In this Blast
Two-spotted Spider Mite
Leather Rot
Blueberry Maggot
Raspberry Cane Blight
Next Blast -
Spotted Wing Drosophila
STRAWBERRY
Two-spotted Spider Mite (Tetranychus urticae)
ID/Life Cycle: Two-spotted spider mites are tiny arthropods that live on the underside of strawberry leaves. Females are slightly larger than males and both have two dark patches (spots) on their backs. They are best viewed with a hand lens as they are difficult to see with the naked eye and form colonies as the numbers build up.
They overwinter in cracks and crevices on the strawberry crowns or in the surrounding duff around the plants. There are many generations per year. Both adult and immature mites feed on plant sap and have a wide host range, feeding on many species of plants.
Damage: Under heavy infestations, mite feeding destroys leaf chlorophyll and causes leaves to have yellowish or whitish speckles, then
an overall bronze color. Leaves will be covered in a fine webbing. Yield reductions may occur from repeated heavy infestations. The most serious reductions in yield may result from early season feeding, so scouting for overwintered mites from May to early June is especially important. (
photos: D. Handley, UMaine Extension)
Management
Monitoring: Mites should be monitored weekly by sampling the field in 5 to 10 locations. Five to 10 leaves should be sampled at each location for a total of 60 leaves. Examine the underside of the leaves for the presence or absence of TSSM. Record the information on a field map so that “hot spots” can be identified and treated. The action threshold is when 25% (i.e., 15 leaves) or more of a 60 leaf sample is infested. When sampling a field, presence of predators as well as pest mites should be noted.
Control strategies
Cultural/Biological:
- Release natural enemies, such as Phytoseiulus persimilis, Neoseiulus fallacis or N. californicus when threshold levels are reached. Follow-up releases may be needed to achieve sustained suppression.
- Preserve natural enemies whenever possible by selecting spray materials that are less toxic to beneficials.
- Be sure to keep the field irrigated during periods of active growth to avoid stress on the plants.
- Prompt renovation when harvest is complete can interrupt the build-up of mite populations.
Chemical:
- Apply recommended miticides when threshold levels are reached. These currently include but are not limited to Acramite, *Brigade, *Danitol, Oberon, Savey, Vendex and Zeal for Conventional Production, and AzaDirect, Defend DF, Des-X Insecticidal Soap, JMS Stylet Oil, and Trilogy (or similar products) for Organic Production. Be sure to read and follow label directions.
- Consult the New England Small Fruit Management Guide for rates and timing.
- If repeat applications are needed, rotate miticides from different IRAC groups to reduce the chance of resistance development in the pest.
*Restricted Use Material
DO NOT APPLY MITICIDES DURING BLOOM.
Anthracnose (
Colletotrichum acutatum)
ID/Disease Cycle: This fungus is an increasingly important pathogen of strawberries in New England. Symptoms of this disease include circular, sunken, water-soaked tan to brown lesions on both green and ripe fruit. It may also infect runners, leaf petioles and crown tissue. In wet or humid weather, creamy pink to salmon colored spore masses occur in the centers of lesions.
This disease can be introduced into a field on transplants or contaminated equipment. It can persist from year to year on infected plant tissue. The incidence of anthracnose fruit rot may be directly related to unusually warm weather in spring. Spread of the fungus from infected tissues to uninfected fruit and crowns occurs primarily by splash dispersal and is aided by wind-driven rain. However, spread may also occur on runners and by the movement of people or equipment through the field, especially in wet weather.
Damage: Fruit infections reduce marketable yield. Stolon and crown infections weaken plants and can ultimately lead to plant death. (
photos: Cornell Berry Diagnostic Tool)
Management
Monitoring: Consult scouting records from previous years to determine if carry-over inoculum is likely to be present. Scout fields weekly in the current year starting in the pre-bloom period for symptoms. Monitor weather conditions especially during bloom to determine if infection periods are imminent or have occurred.
Control strategies:
Cultural/Biological:
- Rotate strawberry fields to alternative cash or cover crops for at least 3 years before replanting to strawberries to disrupt pest buildup.
- Plant only disease free transplants obtained from a reputable nursery.
- Use drip irrigation to avoid the splashing water that results from overhead irrigation.
- Maintain a good mulch cover on the soil to lessen splashing from rain or overhead irrigation.
- Remove promptly any infected plant tissue as soon as it is seen.
Chemical:
- Apply recommended fungicides starting at prebloom if field history or scouting indicates risk of infection. These include but are not limited to Abound, Cabrio, Captan, Merivon, OSO, and Pristine for Conventional Production, and Double Nickel, PERpose Plus, Serenade and Trilogy for Organic Production. Be sure to read and follow label directions.
- Repeat fungicide applications at recommended intervals if weather conditions are conducive to infection.
- Consult the New England Small Fruit Management Guide for rates and timing.
- If repeat applications are needed, rotate miticides from different FRAC groups to reduce the chance of resistance development in the pest.
Rotate fungicide materials from different FRAC groups to avoid promoting the development of resistant strains of this disease.
BLUEBERRY
Blueberry Maggot
ID/Life Cycle: The adult fly, similar in size to a house fly, is black in color, with a pattern of dark and clear bands on its wings. The maggots are small, white, legless, and are found inside infested fruit.
