Various Types of Treatment

Mites and aphids in strawberries

STRAWBERRY PEST MANAGEMENT

Jerry Brust, Vegetable IPM Specialist

Taken in part from: T. P. Kuhar and

D. G. Pfeiffer, Virginia Tech

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Strawberry bud weevil (Clipper)
Anthonomus signatus Say

Description:

The adult is a snout beetle about 1/10 inch long, chestnut brown in color, and possessing two black spots on its back. Larvae are tiny creamy white-colored grubs found inside unopened flower buds.

Biology and damage:

The strawberry bud weevil is one of the most important direct pests of strawberries in the United States. This pest has been shown to cause yield losses from 50 to 100% in some areas. The strawberry bud weevil is widespread and occurs throughout practically all the strawberry-growing regions of this country. The weevil has one generation per year. Adults that overwinter emerge early in the season from ground litter in wooded areas and migrate to strawberry fields (around late April in the Mid-Atlantic region). Females puncture unopened buds with their long beaks and deposit a single egg into the bud. Damage results when females cut the strawberry bud from the pedicel following oviposition, causing it to hang by part of the stem, or fall to the ground, thus, preventing fruit formation. Larvae develop in the buds and reach maturity in 3-4 weeks. Adults emerge in June, feed on flower pollen, then enter their summer dormancy in mid-summer and remain inactive the rest of the season.

Monitoring:

Sample weevils during the early blossom/bud stage with a threshold of 1 female beetle per 40 row feet. Another sampling program uses bud damage as an index where 2 row feet of plants are sampled at 5 locations with treatment recommended if an average of 1.2 clipped buds per 2 row feet is found.

Management:

Recent research in New York indicates that only rows along field edges near woods may need to be sprayed. If compensatory varieties such as Seneca are used, sprays may not be needed at all.

CHEMICAL CONTROL:

Danitol applied when threshold is reached and repeated 10 days later.

CULTURAL CONTROL:
Pistillate varieties of strawberries are relatively immune from attack since only varieties with staminate flowers seem to provide adequate food for developing larvae. Early-fruiting varieties are more susceptible to attack than later-fruiting varieties. Other cultural practices include avoiding field site selection near wooded areas to prevent high numbers of overwintering adults from entering the field in the spring. Mulches and full canopy beds encourage adults to overwinter and remain in the field, thus plowing of old beds immediately following harvest causes adult mortality.

Tarnished plant bug (Lygus bugs)
Lygus lineolaris(P. de B), L. hesperus Knight

Description:

Adults are about ¼ inch long, oval, and rather flattened. They are yellow, green and brown, and have dark markings on their wings. The immature forms are pale green and look similar to an aphid. They can be distinguished from aphids by their more rapid movements.

Biology and Damage:

The piercing-sucking feeding by these bugs is one of the causes of irregularly-shaped, catfaced strawberries. Fruit is damaged by the puncturing of individual seeds, which stops development of the berry in the area surrounding the feeding site. Straw brown seeds that are large and hollow are a good indication of lygus bug damage. There are 3 to 6 generations of this pest each year. Adults become active in early spring and deposit their eggs into stems, and leaf midribs. Egg hatch takes place about 1 week later depending on temperature, and the green-yellow nymphs undergo 5 instars, reaching the adult stage in approximately 30 days.

Monitoring:

One method of field scouting involves shaking flower clusters over a sheet of white cardboard. An action threshold of 1 nymph per cluster is recommended. A tentative threshold of 20-25 TPB per 50 clusters is suggested.

Management:

CHEMICAL CONTROL:

Brigade, Danitol or Thionex can be sprayed when thresholds are reached.

BIOLOGICAL CONTROL:
Predators that feed on the nymphal stages of lygus bug include bigeyed bugs, Geocoris spp., damsel bugs, Nabis spp., pirate bugs, Orius spp, and several species of spiders.

CULTURAL CONTROL:
Control weeds along roadways, ditches, and field borders to help prevent spring buildup of lygus bugs. Overwintered lygus bugs lay eggs in weeds in January and they hatch in March. Weed control should be carried out in March and early April while the bugs are still nymphs. Once adults are present on weeds, they will migrate into strawberries when the weeds are removed. To avoid adult migration in spring, mow or disc under cover crops, especially legumes, before they flower and while lygus are still in the nymphal stages. Crimson clover is a particularly favorable cover crop for lygus bugs.

