9 Chemical Control
Chemical control aims to kill the eggs or the larvae before the larvae can damage the fruit. Chemical control is effective for the backyard gardener because the larvae do not move around. It is true that a backyard orchard is reinfested by adults from nearby properties, but it is also true that their larvae can be met with scheduled chemical applications.
In contrast to the other methods described, above, the chemicals used to control codling moth are poisons and should be handled with care. Particularly, they can, if misapplied, harm the user, his family, and his pets, not to mention neighbors and bystanders. Some localities may require the user to be certified in safe handling of the chemicals themselves and in correct disposal of chemical residue.
Furthermore, chemicals poison not only codling moths but also other insects — pests and beneficials alike — and can upset the balance between pests and their natural predators. Unlike the predatory insects and insect diseases described, above, which are cultured specifically to control codling moth, there are no chemicals that work specifically against only one species or even genus of insects. It should be anticipated that chemicals will have side effects. Some side effects will be advantageous. Chemicals applied for control of codling moth may help control other pests, as well, and vice versa. Chemicals must not be applied to flowers or even allowed to drift. This will have the side affect of damaging populations of pollinating insects, which are necessary for fruit set during the next year.
The saving grace of using chemicals in the backyard is that, in contrast to commercial settings, here they are applied only to limited areas. Also, the compounds available to the backyard gardener do not persist for long in the environment. Thus, just as reinfestation by pests readily occurs, collateral damage to beneficials repairs itself because they, too, re-enter from neighboring properties.
Differing chemicals should be employed to treat the second flight than were used to treat the first flight. This reduces the probability that codling moth populations will develop resistance to certain chemical controls. This is of less concern in the backyard than in commercial settings because reinfestation is typically from populations unaccustomed to chemical control, which hopefully are less likely to have developed any resistance.
Some sprays that are available at retail contain one or two of the chemicals listed below (possibly in combination with other chemicals). It should go without saying that only one formulation for treating codling moth may be used at a time and that the label on the formulation should be followed. That is, separate formulations should not be tank mixed. Guidance presented here about individual chemicals is not authoritative for retail formulations. Cooley et al. has an extensive cross-reference of chemical names and trade names.
Here is a description of some chemicals currently available to the backyard gardener in the United States to control codling moth. They are divided into ovicides that are applied before egg laying (under the eggs), ovicides and larvicides that are applied after egg laying but before egg hatching (over the eggs), and larvicides that are applied after egg hatching. This outline is taken primarily from Wise et al.
Whatever chemicals are applied, they will need to be reapplied once or twice throughout the duration of first flight and egg laying. Alternatively, a combination of an ovicide followed later by a larvicide may be chosen. See, below. Look for reapplication interval on the label.
9.1 Author's Apology
You may have noticed the lack of first and second person inflection in this document. I have tried to hew to an academic tone, but, while contending with the subject matter of this section, I've decided that I risk going too far.
Particularly, citing one or two sources doesn't do justice to the apparent complexity of chemical control. The more comprehensive sources tend to be a decade old or more, while the newer sources seem to be more scatter-shot. I've always felt there ought to be a concise cookbook of current recommendations about when, what, how much, and how often to spray, but, in a decade of casual perusal of instructions aimed at backyard gardeners, I've never found one.
There may be reasons for this:
- It could be all in my head. Maybe the world doesn't need or even want such a cookbook.
- It could be in everybody else's head. Maybe it's like Fermi's Paradox. Everybody believes in extraterrestrial intelligence, and even the geniuses can't explain why they haven't made contact, but the truth is out there, anyway.
- Maybe the best sources have gone behind paywalls. To maintain my amateur status while assembling sources, I've avoided going to the library as much as possible. I surely haven't taken any recent classes that would qualify me to speak with authority of my own or entitle me to have access to inside knowledge.
- Perhaps materials go out of date more quickly than they used to. Academics who write most of the authoritative instructions for chemical control on the Internet may be having a more difficult time keeping current than before. I'm still looking for historical descriptions of chemical control that tell me what materials used to be listed for codling moth and why they aren't any more, let alone one that tells me what materials are likely to be delisted in the near future and why.
