Description of the Pest
Twospotted spider mites are web-forming mites that pierce plant cells and remove their contents. All spider mites have two body segments and four pairs of legs as adults. Twospotted spider mite adults, as the name suggests, have two large dark spots on the sides of their yellowish green bodies. These mites lay round eggs that hatch into six-legged larvae. The subsequent stages, the protonymph and deutonymph stages, are eight-legged as are the adults. Since the entire life cycle can take as little as 8 (77° to 95°F) to 28 (50° to 68°F) days, spider mites have many generations per year and can rapidly increase in number.
Twospotted mites suck cell contents from leaves, initially stippling leaves with a fine pale green mottling. As feeding continues, the stippling increases and leaves turn yellow with bronzed or brown areas; damaged leaves frequently fall. Undersides of leaves may have many cast skins of mites, and the webbing on foliage is unaesthetic. Plants may become severely stunted when large mite populations are allowed to feed and the plants may die.
Many different species of predatory mites are available for control of these mites under different conditions. Phytoseiulus persimilis is a commercially available predator of twospotted spider mite, and it has been used to control mite populations in greenhouses and field situations. It can reproduce faster than its prey, yet best results have been obtained when it is released into the crop well before the spider mite populations have built up. For more information, see BIOLOGICAL CONTROL.
Because spider mites feed on a large variety of plants, keep production areas free of weeds, which can serve as hosts to the mites. Carefully inspect plants being brought in to start a new crop to ensure that they are free of mites. Rogue or treat infested plants.
Monitoring and Treatment Decisions
Monitor the crop regularly, as indirect sampling methods (such as sticky cards) are ineffective. Observe the undersides of leaves with a 10X hand lens, and watch for changes in plant foliage that are characteristic of mite feeding.
Except as noted, the materials listed only kill active stages of mites, so more than one treatment may be necessary to break the life cycle. Follow label directions regarding reapplication times. For guidelines on when to treat, see ESTABLISHING ACTION THRESHOLDS.
Selected Materials Registered for Use on Greenhouse or Nursery Ornamentals
Read and follow the instructions on the label before using any pesticide. Before using a pesticide for the first time or on a new crop or cultivar, treat a few plants and check for phytotoxicity. Also consider pesticide resistance management and environmental impact.
|Manufacturer||REI1||Mode of action2||Comments|
|Proguard||4||—||Use product within 10 days of breaking seal. May cause phytotoxicity to tender tissue growth on plants. Do not apply to stressed plants or newly transplanted material before roots are established.|
|Gowan||24||1A||Apply in 50 gal water. Repeat as necessary up to 4 applications/season. Do not apply with oil or foliar fertilizer.|
|Gowan||12||10A||No chemigation. Ovicidal/larvicidal action. Use only 1 time per crop or once a year.|
|Chemtura||12||un||Do not use in successive applications; apply at least two alternative products between treatments of bifenazate. Primarily effective against motile stages but has some ovicidal activity.|
|Novartis||12||6||Label permits low-volume application.|
hydrophobic extract of neem oil#
|OHP||4||un||Do not spray plants under stress. Target pest must be completely covered with spray. Check label for list of plants that can be treated. May cause injury to flowers.|
(JMS Stylet Oil)
Use as above for neem oil. Also, do not use with sulfur fungicides; check label for tank mix restrictions.
|SePRO||12||21A||Do not apply more than 10 gal spray/1000 sq ft/application. Do not exceed 48 oz/crop cycle or growing season, whichever is longer.|
|12||3||Check label. A fogger for greenhouse use only.|
|12||3||Label permits low-volume application.|
(Tame 2.4EC Spray)
|Valent||24||3||Label permits low-volume application.|
|Wellmark||12||3||Label permits low-volume application. Also labeled as a cutting dip at 5 fl oz/100 gal.|
|BASF||12||21A||Use at least 2 different chemicals between applications of Sanmite. Do not use fertilizers containing boron. Do not exceed 10.67 oz/acre/application.|
|OHP||12||13||Greenhouse use only. Do not exceed 3 applications/growing cycle.|
|12||—||Must contact mite, so thorough coverage is important. Repeat weekly as needed up to 3 times. Test for phytotoxicity. Do not spray new transplants or newly rooted cuttings. Do not add adjuvants.|
|4||5||Miticidal activity of this material is due mainly to the surfactants and other inert ingredients. This material is not recommended for use against mites unless control is also needed for other pests (caterpillars, leafminers, thrips) against which the active ingredient in this product is effective. Do not apply more than 10 times in a 12-month period. Compatible with most beneficials but highly toxic to bees and hymenopteran parasites. Direct contact can cause significant mortality to Phytoseiulus persimilis.|
|1||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing.|
|2||Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee).|
|3||Note that single doses of soaps or oils can be used at anytime in a pesticide rotation scheme without negatively impacting resistance management programs.|
|4||Check with certifier to determine which products are organically acceptable.|
|*||Restricted use pesticide. Permit require for purchase or use.|
|#||Acceptable for use on organically grown ornamentals.|