Pre-Harvest
Biology and Monitoring
Insects |
Diseases |
• Black Vine Weevil • Dryberry Mite • Orange Tortrix Leafroller • Raspberry Crown Borer • Spotted Wing Drosophila • Strawberry Crown Moth |
• Blackberry Rust * • Fruit Rot Botrytis * • Dry Cell Syndrome ** |
*More commonly found on ‘Evergreen’ cultivar.
**More commonly found on ‘Marion’, ‘Kotata’, and ‘Boysenberry’ cultivars.
Biology
Insects
Black Vine Weevil
A variety of caterpillars which feed on foliage can be present during mid-summer. Their feeding does not usually cause significant damage to plants, but they can be serious harvest contaminants. Most of these are nocturnal and they are very difficult to detect within a thick raspberry canopy. Often, growers are not aware of their presence until harvesting begins.
Dryberry Mite
Most OBLR are now in the late larval or pupal stages, preparing for their metamorphosis into adult moths which start flying in June. OBLR moth flight doesn't usually start until late May, with peak catch occurring in late June and early July. The larval stage of this insect is the dominant stage found during April and May.
Orange Tortrix Leafroller (OT)
Adults begin emerging late April to May and lay eggs in flat masses on canes and on the lower surface of leaves. This next generation will potentially coincide with harvest and therefore contaminate fruit. Due to overlapping generations and successive egg hatches it is common to find eggs, larvae, pupae, and adults. Thus, it is important to continue monitoring pheromone traps to determine when peak flight occurs.
Raspberry Crown Borer
Adult, egg and larval stages of this insect may all be present during this period, particularly if beetles were present and were not treated prior to bloom. Adult beetles feed on the flower parts and young larvae feed on the receptacle of developing fruits. Larvae can contaminate harvested fruit, but are very difficult to control as they feed within the berries. Control at this time is complicated due to presence of honeybees and multiple stages of the insect.
Spotted Wing Drosophila
SWD is a “vinegar fly” but unlike other vinegar flies, which attack rotting fruit, this fly damages ripening and decaying fruit. Although weather dependent, the flies can be active beginning in April. There may be as many as 10 life cycles in a season with a single life cycle lasting eight to fourteen days. Females typically will insert their ovipositor into the fruit; lay one to three eggs per fruit, 7–16 eggs per day, and more than 300 eggs in their lifetime. Pupation can take place both inside and outside of fruit. The fly thrives at cooler temperatures (68˚F), while decreasing in activity, egg laying and longevity at higher temperatures (above 86˚F). Adults are small flies (2-3 mm) with red eyes and a pale brown thorax and abdomen with black stripes on the abdomen. The most distinguishable trait of the adult is that the males have a black spot towards the tip of each wing.
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. Adults are clear winged moths that resemble yellow jackets, with a wingspan of about ¾ inch. The forewings are nearly opaque with the edges dark bronze to almost black. The hindwings are transparent with dark veins and dark fringe. The abdomen is black, and banded with yellow on the second, fifth, and sixth segments.
Diseases
Blackberry Rust
Initial infection of fruit begins during early bloom when spores are dispersed by wind and splashing water to infect developing flower parts. These early infections remain inactive (latent) until fruit develops and conditions are favorable for the fungus to further infect the fruit, causing gray mold on infected berries. Mold releases spores which cause additional fruit and cane infections.
Fruit Rot Botrytis
Primocanes are commonly affected by this fungal disease which overwinters on canes infected the year before. Spores released from lesions on these canes can infect floricane and primocane foliage, usually appearing as a brown, wedge-shaped lesion. This symptom may be seen at this time of the season. The fungus then moves through the leaf and petiole and is most apparent as a purplish/brown lesion around the bud on the lower portion of primocanes. This symptom on primocanes may not be seen until mid-harvest.
Dry Cell Syndrome
Leaf infections in spring and early summer appear as yellowish spots on the upper leaf surface. Initially these spots are very small, but as the disease develops, additional spores (aecia) are produced in a ring around the initial infection. By summer, another yellow spore stage (uredinia) appears on the lower leaf surface as the disease cycle continues.
Monitoring
Follow general guidelines in the “Introduction” section. For each pest below, record pest numbers or symptoms on record sheet.
