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Thrips Cocktail© 2007
Richard K. Lindquist & Jeff Dobbs

The most important aspect of thrips management is to have a scouting and monitoring program. By using such a program you will be able to keep track of population trends. 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 thrips numbers are low, are found only on leaves and not in flowers. 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.

I. Pesticides and pesticide tank mixes that can be used to reduce an 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 greenhouse ornamental crops, but has been effective against western flower thrips.

Mesurol 75WP (8-16 oz/100 gallons). Mesurol is a carbamate insecticide that has been effective against western flower thrips.

Mode of action groups 1 & 3

B. Tame/Orthene TR (Use amount depends on canister size and area to be treated). This aerosol “tank mix in a can” combines an organophosphate and a pyrethroid insecticide. The combination and application method should be useful for controlling thrips in flowers.

C. Mode of action groups 6 & 18

Avid (8 fl oz/100 gallons). Avid, a glycoside pesticide, has been effective against western flower thrips. A tank mix with Azatin XL (12 to 16 fl oz/100 gallons) should improve control. Azatin is a biopesticide insect growth regulator.

D. Mode of action groups 3 & 18

Decathlon (1.9 oz/100 gallons) + Azatin XL (12 to 16 fl oz/100 gallons) tank mixes have been effective against thrips.

E. Mode of action group 5

Conserve SC (6 – 22 fl oz/100 gallons). Conserve is a spinosyn pesticide that has been very effective against western flower thrips. It can be used on mature crops to kill thrips in flowers.

F. Mode of action group 5&6

Conserve SC (6 – 22 fl oz/100 gallons) + Avid (8 fl oz/100 gallons). This tank mix combination has been effective in research trials.

G. Mode of action group 13

Pylon (5-10 fl. oz/100 gallons). Pylon is a pyrrole miticide/insecticide that has provided excellent thrips control.

II. Pesticides and pesticide tank mixes that can be used when western flower thrips populations are low and/or virus disease is not a factor.

A. Mode of action groups Biopesticides & 18

Naturalis L (30-100 fl oz/100 gallons) or BotaniGard 22WP (1-2 lb/100 gallons), Botanigard ES (1-2 qts/100 gallons) + Azatin XL (12 to 16 fl oz/100 gallons). Naturalis  and Botanigard are classified as biopesticides, and contain strains of a naturally-occurring fungus (Beauveria bassiana). A tank mix with Azatin XL will significantly increase the activity of the B. bassiana.

B. Mode of action group 4A

Marathon II (1.7 fl oz/100 gallons) or Marathon 60 WP (1 20 gram packet/100 gallons). Marathon is a neonicotinoid insecticide. Activity against thrips is listed as suppression. The addition of a spray adjuvant is suggested to improve coverage. Tank mixing with a pyrethroid insecticide (mode of action 3) may improve control.

Safari 20SG (4-8 oz/100 gallons). Safari is a neonicotinoid insecticide. Activity against thrips is listed as suppression. The addition of a spray adjuvant is suggested to improve coverage on hard to wet foliage.

Tristar (3-6 packs/100 gallons). Tristar is a neonicotinoid insecticide It is applied as a spray. The label suggests that adding a surfactant to the spray mix will improve control.

C. Mode of Action group 4

Nicotine (1 can/20,000 sq. ft.). Nicotine is a botanical insecticide that is applied as a smoke fumigator. Nicotine is effective against thrips and aphids.

D. Mode of action group 7

Preclude Total Release Aerosol (The number of cans to use depends on can size and area to be treated) is classified as a carbamate insect growth regulator.

Enstar II (5-10 fl oz/100 gallons) is an insect growth regulator now labeled for thrips control. \

E. Mode of action group 15

Pedestal (6-8 fl oz/100 gallons). Pedestal is a benzoylurea insect growth regulator. The addition of a spray adjuvant is suggested to improve coverage.

F. Mode of action groups oils and soaps

Spray Oils such as Triact 70 and Ultra-fine Oil, or Insecticidal Soaps (0.5 – 1.0 gallons/100 gallons) will kill thrips hit directly by sprays, and may repel thrips (and other insects) for a time after the spray has dried.

III. Some suggested rotation programs for western flower thrips control

Here are some examples of rotation programs for thrips control. The application intervals can be adjusted for temperature and insect pressure. These are just examples. Each rotation program will need to be adjusted according to crop, thrips pressure and other insects, mites or plant pathogens. Feel free to mix and match, add your favorites, etc.

1. Conserve, two applications 7 days apart; Pylon, two applications 10-14 days apart; Avid + Azatin, two applications 7 days apart; Tame/Orthene aerosol, two applications 5-7 days apart; Decathlon + Azatin, three applications 5-7 days apart; Mesurol (or Orthene on tolerant crops), two applications 7-10 days apart; repeat Conserve, etc.
2. Conserve, two applications 7 days apart; Neonicotinoid, two applications 14 days apart; Pylon, two applications 10-14 days apart; Decathlon + Azatin, applied twice 5-7 days after each neonicotinoid application; Avid, two applications 7 days apart; repeat Conserve, etc.
3. Here is a “soft” rotation: Naturalis L+ Azatin, 3-4 applications, 5-7 days apart; Pedestal, two applications 30 days apart; between Pedestal applications apply Preclude aerosols or Enstar II sprays 2-3 times beginning 5 days after the first Pedestal application; repeat Naturalis L+ Azatin, etc.

Summary: As with controlling any other insect or mite 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 below the benches have helped reduce thrips numbers. The mites feed on thrips transformation stages that drop off plants onto the soil. Some growers introduce other predatory mites that will feed on thrips on plants. If this is done, pesticides must be selected and used carefully to avoid harming the predatory mites. Your goal should be to prevent thrips numbers from building to damaging levels rather than trying to control a heavy infestation.