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How to Manage Pests
UC Pest Management Guidelines
Caneberries
Twospotted Spider Mite
Scientific Name: Tetranychus urticae
(Reviewed 5/08,
updated 5/08)
In this Guideline:
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Twospotted spider mites are an occasional pest of caneberries. They infest
the undersides of caneberry leaves, where they may form colonies and produce
light webbing when abundant. Twospotted spider mites are very small (about
0.017 of an inch in length) and are barely visible to the naked eye. Nymphs, adult
males, and reproductive females are green to a yellowish hue in color.
Reproductively dormant females are bright
orange and should not be confused with the predatory mite, Phytoseiulus persimilis,
commonly found in mite colonies. Under a
hand lens, one can see two dark blotches on either side of the adult twospotted
spider mite's body and two red eyespots on the head.
In areas where temperatures are cold in winter, twospotted spider
mites overwinter as dormant adult females at the base of the caneberries or
weeds in and around the field. With the onset of warm weather, these mites
migrate to the foliage of the plant and begin to lay eggs. In mild winter
coastal-growing regions of California, it is unusual for a large percentage of
mites to become dormant; instead they continue to grow and lay eggs, although
at a slower pace during the winter months than in summer. The twospotted spider
mite undergoes one larval and two nymphal stages before becoming an adult. The
life cycle, under ideal conditions of hot, dry weather, can take place in 10
days.
Spider mites feed by sucking juices from the plant and cause a gray
stippling on the leaf surface. As the population grows and feeding progresses,
leaves turn yellowish brown before drying up and falling off. Feeding by
twospotted spider mites on fruiting floricanes reduces plant vigor and fruit
yield and size. Mite feeding can also weaken primocanes, predisposing them to
winter injury in areas of cold winters and reducing yield the following season.
The key to successful management of twospotted spider mites is to
monitor populations and to initiate control measures in a timely manner. Once
populations are large, much damage has been done, and the mite populations are
difficult to control.
Biological Control
The most effective biological control agent of twospotted mite is
the predatory mite Phytoseiulus
persimilis, which is an introduced species. Phytoseiulus does best in temperatures of 60o to 80o
F and will not do well above 100oF. This predatory mite has
established itself in some locations and provides some natural suppression in
these areas. This mite may also be purchased and released in fields for
additional control.
Cultural Control
Normal pruning of primocanes and removal of dead floricanes
in caneberries can reduce the buildup of twospotted spider mite. Varieties with
heavily pubescent leaves can make establishment difficult for twospotted spider
mites, and may be useful for those situations where twospotted mites are a
significant problem. Controlling dust by watering or oiling surrounding roads
is an important factor in limiting twospotted spider mite populations.
Organically Acceptable Methods
Cultural and biological controls including the release of
predatory mites, and narrow range oil sprays, such as Organic JMS Stylet oil, are
organically acceptable methods.
Monitoring
and Treatment Decisions
No precise treatment thresholds have been established for
twospotted mites in caneberries. Monitor to keep track of increasing pest mite
populations as well as predatory mite populations. A ratio of 1 predator to 10
twospotted mites is considered favorable for biological control. When using
chemical controls, it is important to know that coverage is very important. In
many cases, especially with the spray oils, mites that escape contact with the
control material will survive.
| Common name |
Amount/Acre |
R.E.I.+ |
P.H.I.+ |
| (trade name) |
|
(hours) |
(days) |
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| When choosing a pesticide, consider information relating
to impact on natural enemies and
honey bees as
well as the environmental impact. Not all registered pesticides are listed. Always read label of product being used.
|
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| A. |
PHYTOSEIULUS PERSIMILIS# |
10,000-20,000–conventional fields |
N.A. |
N.A. |
| |
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40,000+ –organic fields |
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COMMENTS: Release mites early in the season before foliage on the canes begins to close the space between canes. |
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| B. |
BIFENAZATE |
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(Acramite) 50 WS |
0.75–1 lb |
12 |
365 |
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MODE OF ACTION GROUP NUMBER1: 25 |
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COMMENTS: Use permited on crops that will not bear for 1 year
after application. Restricted
entry interval: 12 hours. Use minimum of 50 gal water/acre. |
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| C. |
HORTICULTURAL OIL# |
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(Organic JMS Stylet Oil) |
4–6 quarts |
4 |
0 |
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MODE OF ACTION: Contact including smothering and barrier effects. |
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COMMENTS: Amount is for 100 gal/acre; may use up to 150
gal/acre water carrier. Spray with ground equipment for optimum coverage of leaf surfaces. Heed label warnings about compatibility with other materials. |
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| D. |
HEXYTHIAZOX |
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(Savey) 50 WP |
4–6 oz |
12 |
3 |
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MODE OF ACTION GROUP NUMBER1: 10B |
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COMMENTS: Do not make more than one application/year. |
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| E. |
NEEM OIL# |
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(Trilogy) |
1–2 gal/100 gal water |
4 |
0 |
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MODE OF ACTION: Unknown. A botanical insecticide. |
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COMMENTS: Apply with sufficient water carrier to provide
complete coverage. Most effective when applied before mites and eggs are
present in large numbers. Repeat applications on 7- to 21-day intervals until mite pest pressure is over. |
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| F. |
CINNAMALDEHYDE |
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(Cinnacure) |
1–2 gal |
4 |
0 |
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MODE OF ACTION: A botanical miticide. |
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COMMENTS: Apply in 100–200 gal water/acre, apply every 10 days and check for phytotoxicity. |
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| G. |
COTTONSEED/CLOVE/GARLIC OILS# |
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(GC-Mite) |
1 gal/100 gal water |
0 |
0 |
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COMMENTS: Good
coverage is essential for control; the use of a spreader/sticker may improve
contact and efficacy of treatment. Apply no more than once in a 7 day period. |
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UC IPM Pest Management Guidelines: Caneberries
UC ANR Publication 3437
Insects and Mites
E. J. Perry, UC Cooperative Extension, Stanislaus County
M. P. Bolda, UC Cooperative Extension, Santa Cruz County
L. J. Bettiga, UC Cooperative Extension, Monterey County
Acknowledgment for contributions to the insect and mite section:
R. M. Tyler, UC Cooperative Extension, Santa Cruz County
E. Show, Driscoll Strawberry Associates Inc., Watsonville, CA
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