WSU Whatcom County Extension

Integrated Pest Management for Raspberries

Harvest

Biology and Monitoring

(July through mid-August)

Insects
Diseases

     • Insect Contaminants in Machine Harvested Raspberries
     • Obliquebanded Leafroller
     • Orange Tortrix Leafroller
     • Spider Mites
     • Spotted Wing Drosophila
     • Strawberry Crown Moth
     • Weevil
 

     • Botrytis Fruit and Cane Rot
     • Cane Blight
     • Phytophthora Root Rot
     • Spur Blight

 

Biology

Insects

Insect Contaminants in Machine Harvested Raspberries

Many insects are dislodged from raspberry foliage during the machine-harvesting process. These may include leafrollers, loopers, cutworms, small gnats, plant bugs and several species of weevils. Spiders are often present. Many of these insects do not directly damage the plant but their presence in harvested fruit can pose a contamination problem. The most serious contaminants are weevils and a variety of cutworms. Leafrollers, such as Orange Tortrix and Obliquebanded Leafroller, are considered a major harvest contaminant. Most of these insects are adequately controlled with an insecticide application prior to harvest.

 

Obliquebanded Leafroller (OBLR)

OBLR can be a harvest contaminate if peak flight is delayed until just prior to or after the start of harvest. Scouting for larvae and monitoring adult traps should continue if this occurs. Overuse of broad-spectrum insecticides can intensify problems by eliminating natural control agents.

 

Orange Tortrix Leafroller (OT)

Overlapping generations and successive egg hatches during harvest can complicate control strategies. Repeat application after pre-bloom may be required. Scouting for larvae and monitoring adult traps should continue through the end of harvest. Overuse of broad-spectrum insecticides can intensify problems by eliminating natural control agents.

 

Spider Mites

All stages of spider mites (eggs, immatures, and adults) are likely to be present during the harvest period. The length of time required to complete one generation depends primarily on temperature and can be as short as 10 days during warm summer months. Spider mite populations can therefore increase rapidly if weather is hot and spider mite predator populations are low. The most common mite predators in raspberries include Stethorus beetles, minute pirate bugs, and predator mites.
At this time of the year, spider mites are found on primocanes as well as floricanes. They are more commonly found on older or mid-shoot leaves rather than on the newer growth. Feeding on the underside of leaves initially causes a white speckling appearance to the upper leaf surface. High populations and extended periods of feeding can cause leaves to appear bronze in color. This bronzing is due to water loss from foliage. Excessive defoliation from heavy mite feeding during and after harvest can reduce yield up to 25% the following season.

 

Spotted Wing Drosophila

At higher temperatures (above 86˚F), fly activity, egg laying and longevity may begin to decrease. This may result in fewer generations per year, but damage may still occur. Infestation of fruit reveals small scars and indented soft spots and bruises on the fruit surface. Eggs hatch and the larvae develop and feed inside the fruit, causing the flesh to collapse around the feeding site within as few as two days. Fungal and bacterial infections and secondary pest may contribute to further fruit deterioration. Larvae are small (<1/8 inch long), cylindrical and white to cream colored. More than one larva may be found feeding within a single fruit.

 

Strawberry Crown Moth

Adults emerge in late June and July, mate, and lay eggs on dead leaves or green leaves around the base of the plant. Eggs hatch in about two weeks and the young larvae begin feeding on the outside of the crown and at the base of small roots. 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 can cause economic damage by girdling the canes causing the plants to become stunted and have poor vigor. Mature larvae are about ¾ inch long, white, with a dark brown head.

 

Weevil

Most adults have emerged from the soil by the beginning of harvest. Peak emergence is usually in late May to early June. Above ground foliar feeding does not usually cause significant damage to raspberry plants but if not controlled prior to harvest, adult weevils are a serious harvest contaminant. In addition, egg laying will occur during harvest which allows for a continuing larval infestation and subsequent adult population the following season.

