ANNUAL REPORT, 1935 



31 



to vines or crop appeared on any of the plots, even where the kerosene was 

 used on vines in full bloom at the rate of ten gallons an acre. Seven gallons 

 to the acre of the kerosene with pyrethrum reduced the leafhoppers and fire- 

 worms effectively. There was about twice as much pyrethrum in the mixture 

 as is used commonly in commercial fly sprays. The success of these tests 

 suggests that further work should be done along this line. 



Trichogramma. It has long been known 1 that the Chalcidid, Trichogramma 

 minutum Riley, is the most important parasite of the cranberry fruit worm. 

 This egg parasite is now bred commercially for use in the control of certain in- 

 sect pests in the South. Through the courtesy of Dr. A. W. Morrill, president 

 and manager of California Insectaries, Inc., Glendale, California, the cranberry 

 station received 150,000 of the yellow form of this parasite (regarded by some 

 as Trichogramma pretiosa) for experimental work with the fruit worm. These 

 parasites were liberated on two sections of the Agawam bog of the Fuller- 

 Hammond Co., near East Wareham, each of these sections being exactly an 

 acre in area. On one section, 50,000 of the parasites were liberated on July 17 

 and 25,000 on July 25; on the other, 25,000 were liberated on July 18 and 50,000 

 on July 26; so there were 75,000 parasites in all put out on each of these sections. 

 They were in good condition and very lively when they were distributed and 

 the weather was warm and dry, no rain occurring for a day or two after any 

 of the liberations. 



Berries were gathered from all parts of the two areas over which the parasites 

 had been distributed as well as from an adjoining section on which no parasites 

 had been placed, and the fruit worm eggs on them were examined for parasitism 

 and hatch, with results as follows: 



Area without 

 Areas with Parasites Parasites 



Date of distributing parasites July 17 and 25 July 18 and 26 — 



Date of examining berries August 1 August 8 August 9 



Eggs unparasitized and hatched 333 276 169 

 Eggs unparasitized and un- 



hatched 12 2 1 



Eggs parasitized \ number 45 13 16 



/percent 12- 4+ 9- 



Examinations were also made of fruit worm eggs on berries collected on 

 other bogs, within five miles of the bog on which the parasites were liberated, 

 with findings as follows: 



Zion Burgess Savary Dodge 



Date of examining berries August 3 August 5 August 7 August 8 



Eggs unparasitized and hatched 38 20 218 50 



Eggs unparasitized and unhatched 4 3 18 29 



Eggs parasitized \ number 173 4 82 17 



/percent 80+ 15- 26- 18- 



The Trichogramma parasitism of fruit worm eggs on three bogs near Harwich 

 was found to be 0, 16, and 17 percent, respectively. 



All this shows that no material advantage was obtained by the liberation of 

 the yellow form of this parasite, in spite of the fact that it readily attacked 



!Bul. 160, Mass. Agr. Expt. Sta., 1915, pp. 110 and 111; and Bui. 168, Mass. Agr. Expt. Sta. 

 1916, pp. 39 and 41. 



