Insects Attacking Flower Clusters and Berries

Multicolored Asian Lady Beetle, Harmonia axyridis (Pallas)

The multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) was first introduced in California by USDA agricultural research scientists as a biological control agent.  This introduction was deemed unsuccessful.  However, it was reintroduced in the eastern United states in the late 1970’s and early 1980’s to control soft-bodied insects like the pecan aphid and pear psylla.  Since its introduction it has spread throughout most of North America.

Adult beetles are domed, round to oval in shape typical of other lady beetles.  The name “multicolored” refers to the many color forms of the adult lady beetles.  Coloration variants are shades of yellow, orange, and red;  with or without black spots on the wing covers.

This species can be recognized and distinguished from other lady beetles by the following characteristics.  On the white pronotum (the middle body segment between the head and abdomen) there are several black markings, which tend to fuse into a regular to irregularly shaped “M” or “W” depending on your vantage point.

Life cycle:  The life cycle from egg to adult requires about a month or so, depending on the weather.  Eggs hatch in 3 to 5 days.  The larval stage lasts up to 14 days, during which time they consume large numbers of aphids, scale insects and other soft bodied insects.  Pupation lasts 5 to 6 days followed by adult emergence.  The adults are rather long lived with some beetles living up to 3 years.  At least two generations with a partial to complete third generation, occurs each growing season.  In the fall when the host plants begin to dry and cooler weather approaches adult beetles begin to seek overwintering sites.  They are attracted to vertical walls or cliffs where they seek shelter in cracks and crevices.  Once one lady beetle lands, many others may follow in an aggregating behavior. 

Behavior:  The feeding habits of the multicolored Asian lady beetle (MALB), are for the most part not well documented in North America.  They are primarily arboreal and spend a great deal of their time in the upper canopy of trees.  Thus, we have little information on their feeding activities.  In 2001 the soybean aphid was quite abundant throughout the Midwest and the lady beetle population exploded causing numerous complaints from home owners and fruit growers.

Control:  Since the MALB is not a native species, few diseases or parasites have been associated with this beetle.  Adult beetles have been associated with vectoring fungal pathogens and therefore their aggregating nature may be favorable to the dissemination of bunch rot and other diseases from one grapevine to another.

Grape Berry Moth, Endopiza viteana Clemens

Description and Life Cycle:  This is the major insect pest of grape berries in the eastern United States and Canada. When vineyards are left unmanaged up to 90 percent of the fruit often is destroyed by the larvae and the diseases facilitated by the damage inflicted upon the fruit. Infestations vary greatly from vineyard to vineyard, from year to year, and within a vineyard. However, vineyards bordering wooded areas are most vulnerable.

The adult is a mottled-brown-colored moth with some bluish-gray on the inner halves of the front wings. The larvae of this small moth are active, greenish to purplish caterpillars about 3/8 inch long when fully grown. Grape berry moths overwinter in cocoons within folded leaves in debris on the vineyard floor and within adjacent woodlots. After emerging in the spring, the adults mate, and females lay eggs on or near flowers or berry clusters. Newly hatched larvae feed upon the flowers and young fruit clusters. Larvae that hatch in June make up the first generation of grape berry moth and will mature from mid to late-July or August. After mating, females lay eggs on developing berries, and this second generation matures in August or September. Larvae of the second generation, after completing their development, form cocoons in which they overwinter. A third generation occurs commonly in the southern range of the pest and occasionally in the northern tier of states.

Damage Symptoms:  First-generation larvae web small flower buds or berries together in early June and feed externally on them or on tender stems. Larvae that attack grape bunches during this time are difficult to see.
Second generation larvae tunnel directly into the green berries and feed internally. Conspicuous reddish spots develop on the berries at the point of larval entry. Berries affected in this manner are known as "stung" berries. The second generation is potentially more damaging than the first. A single larva may destroy 2 to 6 berries in a cluster, depending on berry size, and several larvae frequently inhabit a single cluster.

At harvest, severely infected bunches may contain several larvae, and many of the berries may be completely hollowed. In many cases, bunches are covered with bunch rot fungi and infested with Drosophila spp. fruitflies, and often having an unhealthy appearance.