Insects
Black Vine Weevil
- Adult weevils can be detected by placing a beating tray under the foliage and shaking the plant gently. A sheet can be used if a beating tray is not available by placing it on the ground and shaking the canopy above.
- Take 10 beating tray samples per site and record the number of weevils found for each inspection.
- Treatment Threshold - Treatment Threshold - Typically 1-2 weevils/ 10 tray samples indicates a pre-harvest spray. Harvest contaminant thresholds will vary according to end product usage and processor. Scout field soon after treatment to verify effectiveness.
Dryberry Mite
- Due to the sporadic and infrequent occurrence of economic damage by dryberry mites, consider field and cultivar history problems to determine if it is economic to monitor for this pest.
- Watch for affected drupelets that become red, dry and die. Symptoms are similar to sun scalded damage. The entire berry may be affected or only individual drupelets. Search within the fruit or at the base of drupelets where they are feeding. Record the percentage of infested hills.
- Examine the underside of leaves showing signs of mite feeding for adults and/or eggs.
- These mites are microscopic; use a 20X hand lens or a dissecting scope to see them.
Orange Tortrix Leafroller (OT)
- Monitor pheromone traps regularly to determine peak flight in order to predict the onset of a second generation which may be a harvest contaminant. Remove, count and record the number of OT moths.
- Select 20 hills and examine shoot tips for presence of caterpillars.
- Examine a maximum of 5 shoot tips/hill to determine if the hill is infested. Once an infested shoot tip is found, do not examine any more shoot tips at that hill, and record the hill as infested. If you examine five shoot tips without finding any caterpillars, record the hill as clean.
- Record the percentage of leafroller-infested hills for each site you sample.
- Treatment Threshold - Chemical treatment may be necessary if 10% or more hills are infested, although check with buyer for their recommended threshold.
- Effective treatment relies heavily on timing applications to newly hatched, small larvae and good coverage.
Raspberry Crown Borer
- Monitoring for this pest is especially difficult this time of the year because both first and second year larvae are hidden within the roots or crown of the plant.
- Scout each site for wilting or dying canes and inspect plant for signs of boring (holes with sawdust-like frass). Feeding may also cause swelling or galls to form at or below the soil.
- Remove collapsed and dead canes from the soil and inspect crown and root structure for signs of larvae feeding.
- Record percent infested hills.
- Treatment Threshold - If more than 5% of the plants have damage, a fall chemical controls is recommended.
Spotted Wing Drosophila
- As soon as fruit begins to ripen place traps in field.
- Using a clear 16oz cup, drill or punch numerous 3/16” to 3/8” holes around the cup for fly entry. Leave a 3-inch space on one side of the container for pouring out vinegar. Add about an inch of apple cider vinegar and place a lid on top. Hang trap from the top wire of the trellis on the cool shady side of the row. Trap should be clear from canopy/fruit with holes exposed so SWD can easily fly in.
- Monitor traps twice per week and record number of adults found. Also monitor for small puncture (oviposition scar) wounds on fruit and soft fruit. Adults are attracted to ripe or ripening fruit.
- Record the number of adults found per trap and the percentage of contaminated fruit.
Strawberry Crown Moth
- Watch for weakened areas in the field containing brittle or collapsed canes.
- Examine the crown and lower canes for signs of boring and record percent infested hills.
- Place pheromone traps in the field by early June and check weekly to monitor for emergence. Record number of adults trapped.
- Hang one to two traps in the field (depending on field size) on the lower wire of the trellis, as SCM are low fliers.
Diseases
Blackberry Rust
- Conduct a visual search at each site for symptoms associated with blackberry rust and record level of damage on a scale of 0 to 3.
- Scout field regularly for new infections occurring as purplish spots on the upper leaf surface, as well as their corresponding yellowish-orange pustules on the lower leaf surface.
Fruit Rot Botrytis
- During wet conditions and/or in fields containing heavy foliage, inspect bloom for disease development and record a level of damage on a scale of 0 to 3.
- Infected flowers turn brown and shrivel when dry conditions exist. Under moist conditions, grey tufts of fungus can be seen on blighted blossoms.
Dry Cell Syndrome
- Examine hills for dry, hard and shriveled berries and record a level of damage on a scale of 0 to 3.
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