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| Figure 24. The adult raspberry fruitworm is often seen on tip foliage in early summer. |
Raspberry Fruitworm,Byturus unicolor Say
With the raspberry fruitworm, it is the worms or larvae that usually cause the most damage. However, the adult beetles are also capable of causing considerable injury to unopened buds and unfolding leaves and open flowers. The raspberry fruitworm prefers red and purple raspberries.
Symptoms
To the unsuspecting, the first evidence of a problem may be the presence
of small yellowish-white worms adhering to harvested fruit. However, there are
actually numerous signs earlier in the season that can lead to detection. Infestations
in early season are to be suspected if longitudinal holes in the foliage give
leaves a tattered appearance. Such foliage injury is caused by adults (Figure 24)
feeding on unfolding leaves, often skeletonizing them. As blossom buds appear,
they are attacked by the adult beetles feeding on the inside. Numerous beetles
may destroy the entire cluster of buds.
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| Figure 24. The adult raspberry fruitworm is often seen on tip foliage in early summer. |
Fruitworms attack raspberry receptacles (Figure 25) and, at times, the carpels
of the berry. In tunneling through the receptacles, the larvae cause extensive
damage, often loosening berries to the extent that they may fall off. In some
plantings, more than half of the berries are infested with larvae. With such
heavy infestations, some of the wormy berries arrive at the market or processing
plant with noticeable presence of worms, leading to rejection of fruit.
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| Figure 25. Note portion of raspberry fruitworm on raspberry receptacle just as fruit is harvested; at times they adhere to the picked fruit, causing much concern. |
Seasonal History and Habits
Adult beetles emerge from the soil during late April and early May, about the
time the first leaves of raspberries are beginning to unfold. They begin to
feed along the midrib of partially folded leaves and are found on the midrib
of young leaves. Beetles later seek protection between the blossom buds where
they attack the soft tissues of the supporting pedicles. As buds begin to separate,
the insects attack the blossom buds, making large entrance holes to feed on
floral parts.
The females deposit their eggs most commonly on swollen, unopened blossom buds. However, at times eggs may be laid inside buds or on developing fruit. The grayish-white eggs (about 1 mm [1/25-inch] long) hatch after a few days, and the larvae commonly bore through the bud and enter the receptacle where they begin to tunnel. As the larvae increase in size, the tunnels are made larger, ultimately becoming grooves in the receptacle adjacent to the berry. When infested fruit is picked, the larvae may become displaced and remain attached to the cuplike interior and thus are transferred to the harvesting basket. Those that remain on the receptacle soon drop to the ground where they pupate and remain over winter.
Description
The fully grown worm is slender, 5.75 to 6 mm (1/4 inch) in length, 0.53 mm
(1/50 inch) wide, nearly cylindrical, tapering towards either end. Each segment
has two transverse rows of sparse, light-colored stiff hairs.
Picnic Beetles, Glischrochilus quadrisignatus and G. fasciatus
The picnic beetles belong to a family of beetles known as sap beetles. Even though the name "picnic beetle" is not an officially accepted common name, it is commonly used in dealing with these two insects. The two species are treated together here because they are similar in size and appearance and cause similar injury to brambles. The name picnic beetle seems appropriate since they are nuisance pests at picnics, being attracted to beer, potato salad, bread, and fruit salad. They have even been known to plunge without hesitation into a jar of pickles.
Symptoms
The adult sap beetles bore into raspberries at picking time and especially
into overripe berries, devour a portion, and may lay eggs. They leave the fruit
undesirable, and damage may be extensive enough in some plantings that the fruit
may be unmarketable. It is almost impossible to produce raspberries for sale
in some areas because of beetle contamination.
Besides feeding damage and physical presence in harvested berries, picnic beetles also disseminate organisms that cause rot and move these within the fruit planting to other fruits as they move around. Late raspberry cultivars tend to be more prone to beetle infestations than early cultivars. This is probably due to a larger beetle population in the late summer.
Life History
Picnic beetles overwinter in the adult stage in leaf litter, under bark,
in downed corn or just about any organic matter that is in some stage of decomposition
and could provide shelter during the winter months. When temperatures reach
60°F to 65°F several days in a row, adult activity is
triggered. However, they return to protected places if ensuing temperatures
fall to the 50s or below. Upon emergence from the overwintering places, they
seek hosts, such as mushrooms, fungal mats, downed corn, sap flows (wounds),
pollen, etc., and begin feeding. Eggs are laid on many such decomposing organic
materials; however, we know that in the Corn Belt states, downed corn ears are
an important substrate for picnic beetle aggregation, egg laying, and larval
development. Beetle populations build to a peak by midsummer. There is but one
generation produced per year.
