MSU Extension Fruit & Nuts

The catastrophic freeze of 2012 resulted in a near collapse of codling moth populations in most regions of Michigan. Codling moth (CM) populations remained suppressed through much of the 2013 growing season. Based on 2014 showing recovering codling moth populations and the current 2015 pheromone trapline data, we expect normal codling moth populations and “pest pressure” this summer.

At the Michigan State University Trevor Nichols Research Center in Fennville, Michigan, we set CM biofix on May 16, thus we can expect continued emergence of codling moth adults and widespread oviposition (egglaying), with first egg hatch (CM bio + 250 growing degree days base 50) predicted for the first week of June. To get the most benefit from a CM control measure, growers should treat a block after moth captures have been recorded and the accumulation of growing degree days (GDD) required for a particular action, as indicated in Table 1, has taken place.

Egg control

Although several insecticides have limited ovicidal activity, only Rimon is considered a strong ovicide material, thus CM egglaying is the optimal timing for this material (Table 2). Rimon applied at CM biofix plus 100 GDD also provides excellent control of obliquebanded leafroller (OBLR) and suppression of plum curculio (sublethal effects on subsequent generation).

Larval control

The vast majority of insecticides used for CM control are aimed at killing larvae, and thus are typically applied beginning at 250 GDD post-biofix (Table 2). Pyrethroid insecticides provide moderate control of codling moth and have a broad activity spectrum, but are generally avoided because their use at this stage that can result in outbreaks of phytophagous mites. Apple growers should be aware that resistance to the organophosphate (OP) compounds has been detected in Michigan orchards throughout the state, such that reliance on OP for CM control is not likely to provide sufficient control. In addition, populations resistant to OP compounds may also be resistant to pyrethroids.

* May cause mite flaring in combination with carbaryl or pyrethroids that kill predacious mites.

Delegate (spinetoram) is in the Spinosyn class of insecticides and provides excellent control of both first and second generation CM. It kills larvae as they hatch and begin feeding, thus should be applied at the larvicidal timings indicated in Table 1. Delegate has very good activity against OBLR, suppression activity on apple maggots (AM), and limited lethal action on plum curculio (PC) when ingested (Table 3).

Exirel (cyazypyr), Altacor (rynaxypyr) and Belt (flubendiamide) belong to the Diamide class of insecticides that work on the insect by activating ryanodine receptors, thus depleting internal calcium and preventing muscle contraction. They provide excellent control of both first and second generation CM, as well as OBLR. Exirel and Altacor also provide suppression activity on AM, Exirel better than Altacor (Table 3).

The neonicotinoids Assail and Calypso (being phased out of market by 2016) will provide very good control of CM with a residual action of 10-14 days. These compounds are primarily larvicidal, but also have some ovicidal activity when applied over the top of the egg. Field trials have indicated that use of Assail in combination with pyrethroids or carbaryl can result in outbreaks of phytophagous mites. Assail and Calypso are fairly broad-spectrum materials. In contrast to the insect growth regulators and Diamides, the major secondary targets of these neonicotinoids are the sucking insects, specifically aphids (green apple aphis and rosy apple aphids) and leafhoppers (Table 3). The initial application of Assail or Calypso targeting first generation CM will also provide control of plum curculio (PC), oriental fruit moth (OFM) and spotted tentiform leafminer (STLM), and they will control AM.

Belay, another neonicotinoid registered for use in pome fruits, is a broad-spectrum material targeting CM as well as aphids, leafhoppers, PC, STLM, OFM and pear psylla. Research trials have indicated that Belay is not as effective as Assail or Calypso for second generation CM.

Proclaim is a CM control material in the Avermectin class of insecticides. It has provided good control of first generation CM in trials at the Trevor Nichols Research Center and in on-farm demonstration trials. Proclaim also has very good activity against OBLR.

There are several new pre-mix insecticides labeled for codling moth control, including Voliam flexi (thiamethoxam + chlorantraniliprole), Tourismo (flubendiamide/buprofezin) and Leverage (imidacloprid + cyfluthrin) that combine two active ingredients as pre-mix formulated compounds. When these are used for codling moth control, care must be taken not to use a product in the following generation that is in the same insecticide class as either of the pre-mix active ingredients.

Codling moth granulosis virus

Growers should not overlook including granulosis virus in their CM management program. This is a naturally occurring virus that goes by the scientific name Cydia pomonella granulovirus (CpGV). Both of the two commercially available products, Cyd-X and Carpovirusine, are effective. Optimal use of the virus is against young larvae before they penetrate the fruit. The best way to target young larvae is to have the virus present on the surface of the eggs when they begin to hatch. Hatching CM larvae will ingest the virus as they consume their eggshells.

There are many options for incorporating virus into your codling moth management program. Deciding how much, when and how often to apply product can be quite confusing. Keep in mind the following factors when trying to sort things out:

• CpGV must be ingested by the codling moth larva and may not kill it immediately.
• The virus breaks down in the environment, thus a spray may only be effective for a week or so.
• The virus is highly lethal, a few OB’s are all that are required to cause death.

Our overall experience is that frequent application of a low rate of product is the best approach for using this biopesticide.

Growers can opt to use the virus as part of a multi-tactic CM control program. Rotating it with chemical insecticides is a good means of combating resistance. Michigan State University Extension suggests the following approaches to incorporating CM virus into a management program. If you want to restrict your use to a single generation, target the first generation. Some virus-infected larvae will not die immediately, allowing them to cause fruit damage and even complete larval development. Fortunately, stings or deeper entries in small fruits attacked by first generation larvae often fall off the tree or are removed by thinning. Additionally, research conducted in 2003 revealed that less than 4 percent of the individuals that managed to complete larval development survived to pupate and emerge as summer generation adults. Thus, applications against the first generation can greatly reduce the size of the summer generation that will need to be controlled.

Regardless of the generation targeted, it is best to make at least two applications. If you want to rotate a CpGV product with other controls, try applying a chemical insecticide as the first spray at the start of egg hatch (250 GDD) and the virus as the second spray. This is because more eggs will be present and covered by the virus spray at the later timing. The insecticide and virus could then be rotated again, or the virus could be applied weekly at a low rate for the remainder of the egg hatch period.

CM-codling moth, OFM-oriental fruit moth, OBLR-obliquebanded leafroller, PC-Plum curculio, STLM-spotted tentiform leafminer, GAA/RAA-green/rosy apple aphid, WALH-white apple and potato leafhoppers, SJS-San Jose scale, TPB-tarnished plant bug
* some activity, ** better activity, *** best activity relative to other insecticides

Drs. Wise and Gut’s work is funded in part by MSU‘s AgBioResearch.