Codling moth management decision-making - Part II: Targeting first generation larvae

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.      

In this follow-up to last week’s article on early season codling moth (CM) management, we focus on controlling CM larvae. 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.

Table 1. Codling moth GDD model and insecticide timings for larval control

 GDD base 50 (Post Biofix)  Event  Action
Pink bud Development of overwintering larvae Set traps
0 GDD equals Biofix (~200 GDD after Jan 1) 1st sustained moth captures Set GDD equals 0
250 GDD  Start of 1st generation egg hatch Timing for 1st treatment if over threshold (for larva targeted materials)
350 GDD  1st generation egg laying & hatch Delayed timing for 1st treatment if pest pressure is low, or for 2nd treatment if an ovicide was applied at 100 GDD)
500-650 GDD  Peak of 1st generation egg hatch Timing for additional larvacide if monitoring of codling moth activity indicates a treatment is needed
1000 GDD Expected end of 1st generation activity  
1200-1250 GDD Start of 2nd generation egg hatch Timing for treatment if over threshold (for larva targeted materials)
2100 GDD Expected end of 2nd generation activity  

Larval control

The vast majority of insecticides used for CM control are aimed at killing larvae (Table 2). This is not an easy task, as young larvae feed and enter the fruit within a few hours of hatching. Options for controlling CM larvae include conventional contact poisons, like the organophosphate (OP) compounds, Guthion and Imidan, and a number of pyrethroid insecticides. These materials kill larvae that crawl across or consume the lethal residues. They primarily target newly emerging larvae at CM egg hatch, and thus are typically applied beginning at 250 GDD post biofix. Pyrethroid insecticides appear to be more effective in the spring for first generation CM, than summer and have a broad activity spectrum. Pyrethroids are highly toxic to mite predators and should be used carefully to avoid outbreaks of phytophagous mites. Apple growers should be aware that resistance to the OP compounds has been detected in Michigan orchards throughout the state, most extensively in the Fruit Ridge and Southwest production areas. The levels of resistance detected were high enough in those orchards that sole reliance on OP’s for CM control is not likely to provide sufficient control. In addition, populations resistant to OP compounds may also be resistant to pyrethroids.

Several new materials have become available for CM larval control and growers are encouraged to include these new products in their CM management programs. Integrating them into CM management programs will not only improve CM control in orchards experiencing problems, but also will help delay the development of CM resistance to OP’s in locations not yet experiencing control failures. The newest options for CM control are three compounds that received their US EPA registration in 2008: Delegate, Altacor and Belt. Delegate and Altacor were commercially available and widely used in 2008, while Belt was registered late in the season and is essentially commercially available for the first time this season.

Delegate (spinetoram) is a new compound in the same insecticide class as SpinTor (spinosad). The active ingredients of both Spinosyn compounds are similar in that they are waste metabolites produced during the growth of bacteria. A major difference between the two AI’s however, is that spinetoram is much more lethal to codling moth larvae. In small-plot and on-farm trials, Delegate has provided 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 also has very good activity against obliquebanded leafroller (Table 3). Although also active against apple maggot (AM), results of small-plot trials have been mixed and more research is needed to determine the level of AM control Delegate will provide.
Altacor (rynaxypyr) belongs to a new class of Diamide insecticides that work on the insect by activating ryanodine receptors, thus depleting internal calcium and preventing muscle contraction. In small-plot and on-farm trials, Altacor has provided excellent control of both first and second generation CM. Our research at TNRC has focused on the larvicidal activity of Altacor, however Dr. Jay Brunner and colleagues at Washington State University have found that Altacor has substantial ovicidal activity as well. However, Michigan apple growers should primarily apply this product at the larvicidal timings. Altacor provides excellent obliquebanded leafroller control (Table 3). It has limited activity on apple maggot, and thus probably has a better fit in Michigan apple IPM programs for first rather than second generation CM control.

Belt (flubendiamide) is a new Diamide compound with the same mode of action as Altacor. Belt has provided excellent control of both first and second generation CM and should be applied at the larvacidal timings indicated in Table 1. Keep in mind however, that if either Belt or Altacor is used to control the first generation, neither compound should be used for second-generation control. Belt also provides excellent OBLR and OFM control (TABLE 3) and appears to be relatively safe on most beneficials.
The neonicotinoids, Assail and Calypso, will provide very good control of CM with a residual action of 10-14 days. Proper timing and coverage is required to achieve control. These compounds are primarily larvicidal, but also have some ovicidal activity when applied over the top of the egg. Assail is labeled for CM control at the rate of 6-8 ounces per acre, but the high rate has shown better performance, especially for second generation CM. Application rates near the high end of the label rate are also recommended for Calypso, especially where CM densities are high or for prolonged control. 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, the major secondary targets of these neonicotinoids are the sucking insects, specifically 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 for second generation CM they will control apple maggot.

