-6- 



PR QSPECTIVE U SE OF DDT A GAINS T FRUIT DTSECTS 



DDT has shown promise for the control of such important fruit-insect 

 pests as the codling moth, apple leafhoppers, oriental fruit moth, grape 

 berry moth, grape leafhoppers, rose chafer, Japanese beetle, little fire 

 ant on citrus in Florida, sucking bugs that cause distortion of peaches, 

 and, in preliminary small-scale tests, some others. It does not appear 

 promising in the control of the plum curculio, orchard mites, or pear psylla, 

 and its value for the control of scale insects and aphids, or plant lice, 

 that infest" various kinds of fruits is questionable. For the control of 

 fruit insects it has, in general, been most satisfactory when used in the 

 form of a water-dispersible pov/der at the rate of l/2 to 1 pound (more often 

 1 pound) per 100 gallons of spray. It can be used in combination with most 

 of the common insecticides, such as lead arsenate, cryolite, and nicotine 

 preparations, with fungicides such as various forms of sulfur and bordeaux 

 mixture, and v;ith oil. For the control of the little fire ant in citrus groves, 

 the best results have been obtained by spraying the trunks and larger branches 

 of trees with emulsified fuel-oil solutions containing 4 to 8 ounces of DDT 

 and 2 to 4 quarts of fuel oil per 100 gallons of final spray mixture. 



Detailed recommendations for the use of DDT to control fruit insects 

 are not given here, as for the most part there will be little reason for such 

 use during the remainer of the 1945 season, and more detailed and reliable 

 recommendations can be made when the results of experimental work now under 

 way become available. 



— A. I. Bourne 



exferhjents y;ith ddt at maine agric. exp. sta. 



Some very interesting results have been obtained by Dr. F. H. Lathrop 

 in the control of fruit insects. Dust containing 3^ DDT, 3 applications, 

 (average .59 pound per tree), at each application, on apples reduced the jium- 

 ber of fruit fly egg punctures by approximately 6G^b. The setup was as follows; 

 An old, neglected orchard at Monmouth, Maine, consisting of 69 trees, including 

 29 V/olf River, was selected for the test. The rest of the trees were Mcintosh, 

 Ben Davis, and a few other varieties intermingled. The dust plot included 43 

 trees. A small backyard planting of neglected and heavily infested trees ad- 

 joined the orchard on the north. The entire neighborhood was severely infeste»l 

 with fruit flies. (The "fruit fly" of Maine is the same as our apple maggot.) 



Examinations were made of Vfolf River apples from the dusted trees and 

 from check trees at harvest time. Several hundred apples were examined to as- 

 certain the percentage of apples stung by the flies. Detailed examinations 

 were made of several hundred additional apples to ascertain the number of egg 

 punctures in e ach apple. All of the examinations were cai*e fully made. The 

 detailed counts of egg punctures, especially, were painstakingly made with the 

 aid of hand lens and binocular microscope, in the plot dusted with DDT &,!% 

 of the apples examined were in the "not stung" class while in the check plot 

 ,8^ v/ere in that class. The average niomber of stings per apple in these two 

 plots were i.68 and 25.92 respectively. 



