42 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 1952 
Oleoresin-Contenl May Affect Pine Resistance to Insect Attack 
In cooperation with the Lnstitute of Forest Genetics, United States 
Forest Service, studies were made to determine the relative resistance 
of a Jeffrey-ponderosa pine hybrid to the three mosl important species 
of hark beetles in California. Preliminary results reveal that the 
hybrid is resistant to western pine beetle attack, hut not to attack 
by the mountain pine beetle and the Jeffrey pine beetle, and that 
resistance or susceptibility of a tree to insect attack i- determined by 
the kind of oleoresins it produces. 
Several Treatments Effective in Protecting Wood Products From 
Attack by Powder Post Beetles 
Several of the new residual insecticides were tested for effectiveness 
in preventing powder-post beetles of various kinds from attacking 
structural timbers, flooring, furniture, and other wood products. The 
value of methyl bromide as a fumigant in controlling infestations of 
these beetles in timber was also determined. Result- show that by 
treating wood with benzene hexachloride, chlordane, or DDT, attack 
by one of the most injurious of these beetles has been prevented for 
3y 2 years. Methyl bromide has been found to completely control 
Lyctus infestations in handles and the large powder-post heetle. llt/- 
lotrupes, in the center of 8-inch timbers when applied at rates of 1. 3, 
and 9 pounds per 1,000 cubic feet of space for periods of 2-i. 12, and 6 
hours, respectively. 
New Developments in Preventing Termite Attack 
Studies were continued to determine the most effective and economi- 
cal soil poisons for use in preventing termite entry into buildings: 
also to determine the toxic effects of various soil poisons on plants that 
grow around buildings in order to recommend how and when these 
poisons should or should not be used. Results show that in addition 
to DDT and sodium arsenite. benzene hexachloride is also an effec- 
tive -oil poison and that chlordane. dieldrin, and aldrin offer promise 
in preventing entrance to buildings. In Mississippi, for example, 
benzene hexachloride has prevented termite entry for 5 years in tests 
conducted cooperatively with the Department of Defense, Corps of 
Engineers. Research on the toxicity of soil poisons to plants is incom- 
plete, hut indications are that formulations of chemicals will be 
developed which may he used in the soil around buildings with little 
hazard to plants. 
In Mississippi, studies were made in cooperation with the Depart- 
inent of the Army to evaluate available chemicals and test new 
Insecticides in an effort to determine their effectiveness, when applied 
to the surface of wood, in prevent ing termite attack. A- a result 
of these studies it has been found that pentachlorophenol, widely 
recommended S^v surface treatment, has given mediocre protection 
against termites. On the other hand, copper naphthenate, never be- 
fore fully tested, Is proving effective in preventing termite attack 
and decay. Finally, an important finding has been the good protection 
provided against termites and decay by benzene hexachloride and 
DDT in combination with a good fungicide, when applied to the but- 