 

Diseases

Botrytis Fruit and Cane Rot

This disease becomes active as the fruit matures. Symptoms include gray mold on the surface of berries and pale brown lesions on the surface of canes. Disease develops faster on overripe mature berries.

 

Cane Blight

Old infected floricanes are the primary source of inoculum which can infect primocanes wounded during harvest. External symptoms are usually not visible on primocanes during harvest. Suspect areas should be checked closely in the fall by scraping away epidermis of primocanes near wounds. In infected canes, a vertical, reddish streaking lesion within the vascular tissue can be seen at that time. This is not a commonly occurring disease in the Pacific Northwest, but can be quite serious if present.

The harvest period is a critical period for cane blight management, because catcher plates on harvest machines, if not adjusted properly, can damage primocanes and open the door for infection. Cane blight symptoms on primocanes cannot be seen until later in the fall.

 

Phytophthora Root Rot

The most common above ground symptom of Phytophthora root rot during the 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.

 

Spur Blight

Spur blight infection of new canes first appears as brown, wedge-shaped lesions usually on lower primocane leaves. The fungus progresses through the leaf and petiole and into the primocane where it causes a chestnut-colored lesion on the surface around a bud. This cane lesion is the most obvious symptom of the disease during the harvest period.

 

Monitoring

Follow general guidelines in the “Introduction” section. For each pest below, record pest numbers or symptoms on record sheet. Continue to use beating trays every two weeks or so to assist with observations made from harvesting machines.

Insects

Insect Contaminants in Machine Harvested Raspberries

  • A single clean up spray to control insects is generally all that is required to achieve effective control through the harvest period. Make sure to check pre-harvest intervals closely on any pesticides used during the harvest period.
  • Ride the harvesters to see what insect contaminants, if any, are coming across the belt. This is one of the best methods to evaluate the effectiveness of your pre-harvest clean up spray.
  • Train workers on harvesting machines to communicate presence of leafrollers, armyworms, and cutworms or other contaminants. Keep a container for the workers to deposit insect contaminants. This can be used to monitor their numbers. Inspect recently harvested flats for presence of larvae.
  • Detection of weevils on the belt indicates that either sprays were not effective or that adult weevils are continuing to emerge.  A spray should be applied to control adult weevils if they are contaminating fruit so that they are controlled before egg laying occurs. This will also help reduce the population in the following season.
  • Most other insects can be removed from the sorting belt by hand as long as they are not too numerous.  
  • Sprays may be necessary to control a variety of cutworms and leafrollers when they are too numerous to be removed from the belt; this is more common in the last weeks of harvest when OBLR, OT, and miscellaneous cutworms may be present at troublesome levels.

 

Obliquebanded Leafroller (OBLR)

  • If peak OBLR flight is delayed until just prior to or after the start of harvest, inspect hills as described in previous section to determine the percent leafroller infested hills.
  • Greater than 10% infestation may warrant control.
  • The bacterial insecticide, Bacillus thuringiensis (B.t.) is effective if timed properly. It has an advantage for use during harvest due to its short, one day PHI (pre-harvest interval).

 

Orange Tortrix Leafroller (OT)

  • Continue to inspect hills as described in previous sections to determine the percent leafroller infested hills. Greater than 10% infestation may warrant control.
  • Continue to monitor pheromone traps weekly to determine if adult trap numbers increase, indicating the onset of an additional larvae hatch. Larvae tend to appear about ten to fourteen days after peak trap catch occurs.

