WSU Whatcom County Extension

Integrated Pest Management for Raspberries

Post-Harvest

Biology and Monitoring

(August through September)

Insects
Diseases
Vertebrates

     • Nematodes
     • Spider Mites
     • Strawberry Crown Moth
     • Raspberry Crown Borer
     • Voles
 

     • Cane Blight
     • Phytophthora Root Rot
     • Spur Blight

     • Voles

 

Biology

Insects

Nematodes

Two types of microscopic nematodes can damage raspberry fields in northwest Washington; root lesion nematodes (Pratylenchus penetrans) and dagger nematodes (Xiphinema americanum and X. bakeri). Root lesion nematodes migrate within the roots and between soil and root tissue, whereas the dagger nematodes stay outside of the roots, feeding on root tips. Both cause direct damage to root tissue. One of the dagger nematodes (X. americanum) causes little or no direct root damage but is capable of transmitting the tomato ringspot virus, which reduces raspberry growth and causes crumbly fruit. X. bakeri is suspected to transmit viruses as well, although this has not been proven. The presence of either species of dagger nematodes is cause for concern.

The nematodes most commonly found in raspberry fields in northwest Washington are P. penetrans and X. bakeri.

 

Spider Mites

Spider mite populations can increase rapidly after harvest through early September. Most of the mite population by this time has moved gradually from fruiting cane to primocane foliage. There is no clear correlation between mite population density and economic injury to raspberry fields. Recent research indicates the importance of maintaining healthy foliage late into the season in order to provide adequate carbohydrate reserves for the plant. With this in mind, it is good management to monitor spider mite populations through early September. Overwintering mites who become more orange in color begin to migrate from the leaves in mid- to late- September.

 

Strawberry Crown Moth

SCM should be in larvae form during this period. Young larvae feed on the outer crown and root surface. As the larvae mature, they bore deeper into crowns and are found in the center of the crown after about one month of feeding. Larvae feed in the crowns until early October and then spin a cocoon to overwinter. There is one generation each year.

 

Raspberry Crown Borer

Adult crown borers can be present in raspberry fields from late July through early October. They look like a black and yellow wasp, but are actually a moth with clear wings. Females produce as many as 100 eggs, which are deposited singly on the undersides of berry leaves. Small caterpillars hatch from these eggs, crawl down to the base of the canes, and form an overwintering cell in the side of the cane. Second year caterpillars, which tunnel into canes and fleshy roots, may be present at this time of the year as well.

 

Diseases

Cane Blight

Cane blight requires a wound to enter the vascular tissue of the primocane. In fields where cane blight has been a problem, a fungicide application is usually made immediately after harvest to suppress infection. If 1-3% of fruiting canes are infected, consider treatment. Make sure that the bottom half of canes receive adequate fungicide coverage. Cane blight infection is likely to be more severe in years with heavy rainfall during the harvest period. The canes become highly resistant to infection in the fall.

 

Phytophthora

The most common above ground symptom of Phytophthora root rot during the post-harvest period is the collapse of fruiting laterals and wilting of primocanes. The pattern of diseased plants is determined by the presence and movement of the disease organism in the soil. Root rot caused by Phytophthora rubi can be found in both well-drained and poorly drained soils.

 

Vertebrates

Voles

Voles resemble house mice; they are 6-9 inches long, and gray or brown in color. They create tunnels in the soil and feed on plant roots and foliage near the ground. Their gnawing and chewing can girdle roots, crowns, canes and may lead to cane loss. Their tunneling creates air pockets in the root zone, which may further impact plant development.

 

Monitoring

Follow general guidelines in the “Introduction” section. For each pest below, record pest numbers or symptoms on record sheet.

