Life After Guthion: Can apple growers make it work?

For the past few decades Guthion (azinphosmethyl) has been a staple in many apple grower's pest management programs. Guthion has been a preferred product by apple growers because of its broad spectrum activity (against a variety of pests and a variety of lifestages of pests), its efficacy against pests and its relatively low cost. Concerns regarding Guthion's effect on aquatic and terrestrial animals (fish, bees, birds and mammals) and its high occupational health risks have resulted in its ongoing phase-out in Canada and the USA. In the US Guthion can be used in apple orchards until 2012 to allow more time for the development of alternatives, and for growers to make the transition to newer chemistries. Currently Guthion can not be used in Canada after December 2007; however, it is possible that the federal government will also extend the phase out period of this product.

IPM programs in Ontario have focused on using Imidan (phosmet) rather than Guthion to manage several key pests of apple for which organophosphate (OP) alternatives are not available. However, many apple growers rely heavily on the use of Guthion to manage plum curculio. Without efficacious alternative products, growers might expect considerable damage to their crop by this direct pest.

Until 2007 it was difficult to imagine growing apples in Ontario without the use of OPs (Guthion, Imidan, Zolone, Diazinon). With the recent registrations of Calypso (thiacloprid), Actara (thiamethoxam), and Rimon (novaluron), apple growers have more options for managing plum curculio, codling moth and apple maggot. These registrations have made it possible for growers to start to working towards reducing their reliance on OPs. We are still learning how optimize pest management programs in the absence of OP insecticides. Researchers in the US have been working on developing pest management programs without OP insecticides for years, and they are still figuring out how to make them work. With this in mind, what are some things growers need to know about using OP alternatives?

1. Educate yourself about the newer products. Newer chemistries don't always work the same as OPs. Some of the newer products have activity against different life stages (egg, larvae, adult) and different modes of action (growth regulators, antifeedants, oviposition deterrents) than OP insecticides (nerve poisons), and as a result their timing may differ from those recommended for more conventional products.
   
2. Not all products work the same. We see a wide variation in the efficacy of products in the same family against pests. Calypso and Assail are neonicotinoids that work effectively against codling moth, while Actara, another neonicotinoid has much less activity against this pest.
   
3. Monitoring is extremely important with these new products. Because many of these new products are so target specific (including insect life stage), monitoring and properly timing a pesticide application is critical to good pest management. It is important to hire a scout or crop consultant to monitor pests in your orchard.
   
4. Start incorporating these new products and technologies now! By starting to use these products now and incorporating them into your IPM program you will know how to use them when you have to.
   
5. Get the most bang for your buck. Often these new pesticides are more costly then OPs (estimates in the US indicate 2-3 times the cost), so growers should select products and timings that give them the most bang for their buck by targeting multiple pests simultaneously. For more information on the timing and options for using these products in an IPM program, refer to the next Orchard Network Newsletter and upcoming Hort Matters issues.

By being proactive and incorporating alternatives to OP insecticides into their IPM programs now, growers are preparing for the future. Many of these OP alternatives are considered to have less impact on human health and the environment, and they fit well into existing IPM programs. If growers are provided enough time to allow for the development of more OP alternatives, and given time to transition to using new chemistries, we can significantly reduce the amount of OP insecticides used in apple orchards.