 

Spider Mites

  • Mite populations can often remain very low during the early summer and then increase rapidly during harvest.
  • Continue to examine leaves for mites and mite predators as well as the bronzing damage spider mite feeding can cause to leaves. Collect 10 leaflets/site and using a hand lens, count and record the number of:
    • Two Spotted Spider Mite (TSSM) adults
    • TSSM eggs
    • Yellow Mite adults
    • Predatory mites and eggs
    • Stethorus adult
    • Minute pirate bug
  • Check fields every ten days to two weeks.
  • Consider the following before applying a miticide:
    • Has the spider mite population increased since the last visit?
    • Are there lots of eggs...potential for rapid increase under hot conditions. (Mite populations can increase more rapidly in drip-irrigated fields and under dusty conditions.)
    • Are mite predators present at most sites; are they on the increase?
    • Is mite damage restricted to just part of the plant or does it appear to be spreading?
    • Is there an effective miticide available with a short PHI (one to two days)?
    • A miticide application may be necessary during harvest if you think the spider mite population is on the rise and the material has a short PHI. Control is usually better if it is timed to catch a building population rather than one that has gotten out of hand. If you apply a miticide, resample about 5 days after the application to determine how effective the spray was.

 

Spotted Wing Drosophila

  • Monitor traps once or twice per week and record number of adults found.
  • Check 20 fruit at each site for larvae and/or small puncture (oviposition scar) wounds on fruit. Record % infested fruit.
  • Check soft fruit on the cane as well as on the harvester/processing belt for the presence of larvae.

 

Strawberry Crown Moth

  • Continue monitoring pheromone traps in the field and check weekly to monitor for emergence.
  • Watch for weakened areas within the field containing brittle or collapsed canes.
  • Examine the crown and lower canes for signs of boring.

 

Diseases

Botrytis Fruit and Cane Rot

  • Examine fruit for grey mold and canes for pale brown lesions (much lighter in color than Spur Blight). Record severity of fruit and cane infection on a scale of 0-3.
  • Berries infected by Botrytis are usually not shaken off the plant by the harvester; hence you will not get an estimation of disease severity by inspecting berries as they come across the belt. Check fruiting laterals for the infected berries. If disease incidence is too high, consider applying a fungicide with a short pre-harvest interval (PHI).
  • Additional fungicide applications during harvest may be necessary in some situations.
  • Botrytis is more likely to be a problem in wet years and in fields with heavy canopies that are slow to dry out following irrigation or rainfall. Cultural practices to reduce Botrytis problems include:
    • Avoid applying excessive amounts of nitrogen.
    • Control weeds to improve air movement within the canopy.
    • Good primocane suppression.
    • Shorten intervals between picking if practical.

 

Cane Blight

  • Inspect 10 hills per scouting site and record % of fruiting canes infected.
  • Adjust catcher plates on mechanical harvesters to minimize wounding.
  • Treatment should be considered during or immediately after harvest in fields with a history of the disease and where monitoring has revealed that 1-3% of fruiting canes are infected.
  • Consider applying a fungicide directed at the base of canes in infected fields.

 

Phytophthora Root Rot

  • Above ground symptoms of this disease are most evident just prior to and during harvest. Look for reduced number of primocanes, wilted primocanes, and fruiting canes with yellow or scorched lateral shoots. These symptoms are more likely to be found in low areas where saturated soil conditions persist, which favor infection and spread of the disease.
  • Poor growth in low-lying areas may also be due to anaerobic (low oxygen) conditions which are unfavorable for normal root function. Phytophthora may not even be present, yet plants show symptoms typical of Phytophthora infection. In this situation, application of fungicides targeting Phytophthora is not appropriate.
  • Pull up some plants and examine the crown area by scraping away the epidermis, which will reveal a distinct margin between healthy (white) and disease (red) tissue, if infected with Phytophthora. A lack of fine feeder roots is also associated with Phytophthora root rot.
  • Presence of both the above ground and root/crown symptoms indicates that Phytophthora is the causal agent and that fall and possibly, spring soil-applied fungicides may be appropriate.
  • Confine treatment to those areas where scouting indicates a problem and lab results confirm presence of the pathogen.

 

Spur Blight

  • Examine primocanes for spur blight lesions, which appear as dark brown areas on the cane around the bud. Petioles may be left attached to the cane. Record severity of damage on a scale of 0-3.
  • Fungicides with a short PHI are available for use during harvest where these symptoms are seen.

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