Clutch, 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 Clutch is not as effective as Assail or Calypso. The best results have been achieved when it is used against first generation CM larvae applied at the egg hatch timing of 250 GDD and at the high 6-oz/ac rate. Even at the high rate, Clutch has not provided adequate control of 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 Complex and in on-farm demonstration trials. Prior to the 2007 season, the label only claimed suppression of CM, but control of first generation larvae is now supported on the label. Proclaim has very good activity against OBLR.

Intrepid is an insect growth regulator that provides good control of CM with a residual action of about 10-14d. This product is an insect growth regulator that primarily affects CM larvae, but also has substantial activity on eggs, and has sublethal effects on adults. The best results have been achieved by taking advantage of the ovicidal and sublethal effects. For example applying an early spray at biofix plus 150-200 GDD or a delayed timing of 350 GDD. At the early timing, Intrepid will also control OBLR larvae that are still present in orchards harboring high numbers of this troublesome pest. The addition of an agricultural adjuvant is recommended to improve initial spray deposition. As a cautionary note, growers should be aware that populations resistant to OP compounds might also be resistant to Intrepid.

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.

Table 2. Chemical class, activity and timing of insecticides used for CM control.

Compound trade name Chemical class Life-stageactivity Optimal spray timing for codling moth Mite flaring potential
Guthion, Imidan Organophosphates Eggs, Larvae, Adults Biofix + 250 DD L - M
Asana, Warrior, Danitol, Decis,Baythroid XL Pyrethroids Eggs, Larvae, Adults Biofix + 250 DD H
Rimon IGR (chitin inhibitor) Eggs, Larvae Biofix + 100 DDResidue under eggs M*
Delegate Spinosyn Larvae  Biofix + 250 DD   
Altacor, Belt Diamide Eggs, Larvae  Biofix + 250 DD   
Assail, Calypso, Clutch Neonicotinoid Eggs, Larvae,Adults (limited) Biofix + 200-250 DDResidue over eggs M*
Intrepid IGR (MAC) Eggs, Larvae,Adults(sublethal) Biofix + 150-200 DDResidue over eggs L
Avaunt Oxidiazine Larvae Biofix + 250 DD L
Esteem IGR (juvenoid) Eggs, Larvae Biofix + 100 DDResidue under eggs L
Proclaim Avermectin Larvae Biofix + 150-250 DD L
Granulovirus Biopesticide Eggs, Larvae Biofix + 250 DDResidue over eggs L
Voliam flexi Diamide + Neonic. Eggs, Larvae Biofix + 200-250 DDResidue over eggs  
Tourismo Diamide + IGR Eggs, Larvae Biofix + 200-250 DD  
Leverage Pyrethroid + Neonic. Eggs, Larvae, Adults Biofix + 200-250 DD H

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 of 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 CM 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: 1) CpGV must be ingested by the CM larva and may not kill it immediately, 2) the virus breaks down in the environment, thus a spray may only be effective for a week or so, and 3) 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. We suggest 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.

Combined use of an ovicide and larvicide

Over the past few years, colleagues in Washington State have been evaluating two novel CM programs that take advantage of the ovicidal or larvicidal properties of various compounds. In one program, an ovicidal material is applied at the start of egg laying and a larvicidal material is applied at a delayed timing of 350-400 GDD. The second program is a delayed timing at 350 GDD of a tank mix of an ovicidal insecticide, such as Rimon, and a larvicidal insecticide, such as Delegate. Growers can learn more about these programs at http://entomology.tfrec.wsu.edu/op-alternative/.

Taking the lead from our Washington colleagues, we have evaluated the early ovicide followed by a delayed larvicide program using Rimon as the ovicide and either Assail, Calypso, Altacor or Belt as the larvicide. All programs proved highly effective in controlling first generation CM. The delayed larvicidal treatment is possible because the early ovicide treatment kills eggs that would have hatched in the period starting at 250 GDD. Another nice feature of this program is that the delayed application of the larvicide is a more efficient timing than the standard first cover timing of 250 GDD. Only a small portion of the first generation egg hatch occurs between 250-350 GDD, about 15 percent while more than 50 percent of the hatch occurs over a two to three week period beginning at 350 GDD. The combined strategy also shortens the period of time that larval control is necessary, presenting an opportunity to reduce the number of sprays needed to achieve control.

Table 3. Relative activity spectrum of compounds against spring and early summer apple pests
Table
CM-codling moth, OFM-oriental fruitmoth, 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

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