December 2001

What’s Going On With Insecticides? By Richard Lindquist

This is the time of year when the editors of GPN ask for information on what has been happening with insecticides and other related chemicals and predictions for where they are headed in the near future. Based on recent events, it's difficult to make general predictions, so I'll confine my efforts to insect and mite management.

Insect and Mite Pest Problems

The easy way out of this question would be for me to simplystate that, yes, there will be insect and mite problems in 2002 — as therewere in 2001. Ah, but which pests will cause the most problems, you might ask.Who knows, but let's take a look at it anyway.

In looking at the pesticide products and biological controlsavailable to deal with the major pest groups, it seems that we are ina pretty good position for controllingspider mites, aphids, fungus gnats and whiteflies. The major "controlgaps" are with pests such as western flower thrips, leafminers andmealybugs. We need additional conventional and nonconventional products to helprelieve overuse of one or two products — which is likely to lead toresistance development (see page 25 for tips about resistance management).Other pest groups such as tarsonemid mites and shore flies continue to causeproblems for many growers, and the list of effective controls is pretty short.

With these limitations in mind, let's take a look at what's going on in chemical development. ç

Happenings with Existing Pesticides

The following may read like a gossip column because most of the developments I refer to have not yet been finalized, but I believe that the information is correct. It was provided by the standard "usually reliable sources." Any errors of interpretation are mine, and as with marriage, I apologize in advance.

EPA continues to look at organophosphate and carbamate pesticides in light of the Food Quality Protection Act, and several products are in various stages of disappearing from the market. The good news is that one will probably be retained.

All registered greenhouse uses of diazinon (Knox Out GH) were canceled in 2001, and retail sales must stop on December 31, 2002. Diazinon is used for controlling fungus gnats and other hard-to-kill pests such as mealybugs.

Most of you probably know that bendiocarb's (Closure — an appropriate name as it turns out — and Dycarb) registration will be canceled at the end of 2001. I believe that existing stocks can be used as long as they last. Bendiocarb is one of the most effective products for mealybug control and is also quite effective against other pests.

Chlorpyrifos (DuraGuard and one of the ingredients in DuraPlex Total Release Aerosol) will become a restricted-use pesticide in 2002, and the current 12-hour REI will go to 24 hours. It could have been worse, folks.

Fenoxycarb (Precision WP or Accu-Pac) will not be available once existing stocks disappear. The Total Release Aerosol product Preclude will remain on the market. The disappearance of the powder formulation of this insect growth regulator is because Syngenta has decided to discontinue producing it. Fenoxycarb is an insect growth regulator, but it is also a carbamate pesticide. ç

In a bit of good news, acephate (Orthene) will apparently remain registered for use on greenhouse and nursery ornamentals, AND will retain the same 24-hour REI. As some of you have heard, there were rumors that the application rates would be reduced and the REI made something like 6 days. Not true.

New Registrations in 2001

Hexygon (Gowan Company). Hexygon (hexythiazox) is a miticide in the thiazolidinone chemical family, which at this time has only one member: Hexygon. Hexythiazox is presently registered in more than 35 countries worldwide under various trade names. In the United States, it was registered only on outdoor ornamentals, but the greenhouse label is now approved. Hexygon is a nonsystemic miticide that is effective against eggs and larval stages, not adults. Activity is by direct contact with spray or with treated plant surfaces. Eggs produced by adults exposed to residues are affected. Residues on treated surfaces are effective for 30 or more days. The label restricts applications to once per crop or per year. Hexygon should not be rotated with Ovation (Scotts Co.), another product that is effective against spider mite eggs and young larvae, although in different chemical classes the two products seem to have the same mode of action.

Pylon (Olympic Horticultural Products). Pylon (chlorfenapyr) is an insecticide/miticide for use on greenhouse ornamental crops. It is called a "pro-insecticide," because the product is not directly toxic, and the insect/mite needs to be exposed to the chemical by direct contact or feeding. The inactive chemical is then made active by enzymes in the insect or mite. Pylon is in the pyrrole chemical class. It acts as a stomach and contact insecticide, with stomach activity thought to be the primary route. Residual control is 21-28 days. Label restrictions are to apply Pylon no more than twice in succession or three times per crop in the same greenhouse. There is no systemic activity, but there is translaminar activity, bringing the active ingredient from the upper to lower leaf surface. Pylon is effective against pests such as two-spotted spider mites and tarsonemid mites (broad mite, cyclamen mite). Additional pests will be added to the label in 2002 — probably fungus gnats, lepidoptera and foliar nematodes. Pylon seems to be easy on beneficials, but research is continuing.

Registrations Expected in 2002

Ultiflora (Gowan Company). Ultiflora (milbemectin) will be introduced sometime during the first half of 2002. The product is naturally-derived ç from soil actinomycetes in a family called milbemycins, which are related chemically to the avermectins (Avid is an avermectin). It is a broad-spectrum miticide that is active against spider mites, tarsonemid mites and some rust mites (eriophyids). Some insects are controlled as well, but the product will be marketed primarily for mite control. Ultiflora is most active against immature mite stages and less active against eggs and adults. It has translaminar activity. As with most of the newer mite control products, residual control on treated plant surfaces is 21-28 days. Assuming there is no cross resistance with Avid (so far, so good), Ultiflora will be another product to consider when developing a mite management program.

Novaluron (Uniroyal). Novaluron (called Rimon in much of the world, but the U.S. trade name is yet to be determined) will be marketed in the United States by Uniroyal. Actually, it is registered as I write this, but will not be marketed until sometime during the first half of 2002. Novaluron is a broad-spectrum insect growth regulator in the benzoylphenyl urea class (same class as Adept). The mode of action is as a chitin synthesis inhibitor. To review, the outer skeleton of insects and relatives is composed mostly of chitin. If an insect can't properly form this stuff as it grows, it's in deep trouble. Novaluron is active against caterpillars, whiteflies and even western flower thrips.

TetraSan (Valent). TetraSan (etoxazole) is a miticide that should be registered sometime around mid-2002. It is yet another chemical class — a 2,4-diphenyloxazoline derivative. The mode of action is as an insect, or in this case a mite, growth regulator and acts by messing up the molting process. As a growth regulator, there are no direct effects on adult mites — but eggs, larvae and nymphs are directly affected. Activity is therefore slow and may not be seen for several days — but it will happen. TetraSan has translaminar movement in plant leaves, which certainly helps get the product to where the mites are. The other good news is that there are few harmful effects on beneficial insects and mites. This product should be useful in mite management rotation programs.

Future Trends

One area that will receive more emphasis is pesticide resistance management (see sidebar page 25). Many of the major grower meetings around the country have this as a topic on their programs. A generally accepted plan to delay pesticide resistance development is to rotate different pesticides in some kind of system. Growers are usually willing to consider this but get confused about what products to rotate among.

Pesticide labels now include resistance management language but do not provide much guidance about rotation plans. There are useful pesticide classification charts published by universities and commercial companies, but this is not the complete story. Pesticides in different chemical classes may have the same, or similar, modes of action (e.g. carbamates and organophosphates, pyrethroids and organochlorines). One proposal that is gaining attention is to place some kind of pesticide mode of action indicator on labels to help select products for rotation — either a color or number — so that it will be easier to avoid selecting products that have the same mode of action. It will be interesting to see what develops here. Happy New Year!