4 BULLETIN 550, U. S. DEPARTMENT OF AGRICULTURE. 



If the infested berries are trimmed out of the clusters the loss of their 

 weight is total in addition to the cost of trimming. 



While the berry moth is not as generally destructive as the grape 

 rootworm or grape leafhopper, it is capable of inflicting greater losses 

 than either to a single season's crop, and neither of these pests will 

 appear in destructive numbers with such alarming rapidity in a vine- 

 yard which has been apparently free from them as will the grape- 

 berry moth. When it is present at all in a vineyard it always causes 

 a loss in weight and is a constant menace to the grape industry in 

 that vicinity. 



SUMMARY OF SEASONAL HISTORY AND HABITS. 1 



Before considering control measures, a summary of the seasonal 

 history and habits upon which these measures are based will be given. 



There are two broods of the grape-berry moth that must receive 

 economic consideration. The first brood, resulting from the hiber- 

 nating generation, is comparatively small, owing to high winter mor- 

 tality of the pupae. The earliest recorded emergence of moths is 

 May 29 and the latest July 26; however, the bulk of the emergence 

 begins between the 10th and the 25th of _June, varying with the sea- 

 son, and usually is ended within 3 weeks. Within 4 to 6 days after 

 emergence the moths (PL I, figs. 4, 5) begin depositing eggs, preferably 

 on grape berries. Incubation requires about 6 days. Thus the hatch- 

 ing period of large numbers of larvae begins from June 20 to July 5, 

 depending upon the season, and continues for about 3 weeks. 



The beginning of this period is almost coincident with the falling of 

 the grape blossoms and the setting of the fruit. The larval feeding 

 period averages 23 days, after which the larvae (PL I, fig. 1) spin 

 cocoons in leaves on the vine, and in an average of 13 days emerge as 

 moths. Some pupae (PL I, fig. 3), however, do not transform at this 

 time but remain in the cocoon (PL I, fig. 2) until the following spring. 



The earliest recorded emergence of summer-brood moths is July 12 

 and the latest is after the middle of September. A heavy emergence 

 of moths begins in a normal season in the latter part of July, and in 

 backward seasons may continue as late as the earlier part of Septem- 

 ber. Although the second brood is only a partial one, it is by far the 

 more numerous and destructive. It may escape serious attention 

 from the vineyardists until shortly before harvest, when the well- 

 grown larvae begin to leave the berries they first attacked and to 

 enter others. 



The development of this brood is slower than that of the first. In 

 a normal season the larvae are cocooning in large numbers by the lat- 

 ter part of September and by the middle of October most of them 



1 This summary is based on the life-history studies of the grape-berry moth by Johnson and llammar, 

 and studies by the writer and his associates, the details of which have not yet been published. 