Management (How to survey vineyard to determine percentage of clusters damaged.):  A protectant insecticide may be needed to prevent damage in areas heavily infested by grape berry moth. The number of spray applications depends on the amount of infested berries the grower is willing to accept. Table grapes require more attention than grapes grown for juice. Corrective measures are usually suggested if more than 5% of the clusters are injured. To determine the percentage of clusters damaged you should randomly inspect 100 clusters along the perimeter of the vineyard and 100 clusters toward the center of the vineyard. This method will tell you if treatment of the entire vineyard is necessary. Treatment of perimeter rows maybe all that is necessary to control this pest. Control of maturing larvae in mid-to late-July is particularly important.

Cultural controls can be used to kill the overwintering pupae in leaves. Leaves can be gathered and destroyed in the fall, or leaves can be buried within the soil in the spring, 2 weeks before bloom, by rototilling or cultivating.

An alternate method of control using pheromone rope ties to disrupt the males of the grape berry moth was approved by the EPA in 1990. This method prevents mating, thus reducing the number of fertile grape berry moth females in a treated vineyard. This method is most effective in vineyards at least 5 acres in size. Ties are dispensed manually at a rate of 400 ties per acre. When a vineyard is under heavy pressure from berry moth, it may require spot treatment with an effective insecticide at the source of the infestation. Studies indicate that vineyards in close proximity to external berry moth sources such as woodlots, may require an application of insecticide in addition to the ties for control of this pest. Vineyards utilizing these ties should continue to scout their plantings in the same manner as previously mentioned. If thresholds are reached the decision to apply an insecticide should be considered.

Monitoring Male Moths:  Pheromone traps are available to monitor the emergence of male grape berry moths during the season. This information may be useful for optimal spray timing; sprays should target egg hatch and young larval activity, which occurs several weeks after the first moths are trapped. A minimum of 3 traps for monitoring a single block of approximately 10 to 15 acres is recommended. Traps hung from the top wire of the trellis should be placed around the perimeter of the vineyard before bloom and should be at least 100 feet apart. Sticky trap bottoms should be checked weekly for moths, and pheromone caps should be changed monthly to obtain accurate flight information. Every vineyard location is unique, and growers should not rely on pheromone trap data from other vineyards for timing insecticide sprays.

Control:  Pheromone traps should be utilized in vineyards with a history of grape berry moth problems. Trapping of adult male moths indicates the beginning of flight activity. Mating and egg laying will occur over a 2 to 3 week period following the first detection of flight activity. A protective cover spray may be required during this period to prevent egg laying and hatch. Early season control of this pest may prevent it from becoming well established within the vineyard, and may eliminate the need for control later in the season. It should be noted that the second flight activity period occurring in late July and August is the most important. These adult moths in late summer produce the eggs which hatch into larvae capable of causing major damage to the maturing fruit. One should not solely depend upon a pheromone trap for detecting this late season threat. Scouting should be implemented on a weekly basis after bloom. If berry cluster damage reaches 6% in grapes used for processing or 3% in those grown for fresh market, a protective cover spray should be applied.

Rose Chafer, Macrodactylus subspinosus (Fabricius)

Description and Life Cycle:  Rose chafer adults attack grapes at bloom as they emerge from the soil. Not only due they destroy the fruit at blossom, in addition, they frequently skeletonize the leaves, leaving only the large veins intact. This insect is especially abundant in areas of light, sandy soil where beetles may appear suddenly as grapes begin to bloom.

The ungainly beetles have a straw-colored body, reddish-brown head and thorax with black undersurface. The adult rose chafer is about 0.5 inches in length with long, spiny, reddish-brown legs that gradually become darker near the tip. As they age, hairs are worn off the head and thorax with normal activity revealing the black color below. Thus, they become mottled in color as they mate and move around in the flower clusters making it possible to distinguish newly emerged adults from older specimens. Females frequently loose more hairs, particularly on the thorax, in the mating process.   Eggs of the rose chafer are oval, white, shiny in appearance, and about 0.05 inches long and 0.03 inches in width. Larvae are C-shaped white grubs about 0.8 inches long and 0.12 inches wide when fully grown. Mature larvae have three distinct pairs of legs, a brown head capsule, and a dark rectal sac visible through the integument. Larvae are found in sandy soil feeding on grass roots and can be identified by a distinctive rastral pattern. The pupae are light yellowish-brown in color and haveprominent legs. They measure about 0.63 inches in length.

