Options for Oriental Fruit Moth Management in Ontario Tender Fruit Orchards

Until 2008, tender fruit growers relied on Lorsban for management of first generation and synthetic pyrethroids for management of second and third generation Oriental fruit moth (OFM). These products are contact nerve poisons that are effective on all larval stages. They are applied within 4 days after peak male flight as indicated by pheromone trap catches. Two "new" synthetic pyrethroid products are UPCyde (same active as Ripcord) and PermUP (same active as Pounce). Pyrethroids have a short period of effectiveness (7 days, less if temperatures are higher than 20 C) so will likely have to be applied more than once per generation. The label for Lorsban allows only 1 application per season.

Two new products were made available for use in tender fruit orchards in 2008: Delegate (Dow AgroSciences) and Altacor (DuPont Crop Protection). These products represent two new insecticide classes that will provide additional options for delaying the development of resistance in OFM populations in Ontario as well as achieving excellent pest management. Delegate belongs to Group 5 of insecticides. It is a nerve poison, but works in a different way than OP's or pyrethroids. Altacor is a Group 28 (anthranilic diamide) compound. Products in this group have a different mode of action from other insecticides that affect the insect nervous system because it affects the muscles of the insect. Once the larva eats the insecticide, it stops feeding almost immediately and dies within a few days.

Altacor and Delegate are registered on all stone fruits, apples and pears for control of OFM as well as obliquebanded leafroller. Both of these products must be eaten by the insect and are most effective on young larvae. Therefore, they will be most effective if applied after egg deposition but before the larvae exit the eggs. Because the products must be consumed, the timing is a lot more critical than it was for the OP's and pyrethroids. These products should be applied earlier than more conventional products, and before peak flight of OFM occurs. A combination of regional and site-specific trap catches and degree day accumulations will be used to help time these products.

Another thing to consider is that since Altacor and Delegate must be eaten by the target pest, coverage becomes critical. Oriental fruit moth larvae move into shoots and fruit very quickly after hatching, and they consume little surface plant tissue in the process. In order to ensure they ingest a lethal dose of insecticide, excellent coverage is required. Make sure to apply the products at recommended rates and with sufficient water volumes.

There are several benefits to using these new products.

1. They are from 2 new chemical families that are different than OP's and pyrethroids so they are useful rotation partners for resistance management. This is particularly important in preserving pyrethroids for pre-pick sprays, as they have the shortest pre-harvest interval.
   
2. Very rainfast. Altacor and Delegate are absorbed into the waxy layer of plant tissues and are not removed with rainfall about 1 hr after spraying.
   
3. Not affected by temperature. The effectiveness of pyrethroids is significantly reduced with temperatures greater than 26 C.
   
4. Long residual activity. The interval between sprays of Altacor or Delegate is 10-14 days while that for pyrethroids is 7 days. Fewer sprays of the newer products will be required; in fact, depending on trap catches, a single application may take care of an entire generation.

Our suggested strategy for integrating these products is to use Lorsban for first generation OFM, Altacor for second and Delegate for third. If necessary, one or two pre-picks with a pyrethroid will protect the tail end of the later season varieties. As other insecticides that will replace Lorsban become registered for use in tender fruit in the (hopefully) near future, our recommendations for managing first generation OFM will change - so stay tuned!

The alternative to working with juggling insecticide timing is to use mating disruption. This is especially effective in large blocks or where multiple crops (apricots, plums, peaches, apples) make spray timing difficult. If Isomate M-Rosso is used, no insecticides are required for OFM in well-managed orchards with low population pressure. The ties are put out in the orchard before first flight and last 150 days, meaning they will protect throughout the season. If Isomate M-100 is used, the first generation of OFM is sprayed with Lorsban and then the ties are put up in time for second generation.

The following table summarizes the cost of a single treatment per ha based on the manufacturer's suggested retail price.

If you look strictly at the cost of application, the Lorsban/pyrethroid rotation is the least expensive. But keep in mind that repeated uses of Guthion resulted in significant losses for several years due to the development of wide-spread resistance. The pyrethroid insecticides are useful to cover the pre-pick period since they have such a short pre-harvest interval. But they are also vulnerable to the development of resistance. While more expensive, rotation with one of the new products that are available is an investment in keeping the pyrethroids for when we need them most. Mating disruption appears expensive if looked at this technology only in terms of the cost per ha. However, at least some of this cost is compensated for by not having to worry about spray timing, no re-entry interval, no pesticide residues, no pre-harvest interval, fewer non-target effects and long-term resistance management.