Thrips Cocktail for the Year 2000By Dr. Richard Lindquist The most important aspect of western flower thrips management is to know what is happening in your greenhouse. A scouting and monitoring program is a must.The pesticide suggestions below have been divided into two categories: I. Products that should be used to reduce a well-established western flower thrips population, or used on crops that are especially susceptible to impatiens necrotic spot virus (INSV) or tomato spotted wilt virus (TSWV). II. Products that are not so-called "rescue" pesticides and which should be used when thrips numbers are low (Determined by scouting and monitoring, of course!), or on crops where thrips do not pose much of a problem for feeding injury or virus susceptibility. Rotate pesticide classes. Do not tank mix pesticides from the same or related classes. Avoid tank mixing entirely if possible, but if a combination of products from different chemical classes improves control do not feel guilty about it. Application rates are given for high-volume ("wet") sprays. However, many pesticides are also labeled for use in low-volume sprays. Low-volume sprays can be very useful against thrips, and are recommended where labels permit. A spray interval is also suggested for the different products. However, this should not be a hard and fast rule. Use your own judgment based on greenhouse environment, crop, and your scouting and monitoring program, and adjust the application interval accordingly. Finally, keep scouting and monitoring so that you will know when stop spraying, or extend intervals between applications. I. Products and product mixtures that can be used to reduced a well-established western flower thrips population. A. Orthene 97 TT&O (8 oz/100 gallons). Orthene, an organophosphate pesticide, 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. If necessary, repeat the application in two weeks. B. Avid (8 oz/100 gallons). Avid, a glycoside pesticide, is not yet registered for thrips control, but a label amendment adding thrips, aphids and whiteflies is expected to be approved soon. Further, in many states, if a product is registered on a particular crop or site, it is OK to use it to control an unlisted pest. Avid's manufacturer, Novartis, does not encourage tank mixes containing Avid. However, tank mixes containing Avid + Azatin XL (12 to 16 oz/100 gallons), or Ornazin (8 oz/100 gallons) may improve thrips control. Both Azatin and Ornazin are neem insecticides containing 3% azadirachtin. Make a second application in five to seven days. Another tank mix possibility is to add horticultural oil (e.g. Ultra-fine spray oil) at 0.5 – 1% by volume to an Avid spray. This will also increase the activity of Avid. If oil is added, do not use a neem insecticide in the mix. As mentioned earlier, if you can get good results with Avid alone there's no need to tank mix.. C. Thiodan 50WP (1 lb=1 bag/100 gallons), a chlorinated hydrocarbon pesticide, + a Pyrethroid (e.g. Decathlon, Talstar, or Tame – at suggested label rates). Make a second application after five to seven days. Note that thrips are not on the Thiodan label, but greenhouse ornamental plants are listed. As in the case of Avid, it is legal in most states to use Thiodan to control non-labeled pests on labeled crops. D. Mesurol 75WP (8 to 16 oz/acre). Closure 76WP, which replaces Dycarb, is another carbamate pesticide that can be used. Application rates for Closure are 11 to 20 oz/100 gallons. Make a second application after five to seven days. E. Conserve SC (6 oz/100 gallons; maximum rate is 22 oz/100 gallons). Conserve, a new insecticide in the spinosyn class, is the newest thrips control product for the greenhouse market, and has been very effective. Use it late in the crop to kill thrips in flowers. Make two or three applications, five to seven days apart. Activity is very rapid, but residual life is short. II. Products and product mixtures that can be used when western flower thrips populations are low (i.e. should not be used in so-called "rescue" applications). A. Beauveria bassiana (BotaniGard or Naturalis-T&O (label rates). These are classified as mycoinsecticides, and contain strains of a naturally-occurring fungus Make at least three applications, 5 to 7 days apart. Use when thrips numbers are low. These products will not control heavy thrips populations. A tank mix with Azatin XL or Ornazin will help incease the activity of the B. bassiana. B. Fenoxycarb (Precision 25 WP, 2-4 oz/100 gallons, or Preclude Total Release Aerosol (rate depending on can size). Repeat after seven days. Fenoxycarb is classifed as a carbamate insecticide but it also is an insect growth regulator. As such, it will not directly affect adult thrips, only immatures. Some growers apply fenoxycarb regularly (e.g. every week or two) along with other products. Some other products that growers are using for thrips control include sulfotepp (Dithio, Plantfume 103), DDVP and Dibrom. These are all organophosphates, so do not apply them immediately following applications of Orthene or any of the carbamate products. Nicotine smoke generators are also used for thrips control. Nicotine is a botanical insecticide, and probably could fit anywhere in a rotation. What else can be done to control thrips? Some soon to be published research conducted at the University of Georgia by Scott Ludwig and Ron Oetting found that media drenches using the insect growth regulators Distance and Adept reduced emergence of western flower thrip adults. Neither of these products is registered for thrips control, but both can be applied to potting media for control of fungus gnats. This research is continuing. As a reminder, thrips undergo a non-feeding transformation from larva to adult – a stage that often occurs in the soil or potting mix. Drenches could therefore reduce emerging thrip numbers making it easier for foliar sprays to control them. |