Sap Beetles

Picnic Beetle Glischrochilus quadrisignatus (Say)

Dusky Sap Beetle Carpophilus luqubris Murray Strawberry Sap Beetle Stelidota geminata (Say)

Description:

Sap beetles often fly to ripening or damaged raspberries, strawberries, melons, early apples, tree wounds, corn and tomatoes. They may bore into the fruit, eat a portion and make it unfit for human consumption. The picnic beetle is usually a secondary invader of damaged plants and decomposing plant tissue. However, the strawberry sap beetle is a primary invader of ripe and nearly ripe strawberries. Picnic beetle adults are about 1/4-inch long and black with four orange-red spots on the wing covers. Eggs are milky-white, sausage-shaped, and about 1/32-inch long. Dusky sap beetle adults are about 1/8-inch long with short wing covers and are uniform dull black in color. Strawberry sap beetle adults are slightly less than 1/8-inch long, light to dark brown, oval, and somewhat flattened. Larvae of all three are white. Pupae are white, turning cream-colored and later tan before adult emergence. Biology and Damage:

Sap beetles overwinter as adults in protected places such as decaying vegetation, debris or fruit buried in the ground. In the spring, picnic beetle adults come out of hibernation and mate. Egg laying begins in April and continues in May and June. Females lay 5 to 15 eggs per day, scattered at random near decomposing plant material rather than on the material itself. Larvae develop in spilled grain, feed, corn ears, waste onion piles, and soil saturated with juices and food material. Full-grown larvae leave their food when mature, wander through the soil and change to the pupa stage. Adults then emerge in June and July. The cycle from egg to adult takes about 30 to 35 days. There is usually only one generation per year. Newly emerged adults do not lay eggs but congregate anywhere food is grown or being served. They are attracted to sweet or fermented plant juices. Beetles are found on cracked tomatoes, damaged sweet corn ears, overripe muskmelons, strawberries, and raspberries.

The life cycle of the dusky sap beetle is about 30 days with three to four generations per year. Some females lay more than 300 eggs and live as long as 147 days. The strawberry sap beetle primarily attacks strawberries. Sap beetles also disseminate organisms that cause rots in the fruits. Some sap beetles bore into the fruit, devour a portion, and lay eggs. Larval damage is usually only slight and often goes unnoticed.

Management:

Chemical:

Prevention of decaying strawberries is your best defense, but Brigade or Danitol can be used if populations begin to build. The REI for both is 24 hrs and the days to harvest is 1 and 2 respectively.

Cultural:

It is helpful to harvest sweet corn, tomatoes, melons, berries and other produce immediately as soon as they ripen. Remove any damaged, diseased or overripe fruits and vegetables from the area at regular intervals. Bury any decomposing fruits and vegetables to eliminate beetle food.

Baits:

Picnic beetles prefer banana, whole wheat bread dough, and muskmelon. As a bait, muskmelon rinds or pineapple scraps, sprinkled with a pesticide, kills the strawberry sap beetle and other scavenger beetles attracted to the fruits and vegetables. Take extra precautions to keep treated baits away from humans, domestic animals and other non-target organisms. Bait trapping shows some promise in the reduction of beetle populations. Discard trap contents frequently, every three or four days. Carbaryl (Sevin) is not a good control for sap beetles.

Western flower thrips and other flower thrips species
Frankliniella occidentalis and F. spp. Description:

Western flower thrips are slender, very small insects, about 0.03 inch long when mature. Adults vary in color from yellow to dark brown; nymphs are white or pale with small dark eyes.

Biology and Damage:

Both nymphs and adult thrips can injure the plant by rasping the plant bud, flower, leaf tissues and then sucking the exuding sap. Thrips feeding on strawberry blossoms cause the stigmas and anthers to turn brown and wither prematurely, but not before fertilization has occurred. Although the flower thrips are often numerous on strawberries when catfacing occurs, thrips do not cause catfacing. This is a result of lygus bug feeding and possibly other factors. As fruit develops, thrips feeding may cause a russeting of the fruit around the cap. This type of injury is seldom economic.

There can be numerous generations each year. Adults become active in early spring and deposit their eggs into plant tissues. Full development from egg to adult takes place in approximately 2 weeks.

Monitoring:

Control is usually not necessary because flower thrips rarely cause economic damage. Sprays applied to control thrips disrupt biological control of other pests such as twospotted spider mites and lygus bugs. Consider treatment only if populations reach 5-10 thrips per blossom. To sample thrips, place randomly collected flower blossoms and shaking them onto black paper.

