Thrips Cocktail, 2003Olympic Horticultural Products The most important aspect of western flower thrips (WFT) management is to have a scouting and monitoring program. By using such a program you will be able to keep track of WFT population peaks and valleys. This will help you decide not only how often to apply pesticides but which pesticide or tank mix to use. Some of the pesticides and tank mixes are best used when WFT numbers are low. Others can be used in a so-called "rescue" program. A monitoring program should include sticky traps, indicator plants and plant inspections. The pesticides and pesticide tank mixes listed below have been divided into two categories: I. Those that can be used to reduce a well-established western flower thrips population, or on crops that are especially susceptible to impatiens necrotic spot virus (INSV) or tomato spotted wilt virus (TSWV); and II. Those that are not so-called "rescue" pesticides and which are best used when thrips numbers are low (Determined by your scouting and monitoring program), to help prevent populations from increasing, or on crops where virus infections do not occur. The pesticides and pesticide tank mixes are grouped according to their mode of action All products except Orthene and Mesurol have different modes of action. The mode of action group(s) is listed for each pesticide and pesticide tank mix. This listing is from the new Olympic Chemical Class Chart, and is based on information from the U.S. Environmental Protection Agency. Except where labels prohibit sequential applications (e.g. Pedestal), make at least two sequential applications of each pesticide or tank mix. The application interval will vary with temperatures. Use your own judgment based on greenhouse environment, crop, and your scouting and monitoring program, and adjust the application interval accordingly. Low volume applications for WFT control can be very effective, when labels permit such applications. I. Pesticides and pesticide tank mixes that can be used to reduce a well-established western flower thrips population. A. Mode of action group 1 Orthene 97 TT&O (8 oz/100 gallons). Orthene, an organophosphate insecticide, is labeled on only a relatively few crops, but has been effective against western flower thrips. Rose and orchid growers should use Orthene in their thrips management programs. Mesurol 75WP (8-16 oz/100 gallons). Mesurol is a carbamate insecticide that has been effective against western flower thrips. Do not apply carbamate insecticides following organophosphate insecticide applications, because the two chemical classes have similar modes of activity. B. Mode of action groups 6 & 18 Avid (8 oz/100 gallons). Avid, a glycoside pesticide, has been effective against western flower thrips. A tank mix with Azatin XL (12 to 16 oz/100 gallons) may improve control. C. Mode of action groups 3 & 18 Decathlon (1.9 oz/100 gallons) + Azatin XL (12 to 16 oz/100 gallons). This combination of an insect growth regulator (Azatin)and pyrethroid (Decathlon) has been effective against a number of insect pests, including thrips. D. Mode of action group 5 Conserve SC (6 oz/100 gallons). Conserve is a spinosyn pesticide has been very effective (probably overused as well) against western flower thrips. Use it late in the crop to kill thrips in flowers. Activity is very rapid, but residual life is short. Do not depend only on Conserve. Use other products in the rotation. II. Pesticides and pesticide tank mixes that can be used when western flower thrips populations are low A. Mode of action groups Biopesticides & 18 BotaniGard or Naturalis-T&O (label rates) + Azatin XL (12 to 16 oz/100 gallons). Botanigard and Naturalis are classified as biopesticides, and contain strains of a naturally-occurring fungus (Beauveria bassiana). Make at least three applications, five to seven days apart. Use when thrips numbers are low. These products will not control high thrips populations. A tank mix with Azatin XL will significantly increase the activity of the B. bassiana. B. Mode of action group 15 Pedestal (6-8 oz/100 gallons). Pedestal is a benzoylurea insect growth regulator that has been recently registered. As an insect growth regulator it is effective only against larval stages. The addition of a spray adjuvant is suggested to improve coverage. Pedestal has a different mode of action than Preclude or Azatin. Label directions are to make only one application, then at least two applications of products with different modes of action before another Pedestal application. Do not make two applications within 30 days. C. Mode of action group 7 Preclude Total Release Aerosol (The number of cans to use depends on can size) is classified as a carbamate insecticide but it also is an insect growth regulator. As such, it will not directly affect adult thrips, only the immature (larval) stages. Repeat after seven days. Some growers apply Preclude regularly (e.g. every week or two) along with other products. D. Mode of action group 4 Marathon II (1.7 oz/100 gallons).Marathon II is a chloronicotinyl insecticide in a liquid formulation. For best results against WFT it should be applied as a spray. It is most effective against aphids and whiteflies, but will provide some control of thrips feeding on foliage. The addition of a spray adjuvant is suggested to improve coverage. E. Mode of action groups oils and soaps Spray Oils such as Triact 70 and Ultra-fine Oil, or Insecticidal Soaps will kill thrips hit directly by sprays, and may repel thrips (and other insects) for a time after the spray has dried. These treatments will be most effective against thrips feeding on foliage. Summary: As with controlling any other pest problem, results will be better if thrips numbers are low to begin with. Help your pesticide program out by promptly removing unsold plants from the greenhouse after harvest. Keep weeds to a minimum inside and around the outside of the greenhouse. Try screening vents and doors to help exclude thrips. When crops are produced on benches, releases of predatory mites in the Genus Hypoaspis have helped reduce thrips numbers. The mites feed on thrips transformation stages that drop off plants onto the soil. Your goal should be to prevent thrips numbers from building to damaging levels rather than trying to control a heavy infestation. |