- Perhaps authority has become more diffuse in an expanding universe of knowledge. It may be that at least some kinds chemical control are more controversial nowadays than heretofore. It may be that those in authority are less willing to set their recommendations in stone, knowing, as they do, the degree and the haste with which the authority behind such recommendations erodes.
At any rate, I've had to draw the following information together from a hodgepodge of sources.
I cannot point to a consensus of all scientists about the virtues versus the downsides of chemical control. Here's where you come in: You're going to have to make up your own mind.
I think it's plain from the non-academic literature that insecticides, particularly the neonicitinoids, have received a lot of criticism about the insidious kinds of damage they may or may not be doing to domestic bees and to wild pollinators. I don't see any consensus today, but that doesn't mean one won't form tomorrow, and, if it does, you'll have to decide whether you and your neighbors will stand with the consensus view or apart from it. Right now, there does seem to be pervasive doubt about how to search for sublethal effects and how to evaluate such effects during safety testing.
Perhaps I'll feel differently someday, or I'll encounter the authoritative help I need to revise this document. I look forward to removing this apology from future versions.
9.2 Under-Egg Ovicides
Under-egg ovicides are applied at biofix + 100 GDDF (cumulative Growing Degree-Days Fahrenheit). This corresponds to the 15th percentile of first flight (Beers) and the beginning of egg laying (Wise et al.).
9.2.1 Insect Growth Regulators (IGRs)
Insect Growth Regulators (IGR) are new insecticides that prevent insects from maturing or hatching. Most IGR’s are relatively easy on beneficial insects and can be alternated with insecticides from other groups. One IGR should not be alternated with another IGR (McCamant).
Novaluron (Rimon) is an insect growth regulator for the control of a range of apple pests including codling moth, oriental fruit moth, obliquebanded leafroller, spotted tentiform leafminer, and redbanded leafroller. This product is an insect growth regulator that disrupts chitin synthesis in immature insects and eggs deposited on residues. It has no effect on adult stages and must be ingested to be effective. Four applications per season are allowed. Novaluron is moderately to highly toxic to many beneficial arthropods but relatively nontoxic to predatory mites. It has a moderate bee poisoning hazard (Cooley et al.).
Pyriproxyfen (Esteem), which is registered for use in all pome and stone fruits, is a juvenile hormone analog (a type of insect growth regulator) that interferes with the insect’s normal metamorphosis and kills by retarding its growth and causing sterility. Ovicidal activity is also exhibited. It shows translaminar properties, so applications on the top surface of the leaf will affect insects on the bottom surface. While it has no activity on adult insects, hatching of eggs laid by treated adults will be suppressed. Although leafrollers and codling moth appear on the label, results from preliminary field trials in the region suggest that it has greatest efficacy on San Jose scale, pear psylla, leafminers and aphids. It has low toxicity or is nontoxic to most beneficial species and has a low bee poisoning hazard (Cooley et al.).
9.3 Over-Egg Ovicides and Larvicides
Over-egg ovicides and larvicides typically are applied at biofix + 200 GDDF. This corresponds to the 40th percentile of first flight (Beers) and the beginning of egg hatching (Wise et al.).
9.3.1 Insect Growth Regulators (IGRs)
Insect Growth Regulators (IGR) are new insecticides that prevent insects from maturing or hatching. Most IGR’s are relatively easy on beneficial insects and can be alternated with insecticides from other groups. One IGR should not be alternated with another IGR (McCamant).
Methoxyfenozide (Intrepid) is the more active successor to Confirm (tebufenozide). It imitates the natural insect molting hormone and works by initiating the molting process within a few hours of ingestion. The premature molt makes it impossible for the larva to complete the shedding of the original exoskeleton. The larva is trapped within the old cuticle, and death occurs, usually within 2—5 days, due to starvation and dehydration. Intrepid is labeled for use in apples and pears, principally against obliquebanded leafroller, although activity against oriental fruit moth, codling moth, and lesser appleworm is also exhibited. Intrepid is essentially safe to birds, fish, and most beneficials; however, it is toxic to aquatic invertebrates. It has a low bee poisoning hazard (Cooley et al.).