Adult rose chafers become active in northeastern North America from late May to early June. The adults appear suddenly. It seems as though the entire population reaches maturity practically at the same time, and multitudes of beetles suddenly make their appearance. Beetles feed and mate soon after emerging from the soil. It is common to see mating pairs in the newly formed grape clusters. Females deposit eggs singly a few centimeters below the soil surface. Mating and egg laying occur continuously for about two weeks with each female depositing 24 to 36 eggs. The average lifespan of the adult is about three weeks.

Approximately two weeks after being deposited, eggs hatch into tiny, white, C-shaped grubs. The larvae feed on the roots of grasses, weeds, grains, and other plants throughout the summer, becoming fully developed by autumn. However, it is not easy to collect the larvae of rose chafer. They have been found occasionally on the roots of orchardgrass but never in proportion to the numbers of adults found in adjacent grapes. Larvae move downward in the soil as soil temperatures decline and form an earthen cell in which they overwinter. In the spring, larvae return to the soil surface, feed for a short time, and pupate in May. After two weeks in the pupal stage the adults emerge and crawl to the soil surface to begin their cycle again. There is but one generation per year.

Damage Symptoms:  Despite its common name, the rose chafer attacks the flowers, buds, foliage, and fruit of numerous plants including grape, rose, strawberry, peach, cherry, apple, raspberry, blackberry, clover, hollyhock, corn, bean, beet, pepper, cabbage, peony, and many more plants, trees, and shrubs. Adults emerge about the time of grape bloom and often cause extensive damage to foliage. Blossom buds are often completely destroyed, resulting in little or no grape production. Feeding activity on various plants may continue for four to six weeks. Damage can be especially heavy in sandy areas, the preferred habitat for egg-laying. A toxin present in the beetles may kill poultry.

Management:  Adult chafers begin emerging in late May and early June at the time of grape bloom. A spray application is recommended if more than 2 beetles per vine are present. If only a few beetles are present , they may be handpicked from the vine and destroyed. The pupal stage is extremely sensitive to disturbance therefore, cultivating between rows may be effective in destroying a good number of chafers, however it is our experience that growers with sufficient numbers of beetles to inflict economic damage will not be able to control this pest by this method of cultural control. An alternative method to chemical control has been developed by the department of Entomology at Ohio State University for this pest. This method utilizes a very powerful feeding attractant and a Japanese beetle trap. Intensive trapping over a 4 year period reduced the population to below the threshold level of two beetles per vine. An application of insecticide may required in combination with the trapping effort if the population is extremely high. It is our experience that it takes a couple years of intensive trapping to reduce the population within a heavily infested vineyard to the point that chemicals are no longer needed to control this pest.

Monitoring:  Scouting for this pest within your vineyard should begin in late May and continue through late June. Newly emerged adults may be found feeding upon young grape buds and foliage. If numbers reach 2 beetles per vine control methods should be utilized. Monitoring may also be conducted by utilizing the attractant developed for rose chafer. Traps should be placed around the perimeter and dissecting the vineyard. For monitoring purposes these traps may be spaced every 100 ft. and should be checked daily for newly emerged chafers. If beetles are encountered, control methods should be considered if beetles average 2 or more per vine.

Control:  When only a few beetles are present one may handpick them from the plant and destroy them. Where populations are large and pose a threat to the grape crop, massive trapping may be a safe alternative to applying insecticide. Results utilizing this new powerful attractant have been very positive. The desired effect of mass trapping, which is to bring the beetle population to below threshold level, is usually achieved after a couple years of trapping. Chemical control methods should be utilized when beetle pressure exceeds an average of two beetles per vine. To determine the number of beetles per vine one should randomly survey 25 vines at all four corners of the vineyard and 25 in the center of the vineyard. This will give you the total number of beetles present on 125 vines surveyed. Divide the number of vines (125) by the number of beetles present to obtain the average number of beetles per 125 vines. If this average is above 2 beetles per vine, then treatment is recommended. It should be noted that, with this survey method, one can determine if the chafer infestation is present throughout the vineyard or just located in a specific area. If the area is localized, spot treatment of the infestation may be all that's required. Treatment with an insecticide should be after bloom when the first newly emerged beetles are detected in adequate numbers to pose concern. A second application may be required if pressure is severe and rainfall is frequent. Protection of the young grape cluster is critical and should be maintained throughout June.

