Read and carefully follow the label directions of the products you use.
- Bacillus thuringiensis (Bt var. kurstaki), available in many products) is a selective microbial insecticide formulation using a byproduct of the naturally occurring bacterium Bacillus thuringiensis as its active ingredient. Susceptible moth and butterfly larvae (caterpillars) are killed after feeding on fruit or foliage sprayed with Bt. Bt is not effective when applied after the larvae are inside the fruit, stem, or trunk. It is very effective against young larvae; much less effective against mature caterpillars, so timing is critical. Multiple applications will be required to control serious pests because it breaks down rapidly and works slowly.
Bt is considered an organic insecticide and is harmless to humans. In orchards, Bt should provide excellent control of variegated leafroller, tufted apple bud moth, red-banded leafroller, oblique-banded leafroller, green fruitworm, Oriental fruit moth, and most forest-orchard species (gypsy moth, tent caterpillar, webworm). When mixing Bt with other products, always add Bt first. It is incompatible with high pH materials such as Bordeaux. Good mechanical agitation is important to quickly mix Bt.
- Botanical insecticides: are derived from plants. These include pyrethrins and neem. Botanical insecticides are less persistent in the environment (have little residual activity) and break down quickly in sunlight, so it is best to apply them early or late in the day. Timing must be precise and multiple sprays may be required. These materials are not necessarily less acutely toxic than synthetics. Follow label instructions and take necessary precautions. These are broad-spectrum insecticides that can also kill non-target organisms, including aquatic species, and beneficial insects, including bees. They are also formulated in combination with each other, with organic fungicides like sulfur and copper, and with soap or oil.
- Neem is derived from the seed of the tropical neem tree. The active ingredient, azadirachtin, acts as an insect repellent, anti-feeding agent, and growth regulator (prevents molting). Labeled for beetles, caterpillars, weevils, aphids, thrips, whiteflies, and other pests.
- Pyrethrin (Pyrethrum) is derived from the flowers of several species of Chrysanthemum. It acts as a contact poison, so the spray must actually hit the pest to be fully effective. Pyrethrin has a “knock-down” effect—it stuns and disorients pests. It can control a wide range of pests.
- General Purpose Mix, GPM (home orchard spray) usually contains an insecticide, typically a pyrethrum, and the fungicides, sulfur, and copper. Can be purchased as a dust or spray. Even though this is considered organic GPMs generally are not recommended, especially early in the season. During the bloom period, a fungicide may be needed but GPMs always contain insecticides. Pyrethrums are broad-spectrum insecticides that are especially harmful to honeybees, other pollinators, and natural enemies. Refer to the product label for the listed fruit and the pests and diseases it controls. Usually labeled for tree fruits.
- Horticultural Oil is an important tool for managing tree fruit pests. It smothers soft-bodied pests, such as scale insects, mites, aphids, and young caterpillars. It can also kill insect eggs. Like soap, it must contact the intended pest to be effective. There are 3 different types of horticultural oil:
- Dormant Oil is applied during the dormant season to all tree surfaces, after leaf drop in the fall, or before bud swell in the spring. Effective at controlling overwintering scales, aphids, and spider mites. Should be applied only if air temperatures are to remain above freezing for at least 24 hours after the spray application.
- Superior Oil with a 60- or 70-second viscosity is recommended as a control measure for preventing San Jose scale, European red mite, and aphids. The 60- or 70- second oil is not a dormant-type oil. It is lighter and more volatile than the original superior oil used as a dormant spray. The main advantage of the lighter 60- or 70-second oil is the reduced possibility of plant injury. It remains on the tree long enough to kill the pest, but not long enough to interfere with vital plant processes or oil-incompatible pesticides that may be applied later. Because of this safety factor, the 60- or 70-second oil can be applied up to the pre-pink stages of apple bud development.
- Ultra-Fine Horticultural Oil sprayed at a summer rate of 1% to 2% can be used to control soft-bodied pests, aphids, mites, scales, leafhoppers, and small caterpillars, in the spring and summer. Avoid applications on cloudy, humid days when the ambient temperature exceeds 85F. The oil will evaporate more slowly under such conditions that may result in leaf burn.