Intrepid is an insect growth regulator that provides good control of codling moth with a residual action of about 10—14 days. This product ... primarily affects codling moth 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.... At the early timing, Intrepid will also control obliquebanded leafroller 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 (Wise et al.).
9.3.2 Neonicitinoids
Neonicotinoid insecticides are chemically related to nicotine. The neonicotinoids show reduced toxicity compared with earlier classes of broad-spectrum materials such as organophosphates and carbamates. Most neonicotinoids show much lower toxicity in mammals than insects, but some breakdown products are toxic to some non-target species, including beneficial insects (Cooley et al.).
Neonicitinoids are synthetic derivatives of a toxic compound isolated from tobacco. Neonicitinoids kill the nerve cells of insects but have a slightly different mode of action than the pyrethroids (See pyrethrin.) and OPs and can be alternated with the above insecticides. Neonicitinoids can control aphids, leafminers, leafhoppers, and plum curculio. Some neonicotinoids have local systemic activity (McCamant).
Acetamiprid (Assail) belongs to the neonicotinoid group of insecticides (along with Provado and Actara). It was registered by the US EPA under the reduced risk pesticide policy and is considered a replacement for older OP insecticides. Assail has a spectrum of effectiveness across several insect groups and is active against pests such as plum curculio, apple maggot, internal leps, aphids, leafhoppers, leafminers, San Jose scale, European apple sawfly, and mullein plant bug, plus pear pests such as pear psylla and Comstock mealybug. It has low toxicity to honey bees and most beneficial insects, although some flaring of mites has been reported by researchers (Cooley et al.).
Thiacloprid (Calypso) is a neonicotinoid registered for use on apple, pear and quince, exhibiting both systemic activity and crop safety. Its mode of action is through interference with the nicotinergic acetylchloline receptor, and it controls pests by both contact and stomach activities. Calypso has activity on apples against aphids (except woolly apple aphid), leafminers, leafhoppers, mirid bugs, codling moth, oriental fruit moth, plum curculio, apple maggot, and European apple sawfly. It will also suppress scale insects (crawler stage). On pears, it is active against pear psylla, aphids, codling moth, mealybugs, leafminers, and the pear midge. It will also suppress scale insects on pears. Calypso has a low acute toxicity to warm-blooded animals and a low bee poisoning hazard; however, it is highly toxic to marine/estuarine invertebrates (Cooley et al.).
Clothianidin (Belay) is labeled for post bloom applications on pome fruits and peaches, but no other stone fruit crops. These uses are currently on a supplemental label which must be in the possession of the user at the time of application. Belay is effective on tarnished plant bug and stink bugs, including the brown marmorated stink bug. This product is toxic to bees exposed to treatment and for more than five days following treatment. Do not apply this product to blooming, pollen-shedding or nectar-producing parts of plants if bees may forage on the plants during this time period (Cooley et al.).
9.3.3 Diamide
Diamide activates the insect's ryanodine receptors, stimulating release of calcium from muscle tissues and causing paralysis and death (Cooley et al.).
Chlorantraniliprole (rynaxypyr) (Altacor) belongs to a new chemical class, the anthranilic diamides.... Altacor is labeled for the control of a range of insect pests in pome and stone fruits, including codling moth, oriental fruit moth, and obliquebanded leafroller. Other species listed on the label include green fruitworm, spotted tentiform leafminer, apple sawfly, European corn borer, and suppression of apple maggot, cherry fruit fly, white apple leafhopper, and plum curculio. It has low toxicity to bees, beneficial mites, birds, fish, and mammals (Cooley et al.).
