[ I R R A R Y
STATE kL.AIV' h.AI1
E-527 U-S February 1941
Insecrt A Invsiain
ENTOMOLOGY AND I
THE RAISIN MOTH ON GRAPES
By George H. Kaloostian, Dwight F. Barnes,
Charles K. Fisher, and Perez Simmons, Division of Fruit
The presence of larvae of the raisin moth (Ephestia figulilella
Greg.) on grapes in the vineyard, often in association with spoilage of the
fruit, suggested a study to determine the extent of the direct damage caused
by the insect to grapes and the relation of this damage to spoilage. The
raisin moth has, of course, been of special importance as a pest of dried
fruits after harvest.
The presence of raisin moth larvae in ripening grapes on the vines
apparently was verified for the first time by entomologists of the Cali-
fornia State Department of Agriculture in 1929. 1 An extensive survey made by
that Department in 1931 revealed infestation in all the 17 grape varieties
examined except Tokay. The survey included about 120 vineyards in the San
Joaquin Valley from Kern County to San Joaquin County. Raisin moth larvae
were found in most of the plantings except in San Joaquin County, where
the insects were scarce.
Observations in 1935, 1936, and 1938
Field work by members of the staff of the Bureau's dried fruit
insect laboratory at Fresno has included numerous observations of the raisin
moth in vineyards. Data recorded September 25, 1935, by H. C. Donohoe
indicated that splitting of the berries had resulted in an infestation of
vinegar flies in Ribier grapes, and mold was observed on another variety
(Olivette Blanche) in connection with punctures evidently made by sucking
insects. A light infestation of dried fruit beetles (Carpophilus hemipterus
(L.)) and of raisin moth larvae was noted.
% Mackie, D. B. Ephestia figulilella Greg. A storage pest taken
feeding upon fresh grapes. Calif. Dept. Agr., Monthly Bul. 21: 311-315.
Infestation by larvae of the raisin moth, associated with mold
damage, was observed near Delano in 1936. The grapes were of the Thompson
Seedless (Sultanina) variety.
L?. v*e of the raisin moth were found in connection with severe spoil-
age in g:-a- of the Carigriane, Thompson Seedless, red Malaga, white Malaga,
Ohanez (AI-.ria), and Ribier varieties, observed in Tulare County in 1938.
Feedi-,:,.g i;nects and dripping of fermented juice had reduced the bunches
in mf.?.i- c.. -.>s to little more than stems, seeds, and skins. In addition to
the raisin moth, dried fruit beetles, vinegar flies (Drosophila), and 2
wasplike parasites of larvae of the raisin moth were found in these rotten
bunches. Honeybees fed on the juice of injured berries.
To find out about the process of attack by the raisin moth on growing
grapes, bunches were enclosed in bags and infested artificially with raisin
moths. C, were laid on the surface of the grapes, on a few raisins that
had formed on the bunches, and on the stem of the bunches, but the most
favored lc..tion wa. on the cap stem of the berries. Newly hatched larvae
often entered the grapes at the point of attachment to the cap stem without
leavi.-.g any outward evidence of infestation. As feeding progressed, v.ebbing
and e--creta e:e deposited around the entrance puncture and inside the berry.
Some larvae entered by eating through the unbroken skin elsewhere than at
the cap stem. Occasional larvae entered where, in crowded bunch.es, the
surface .I teen scarred. Black mold and other microorganisms grew readily
on the excreta and on the pulp exposed by larval feeding.
Observations in 1939
During the growing season of 1939 a field study of the raisin moth in
growirin', .- in seven vineyards in Tulare and Fresno Counties gave new
The first larvae were found in Thompson Seedless giajes during
general vl..,yard examinations on July 20. Since the insects apFeared to be
about 2 weeks old wl.eni found, infestation probably had tecon.e established
during `i.e fist week of July.
p., "in:_ r May 8, when lthle grades were in blossom, and continuing at
inte.'v.2. of :;lout 10 dtNys until August 10, '-uncl es were bagged and infested
artificially by liberatii:g raisin moths in the bags. Later examinations
sho,.d (! i6 t larvae had established themselves in all bunches that had been
bagged ...i infested on and after June 30.