Management:

CHEMICAL CONTROL:

If needed Spintor will control all thrips species without disrupting natural enemy populations.

BIOLOGICAL CONTROL:
Minute pirate bugs and other generalist predators can be important natural enemies of thrips.

Twospotted spider mite Tetranychus urticae Say

Description:

These mites are typically found on the bottom surface of leaves. Spider mite eggs are spherical and colorless when first deposited, but later become white as hatch approaches. Nymphs and adults are oval shaped and generally yellow or green in color. There are usually one or more dark spots on each side of their bodies.

Biology and Damage:

Feeding by the twospotted spider mite, which consists of piercing and sucking of cell contents, occurs on the under surface of leaves. Damage appears as stippling, and bronzing of the leaves and leaf veins. Feeding is particularly damaging during the first 4 to 5 months following transplanting in fall. Their rapid developmental rate (approx. 1-2 weeks) and high reproductive potential (about 50-100 eggs per female) enables them to reach damaging population levels very rapidly under good growing conditions.

Monitoring:

Field scouting involves direct counts of mites on leaf undersides. Although there is some disagreement on a reliable threshold for strawberry, an economic threshold of 5 mites per leaf is suggested following transplanting (before July 1), then approx. 20 mites per leaf later in the season. Mite densities of five per leaflet during the critical period of plant growth substantially reduce berry number and overall yield. Plants that sustain infestations of greater than 75 mites per leaflet may become severely weakened and appear stunted, dry, and red in coloration. The highest mite populations are often observed following the peak spring fruit harvest, and this peak is typically followed by a rapid, natural decline in mite density.

Management:

CHEMICAL CONTROL:

Be sure to control mites early in the season, before their populations begin to build. Agimek, Danitol, Kelthane, Oberon, Savey, and Zeal are some of the mitecides available for mite control. Thorough under-leaf coverage of sprays is necessary for good control.

BIOLOGICAL CONTROL:

Predators play an important role in keeping twospotted spider mite populations in check. The predatory mites Phytoseiulus persimilis, Metaseiulus occidentalis, and Amblyseius will give good control of twospotted spider mites if insecticide sprays are kept to a minimum early in the season.

CULTURAL CONTROL:

Strawberry cultivars vary in susceptibility to twospotted spider mite. Short-day cultivars are generally more tolerant of mite feeding than day-neutral cultivars, particularly later in the fruit-production season. Vernalization directly promotes plant vigor. Supplemental cold storage can affect a plant's vernalization. Plants with low amounts of chilling will have low vigor and will often develop intolerable mite infestations. Excessive chilling will promote increased vigor and reduce mite abundance, but other production factors are adversely affected (i.e., delayed flowering, large plant size, increased vegetative runner production).

Strawberry crown borer
Tyloderma fragariae (Riley)

Description:

Adults are dark brown flightless snout beetles possessing 3 darker spots on each wing cover and approximately 1/16 inch in length. Larvae are creamy-white in color, legless, and can be found feeding in the crowns.

Biology and Damage:

The strawberry crown borer is considered to be native to North America, and is prominent in the eastern half of the United States. As the name of this insect would suggest, damage is caused by the larvae boring into the crown of the plant. The crown can be so hollowed out following the weevil feeding that plant death occurs. In addition, adults feed on leaves and may chew holes in the crown prior to oviposition. There is one generation per year. Adults overwinter and become active around the time of strawberry blossom. Eggs are deposited in the crown.

Management:

CULTURAL CONTROL:
Crop rotation helps to control this pest since the beetles migrate only by the adult crawling along the ground. Also, avoid planting strawberry patches closer than 300 yards to old plantings. In addition, deep plowing of the soil destroys many hibernating weevils.

Strawberry leafrollers (tortix)
Ancylis comptana (Froelich)

Description:

Adults are small, bell-shaped tortricid moths that are rust-brown in color with markings of light yellow on the wings. The slender larvae are nearly 1/2 inch long when mature. Larvae are slender, have light green-brown bodies and reach just over 12 mm when fully grown.

Biology and Damage:

Strawberry leafrollers are common pests in the eastern half of the United States. The insect has several, usually 2-3 generations per year. Adults emerge in early April to May and deposit eggs on foliage. Hatching occurs in about 1 week, and the larvae complete their development in 40 to 59 days. Damage results from larvae feeding on leaves and rolling the leaves by means of silk webbing. Once enclosed in the rolled leaf, larvae continue to feed. Some leafrollers may consume whole leaf tissue. Leaf feeding results in reduced runner formation, interference with ripening fruit, and plant kill. Strawberries are quite tolerant of the leaf feeding species and can support high population levels without economic loss.

