Small Fruit Pest Management

Pest management is considering all possible control techniques to suppress a pest population. Effective control may be achieved when various techniques are integrated for their combined actions.

Always use proven techniques that are economic, ecologically sound, and effective for pest control. Integrated pest management is a system that includes economic thresholds, scouting, resistant varieties, cultural practices, use of natural parasites, predators and diseases, and chemical pesticides. However, when too much dependence occurs on repeated applications of pesticides, problems are created, including insect resistance, emergence of secondary pests, and environmental contamination.

Be sure you have a pest problem before you apply pesticides, because you can create other insect problems if you don't. Identify the insects correctly to help determine if they are harmful or beneficial. Know the habits of the insects attacking your crop, determine the stages (adult, larva, nymph) causing damage, and familiarize yourself with their injury characteristics. Select the correct insecticide to control your pests. Most insecticides have specific activity and will control some pests but not others.

Timing and placement of your pesticides are critical for control. Apply the insecticide when insects are at stages easiest to control, and place the insecticides on the target areas. Practically all insecticides recommended for use on small fruits control insects by contact activity, which means the insecticides must come in contact with the insects. Remember fruit sprays generally give better control, with less drift, than do dust formulations.

Weekly inspections of small fruits help prevent damage before it reaches severe levels. When signs of infestations first appear, apply control measures. Repeat only if necessary.

Always read pesticides labels carefully. Observe the time interval between your last application and harvest.

Major Insects

Aphids, or plant lice, are small, soft-bodied insects that may or may not have wings. They are generally green, although some are pink, black, or yellow. They remove the sap from leaves, terminals, or stems, causing curled leaves and yellowish plants on many small-fruit crops. They can also inject poisonous saliva or disease-causing organisms during feeding. They give birth to living young, resulting in tremendous numbers occurring in muscadines, bunch grapes, blueberries, blackberries, and strawberries. These insects secrete a material called "honeydew" that harbors sooty mold fungus, which can further spoil fruits.

Crown borers are serious problems in blackberry fields. Moths lay their eggs on the foliage in late summer; larvae crawl to the base of canes, bore in, and overwinter. The next summer they feed in the crown and roots, causing larger galleries as they grow. They overwinter a second winter and mature and pupate early the second summer. Life cycles overlap, so both one- and two-year-old larvae can occur in a given planting. Monitor plantings in May-July for wilted or dying canes, dig up, and burn. Diazinon may be used as a soil drench in the spring, before fruiting begins, or in the fall after harvest.

Grape root borers are serious problems in grape and muscadine vineyards. Moths lay their eggs on foliage or trunks of muscadines or grapes in July and August. On hatching, larvae burrow into the soil and tunnel the roots for almost 2 years. They then leave the roots and pupate in cocoons near the soil surface in June. A single larva feeding on the trunk base (crown) can cause severe yield reduction. Monitor plants closely in May-July for poor vigor. It may be necessary to dig up plants to determine the infestation. Lorsban 4 EC is the only insecticide cleared for borer control in grapes and muscadines. Based on data from the trap catches, a single application of Lorsban should be made on or around July 20. Mix 4 1/2 pints of Lorsban with 100 gallons of water, and apply 2 quarts of the diluted spray mixture to the soil surface on a 15-square-foot area around the base of each vine. Do not allow spray to contact fruit or foliage. Store Lorsban in original container in secured, dry storage area away from dwelling. Do not apply within 35 days of harvest.

Spider mites usually reach damaging populations in hot, dry weather. Leaves become blotched, with pale-yellow to reddish-brown areas, and may eventually drop. Close examination (with a hand lens) of the underside of the leaf may reveal a fine webbing of silk. Mites can be found in this webbing or on the leaf surface. In severe cases, mites also can be found on the upper surfaces of the leaf. For adequate control of this pest, make several sprays at weekly intervals. Be sure to get good coverage of upper- and lower-leaf surfaces.

Stink bugs can be brown or green. They give off a disagreeable odor when crushed. They are large, shield-shaped insects and may or may not have any distinguishing marks. They suck sap from developing fruit; this scars developing fruit, causing a "cat-facing" effect. The outside of the fruit may be marked with a small, pimple-like structure at the puncture site.

Strawberry weevils are small, reddish-brown weevils and can be a serious pest in blackberry and strawberry fields. They lay their eggs at the base of flower buds, and the larvae girdle the stem just below the bud. Apply an insecticide when cut buds are first noted near the beginning of bloom and as needed thereafter. Only one generation occurs per year; however, emergence may occur over several weeks' time.

Minor Insects

Bees and wasps are sometimes a nuisance in and around fruit or berry fields. Spraying with malathion, diazinon, or sevin helps suppress them.

Berry moths web grape or muscadine berries together and cause them to turn black and drop from the stems when they are about the size of garden peas. Later generations eat small holes in the nearby ripened fruits and attach them with a web to a nearby leaf or another berry. The moths pupate in small silken cocoons folded in small semicircular flaps cut in leaves. The last generation of the season will spend the winter as a cocoon in these flaps in the fallen leaves.

Caterpillars--including yellow-necked caterpillars, bagworms, fruit worms, cutworms, and armyworms--may feed on fruit or foliage. They vary in size and color, but the control for this group is the same. Good insecticide coverage on the plants is essential for best control. A combination of two insecticides may be necessary for control, depending on the pest or pests present. For example, if sucking (aphids) and chewing (caterpillars) insects are present, a mixture of two insecticides may be necessary. Read labels for instructions.

Chiggers, often called red bugs, make up a family of mites. They cause intense itching and small reddish welts on the skin. Chiggers generally are found where berries or fruits are grown in low, damp places where vegetation is heavy. Protect yourself against them by using a repellent such as N,N-diethyl-m-toluamide (Deet). Apply as directed by the label.

Grasshoppers may cause defoliation by feeding on young green plants. Eggs are laid in the soil in the fall. Adults usually die in the fall or early winter. Overwintered eggs hatch in April, May, and June. Nymphs (immatures) grow slowly, reaching the winged adult stage in late summer. Most damage occurs in mid- to late-summer when grasslands dry up.

Leaf rollers are small caterpillars that attack many of our small fruits. The larva spins a silken thread and folds over the edges of the leaves, feeding on the inside tissue. It spends the winter as a pupa inside this fold in the fallen leaves. Infestations may occur in the same field year after year if control measures are not used. Insecticide applications should be made before leaves have become folded to any extent to be effective, since they must come in contact with leaf rollers before they construct their silken cases. Thorough coverage is necessary.

Insecticide Selection

Table 1 shows recommended insecticides for use on small fruits (blackberries, blueberries, grapes, muscadines, and strawberries). Apply choice of insecticide to the point of runoff. Be sure the chosen insecticide is labeled for use on the crop before applying. Refer to product labels for rates, usages, and precautions.

Table 1. Insecticide effectiveness.

Y = Yes; insecticide is registered for use on this crop.
N = No; insecticide is not registered for use on this crop.
X = Controls pest.

Publication 1818
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director

(rev-500-10-00)