|
|
|
Predatory
Mites PO Box 1555, Ventura, CA 93002 800-248-2847 * 805-643-5407 * fax
805-643-6267 questions bugnet@rinconvitova.com orders orderdesk@rinconvitova.com www.rinconvitova.com |
|
|
MANAGEMENT OF
PEST MITES BY USE OF PREDATORY MITES
The
use of predatory mites is an economical biological control for two-spotted
spider mites, a complex of harmful spider mite species, which feed on the
undersides of plant leaves. Predatory mites are more effective than chemical
control because the pest mites do not build up resistance to predatory mites
and growers can reduce or eliminate the use of chemical pesticides. Spider
mites are often a ‘secondary’ pest outbreak after spraying – break the cycle by
using predatory mites! Crop yield and
quality also improves when growers stop using broad spectrum chemical sprays.
Predatory mites do not bother plants, people or animals.
Because
predatory mites do not give immediate control, they need to be released at the
first signs of a pest mite problem. If there are no pest mites for food,
predatory mites will not survive and reproduce. Some species (N. californicus
and A. fallacis) persist at low pest densities. In these conditions, it is advantageous to use the ‘bean leaf’
product that carries a food source for the mites while they establish in the
crop. A ratio of 1 predator per 10 prey
mites is often adequate to suppress a pest population. It helps to tolerate a
small population of two-spotted spider mites in hot spots to maintain the
predators as long as possible during the season and be ready to recolonize each
year. High density hot spots can be knocked down with “selective” miticides
before and after the release of predators. Other insects are also important
predators, including six-spotted thrips, Stethorus
punctillum, the cecidomyid Feltiella
acarisuga, and general predators, such as minute pirate bugs, big-eyed bugs
and lacewings.
PREDATOR MITE SELECTION CHART
Beneficial |
Host |
Host Plants |
Temp range |
Humidity |
Notes |
P. persimilis |
Two-spotted spider mite (TSSM) only |
Strawberries, greenhouse plants |
59-86°F |
at least 60%RH, 70%RH ideal |
consumes 5-20 pest per day, reproduces faster than TSSM below 82◦F |
A. fallacis |
TSSM, European red mite, spruce mite, Pacific mite, bamboo mite, others |
Strawberries, peppers, raspberries, mint, greenhouse plants |
48-85°F |
at least 50%RH |
can survive at low pest densities |
G. occidentalis |
Spider mites, eriophyid mites, not Red mite eggs |
Fruit trees, grapes, corn, cotton |
60-120°F |
tolerates low humidity, not below 30%RH |
will diapause in cool weather and day length <11hrs |
N. californicus
|
Spider mites, Persea mite, Avocado brown mite, Tumid mite, broad mite, cyclamen, Willamete mite, others |
Roses, vegetables, strawberries, avocados, corn |
55-105°F |
prefers humid, but tolerates low to 40%RH |
versatile and fast, persists at low pest densities, but will eat other beneficial mite eggs |
Persea mite |
Avocado trees |
55-90°F |
best over 40% |
Release 100 per avocado tree (5k/acre) when Persea mites on >25% of leaves |
|
M. longipes |
Spider mites on greenhouse plants |
Greenhouse plants |
70-100°F |
at least 40%RH at 70◦F |
great in greenhouses, hotter temps than Persimilis, not as successful outdoors |
DESCRIPTION OF PREDATORY MITES
SPECIES
Predatory
mites are shipped in the adult stage in plastic bottles with a natural medium,
such as corn grit or vermiculite, or in plastic trays with bean leaves. They
are shipped at cool temperatures and should be released on infested plants
immediately on arrival. The predatory mites have pear-shaped bodies and the
front legs are longer than those of pest mites. They are distinguished from the
two-spotted spider mite by the lack of spots on either side. They tend to move
more quickly when disturbed or exposed to bright light.
METHODS OF APPLICATION
Predatory
mites will have the best chance of success if not more than 10 percent of
leaves have pest mites on them. If there is more than an average of one pest
mite per leaf, it is best to reduce the population with an insecticide soap or
selective miticide. Broad-spectrum pesticides must be avoided for two to three
weeks before the introduction. Distribute predatory mites when cool and avoid
irrigation or hosing down foliage immediately afterward if the mites are in a
natural medium. Water or sugar water sources and higher humidity improve their
performance. Under good conditions pest mite control is possible in four to six
weeks.
Recommended
quantities depend on many factors, including level of infestation carried over
form the previous season, ant control and whether selective miticides will be
used to treat hot spots. When leafhoppers are also a problem, a combined
program with green lacewings will aid mite control.
INTERIOR PLANTINGS
Recommended
quantities for early releases in greenhouses and interiorscapes range form 1
predator per square yard for potted plants to 5 predators per square yard for
tomatoes and peppers to 13 predators per square yard for cucumbers. Control in
heavily infested and very leafy plants and trees may require as many as 500 to
2,000 predators per tree or planter, in weekly or biweekly releases.
STRAWBERRIES AND LOW-GROWING
FIELD CROPS
Predators
are best applied at or before the two percent level of infestation at 10 -
20,000/acre per week to a total of 30 - 60,000/acre per week over a three week
period. Growers usually start with P.
persimilis and introduce G.
occidentalis gradually, so that the more heat tolerant species is already
reproducing in the field when temperatures reach 85º F or higher.
GRAPES
Applications
in grapes generally start in April or early May until the end of June. A
minimum of 1,000 per acre is applied in each of five or six weekly or biweekly
applications for a total of 5 - 6,000 predatory mites per acre for the season.
Heavy infestations could require applications of up to 5,000 predators per
acre. It is possible to start with N.
californicus when the weather is cooler and introduce G. occidentalis gradually in combination, so that when temperatures
reach 85 F or more, G. occidentalis
is already reproducing in the field and can continue to offer control at the
higher temperatures. It is most effective to release predatory mites in the
chronic hot spots which are often associated with ant infestations and other
beneficial insect interference factors, such as, pesticide drift, excessive
road dust and conditions associated with the edge of the field.
ALMONDS AND WALNUTS
There
is some success with predatory mites wintering over, but applications should
resume when the predator/pest ratio is less than 1:10. Several weekly or
biweekly applications are made using a minimum of 1000 per acre. Both lacewing
eggs and predatory mites can be blown into each tree form the top of a truck
using a leaf blower adapted with a PVC pipe applicator and mites in a corn grit
medium.
Releasing predatory mites in trees using paper bags or envelopes cut in half.
The predators are shipped in vials of 1,000, packed in a medium of ground-up corn cob. The vials should be gently turned over for about a minute to be sure that the predators are evenly distributed throughout the medium. The mixture is then poured into the bags.) The bags are then fitted around the ends of the branches or clusters of leaves and stapled in place so that the predatory mites can easily climb onto the tree and get to work.
|
|
HELPFUL HINTS
• Introduce
predatory mites early in hot spots. Follow with whole field applications.
• Be
proactive, not reactive.
• Pest
mites can be tolerated below the 2% level.
• Selective
miticides can be used on hot spots of heavy pest mite infestation.
• Distribute
the predators when temperatures are cool.
• Humidity
favors the predator.
• Monitor
to maintain at least 1 predator to 10 pests.
• Release
mites on bean leaves by onto plant, staple or paper clip to another leaf if
necessary.