Mite Control
Spider Mites, Two spotted spider mites (tssm), Eriophyid mites (broad/russet), etc..
Among the predatory mites commercially available to attack two-spotted spider mite, Tetranychus urticae, (TSSM), Phytoseiulus persimilis and Amblyseius fallacis are the most aggressive as long as conditions are not too hot or dry. TSSM reproduces faster at higher temperatures and low humidity, e.g., > 77° F and 40% RH. Therefore, the hotter and drier the weather, the worse a mite flare-up can get. Raising humidity by misting favors most predators over spider mites. For drier conditions especially outdoors, use Amblyseius californicus or Galendromus occidentalis. Indoors, use Mesoseiulus longipes. A. fallacis and A. californicus will eat other pest mites besides TSSM. Both are good for low-density infestations or preventive use. Make early, proactive releases of mite predators. In most systems the goal to assure control is a predator to prey ratio of 1:10. Stethorus and Feltiella (page 18) and Green Lacewing (page 5) also work on mites, especially in hot spots. The first two are more effective in longer crop cycles. Lacewing can help solve an immediate problem. One lacewing larva can eat over 11,000 mite eggs. They are often released with Occidentalis predatory mites in hot, dry field conditions. Using more than one predator and/or at least three different interventions in an integrated strategy adds diversity and stability to a biological control program.
COMBINING DIFFERENT MITE SPECIES
Releasing more than one kind of mite sometimes has advantages. Mixes of Californicus OR Persimilis with Fallacis, Occidentalis, or Longipes take advantage of each mite’s food and habitat preferences. Californicus can survive on pollen and small insects so it will persist at lower pest densities than the other predator mites. If you are torn between using two different predator mites because environmental conditions aren’t quite ideal for either, a combination may be better than guessing. Californicus is not to be used with Persimilis since it will cancel out the benefit of the more aggressive Persimilis by eating Persimilis eggs.
Soft Pesticides / Knock-Down Sprays
FURTHER INFORMATION ON SPIDER MITES AND PREDATORY MITES
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.
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.
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.
Strategy for releasing mites on trees:
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.
Release mites as soon as you can after receiving them, concentrating on hot spots. Hold most mites at 50 ºF (cold pack in a styrofoam box) for maximum one day. Do not place in a refrigerator (40 ºF) as this is too cold for many mites and will kill them. Persimilis and Longipes tend to move vertically upward, so release low on the plants. Fallacis moves laterally, and usually away from light.
For mites shipped on leaves, lay the bean leaf over a branch or tuck into foliage. You have to assess the numbers per leaf and put more where you see more pest mites and less where you see less.
Mites packed in corn grit, bran or vermiculite carrier can be divided into release stations made of post-it notes, French fry bags or sealed envelopes cut in half. Or they can be sprinkled directly onto leaves if the carrier will stick. If not, spray leaves with a little water and sprinkle grit onto wet leaves. The water will not affect the predator mites, which will walk off the carrier onto the leaves.
(LOCALIZED OUTBREAKS) (70°-85°F, 70% RH)
Phytoseiulus persimilis Two-Spotted Mite Predator(Acarina: Phytoseiidae)
Common Name: Persimilis
Aggressive and economical predatory mite for TSSM. Does best on dense, low growing plants. High reproductive rate enables Persimilis to overcome its slower reproducing host in a relatively short time. Shipped in bottles and vials with vermiculite carrier. Vials have less carrier so they are more compact for shipping in large numbers. Ideal conditions: 70°- 81° F, 70% RH. Inactive at < 54° F. Not effective in hot greenhouses or dry interior valleys. With increasing humidity, above 60%, Persimilis can tolerate higher temperatures, but is generally not effective above 86° F.
Shipped Tuesday, order by previous Wednesday.