CONTROL OF THE GBAPE-BERBY MOTH. 3 
The extensive grape regions of Michigan have been the source of 
very few complaints of loss due to the grape-berry moth. In the 
summer of 1915 the writer visited many vineyards in the vicinity of 
Benton Harbor, St. Joseph, Paw Paw, and Lawton, Mich., and found 
the berry moth present in practically all of them, although usually 
in small numbers. Its destructiveness in this region is obscured by 
the greater and more consistent injury by the black-rot fungus, and 
probably injury by the grape-berry moth is often attributed to the 
black-rot fungus. In contrast to this, in the Ohio grape regions it 
has been consistently destructive and the leading grape pest for years. 
Even in a region where the grape-berry moth is a recognized pest 
it is by no means consistent in occurrence, and may be erratic and 
local even within a vineyard. In the vicinity of North East, Pa., 
in the western part of the Erie-Chautauqua grape belt, in most sea- 
sons fully half of the vineyards are practically free from it. In others 
the outside rows, ends of rows, or irregular spots are heavily infested, 
while the rest is practically free. Yet there are many vineyards that 
annually sustain the loss of from one-fourth to one-half the crop. 
DESTRUCTIVENESS WITHIN A VINEYARD. 
The destructiveness of the grape-berry moth is underestimated 
greatly even in vineyards where it is recognized as the chief pest, and 
where the infestation is light it is usually ignored. This is due to the 
fact that " wormy" grapes, unless very heavily infested, will bring 
a price comparatively near the standard price, seldom with a reduc- 
tion of more than 10 per cent. Even when the infestation approaches 
total, the price may be much nearer to the standard for grapes than 
the price for cider apples is to the standard price for apples. Because 
of this the vineyardist is apt to consider the reduction in price as the 
chief loss and largely disregard what may be a greater charge against 
the berry moth — the reduction in weight. 
The berries infested by first-brood larvse (see PL II, fig. 1) are 
totally lost, although if they are destroyed very early in the season 
this loss may be partially offset by increased weight in the rest of 
the cluster. Those infested by the second brood (see PL II, fig. 2), 
which the larvse have left or in which the larvse are well grown, lose 
weight rapidly; by the end of the season they are little more than 
dry shells and have but a fraction of their former weight (PL III, 
fig. 1). This loss varies greatly, depending upon the time when the 
berries are infested and upon the time of harvest. 
" Wormy" grapes are of course largely excluded from the market 
for basket grapes, for unfermented juice, and for some wines, unless 
all of the " wormy" berries are trimmed out. This exclusion from 
certain markets may in certain years represent a considerable loss. 
