ANNUAL REPORT, 1936 53 



to the low emergence record. In spite of the small number of flies, a greater 

 emergence in the sun, cultivated, and light-soil cages was consistent with 

 previous records. 



Introduction of Parasites of Oriental Fruit Moth in Peach Orchards. 



(A. I. Bourne.) No new introductions of Macrocentrus parasites were made 

 during 1936. Curtailment of funds and personnel at the Federal Laboratory- 

 prevented the cooperative arrangement by which such material was secured. 

 Many of the growers, however, purchased and released colonies of the egg para- 

 site, Trichogramma. 



The early twig infestation of the Oriental fruit moth was very light through- 

 out the State; and apparently the pest had not fully recovered from the heavy 

 mortality caused by the severe winters since 1933, for no serious damage to the 

 crop was reported although the late twig infestation gave promise of a rapid 

 recovery of the insect. 



Potato Spraying Experiments. (A. I. Bourne.) Flea beetles were present 

 in about normal abundance and were again the most serious single pest of 

 potatoes throughout the State, although held in check quite satisfactorily in 

 the well-sprayed fields. Leafhoppers, usually very generally abundant in late 

 summer, were later than usual in appearing and the infestation was lighter. 

 Very few fields suffered appreciably from their attack. Potato aphids were 

 more abundant than usual although the infestation was uneven. Many fields 

 of Irish Cobblers suffered severely in late July, and the hot, dry weather of 

 early August favored a rapid development of lice which seriously threatened 

 many fields of Green Mountain. The high temperature, however, favored a 

 rapid action of nicotine sprays or dusts and well-timed applications were very 

 effective. 



In the plots devoted to field tests of different insecticides on the standard 

 variety Green Mountain, eleven applications of Bordeaux mixture were made 

 from June 10 to August 24. Insecticides were added to 5-5-50 Bordeaux in 

 five applications from July 15 to August 14. The treatments were duplicated 

 on 1/100 acre plots. Bordeaux mixture itself is an effective repellent for flea 

 beetles, yet each additional material produced increased control. The ranking 

 of the spray mixtures in this respect, measured by successive counts of leaf 

 punctures, was as follows: 



(1) Bordeaux plus Calrite (a brand of calcium arsenate). 



(2) Bordeaux plus Cubor (rotenone). 



(3) Bordeaux plus Niagron (rotenone). 



(4) Bordeaux plus Ku-ba-tox (rotenone and pyrethrum). 



(5) Bordeaux plus Nicotine Tannate. 



(6) Bordeaux alone. 



In other words, although good control of flea beetle was obtained in all plots, 

 the best results were secured from calcium arsenate, due to its cumulative 

 effects and greater lasting properties. The rotenone and pyrethrum sprays, 

 while functioning as both contact and stomach poisons, are more temporary, 

 the effective ingredients lasting only a few days before deteriorating, so that no 

 protection is furnished against reinfestation by beetles migrating into the fields. 



From the standpoint of aphid control the contact poisons proved very effec- 

 tive in preventing the building up of a serious attack. The nicotine-tannate 

 plots were outstanding in this respect, having an appreciably lighter attack 

 than the others. A serious attack which developed in the Bordeaux and Variety 

 plots was satisfactorily checked by an application of nicotine sulfate on August 