Description
The fully grown larva is 3.44 to 9.20 mm (1/8 to 3/8 inch) long, white in color
with a brown head capsule ranging in width from 0.88 to 1.04 mm (1/32 to 1/16
inch). Adult beetles are about 4 to 6 mm (3/16- to 1/4-inch) long, shiny black
in color, and have two yellow-orange spots on each wing cover (Figure 26). Wing
covers extend over the entire abdomen. The antennae of adult picnic beetles
are knobbed on the tips.
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| Figure 26. Picnic beetles often infest ripe bramble fruit, causing considerable injury. |
Cultural Control
We know from practical experience that the adults of the picnic beetles
are attracted to ripe and particularly overripe and fermenting fruits. Do not
allow damaged, overripe, and fermenting fruits to accumulate in the field as
they serve as powerful attractants for the beetles. Remove picked raspberries
from the field as soon as possible or use a protective cover if a long interval
between picking and transport to market is likely to occur.
Provide pickers with special containers for unmarketable berries. Damaged berries should be buried soon after they are gathered.
Japanese Beetle, Popillia japonica Newman
Adult Japanese beetles are general feeders, ravaging the foliage and fruits of more than 250 plants, including nearly all of the deciduous fruits and small fruits, shade trees, shrubs, corn, soybeans, garden flowers, vegetables, and weeds. The larvae are serious pests of lawns and golf courses, vegetables, and nursery stock.
Symptoms
Adults are most abundant in July and August, flying about and feeding
actively on warm, sunny days. They prefer to feed on ripe bramble fruit exposed
to sunlight. There is a preference for red raspberries over black raspberries;
however, they will feed on either. Bramble cultivars that bear fruit late in
July through mid-September may be damaged severely by adults feeding on mature
fruit. Often, several beetles are encountered feeding on the same ripe berry
(Figure 27). When such beetles are removed, holes eaten into the berry are conspicuous.
Fruits may be gouged in irregular shallow patches or nearly devoured. Infestations
can be so severe that the fruit is left unmarketable. In addition to damaging
the ripe fruit, the exposed injured fruit is susceptible to fruit rots. Beetles
flying from one fruit to another carry rot pathogens along with them, aggravating
this problem.
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| Figure 27. Japanese beetles attacking fruit of ripe red raspberries. |
A secondary injury to bramble crops by Japanese beetles is often due to feeding
on leaves. In severe cases, foliage exposed to sunlight may be completely skeletonized.
The grubs feed mainly on decayed vegetation at first but later feed on the fine roots of grasses and other plants. Thus, problems from adults are more likely to occur in areas in or near large turf plantings.
Life History
The beetle has one generation a year in the areas where it is established
in the United States. The winter is passed in the soil as a mature larva or
grub, about 12 to 19 mm (1/2 to 3/4-inch) long. The larval cycle is completed
in late May or early June and is followed by the pupal stage. Adults can still
be found feeding on foliage and mature fruit until a killing frost occurs.
The length of life of the adult beetle varies considerably, depending on its environment. Its life expectancy is relatively short at high temperatures and relatively long at low temperatures. It is generally accepted that the normal life of the beetle is usually from 30 to 45 days, with females living slightly longer than males.
Description
The adult beetle is a brilliant metallic-green-colored oval insect,
varying in length from 8 to 11 mm (5/16 to 7/16 inch) and in width from 5 to
7 mm (3/16 to 5/16 inch). The female is usually larger than the male. A row
of five lateral spots of white hairs on each side of the abdomen and a pair
of these spots on the dorsal surface of the last abdominal segment help distinguish
this beetle from all others that resemble it.
The larva or grub is white in color, about 1.5 mm (1/16 inch) long at hatch, and is covered with rather long scattered brown hairs, which are interspersed with short blunt brown spines. Its head is equipped with biting mouth parts. Each of the three thoracic segments bears a pair of legs, and there are 10 abdominal segments. After feeding, fecal matter accumulates in the hind gut, giving the posterior part of the abdomen a grayish to black appearance.
The eggs, which are laid in turf in July and August, vary considerably in size, shape, and color. Some are spheroids about 1.5 mm (1/16 inch) in diameter, some are ellipsoids measuring 1.5 mm (1/16 inch) in length and 1 mm (1/25 inch) in width, and others tend to be slightly cylindrical. Color of the egg ranges from translucent white to creamy.