Life after Guthion part 2: incorporating OP alternatives into apple IPM programs

Currently, Ontario apple growers rely on the use of broad-spectrum organophosphorus (OP) insecticides (Guthion, Imidan) to manage several economic pests of apple including plum curculio, apple maggot, European apple sawfly, codling moth and mullein bug. As a result of recent (and anticipated) registrations, the 2008 season will be the first year that apple growers have access to non-OP alternatives for managing many of these economically important pests. Access to new products and the phase out of Guthion will hopefully result in growers incorporating many reduced-risk products into their IPM programs. Incorporating recently registered products into pest management programs now will help growers and consultants become accustomed to using new chemistries, decreasing the impacts associated with the loss of Guthion.

In preparation for the loss of Guthion growers should become educated about how the new products work, and their timing. Many of the newer products work differently than OP insecticides, may be more selective, and / or more timing-specific. This must to be taken into consideration when using them. Fortunately, a number of the newly registered products (notably several neonicotinoids) control multiple pests simultaneously. When choosing which product to use, it is important to take into consideration the activity of the product on other pests which are present in the orchard - this gives growers better bang for their buck. The best placement for a product in a grower's pest management program will vary from region to region depending on the type of pests present and pest pressure. Be aware that chemicals in the same family (example: Assail, Calypso, Actara) do not necessarily have the same activity or relative efficacy on pests. Check the labeled rates carefully, as these may vary depending on the target pest.

Avoid the temptation to over-use products, or their efficacy will be compromised due to the development of resistance. Multiple generations of a pest should not be exposed to products from the same chemical family.

Options for managing plum curculio

There are several alternatives to Guthion for the management of plum curculio (PC) in apple orchards. These include the OP insecticide Imidan, as well as the neonicotinoids Calypso and Actara. Timing of insecticides for managing PC are recommended at petal fall or when damage is noted on fruit trees located in the orchard perimeter. Calypso or Actara may be applied at petal fall +3 days and / or earlier if monitoring indicates PC is present (petal fall). These products are very effective tools for managing PC. Research conducted in Michigan (Wise et al., 2006) has suggested that these products are lethal to adults and act as oviposition deterrents (insects avoid laying eggs), antifeedants, and have repellency activity. Maintaining good fruit and leaf surface residues are important for achieving good efficacy with both products.

Both Calypso and Actara belong to the same chemical family, but they do not both control the same insect pests. To determine which product will be the best fit in your IPM program, evaluate what other pests are present in the orchard when PC is active. Growers east of Toronto may want to use Calypso at petal fall for PC since research in the US suggests that it also has activity against European apple sawfly, a regional pest in this area. In the Norfolk /Leamington area, growers who apply Calypso at petal fall will also control oriental fruit moth (OFM), a pest which may be active at the same time within the orchard (make sure to monitor OFM activity with pheromone traps). Note that Actara is not considered to provide effective control of OFM and is not labeled for this insect. Both Actara and Calypso are also effective on mullein bug and spotted tentiform leafminer. Please note that very little research has been conducted on the
effectiveness of border sprays using neonicotinoids. Because these products have repellency activity against some insects, it is possible that pests may avoid treated trees and move beyond borders into the orchard interior. As a result, we are not recommending the practice of border sprays for either Actara or Calypso at this time.

Options for managing codling moth

There are several alternatives for managing codling moth (CM) in apple orchard. The traditional timing for OP insecticides (including Imidan) is at 100 DDC after biofix (first sustained moth catch) using base 11ºC). OP insecticides kill larvae when they walk on or consume treated fruit. The newer products have different modes of action and consequently, their timing differs. The insect growth regulators Intrepid and Rimon, as well as the neonicotinoids Calypso and Assail, are active on both eggs and larvae Intrepid should be applied 2-3 days earlier than OP insecticides (just before eggs hatch), so that eggs / developing larvae are exposed to the pesticides. Rimon is best used when applied before egg laying begins (apply at petal fall). Both Intrepid and Rimon have sublethal effects on adults, so that eggs laid by exposed females fail to hatch.

Assail/Calypso work best when applied on top of the eggs and thus are optimally applied 2-3 days earlier than OP insecticides. All of the newer products act as larvicides when consumed by the insect. Residual activity varies from 10-14+ days, depending on the product. Several of the new products are effective against other orchard pests, and their use against CM may provide control of these insects if the activity is synchronous, as indicated by monitoring. Check product labels for recommended timings, rates and pests controlled. The efficacy of border sprays against CM using any of the new chemistries (Calypso, Assail, Intrepid, Rimon) has not been assessed and consequently, we are not recommending their use as such at this time.

Options for managing apple maggot

OP insecticides should be applied 7 days after the first adult fly is caught on a sticky board. In contrast, Calypso is an oviposition deterrent (prevents females from laying eggs in the fruit) and should be applied immediately after first adult fly is caught. Assail is not registered for controlling apple maggot in Canada, however it is used to control this pest in the US. Both Assail and Calypso are toxic to adults and are oviposition deterrents. Maintaining residue on the fruit is important. Calypso also provides subsequent control of codling moth. Once again, border sprays are not recommended with Calypso and Assail. Surround WP Cop Protectant is also labeled for use against apple maggot. This product is not an insecticide, but acts as a barrier against oviposition. If using this product to manage apple maggot, maintained coverage is essential, and the product must be applied prior to egg-laying.

Although Guthion has been a staple in pest management for apples over the past few decades, we are now starting to see the registration of some exciting new replacements that are more environmentally friendly, and less harmful to applicators. It is important for apple growers to try to incorporate these new products into their IPM programs to prepare for the loss of Guthion in 2012.

Relative activity spectrum for new materials - Apple
Michigan State University (J. Wise and L. Gut)

(NR) - indicates products are not registered in Canada.
More stars indicates higher efficacy.

Activity spectrum for conventional materials - Apple
Michigan State University (J. Wise and L. Gut)

(NR) - indicates products are not registered in Canada.
More stars indicates higher efficacy.

Learn more

• Life After Guthion, part 1: Can apple growers make it work?