This insect overwinters as pupae in the soil beneath the blueberry bushes. Emergence of overwintering adults coincides with the ripening of blueberry fruit and spans several weeks, which extends their period of activity in the field. Females lay their eggs singly beneath the surface of a ripening berry. The emerging larva feeds inside the berries for a two-week period. When full grown, the larva drops to the ground, if the berry has not already fallen. It pupates in the soil, where it will remain for the winter. There is one generation per year.
Damage: Flies lay eggs under the fruit skin just as the fruit begins to turn blue and larvae feed within the fruit. Maggots are later found in ripening and harvested fruit. Maggots feeding within developing fruits render fruit unmarketable. Berries become soft and mushy. Undetected infested berries contaminate pack-out.
(
photos: R. Isaacs, Michigan State Univ.)
Management
Monitoring: Yellow sticky rectangle traps can be used to monitor blueberry maggot populations in the planting. Traps are placed in the upper third of 4-8 bushes around the perimeter of the planting and another 2-4 traps on interior bushes. Bushes with traps should be marked with flagging tape so they can be easily found. Traps should be set out prior to any fruit ripening and checked every few days to determine when Blueberry Maggot flies are becoming active. Sustained catch of the blueberry maggot fly in traps indicates that it is an optimal time to make an insecticide treatment; sustained catch means not just the first one or two flies, but consistent catch of several flies per week. (
photo: R. Isaacs, MSU)
Control strategies
Cultural/Biological:
- Preserve natural enemies whenever possible by selecting spray materials that are less toxic to beneficials.
- Prune to achieve small, open bushes with good sunlight penetration through the canopy, reducing shading on the soil surface to generate a less favorable habitat for build-up of this pest.
- Set out a high density of traps (1 trap per bush) in small plantings to trap-out this insect.
Chemical:
- Apply recommended insecticides when trap catches indicate a sustained population. These include but are not limited to *Asana, Assail, *Brigade, Exirel, Imidan and Malathion for Conventional Production and AzaDirect, GR-120 Naturalyte Bait, and Surround for Organic Production. Be sure to read and follow label directions. Many of these materials will also control Spotted Wing Drosophila (SWD).
- If repeat applications are needed, rotate insecticides from different IRAC groups to reduce the chance of resistance development in the pest.
- Consult the New England Small Fruit Management Guide for rates and timing.
- If repeat applications are needed, rotate miticides from different IRAC groups to reduce the chance of resistance development in the pest.
- Be aware of pre-harvest intervals for materials applied close to harvest.
RASPBERRY
Raspberry Spur Blight (Didymella applanata) and Cane Blight (
Leptosphaeria coniothyrium)
ID/Disease Cycle:
Spur blight causes brown or purple blotches to appear on the canes, usually centered on a leaf stem. Symptoms appear on new canes in mid to late summer. On second-year canes, the blotches become gray areas on the bark with tiny black spots on them, which are the fruiting structures of the fungus. Leaves on infected canes may show yellow or brown areas that begin at the mid-vein and spread out to the leaf tip.
Cane blight is characterized by large brown and purple lesions on the canes. These lesions can sometimes split lengthwise along the canes. Unlike spur blight, these lesions are not typically located at a leaf stem and may involve whole stems.
Damage: Infected canes are weakened, and produce fewer fruiting branches than healthy canes. (
photos: Washington State University Raspberry IPM Manual)
Management:
Monitoring: Maintain and consult scouting records from past years to determine if disease has occurred in prior years. Begin scouting fields for symptoms from bloom through harvest. Monitor weather conditions that may promote disease development.
Control strategies:
Cultural/Biological:
- Eliminate wild and untended brambles surrounding the raspberry stand, since they harbor disease-causing organisms.
- Plant and prune to promote good air circulation, drying conditions and spray penetration into the canopy.
- Prune out symptomatic tissue as soon as it is seen.
- Avoid over-fertilizing that can result in a dense canopy.
Chemical:
- Apply dormant fungicides to reduce overwintering inoculum.
- Apply summer fungicides if field history, scouting and weather monitoring indicate risk of infection. These include but are not limited to Abound, Cabrio, Ph-D, Pristine, QuiltXcel and Tanos for Conventional Production and Badge, PERpose Plus, NuCop, Trilogy and Serenade for Organic Production. Be sure to read and follow label directions.
- Consult the New England Small Fruit Management Guide for rates and timing.
- For repeat applications, rotate fungicide materials from different FRAC groups to avoid promoting the development of resistant strains of this disease.
WEED SPOTLIGHT
Common chickweed (
Stellaria media) is a winter annual broadleaf weed, weakly tufted, that reproduces by seeds and creeping stems that root at the nodes. The root system is fibrous and shallow. The stems are heavily branched, trailing and matted, forming a low spreading plant, 4 - 72” high. The leaves are small, opposite, simple, smooth and pointed at the end. The flowers are small and white with deeply notched petals. Chickweed may flower throughout the growing season.
Seedling Flowering Mature plant
Chickweed can be especially troublesome in strawberry plantings. Close mowing will not control chickweed, but it can help to discourage seed production. Small patches can be hoed out since the weed has shallow roots. Chemical control is appropriate. See New England Small Fruit Management Guide
Strawberry Weed Management section for recommended materials, rates and timing.
Archived IPM Berry Blasts are available at the UMass Extension Fruitadvisor website.
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