Flubendiamide (Belt) is labeled for use in stone fruits and pome fruits against many Lepidoptera, including leafrollers, codling moth, oriental fruit moth, lesser appleworm, fruitworms, and leafminers. The active ingredient is in the same class of ryanodine receptor modulators (IRAC Group 28) as chlorantraniliprole, found in Altacor and Voliam Xpress. PHI is 14 days in pome fruits and 7 days in stone fruits. REI is 12 hours. It has a low bee poisoning hazard (Cooley et al.).
9.3.4 Pre-mixes
There are several new pre-mix insecticides labeled for codling moth control ... 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 (Wise et al.). For best effectiveness and insecticide resistance management, their use should be reserved for situations when multiple pest species are present [which are appropriately controlled by] the combination of active ingredients and modes of action contained in the product (Cooley et al.).
Chlorantraniliprole + thiamethoxam (Voliam Flexi) is registered for use against a range of pests in pome and stone fruits. This product is a mixture of thiamethoxam, the active ingredient of Actara, and chlorantraniliprole, the active ingredient found in Altacor and Voliam Xpress. The label lists lepidopteran pests such as codling moth, oriental fruit moth, obliquebanded leafroller, leafminers and green fruitworm; plum curculio; European apple sawfly; leafhoppers and aphids (except woolly apple aphid); pear psylla; plus (in stone fruits only) cherry fruit fly, stink bugs, tarnished plant bug and thrips. It has a 12 hour REI, and a PHI of 35 days in pome fruits and 14 days in stone fruits. No more than a total of 14 oz/acre of formulated product may be applied per season. This use corresponds to the 0.172 lb active ingredient/acre of thiamethoxam allowed, whether applied as Voliam Flexi, Actara, or Endigo. This product is highly toxic to bees exposed to direct treatment on blooming crops or weeds. It may not be applied between early pink and petal fall in apples, between green cluster and petal fall in pears, and between swollen bud and petal fall in stone fruit (Cooley et al.).
Flubendiamide + buprofezin (Tourismo) is labeled for use in stone fruits and pome fruits against many Lepidoptera, including leafrollers, codling moth, oriental fruit moth, lesser appleworm, fruitworms, and leafminers. The flubendiamide is in the same class of ryanodine receptor modulators (IRAC Group 28) as chlorantraniliprole, found in Altacor and Voliam Xpress. Buprofezin is the same active ingredient as Centaur. It is an insect growth regulator for the control of the nymphal stages of San Jose scale, mealybugs, leafhoppers, and pear psylla. It works by inhibiting chitin biosynthesis, suppressing oviposition by adults, and reducing viability of eggs. Treated susceptible pests may remain alive on the plant for 3—7 days, but feeding damage during this time is typically very low. It is not disruptive to beneficial insects and mites and has a low bee poisoning hazard (Cooley et al.).
9.4 Larvicides
9.4.1 Application
Larvicides are applied at biofix + 250 GDDF. This corresponds to the 50th percentile of first flight and the third percentile of egg hatching (Beers).
9.4.1.1 Delayed Application
If an under-egg ovicide is applied at biofix + 100 GDDF, a follow-on larvicide application may be delayed until biofix + 350 GDDF, which corresponds roughly to the 60th percentile of the first flight and the 15th percentile of egg hatching (Beers).
The delayed larvicidal treatment is possible because the early ovicide treatment kills eggs that would have hatched in the period starting at 250 GDDF. 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 GDDF. Only a small portion of the first generation egg hatch occurs between 250-350 GDDF, ca 15 percent, while more than 50 percent of the hatch occurs over a two to three week period beginning at 350 GDDF. 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 (Wise et al.).
9.4.1.2 Advanced Application
If high trap counts are experienced, treatment is more urgent, and waiting for 250 GDDF may risk an unacceptable amount of damage from the larvae that are likely to hatch early. In these cases, consider treating at 160 GDDF (U. C. Agriculture and Natural Resources, Management Guidelines), which corresponds to the 30th percentile of the flight and precedes egg hatch (Beers).
