4f) ANNUAL REPORTS OP DEPARTMENT OF AGRICULTURE, I 
while effective against the flea beetle, also under certain conditions produces 
injury to the tobacco plants; 
M.ni.x materials have been tested as substitutes for lead arsenate and parti 
green for (he control of the tobacco hornworm, but as yet no promising 
materia] has been found. 
The work on stored-tobacco pests has been directed primarily to the use 
of a light trap in warehouses, combined with fumigation. In control 
these measures have effected a very decided reduction in the amount of 
store! tobacco destroyed by the cigarette beetle and the tobacco moth. 
BERKV INSECTS 
Investigations of berry Insects have consisted mainly of a Btudy of the 
control of the raspberry fruitworm and the red berry mite In the Puyallup 
Valley of Washington. Control tests have been conducted against the straw- 
berry weevil at Chadbourn, X. ('., to develop insecticide treatments and cul- 
tural control measures thai will avoid the presence of objectionable residues 
on the berry ;it harvest time. The strawberry crop on the Coastal Plain 
develops fruit rather slowly in some seasons and' oftentimes it is necessary to 
treat the crop to prevent damage from the Strawberry weevil when there' are 
Large green berries on the plant. The use of an arsenical at such a \ 
wotdd leave an Objectionable residue On the berry at harvest. The results of 
these tests were inconclusive. 
STUDIES OF NONARSENICAL INSECTICIDES 
Laboratory experiments and large field-plot tests to determine the relative 
toxicity of pyrethrum and derris mixtures for the control of several species 
of cabbage worms have been carried on at several laboratories. The field-plot 
tests on cabbage have shown definitely that derris dust mixtures containing 
from 0.5 to 1 percent of rotenone are effective againsl the common cabbage 
worm, less effective againsl the cabbage looper, and stiil less effective against 
the diamond-back moth. The indications, nevertheless, are that derris powder 
will be a useful material in the control of all three species of these cabbage 
pests, in genera] pyrethrum dust mixtures were less effective than those <>f 
derris against all three species. An outstanding feature of the laboratory 
toxicity tests is the different action of derris on the insects tested. For ox- 
ample, the celery leaf tier is not affected by derris powder: the semitropical 
army worm, while repelled by derris. is not otherwise affected; the common 
cabbage worm, on the other band, readily succumbs to derris powder. 
MISCELLANEOUS VEGETABLE INSECTS 
Fumigation of sweetpotatoes do be used for seed purposes) with paradi- 
chlorobenzene has yielded some very promising results. 
In California the cleaning up of nightshade, the winter host plant ^f the 
pepper weevil, has proved to be of value in reducing injury from this pest 
Experiments on the turnip aphid in Louisiana indicate that derris dust may 
satisfactorily protect the turnip crop from damage. 
GREENHOUSE AND BULB INSECTS 
Tests to determine the value of hot water Cor 'he control of mites >how 
thai delphinium, gerbera, and cyclamen, as well as vigorous cuttings of 
certain varieties of chrysanthemum, may be successfully treated without plant 
injury, and that other varieties will suffer Slight to moderate injury but will 
recover sat [sfactorily. 
Experiments with hot water for the control of the Iris thrips show that the 
Japanese Iris may be effectively treated either in the Bpring or fall, but that fall 
t reatmenl is preferable. 
The Mexican mealybug became an important pest in several greenhouses in 
the Eastern States and the control work showed that this pest Is susceptible to 
Fumigation with hydrocyanic acid gas. 
it has been definitely shown that fumigation <>f gladiolus conns with 
napthalene toward the end of the Btorage period, for the control of the 
gladiolus thripS, will reSUll in a decided retardation of ihe growth of the 
conn and in some instances may prevent germination. The gladiolus thrips 
has continued as a pest Of gladiolus and has been reported from practically 
the entire United states. 