- Insecticidal Soap is an organic pesticide for insect and mite control on fruit trees. This soap-like material, consisting of long-chain fatty acids, is thought to disrupt the cellular metabolism of insects and mites. It has been used to control a variety of insects on various crop and noncrop plants. Insecticidal soap is effective only in the liquid state as it contacts the insect or mite. Once dried, it is not toxic to the pest. It is extremely safe for humans and other animals. Sprays can be applied up to the day of harvest.
However, be careful not to spray open blossoms. Soap has caused russeting (browning and hardening of skin tissue in a spider web pattern) on certain apple cultivars (Red and Golden Delicious) and pear cultivars (d’Anjou, Comice, and most Asian pears).
On apples, insecticidal soap has proven effective against mites, scale insects, and white leafhoppers. On pears, insecticidal soap is effective against pear psylla, pear slug, and mites in post-bloom applications at the same rate recommended for apples. However, it is not effective against many other pear pests during post-bloom. It can be mixed with a one-half rate of another insecticide to provide a broader range of effectiveness.
- Spinosad is an insecticide developed in the late 1980s. It is a metabolite from the aerobic fermentation of a naturally occurring microorganism, Saccharopolyspora spinosa. Organic farmers like it because it has very low toxicity to people and animals and has proven effective against many important insect pests—caterpillars, beetles, thrips, sawflies, and flies. It also does not seem to have a significant negative impact on beneficial insects in the orchard. Spinosad works by overexciting the nervous system of target insects resulting in paralysis and death in 1-2 days. It must be ingested by the target pest insects to be effective.
- Surround is finely pulverized kaolin clay that is mixed with water at the rate of 1/4 lb. (1 1/2 cups) to 1/2 lb. (3 cups) per gallon of water and sprayed on a wide variety of plants to create a white protective barrier. This “whitewash” suppresses the feeding of some key insect pests, like codling moth larvae and oriental fruit moth larvae, and is widely used by organic apple growers. The white coating makes it more difficult for pests to locate the host plant, groom themselves, and to feed and lay eggs on the leaves. Thorough coverage is important—three early applications should be made to create a thick barrier and additional applications are made throughout the growing season to maintain the coating. The material is harmless to people and can be sprayed right up to harvest. The white coating does not reduce leaf growth or yields. In fact, it is believed that the white coating keeps leaf surfaces cooler during hot summer days and enhances plant growth.
- Carbaryl (Sevin) is a relatively safe, carbamate insecticide. But, it is highly toxic to bees and pollinators and should not be used near bloom. When applied 2 to 3 weeks after bloom, carbaryl acts as a fruit thinner on many varieties. Normally, mite populations build up rapidly following carbaryl applications because it is toxic to mite predators and because it acts as a hormonal stimulant for mites and promotes egg-laying.
- General Purpose Mix, GPM (home orchard spray) contains both a fungicide and an insecticide to control a range of insects and diseases. Captan is usually the fungicide. Methoxychlor, malathion, or carbaryl (Sevin) are the insecticides. There are newer GPMs on the market with the active ingredients lambda-cyhalothrin (pyrethroid-insecticide), pyraclostrobin (fungicide), and boscalid (fungicide). GPMs generally are not recommended, especially early in the season. During the bloom period, a fungicide may be needed but GPMs always contain insecticides. Carbaryl (Sevin) is a broad-spectrum insecticide that is especially harmful to honeybees and kills spider mite predators, thus encouraging large spider mite populations. Refer to the product label for the listed fruit and the pests and diseases it controls. Usually labeled for tree fruits.
- Malathion is a widely used broad-spectrum insecticide with a short residual (2 to 3 days). It is very effective against aphids and moderately effective against mites, leafhoppers, and scale crawlers. It is available in wettable powder and liquid forms. The liquid form may be injurious to the foliage of sensitive plants, such as raspberries.