Grape Blossom Midge, Contarinia johnsoni Felt (Diptera: Cecidomyiidae)

The grape blossom midge is a small fly that lays its eggs in unopened grape flower buds. Small maggots, or larvae, hatch and eat the inner portions of the flower. Buds affected in such a manner are incapable of forming a flower and thus a berry. Infested flower buds are slightly enlarged and lower portions are red. This is in contrast to normal flower buds, which are completely green. The grape blossom midge has one generation per year; it passes the winter as a full-grown larva.

This midge is most often present on vines near brushy or wooded areas, and it rarely causes much damage.

Red-banded Leafroller, Argyrotaenia velutinana (Walker) Lepidoptera: Tortricidae)

Larvae of the red-banded leafroller occasionally infest grape clusters. This insect overwinters as a pupa. Moths emerge in late April and lay eggs on newly set grape clusters. The larvae eat shallow holes into the berry; they web several berries together and feed on them and the cluster stems. These first-generation larvae mature in early June, pupate and emerge as moths, which lay eggs during June. The second generation larvae emerge and complete development about mid-August. Second generation moths emerge in late August and lay eggs, which give rise to the third generation.

Ordinarily, the third generation of this moth species is the most conspicuous and abundant. The larvae construct webbing within the grape clusters, chewing holes into the berries and feeding on the cluster stems. The third generation may cause considerably more damage than the first two.

Serious infestations of the red-banded leafroller are not common. A few infested clusters may be found every year, and the larvae may be present on other fruit such as apples.

The larva of the red-banded leafroller is a pale green caterpillar and is 5/8 inch long when mature. The adult moth is light brown with an irregular, reddish-brown stripe across each front wing; it is about 1/2 inch long.

Grape Seed Chalcid, Evoxysoma vitis (Saunders) (Hymenoptera: Eurytomidae)

The grape seed cha1cid is a small, wasp-like insect that lays its eggs in grape berries when the berries are nearly full size but still green. Larvae hatch, enter the seeds and feed on the contents of the seeds. The fruit around the infested berries shrivels and dries out. The grape seed chalcid overwinters within grape seeds on the ground. Adults emerge in late May or June.

Outbreaks of this insect are rare. Grape cultivars having smaller berries appear to be preferred over those which bear larger fruits. The grape seed chalcid attacks generally are confined to wild grapes.

Grape Curculio, Craponius inaequalis (Say) (Coleoptera: Curculionidae)

The grape curculio is a black snout beetle, about 1/8 inch in length, which lays its eggs in grape berries. The developing larvae feed on the berries, consuming the pulp and seeds. Damage by this insect is commonly confused with that of the grape berry moth.

In the spring, adult beetles become active around the time of ‘Concord’ grape bloom. They feed for about two weeks before laying any eggs. The beetles feed on the upper surfaces of grape leaves; the damage appears as short, curved lines arranged in groups. The female deposits eggs in cavities she makes under the skin of grape berries. The white larvae are legless, which is in contrast to grape berry moth caterpillars. In about three weeks, larvae complete their development, drop to the ground and pupate. New adults emerge several weeks later and feed on grape foliage until the onset of cold weather at which time they seek a place to hibernate. There is one generation of grape curculio each season.

Yellowjackets, Hornets and Paper Wasps (Hymenoptera: Vespidae)

Grape berries that become overripe and split open commonly are attacked by yellowjackets, hornets and paper wasps. These insects feed on the pulp and juice that become available when conditions leading to berry splitting are prevalent. Because these wasps are often present in clusters at harvest time, they are a nuisance to pickers. Economic damage to the crop by these stinging insects is rare.

Current pesticide recommendations may be found Here