173 



Hymenopterous parasites have been sent from the Middle West to 

 New Jersey. The plum curcuho [Conotrachelus nenuphar] having 

 continued to do severe damage in peach orchards in Georgia, an 

 intensive campaign was outlined in December 1920 and then 

 apphed with such success that an excellent crop was marketed 

 with comparative^ httle damage. Work on the codling moth [Cydia 

 pomonella] has been continued. Shipments of parasitised caterpillars 

 have been sent from the East to the State of Washington. Against 

 the peach borer [Aegeria exifiosa] the paradichlorobenzene treat- 

 ment has continued to prove effective and safe and is in 

 general commercial use. Nut insects were dealt with at some length 

 in the previous report [R.A.E., A, ix, 112]. Experiments with 

 arsenical dusts and sprays show that the pecan case-bearer [Acrohasis 

 nebtilella] is kept under by them. The obscure scale [Chrysomphalus 

 ohscunis]. on pecan can be checked by spraying with lime-sulphur or 

 with oil emulsion during the dormant season. In the grape-growing 

 industry a marked improvement has followed the general adoption 

 of the sprays developed by the Bureau of Entomology. The two- 

 spray schedule against the grape-berry moth [Polychrosis viteana] has 

 yielded a high percentage of sound fruit. Sulphur fumigation against 

 the grape mealy-bug [Pseudococciis bakeri] has been abandoned, and 

 experiments are being made with miscible oils. The grape sphinx 

 moth [Pholus achemoti] occurred in alarming numbers in Merced 

 County, California. 



A comparative study of arsenicals as insecticides was concluded in 

 the course of the year, many results of practical appHcation being 

 reached. In a study of the insecticidal constituents, 180 preparations 

 from 46 kinds of plants were examined ; only a few, however, were 

 found worth further study. In an investigation of contact insecticides 

 as substitutes for nicotine or tobacco extract, the most poisonous 

 were found to be among the organic nitrogen compounds. 



As a result of work against the sweet potato weevil [Cylas fonni- 

 carius] in Florida and Georgia, two-thirds of the previously infested 

 area can be declared weevil-free. The spread of the Mexican bean beetle 

 [Epilachna cornipta] is evidently beyond the bounds of human control, 

 so that future work must be based on research. Resistant or semi- 

 resistant varieties of beans and natural enemies are being sought for. 



Insects injurious to potato, tomato and related crops include the 

 Colorado potato beetle [Leptinotarsa decernlineatd], potato leaf -hopper 

 [Empoasca niali] and tarnished plant bug [Lygtis pratensis]. Calcium 

 arsenate gave good results against the tomato fruit-worm [Heliothis 

 obsoleta], and trap-crops of sweet maize were also useful. 



Among the pests of cabbage and similar crops are a flea-beetle, 

 previously unknown as a pest, in New York. A related species, 

 the brassy cabbage flea-beetle, has been studied in Louisiana ; it is 

 likely to iDccome a serious pest in the absence of its wild food-plants. 



Against the striped cucumber beetle [Diabrotica vittata] in the 

 district of Columbia nicotine sulphate in dust form has proved most 

 promising. In the work against the sugar-beet hopper [Eutettix 

 tenella] the studies with the 350 types of resistant beets mentioned in 

 the previous report are giving promising results. 



The gipsy moth [Porthetria dispar] was discovered in New York, 

 and it was found that shipments from the infested centre had been 

 made to a number of States. It is thought that all these have been 

 traced. Operations have been carried out to eradicate or limit the 