Management:

CHEMICAL CONTROL:

Usually one spray 10 days after bloom will suffice if this pest has been a problem in the past. Brigade, SpinTor and Sevin will work as controls.

BIOLOGICAL CONTROL:
Strawberry leafroller has a large complex of parasites that play a major role in lowering pest populations. Keep to a minimum the number of early season insecticide applications.

CULTURAL CONTROL:
In areas with a chronic leafroller problem, it may be feasible to remove accumulated trash in spring around the plants with either blowers or suction devices to limit the potential for a large population buildup.

Potato Leafhopper Empoasca fabae Harris

Description:

Potato leaf hopper (PLH) has a wide host range. It is a pest of alfalfa and potato in our region, in addition to strawberry, apple, grape and other species. Adults and nymphs are both green in color. Legs are spinier that WLH. There is a series of six white spots on the area immediately behind the head. This species is more active on the leaf than WLH. Nymphs will run sideways, quickly running to the other side of the leaf as the leaf is examined.

Biology and Damage:

PLH overwinters in the Gulf Coast states, and must reinvade the mid-Atlantic region each spring. Adults reach Maryland in late May. This species, unlike WLH, has a toxic saliva which causes xylem and phloem tubes to collapse, causing the inability of water and nutrients to reach the leaf and of photosynthates to leave the leaf. There are several (usually 2-4) overlapping generations. Nymphs emerge until mid-September and adults are present until mid-October, although densities are usually very low by this time because of the lack of young leaves. The cellular injury caused to the leaf of the various food plants causes a typical "hopperburn". The edges of the leaf curl downward, first turning lighter green, then yellow, and finally brown and necrotic.

Management:

Monitoring:

Young blocks should be frequently inspected from mid-May. Weekly sampling may be insufficient. Experience has shown that adults may invade in sufficient numbers to initiate hopperburn in the interval between two weekly scouting visits. No threshold is currently available. Consider treating when adults first appear in young blocks, especially if PLH has been a problem in the area in the past.

CHEMICAL CONTROL:

Malathion at threshold.

Strawberry root weevil complex

Cribrate weevil: Otiorhynchus cribricollis

Woods weevil: Nemocestes incomptus

Black vine weevil: Otiorhynchus sulcatus

Fuller rose weevil: Pantomorus cervinus

Description:

Adult root weevils are snout beetles of various species. They are light brown to black in color, and all possess hard-shelled bodies with rows of pits on their backs. They feed at night and hide within the crowns of plants during the day. Root weevil adults do not fly. Root weevil larvae have curved white or pink bodies that are about 0.38 inch long when fully grown. They have distinct brown heads, but no legs.

Biology and Damage:

Larvae feed on the roots of strawberry plants and can completely devour small rootlets and destroy the bark and cortex of larger roots. Injured plants often wilt because the roots can no longer provide moisture for leaves. Weevil larvae can also be found burrowed into the lower portion of the plant's crown. Adults feed on foliage and remove large scallops from the leaves. Such leaf damage is a good indication that weevils are present, but is not economically damaging to the plants. Root weevils have a single generation each year. The flightless adult females reproduce parthenogenetically. Adults emerge in late spring or summer, feed on strawberry foliage, and females lay their eggs around the crowns about 1 month after emergence. After hatching, weevil larvae burrow into the soil and feed on strawberry roots and crowns. The insects overwinter as mature larvae in the soil. In spring, they resume feeding and can cause extensive damage before they pupate.

Management:

CHEMICAL CONTROL:

Chemical treatment is not needed each and every year since these flightless beetles are slow to colonize a field. Controls are now directed against adults while they are feeding on crop foliage. Brigade or Malathion can be used for control of adults at the first sign of leaf feeding.

BIOLOGICAL CONTROL:

Very few natural enemies.

CULTURAL CONTROL:

Crop rotation. Avoid planting strawberries after sod. Delay plowing until fall in order to use old planting as a trap crop for weevil oviposition. Sticky barriers can be used to prevent movement of adult weevils from infested second year berries and host areas to newly fumigated plantings.

For more information, contact Dr. Gerald Brust

Last updated: 03/10/2009