Insects

Nematodes

  • Scouting should be done in two ways: monitoring the plants and sampling the soil.
  • Plants should be inspected throughout the growing season to identify weak stands and plants that have been infected with tomato ringspot virus through nematode transmission.
  • Because root lesion nematodes (Pratylenchus penetrans) are found within the actual roots as well as in the soil, it is important to collect both soil and roots when evaluating them.
  • Soil samples should be done using a standard soil sampler. Place soil in a plastic bag, label, chill, and immediately delivered to the lab for testing. Two types of sampling can be done: predictive and diagnostic. 
  • Predictive Sampling
    • Partition fields into blocks based upon soil type, drainage, crop history & etc.
    • Prior to planting a field, use a soil sampling tube to take a minimum of 20 - 1ft. deep cores to represent a block no larger than 5 acres.
    • Collect samples while walking a “W” pattern throughout the block.
  • Diagnostic
    • Try to take at least two samples (representing 10 plants) from each field, comparing good versus poor areas if possible. Sample around severely weakened plants as well as healthy plants for comparison.
    • Using a shovel and pruning shears, collect a handful of soil and feeder roots in the plant row or hill within 12-15” of the crowns from the top foot of each plant sampled.  Be aware of where your drip tape is located when sampling.
    • Roots and soil can be placed together in a plastic bag and shipped to the lab for analysis.  Keep samples cool and out of direct sunlight.

 

Spider Mites

  • Examine leaves immediately after harvest to determine population density of spider mites and mite predators. Predators can become quite numerous this late in the season, particularly in fields with low insecticide use. Treatment is considered unnecessary unless the population reaches 25 mites per leaflet by September 1.
  • Sample by collecting at least ten leaflets per site in a minimum of four locations in the field.
  • Record the number of mites at each site to illustrate the variation across a field and to decide which areas, if any, require treatment.

 

Strawberry Crown Moth

  • Check lower canes and crown material closely in weak areas of the field for signs of feeding
  • Fall is a good time for treating infested fields, which usually will correspond with chemical drench used to control the raspberry crown borer.

 

Raspberry Crown Borer

  • Check lower canes and crown material closely in weak areas of a field for first or second year caterpillars, particularly if adult crown borers are seen during the late summer months. Record percent infected hills.
  • October is the preferred month for treating infested fields.

 

Diseases

Cane Blight

  • Monitor cane blight in the late fall by scraping away the epidermis on the primocanes near the catcher plate height.
  • Look for a brown stripe lesion spreading from a wounded area.
  • Record the number of plants with infection, and consider treatment the following season if 1-3% of canes are infected.
  • Infected canes become brittle the following spring and can be easily broken at that time.

 

Phytophthora Root Rot

  • Identify areas which show symptoms of Phytophthora infection. These include premature decline of fruiting canes and primocane wilt.
  • Examine the crown region of suspect plants by scraping away the epidermis. Diseased plants have red or brown rotted tissue with a clear demarcation between the diseased and adjacent healthy white tissue.
  • There are several tactics to control this disease. They include:
    • Tiling and/or ripping soil to improve drainage.
    • Consider hilling or replanting into raised beds.
    • Clean tillage equipment used in known Phytophthora infested soils before moving to healthy fields.
    • Apply fungicides in only those fields known to be infected with the disease organism.
    • Avoid planting raspberries in fields with a history of Phytophthora.
    • Do not introduce Phytophthora on plant material. Do not plant root stock that has been under a suppressant fungicide program to control Phytophthora.

 

Spur Blight

  • Monitor spur blight by looking for the characteristic chestnut colored lesions which are associated with nodes on the primocanes. It is too late to control the disease this season, but findings will be useful for managing the disease the following year. Record % of hills infected.
  • Examine leaves for irregular shaped brown lesions with yellow margins on fruiting laterals and brown wedge shaped lesions on newer primocane leaves. Record percent hills infected.

 

Vertebrates

Voles

  • Fall monitoring is done to determine populations before winter when crop damage can occur.
  • Look for tunnel entrance holes about one inch in diameter, surface runways through grass, droppings and/or chewing marks on canes and roots.
  • Monitoring stations can be constructed using a protected shelter to cover a runway or tunnel entrance. Shelters can be constructed using a roofing shingles or PVC piping. Place an apple wedge as bait underneath the shelter. Check the apple bait every 24 hours for 2-3 days. Inspect the apple wedge for feeding damage. Four to eight bait stations per acre can provide an accurate assessment of vole populations. Record % of stations positive for feeding damage.
  • Treatment threshold - management is needed when 40% of the bait stations show positive feeding damage after 24 hours. Monitor again 2-3 weeks following treatment to determine efficacy.

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WSU Whatcom County Extension 1000 N. Forest St., Suite 201, Bellingham, WA 98225 (360) 778-5800 whatcom@wsu.edu