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Insecticide Options in Organic Apple Production

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While the organically accepted fungicides and insecticides individually do not offer the same degree of efficacy or longevity as their conventional counterparts, when used in concert with each other along with conservation of biological control agents and cultural practices to reduce inocula, it is possible to produce a high percentage of fruit free of insect damage and disease symptoms within organic certification restriction on allowable materials (Berkett et. al., 2013).

Ideally, organic fruit production involves a whole systems approach not just a substitution of organically-acceptable pesticides for non organically-acceptable ones. Research is continuing in New England to examine the challenges and opportunities of organic apple production. Information from this and other research will be incorporated into future extension publications. The following information is based on observations by researchers and Extension specialists in Vermont and New York.

Kaolin clay (Surround), when used properly, has proven an effective organic option to deter pear psylla on pears, and plum curculio and first generation codling moth damage on apples. Later season use can suppress apple maggot damage and second generation codling moth, but when used past early July when apple maggot becomes a threat, the increased chance of a bothersome amount of Surround residue remaining on apples at harvest becomes a limitation. Also, full season use of Surround has been associated with an increase in phytophagous mite populations. To be effective, Surround must be applied in dilute (100 gallons water per acre minimum) applications, and a complete base layer must be present prior to target insect activity in the orchard. Application to manage plum curculio should begin in late bloom to prevent colonizing of trees by migrating adults.

Azadirachtin (e.g. Aza-Direct, Neemix) is derived from the seeds of the neem tree, Azadirachta indica, which is widely distributed throughout Asia and Africa. Azadirachtin has been shown to have repellent, antifeedent, or growth regulating insecticidal activity against a large number of insect species and some mites. It has also been reported to act as a repellent to nematodes. Neem extracts have also been used in medicines, soap, toothpaste and cosmetics. It shows some activity against leafminers, leafhoppers, mealybugs, aphids, caterpillars, tarnished plant bug and pear psylla, but repeated applications at short intervals are probably necessary for acceptable control of most pests. Azadirachtin is relatively short-lived and mammalian toxicity is low (rat oral LD50 >10,000). It can be used up to and including the day of harvest and reentry is permitted within four hours following application. It is relatively nontoxic to beneficials, but toxic to fish, aquatic invertebrates, and bees exposed to direct treatment, although relatively non-toxic when dried. It is therefore categorized as having a moderate bee poisoning hazard.

Clarified Neem oil (Trilogy) is labeled for a wide range of pest control or suppression uses, including use as a fungicide, insecticide, and miticide. Specific uses have not been well-studied for every labeled pest; rates suggested on the label also vary widely. Neem oils have been found to suppress European apple sawfly and may deter feeding or egg laying of other insect pests. Research on its use as a scab fungicide has shown that it is ineffective as a stand-alone material. Because Trilogy is an oil-based material cautions against mixing with other pesticides incompatible with oil, such as sulfur, should be followed. Trilogy applications have been found to form a persistent film on fruit and foliage that may make removal of residues such as kaolin difficult at harvest or packout. This product is toxic to bees if exposed to direct treatment and is hazardous to fish and aquatic invertebrates.

Bacillus thuringiensis (e.g., Dipel, Deliver, Biobit, Javelin, Agree) is a microbial insecticide specific for the control of caterpillars. It contains spores and crystalline endotoxin that must be ingested by larvae with high gut pH to provide control. It is effective against many fruit pests, including leafrollers and fruitworms. Although this material will contribute to management of codling moth and other internal lepidopterous apple pests, it is not as effective as most conventional insecticides. One exception is the obliquebanded leafroller, which has become so difficult to control with conventional toxicants that the Bt products work at least as well as any material available. Compared to conventional insecticides used against these pests, Bt insecticide coverage should begin earlier and requires shorter intervals between spray applications. This material is exempt from requirements for a tolerance on all raw agricultural commodities, thus it can be sprayed up until harvest. It is harmless to humans, animals, and beneficial insects, including the honey bee.

Spinosad (e.g., Entrust, GF-120) is an active ingredient derived from fermentation of a naturally ocuring soil bacteria.Entrust is an organically accepted formulation that can provide good control of codling moth, leafollers, and fair control of apple maggot and spotted tentiform leafminer. Formulations with an attractant bait (GF-120) can be used at low rates to manage fruit flies.

Pyrethrum (e.g., Pyganic) is a material that has been used against European apple sawfly and for short term (relative to conventional insecticides) control of plum curculio, codling moth and apple maggot. Pyrethrins are rapidly broken down when exposed to UV-light and therefore applications in late evening are recommended. For the duration of control it provides, Pyganic would be more expensive than conventional insecticides or other organic options as the foundation for an insect pest management program.

Insecticidal soaps (e.g., M-Pede) are concentrates made from biodegradable fatty acids and are contact insecticides that can be effective against such soft-bodied arthropods as aphids, mealybugs, and psyllids. They can provide suppression of pear psylla when used in a seasonal spray program, but the residual period is short, and uniform drying conditions are required to prevent droplet residues on the fruit surface. They have a low bee-poisoning hazard.

Horticultural oil is an effective tool against mite pests, San Jose scale, and pear psylla, and can contribute to suppression of codling moth and spotted tentiform leafminer. Oils act as physical pesticides by creating a film over eggs, spores, or soft-bodied insects, thus suffocating them. A dormant (or prebloom) oil application can help manage mite populations; additional summer oil applications can also lower populations. However, some apple varieties have different sensitivities to summer oil sprays and use may result in fruit and foliar damage.

Codling Moth Granulosis Virus (e.g., Carpovirusine, Cyd-X, Madex HP). These products contain an insecticidal baculovirus, Cydia pomonella granulovirus, which is specific to the larval form of the codling moth, and is registered for use in apples, pears, and (Cyd-X and Madex HP only) plums. Madex HP is also registered for use against oriental fruit moth.  This biological insecticide must be ingested in order to be effective. The virus infects the moth larvae and causes it to stop feeding and eventually die. After death, the larva disintegrates, releasing the virus, which may infect other codling moth larvae upon ingestion. Applications are recommended at egg hatch, before the larvae penetrate the fruit. Best results are seen with repeated applications for each generation during the growing season. No adverse effect to fish, wildlife or beneficial organisms has been observed; it has a low bee-poisoning hazard.

Chromobacterium subtsugae (Grandevo) is a relatively new bioinsecticide registered for use against multiple insect pests on tree fruit. Its mode of action is complex, and is generally effective when consumed by target insects. Grandevo may be used against codling moth and other lepidopteran pests and may be useful in rotation with other materials including granulosis virus or Bt to improve efficacy and manage development of pest resistance to those materials.

Burkholderia rinojensis metabolites (Venerate XC) is labeled for control of pear psyllid and plum curculio and suppression of stink bugs on apple; as well as lepidoptera and plum curculio control and aphid, mealybug, mite, stink bug, thrips, and whitefly suppression on stone fruit. Field research trials are lacking however for these uses of this product, so use beyond trial applications is not recommended.

Synthetic pheromones are available for disrupting the chemical communication of certain insect pests, thereby preventing them from mating and producing larvae that injure the crop. Pest-specific pheromones are released from dispensers or microcapsules placed in the orchard before the initiation of flight, and can reduce or in some cases eliminate the need for supplementary insecticidal sprays. This approach works best in large (5-10A or more), rectangular plantings, where the pheromone concentration in the air is more uniform and can be maintained at a high level. Border insecticide sprays may be needed in orchards adjacent to sources of adult immigration or in other high pressure situations. Growers should contact their certifying agencies to determine which specific pheromone materials are acceptable in their state.