeonpea, and cocklebur in the vicinity of crop areas.
Flies are rarely present in the field before sunrise. As the day gets
brighter and warmer, they become active, and the gravid females,
which have spent the night in vegetation near the field, fly into the
field to lay egs. After laying their eggs, the flies return to the vegetation
near the field. Here they feed on plant exudations, honeydew
secretions of aphids and other insects, and on pollen and nectar of
flowers.
After discovering the habits of the flies, a mist blower was used to
apply a 5-percent DDT-oil emulsion directly to the flies in the vegetation
bordering crop areas. Tomato samples taken within a 3-acre
field thus treated had an average infestation of 2.7 percent as compared
with 64.7 percent in an untreated field. Some other insecticides
are also effective as border sprays.
Pea Aphid Control
The Maryland experiment station has developed a practical control
measure for pea aphids in the State. The station reports that
use of DDT and parathion to control pea aphids, in accordance with
station findings, has proved satisfactory and profitable to Maryland
growers. From 20 to 80 percent of Maryland's 9,000- to 12,000-acre
pea crop requires annual protection against the aphid. On the Eastern
Shore it has been necessary to use control measures against this
insect in 17 of the past 18 crop years. Cost of treatment varies from
$2.50 to $7 per acre according to the method used. For the period
1936 to 1944, before DDT and parathion came into use, the average
per acre production of peas was 1,588 pounds. From 1945 to 1951,
after the use of DDT and parathion, the average production was 2,276
pounds per acre, which represents an average increase of 43 percent
above the 1936-44 production.