ENTOMOLOGY AND PLANT QUARANTINE 
55 
spp.) showed that none of the arseuicals now availahle were more toxic than 
the paris greeii-hj-drated lime dust mixture which is now advocated for com- 
bating these insects. A satisfactory substitute for paris green and other 
arsenicals has not been found among the organic compounds tested. 
Elxperiments in tobacco wareliouses of the closed type in Virginia showed 
that dusting with pyrethrum was a very effective method of combating the 
adults of the tobacco moth. A reduction of approximately 97.5 percent in the 
population of this insect was obtained in wareliouses where this method of 
control was utilized. 
GREENHOUSE AND BULB INSECTS 
During 1936 it was found that gladiolus corms infested by the gladiolus 
thrills lost weight during the storage period faster than noninfested corms, 
and that, after planting, the infested corms were retarded and made an uneven 
growth ; also, that the blooming of such corms was delayed and subsequent corm 
production reduced greatly as compared with noninfested corms. Although 
many different spray combinations were tested against the gladiolus tlirips, 
the arsenical-brown sugar combinations gave the best degree of control. With 
the possible exception of lead arsenate, however, such combinations burned 
the foliage rather sovi'i;"ly. 
Observations at Charleston, S. C, on the insect vectors of the azalea flower 
spot disease revealed that insects did not bring the organism causing this 
disease into gardens or nurseries to cause infection on the tlowers appearing 
early in the season. The appearance of the earliest infections on flowers 
close to the grotind indicated that the soil or mulch may be the hold-over 
sotirce between flowering seasons. It was found that with the increase in the 
number of insects that visited azalea flowers, notably several species of bees 
{Bombus spp.), a decided increase occurred in the local spread of the disease 
on all parts of the azalea plants. The percentage of infective insects increased 
in the daily collections as the disease became more prevalent. Evidence was 
obtained that insci is r<»n!d carry azalea flower spot infection for a distance 
ranging from 1 to 5 miles. 
A high percentage of the common red spiders were killed on greenhouse- 
grown lima beans and sweetclover by spraying with an organic thiocyanate 
applied under 300 pounds of pressure. Similar results were obtained by dipping 
strawberry plants infested by the red spider in an organic thiocyanate spray 
mixture or in a water suspension of derris. 
MUSHROOM INSECTS AND MITES 
Tests made against various species of mushroom flies (Sciara spp.) and 
other pests in the mushroom houses at Beltsville, Md., demonstrated that free 
nicotine (40 percent) in water at dilutions of 1 to 100 and 1 to 200 (contain- 
ing 0.4 and 0.2 percent of free nicotine, respectively), applied as a drench to 
the mushroom beds at the rate of 100 cc per sqtiare foot, gave a promising 
degree of control of the flies and other pests and caused a marked increase in 
the prodtiction on the beds receiving this treatment. Beds treated at 4-day 
intervals with a total of five or six treatments yielded approximately one-third 
more mushrooms than those treated at *^-day intervals and gave approximately 
twice the yield of the imtreared beds. Analysis of tlie mushrooms treated with 
the free nicotine solutions showed that the highest nicotine content of any 
sample was 29 parts per million by weight, a quantity not believed to be 
harmful to the consumer. Paradichlorobenzene. when used as a fumigaut at 
the rate of 1 pound per 1,000 cubic feet of air space for an exposure period of 48 
hours, gave good control of sowbugs but did not control mites {Ti/roglyphus 
spp.) or springtails (Lepidoryrtus spp. and Achorutes spp.). Taxonomic studies 
indicated that the most common species of mushroom mite in the United 
States may be a different species than was formerly recorded. 
COTTON INSECT INVESTIGATIONS 
In February 1937 the station at Tlahualilo, Durango, Mexico, was discon- 
tinued. This station was established before there was opportunity to conduct 
pink bollworm investigations in the United States, but since these investiga- 
tions may now be conducted in the vicinity of Presidio, Tex., where this Bureau 
has a station, the special need for a station in Mexico no longer exists. 
During the spring of 1937 investigations were begun at five new seasonal 
field stations. Investigations of boll weevil control on sea-island cotton were 
started in Alachua County, Fla., in cooperation with the Florida Agricultural 
Experiment Station, in Mcintosh County, Ga., in cooperation with the State 