9.4.2 Organophosphates (OPs)
Most organophosphate insecticides are highly toxic to warm-blooded animals when inhaled, swallowed, or absorbed through the skin. Persons handling or applying these materials should take every precaution for their own safety and for that of others. Although the organophosphates in general are less persistent than the chlorinated hydrocarbons, their toxicity often prohibits their use close to harvest. Organophosphates are contact insecticides as well as stomach poisons. Therefore, they are useful for a quick kill of all insect forms present at the time of application, as well as for reasonable residual protection. When used alone or in combination with other materials, some organophosphates cause phytotoxicity on fruit varieties (Cooley et al.).
Phosmet (Imidan) is a broad-spectrum material with a lower toxicity to mammals than many other commonly used organophosphates. It is compatible with most commonly used insecticides and fungicides but is incompatible with alkaline materials such as Bordeaux mixture and lime. It may cause severe leaf injury to sweet cherries, particularly those of Emperor Francis parentage. It can be used in summer sprays in integrated mite-control programs because of its low toxicity to predator mites. In some seasons in which rainfall has been negligible during the late summer, the fruit occasionally shows a buildup of the carrier used in the wettable powder. Imidan is effective in controlling codling moth, apple maggot, redbanded leafroller, plum curculio, peach twig borer, and oriental fruit moth on apple, pear, peach, apricot, nectarine, and plums to be used for prunes. It has been ineffective against phosphate-resistant populations of pear psylla. It has a high bee poisoning hazard (Cooley et al.).
9.4.3 Spinosyn
Spinosyns have only been available for the last ten years. Spinosyns are derived from a soil microorganism and thus are approved for organic production systems. Spinosyn is highly effective at low rates. Although spinosyns are relatively broad spectrum, they do not kill predatory mites (McCamant).
Spinetoram (Delegate) is a new spinosyn insecticide related to spinosad, which has been chemically modified to be more active and effective against a broader range of insects. It has efficacy against internal feeding Lepidoptera such as codling moth and oriental fruit moth, plus leafrollers and leafminers. It is also labeled for control of pear psylla, thrips, and cherry fruit fly and shows suppression of apple maggot and plum curculio. Like spinosad, it acts by disrupting insect nerve function. It is nontoxic to birds, fish, aquatic invertebrates, and most beneficial arthropods. It has a low bee poisoning hazard (Cooley et al.).
9.4.4 Oxydiazine
The oxadiazines have a unique mode of action, of disrupting communication between nerve cells. Avaunt is relatively broad spectrum, and does not kill predatory mites. In some tests, Avaunt had relatively little activity against codling moth and some leafroller species (McCamant).
Indoxacarb (Avaunt) is a broad-spectrum oxadiazine labeled in apples and pears against plum curculio, apple maggot, and European apple sawfly with some activity also on Lepidoptera such as codling moth, oriental fruit moth, and leafminers, as well as leafhoppers. The active ingredient is activated by the insect to an insecticidal form only upon ingestion or absorption through the cuticle, after which it causes paralysis by interference with the sodium flow into nerve cells. It has generally slight to no effects on beneficial insects and mites but is highly toxic to bees exposed to direct treatment and relatively non-toxic when dried. It is therefore categorized as having a moderate bee poisoning hazard (Cooley et al.).
9.4.5 Carbaryl
Carbamates are broad spectrum insecticides with a similar mode of action to the OPs but less toxic to humans. Several carbamates are systemic, meaning they can be absorbed by the plants. Carbaryl ... has plant growth regulator activity and can be used to thin apples. Many carbamates are highly toxic to predatory mites and should be applied carefully (McCamant).
Carbaryl (Sevin) applications made within 30 days after petal fall have a pronounced thinning effect on most apple varieties. Sevin does not thin pears. It is a broad-spectrum material that acts as a stomach as well as contact poison and controls various fruit insects, including organophosphate-resistant pests such as white apple leafhopper. It is one of the low-hazard insecticides and can be used up to one day before harvest on most fruit crops ... in home orchards. Sevin is very toxic to bees and, therefore, should not be used just before bloom. It is also toxic to certain predator mite species (Cooley et al.).