.'-..',l feediir; by larvae of the raisin moth brought about the
initial injury in some iazes, the leading primary cause of damage to grapes
was cus ing within the bui.ch, by pressure of trellis wires and leaf stems,
and c.: l.iijig due to inter-ial pressure.
*'lree sets of records showed tl-e following average percentages
of l.'_. I inches ascribed to three primary causes;
- 3 -
Crushing and cracking 71 percent, insects 6 percent, birds 23 percent.
Crushing and cracking 51 percent, insects 22 percent, birds 27 per-
Crushing and cracking 92 percent, insects 7 percent, birds 1 percent.
Observations in 1940
During the ripening season for grapes in 1940 one of the writers
(Kaloostian) continued the type of survey work done in 1939. In addition,
counts of the number of bunches per vine and of loose and tight bunches were
made. Five vineyards in Fresno and Tulare Counties were surveyed, 3 of them
twice. Of the 8 examinations, 6 were of the Thompson Seedless variety, 1 of
red Malaga, and 1 of Carignane. At each visit all the bunches on 20 vines
were examined. The total was 4,974 bunches. Spoilage was found in 696
(14 percent), of which 525 were tight bunches and 171 were loose ones.
The primary causes of spoilage were recorded as follows:
Crushing and cracking 86 percent, insects 12 percent, birds 2 per-
Crushing and cracking were recorded as primary causes of injury in
484 tight bunches and in 116 that were classified as loose. Birds and
insects showed no very definite preference as between the two types of
clusters. Practically all the primary insect damage was caused by the
raisin moth. This amounted to 1.7 percent of the crop.
Conditions found in the damaged clusters, without reference to
primary causes of spoilage, were:
Rot alone, 20.3 percent.
Rot followed by secondary invasion by vinegar flies and dried fruit
beetles, 64.8 percent.
Rot and infestation by the raisin moth, 6.6 percent.
Rot and infestation by the grape leaf folder (Desmia funerals
(Hbn.)), 0.3 percent.
Infestation alone, by the raisin moth, 8.0 percent.
2 These figures are rough averages of records which were made from
July 18 to September 5 and which therefore included both the beginning stage
and the advanced stage of spoilage. As bunch rot proceeds through the
drippintg stage to a matted, dry condition the difficulty of deciding as to
the primary cause of spoilage increases.
UNIVERSITY OF FLORIDA
4 3 1262 09224 7807
The raisin moth occurred (not always as a primary cause of spoilage)
in 14.6 percent of the damaged bunches and in 2 percent of the crops, as
indicated by the samples.
The conditions which bring about the crushing and cracking of ripening
grapes appear to be incompletely understood. Whatever the reasons may be in
individual vineyards, it is apparent that the exposure of pulp which results
is the outstanding cause of the type of bunch spoilage discussed herein.
Exposure of pulp caused by crushing, cracking, insects, or birds
leads in most cases to rapid growth of microorganisms on this favorable
medium. The writers obtained no determinations of the names of the yeasts,
molds, and bacteria involved. The conditions which resulted from their
growth are referred to here under the general term "rot," which does not
include mildew or other diseases which appear on the surface of the skin.
Fermentation and other types of decay attract, as secondary agents in
the breakdown of the fruit, vinegar flies, dried-fruit beetles, and the
raisin moth. Berries that have prematurely turned to raisins because of
early injury, as by birds, while the remainder of the fruit on a bunch is
still firm, are especially attractive to the raisin moth.
Although the raisin moth appears to be of minor importance as a
primary or secondary pest of growing grapes, its ability to maintain itself
in the vineyard during much of the season aids the insect to build up its
numbers during July and August. As a consequence, infestation of raisins on
trays later in the season may be increased. Infestation which is present
in boxed raisins in October and November no doubt consists in part of the
progeny of moths which developed on grapes.