6 



BULLETIN 837, U. S. DEPARTMENT OF AGRICULTURE. 



3 weeks. It is important to note that the rise in the early part of 

 the hatching is abrupt and the subsidence of hatching more gradual. 

 It has been the opinion of other writers that the largest part of 

 the second-brood larvae hatch within a shorter period of time than 

 the first brood. The rearing records here illustrated do not support 

 that belief but show the hatching periods to be of about equal 

 length. 



NATURAL CONTROL OF FIRST-BROOD LARVyE. 



It was observed that the grape" berries infested by first-brood 

 larvae dropped readily from the vines when touched. It was thought 

 that if these infested berries dropped in any great numbers at any 

 particular time some cultural method such as covering these berries 

 with soil might aid in the control of the insect. To determine this 



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Fig. 1. — Diagram showing relation between dates of spray application and periods during 

 which the grape-berry moth larvae were hatching for the seasons 1916, 1917, and 1918 

 at Sandusky, Ohio. 



point the following experiment was undertaken in 1916 : Wooden 

 frames were made, G feet long, 30 inches wide, and G inches deep 

 with cheesecloth stretched on the bottoms. These trays fitted be- 

 tween the vines directly under the trellis and were placed in six 

 different locations in the vineyard, under vines heavily infested with 

 first-brood larva?. Fresh leaves were supplied in the trays for the 

 cocooning of any larvae that might drop. The trays were put in 

 place July 5 when first-brood infestation was about at its height 

 and were left until August 15, when practically all first-brood larvae 

 had left the grapes. These trays were examined every three days. 

 Practically no grapes dropped from the vines and not a single larva 

 was taken throughout that period. From these negative results it is 

 concluded that practically no natural control occurs from the drop- 

 ping of grapes infested by first-brood larvae. 



