10 ANM Al. REPORTS OF DEPARTMENT OF AX5BICUL.TDBE, 1940 
ease appeared in a Dumber of additional localities in the southern 
pari of the infested area. At one point in northeastern Maryland 
a population of more than 38 grubs per square fool in the fall droj >pe< I 
to about 6 per square foot by mid-June 1940. Two-thirds of these 
were affected by the disease, which was naturally present and was 
evidently an important cause of the marked drop m grub popula- 
tion, From many other heavily infested points the disease >till 
appears to be absent, and a program to accelerate its natural spread 
is being developed in cooperation with various State-. 
During the summer of 1930 a program was undertaken, in coop- 
eration with the New Jersey Department of Agriculture and the 
Division of Japanese Beetle Control of the Bureau, for colonization 
of the type A milky disease and the nematode Neoaptectana aimed 
Steiner in New Jersey. In 1939, 161 locations were treated in G 
counties in New Jersey. During the winter and spring of 1939-40 
the Bureau assisted in a program of the University of Maryland for 
distribution of the type A milky disease organism. Fresh cultures 
of the organism were furnished, together with full directions for 
preparing the spore material for field application, and part of the 
necessary equipment. 
The work of the 1939 season indicated that a trap painted yellow 
is definitely superior to one painted any other color. Traps painted 
yellow have captured more beetles than those painted red. blue, white, 
or aluminum. The addition of yellow to other pigments consistently 
increased the effectiveness of the traps. 
Laboratory testing of insecticides and repellents for use against 
the adult beetles was continued. In this work 1,4(14 cap' tests were 
made, in which 280,000 beetles were used. Forty-five new materials 
were included in the tests, only one of which proved sufficiently 
repellent and safe on foliage to be considered as a possible Mib-titute 
for lead arsenate. 
During 1939 and the winter of 1939-40 a detailed investigation 
was made on the fumigation of balled and potted nursery stock with 
methyl bromide for control of the larvae as well as the eggs and 
adults. Twenty-two thousand eggs. '225.000 grubs, and (m.Gih) adult 
beetles were used. The adtdt beetles proved least resistant to the 
.action of this fumigant, the <rrubs more resistant, and the eL r L r ^ the 
most resistant. Detailed dosage requirements for complete mortality 
were worked out for temperatures ran<rin<r from 35 to 100 F. The 
most significant development of the work is that the results em- 
phasize the importance of the conditions under which the material 
i- held during the postf limitation period. Treatments of Japanese 
beet le grubs in Soil balls or potted plants that appeared only partially 
effective at the completion of a fumigation of 2 to 4 hour- gave 
loo percent mortality when the stock was held at approximately the 
same temperature for l\ days, whereas the results at the close <>f the 
same period were poor when the stock' was transferred after fumi- 
gation to locations where the temperatures were much low. ;. 
The distribution of the 2 most valuable Bpecies of wasp parasites 
of the Japanese beetle was continued. Thirty-three colonic- of the 
fall Tiphia (Tiphia popiUiafvora Roh.) were distributed late in the 
summer of 1989 and L51 colonics of the spring form ( /'. vemalii 
