BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 61 
ONION" TUMPS IN PUERTO RICO 
The profitable growing of onions in Puerto I i I < - > has been restricted greatly 
.during recent years on account of the damage caused by the onion thrips. This 
insect has constituted such a limiting factor in the production of unions that it 
has been necessary to import onions in order to obtain a sufficient supply for 
domestic use. It has heen felt that if the onion thrips could he controlled, ihe 
production of onions could he Increased sufficiently to meet domestic demands 
.and possibly to provide for export to the United States during the winter season. 
Preliminary tests with a nicotine sulphate spray, and with a naphthalene- 
hydrated lime dust mixture, both of which have heen used successfully in colu- 
bating the onion thrips in the United States, gave promising indications that 
these materials may prove useful in the control of this insect under Puerto 
Rican conditions. Encouraging results were also obtained in the tests with the 
more recently developed sprays containing rotenone. in combination with wetting 
agents and spreaders, and with a dust mixture composed of lime-free sulphur 
in combination with manganese dioxide. 
COLE-CROP INSECTS 
Experiments on the control of insects affecting cole crops have involved the 
treatment of large field plots of cabbage for the control of several species of 
cabhageworms as well as laboratory tests to determine the relative toxicity of 
pyrethrum, derris, cube, cryolite, the ground root of devil's shoestring (Cracca 
virginiana L.), calcium arsenate, and paris green. 
On cabbage, derris dust mixtures were more effective against the imported 
•cabbageworm than pyrethrum, cryolite, or calcium arsenate ; derris and cryolite 
were approximately equal in effectiveness in controlling the cabbage looper, and 
both of these materials were more effective than paris green, pyrethrum, or 
calcium arsenate; while derris and calcium arsenate were approximately equal 
in effectiveness in controlling the larvae of the diamond-back moth and more 
effective against this species than pyrethrum, cryolite, or paris green. Experi- 
ments in California demonstrated that dust mixtures of derris, cube, or pyre- 
thrum gave satisfactory results in the control of the three more common species 
of cabbageworms on cauliflower. 
In laboratory tests the ground root of devil's shoestring, a domestic product, 
was found to be as effective against the common species of cabbageworms as 
derris or cube containing equal percentages of active ingredients. During the 
fall of 1935 the corn earworm and several species of cutworms were destructive 
to cabbage in several plantings in the Charleston, S. C, district, but the derris 
dusts used for the control of the ordinary species of worms attacking cabbage 
were not effective against these noctuids. 
BERRY INSECTS 
Investigations directed against the strawberry weevil in North Carolina have 
shown that the most satisfactory material for reducing the number of weevil- 
cut buds on the strawberry plant consists of a mixture of calcium arsenate 
and sulphur. Nonarsenical insecticides proved to be less effective, although 
dust mixtures containing rotenone resulted in the production of larger quan- 
tities of marketable fruit than any of the other insecticides tested. These 
experiments disclosed that the application of the calcium arsenate-sulphur mix- 
ture, while it greatly reduced the number of weevil-cut buds, apparently caused 
some injury to the plant which resulted in a decrease in the production of 
marketable fruit. 
Biological and control studies on the strawberry root aphid in North Carolina 
indicated that damage by this pest may be avoided to a great extent by selecting 
fields for strawberry planting that have received fall cultivation and that are 
distant from crabgrass and other favored host vegetation of the cornfield ant. 
which is the attendant of the strawberry root aphid. 
Large-scale tests directed against the raspberry fruitwonn in the Puyallup 
Valley of Washington showed that two sprays of lead arsenate applied to the 
plants prior to blooming, followed immediately after the blooming period by one 
spray containing derris root, gave a satisfactory commercial control ot' the 
raspberry fruitwonn and produced fruit free of arsenical residues. 
