Pest and Control

Grape Root Borer, Vitacea polistiformis

The grape root borer is a clearwing moth that resembles a paper wasp. The female lays eggs on or near the vine, and newly hatched larvae must find their way into the soil and then to a root. Larvae feed in the roots for up to two years (perhaps longer), moving to larger roots as they grow. Young vines may be killed if girdled and older vines may decline over a period of years. Control is difficult because larvae are so well protected once they enter a root to feed. It can be difficult to tell if an infestation exists, because, in many cases, vine decline is gradual. Soil must be removed from around roots to observe the characteristic tunnels, packed with reddish brown frass, left by the feeding larvae. A less damaging way to check for the presence of grape root borer is to examine the surface of the soil at the base of the vine for cast pupal casings, the translucent, light brown, shed skin of the pupa from which the moth emerged. These will be found at the time of peak moth flight activity.

Insecticide treatment is aimed at newly hatched larvae still on the soil surface. The only chemical insecticide labelled for grape root borer, Lorsban (or Nufos), is applied to the soil at the base of the vines at or slightly after the peak of moth flight activity (see label for directions). The soil under the vines should be as free of weeds as possible to get good coverage of the surface. Lorsban 4 E may be applied only once during the growing season and not within 35 days of harvest (but may be applied immediately after harvest). Peak flight is later as one travels south in Florida. In north Florida, peak activity is generally in August and September. From Leesburg south to the Fort Myers area, peak activity is in late September to early October. Near Miami, the peak is shifted to October. Pheromone traps have been used for research purposes, but the specific pheromone for grape root borer is not yet available commercially.

Grape Flea Beetle, Altica chalybea

Often the first insect damaging grapevines in the spring is a small, metallic blue beetle, about 0.2 inches in length. Adult beetles feed on buds and unfolding leaves. Females lay eggs on bark, buds and leaves. Small, brown, black-speckled, caterpillar-like larvae then feed on flowers, flower buds, and leaves for 3 to 4 weeks, leaving behind clusters of brown, hollowed-out flower buds. Yields may be severely reduced if beetle populations are high. Vines should be carefully observed in the spring (bunch grapes seem particularly susceptible) and a recommended pesticide (see Table 1) applied when necessary.

Grape Leafhopper, Erythroneura vulnuerata

Leafhoppers appear early on bunch grapes and can be found all season. These small, pale yellow insects have bright red markings and feed on the undersides of leaves, puncturing cells and sucking out the contents, giving the leaf a speckled appearance. If a leaf is heavily damaged it may dry up and fall off. Studies in California indicate that a vine can tolerate up to 20% leaf loss a month after fruit set before yield is affected.

Grape Seed Chalcid, Evoxysoma vitis

This tiny (1/8 inch) wasp lays her eggs in developing grape seeds. Larvae develop in the seeds and emerge as adults just before the grapes ripen. Damage has only been observed on the bunch grape varieties Blue Lake, Lake Emerald, Stover, and Norris. The presence of the wasps can be monitored with yellow sticky cards suspended under the vine canopy beginning in early to mid April. In one study conducted in a central Florida vineyard, wasps were caught from late April to mid July but grapes were attacked only for the first three weeks in May, possibly because the grape seeds were at the proper stage for wasp survival for only a short time. Malathion has been found to give good control and may be applied after wasps have been detected on sticky cards.

Grapeleaf Skeletonizer, Harrisina americana and Grape Leaffolder, Desmia funeralis

The caterpillar stages of these two moths damage leaves but are not often present in large numbers. Skeletonizer larvae are brightly colored (striped) and feed in groups. Leaffolders feed on both muscadine and bunch grape leaves. On muscadines, early stage larvae will tie together several leaves and feed in a group. Older larvae construct leaf rolls. On bunch grapes, which have thicker leaves, larvae fold, rather than roll leaves. Very high populations can cause premature defoliation. If natural biological controls do not seem to be keeping populations in check, insecticides may be used, including the biological insecticide, Bacillus thuringiensis (Bt).

Grapevine Aphids, Aphis illinoisensis

Grapevine aphids are dark brown, shiny, soft-bodied insects that feed on the new shoots and leaves, particularly in the spring and fall. Many other insects attack aphids and chemical control is necessary only when high populations are found.

Grape Phylloxera (Leaf Form), Daktulosphaira vitifoliae

Another sucking insect related to aphids, the phylloxera feeds protected in raised galls that form on the upper surface of the leaf. The leaf form of phylloxera does not appear to cause much damage. To control it chemically, vines must be treated just when galls are opening. Endosulfan is labeled for phylloxera control.

Sharpshooters, Homalodisca coagulata, Oncometopia nigricans

Large leafhoppers of several species are vectors of Pierce's disease, including brown and blue sharpshooters. Only varieties of grapes resistant or tolerant to this disease can be successfully grown in Florida. Chemical control of the vectors is not effective.

Other Pests

Because Florida hybrid bunch grapes are being planted in greater numbers in areas where they have not been grown before, other insects not mentioned here may be found as occasional pests and should be brought to the attention of county extension personnel. Some additional minor pests include grape curculio, Craponius inaequalis; grasshoppers; scarab beetles, Anomala nigrapicta; and a gall midge which caused grape tomato galls, Lasioptera vitis.

Tables