How to Manage Pests

UC Pest Management Guidelines

Caneberries

Redberry Mite

Scientific Name: Acalitus essigi

(Reviewed 12/09, updated 1/10, corrected 1/10)

In this Guideline:


Description of the Pest

The redberry mite is a perennial pest of both cultivated and wild blackberries but is not an economic pest of raspberries. These mites belong to a group of microscopic mites known as eriophyid mites. This eriophyid mite has two pairs of legs; it can be seen with a 10 to 20X hand lens but is best seen with a dissecting microscope. The adult is wormlike and translucent white.

Redberry mites overwinter in bud scales or deep in buds. As shoot growth develops in spring, the mites move onto the developing shoots. As flower buds appear, the mites work their way into the unfolding buds, into the flowers, and down among the developing drupelets of the berries, especially near the bases and around the core of the fruit.

Damage

Fruit infested with redberry mites do not develop normally colored drupelets. Affected drupelets usually remain hard and have a green or bright red color. The fruit is unmarketable. Fruit partially affected may have some drupelets remain red and hard with the remaining drupelets developing proper ripening. If not controlled, redberry mite can spread from isolated infestations to sizable portions of a planting in the next season. Very high populations can result in significant crop loss. The pest is most damaging to late-maturing blackberry cultivars.

Management

The best time to control redberry mite depends upon variety grown and miticide that will be used. Note that oil and sulfur products should never be tank-mixed because of the risk of phytotoxicity. If oils are used after or before sulfur products, be sure to observe all recommended label precautions.

Lime Sulfur

Timing of lime sulfur applications depends upon variety grown and redberry mite severity. For blackberry varieties that retain a leaf canopy through the winter, begin lime sulfur applications at bud break and continue at 3-week intervals up to 12 days before the start of harvest. For blackberry varieties that naturally defoliate over the winter, apply lime sulfur before buds break dormancy and then not again until canes have a full leaf canopy and first bloom appears.

Horticultural Oils

Horticultural oils, such as Golden Pest Spray Oil, when used at the rate of 1.2 to 2% volume to volume, applied after green fruit or first pink fruit stage in four consecutive applications spaced 2 or 3 weeks apart give significant control of redberry mite, while causing less harm to fruit yield than sulfur sprays.

Complete plant canopy coverage is important when using horticultural oils, so the minimum amount of water carrier should be 50 gallons per acre.

The potential for phytotoxicity of oil product and/or oil product mixes has not been fully evaluated for all blackberry varieties in all growing areas. Small plot tests are prudent to determine safety margins of particular blackberry varieties for specific environmental conditions in different growing areas.

Common name Amount per acre R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
 
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
DELAYED DORMANT
 
A. LIME SULFUR# 8 gal/100 gal water 48 NA
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M2)
  COMMENTS: Apply 200 gal water/acre.
 
FIRST BLOOM
 
A. LIME SULFUR# 2.5 gal/100 gal water 48 0
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M2)
  COMMENTS: Apply 200 gal water/acre.
 
B. MICRONIZED SULFUR#
  (Microthiol Disperss, Sulfur 90W) 6–15 lb 24 0
  MODE OF ACTION: Unknown. An inorganic insecticide.
  COMMENTS: Sulfur is phytotoxic to some varieties, especially when temperatures exceed 90°F.
 
GREEN FRUIT OR FIRST PINK FRUIT
 
A. HORTICULTURAL OILS# 1.2-2 gal/50–200 gal water See label 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: The potential for phytotoxicity of oil products and oil product mixes for all blackberry varieties in all areas has not been fully evaluated. Growers are encouraged to test product and product mixes for phytotoxicity before field application to determine safety margins. Check with your certifier for organically acceptable products.
 
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
# Acceptable for use on organically grown produce.
NA Not applicable

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Caneberries
UC ANR Publication 3437

Insects and Mites

  • M. P. Bolda, UC Cooperative Extension, Santa Cruz County
Acknowledgment for contributions to Insects and Mites:
  • E. Show, Driscoll Strawberry Associates Inc., Watsonville, CA
  • E. J. Perry, UC Cooperative Extension, Stanislaus County

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