Fruit IPM Fact Sheet
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Beneficial Insects and Mites

Reference:  Common Tree Fruit Pests Angus Howitt, 1993,
NCR 63 - Michigan State University

Growers and consultants need to recognize beneficial predators and parasites in the orchard. Knowing the natural controls of the secondary pests in the orchard allows growers to use natural controls when they are present and avoid costly sprays to control pest which do not pose a problem. Here are some descriptions and pictures of some of Michigan's most common beneficial insects and mites.

Predator Mites

Amblyseius fallacis

This insect is about the same size as a spider mite but is longer and has a broad abdomen. Its color will vary from white to pinkish. When exposed to direct sunlight, this predator, which is usually found on the underside of the leaf, will move rapidly across the leaf surface. Its eggs are larger than two-spotted mite eggs, oval and almost transparent. The insect lays between one and five eggs per day, usually along the leaf midrib or near leaf hairs.

Like the adults, the immature stages are transparent or colored. Development from egg to adult takes about a week at 70 degrees F. Populations can multiply within two to three weeks from 10 per 100 leaves to 200 to 500 per 100 leaves. Adult females over winter at the bases of apple trees or in ground cover litter. In the spring, they feed on two spotted or other plant-feeding mites on the ground cover until around mid-June or July before migrating into the apple trees.

In summer, this predator is most commonly found on the undersides of leaves on spurs in the lower and innermost portions of the tree. As populations increase, A. fallacis will disperse throughout the tree. The insect has the potential to nearly eliminate phytophagous mites from apple trees.

Agistemus fleschneri and Zetzellia mali

These two mites are very similar. The eggs of both species are round, smaller then two spotted mite eggs and bright yellow. These mites later turn reddish yellow after feeding on pest mites. Adults are almost oval but have a more pointed posterior than spider mites, and they are slightly smaller then either adults spider mites or A. fallacis.

Both of these predaceous mites feed on all stages of spider mites and rust mites. A. fleschneri and Z. mali require nearly double the time that phytoseiid mites, including A. fallacis, require for egg-to-adult development. Both also have a much lower intrinsic rate of increase, a longer generation time and a much lower reproductive rate. They consume about one to two mite eggs a day.

Though these predaceous mites have neither the reproductive potential nor the high prey consumption potential of phytoseiid mites, both can maintain themselves at low densities. Under detrimental environmental conditions, they can develop high population densities on orchards. To some extent, the relatively large populations of these predator mites compensate for their relative inactivity, and they can considerably reduce overwintering phytophagous mites. Both species can survive pyrethroid applications.

Stigmaeids do no interfere with phytoseiid mites’ control of phytophagous mites. There is little direct predator between these predator species and relatively little overlap between preferences for European red mite at low densities, a combination of one stigmaeid and one phytoseiids, even though the maximum phytoseiid rate is about four times that of stigmaeids.

Stethorus punctum

This insect is considerably larger than phytophagous and predator mites. Both the larval and adult stages feed on spider mites in apple trees. The larva is about 3/16 inch long when full grown. Color varies from light black to brown. Stethorus pupae are black, flattened and generally fastened to the upper sides of apple leaves.

The adult beetle is jet black, has wings, and is very round and shiny. In the winter, adult Stethorus hibernate in debris at the bases of apple trees and in fields and woodlands adjacent to the orchard. In summer, adults fly to the apple leaves where high densities of mites are present. Here, on the lower surface of the leaves, they lay about 95 percent of their whitish, elongated eggs.

They need a minimum of five mites per leaf to stay active and eight to 10 mites per leaf to encourage reproduction. They will feed on all stages of mites. They typically feed on European red mites early in the season and then on both European red mite and two spotted mites later in the summer. S punctum larvae feed on motiles. The adults prefer eggs and can consume up to 60 eggs.

The development from egg to adult requires about a month at 70 degrees F. Depending on the location, two or three generations are produced in a season.

S. punctum requires large spider mite populations and will leave a tree in search of new spider mite populations when the phytophagous mite population declines. S. punctum will generally not lay eggs until there are eight mites per leaf. When S. punctum is the major predator, miticides should not be applied until there are at least 15 mites per leaf, and perhaps not then if it appears that S. punctum is present in sufficient numbers to control the phytophagous mites.

Climatic conditions appear to limit the spread of this insect – it is not abundant in many northern apple-growing regions.

These are predaceous bugs whose adults and nymphs feed on aphid, leafhoppers, scales and caterpillars. Many true bugs are pests, such as the tarnished plant bug, but some have adopted predaceous habits. The predaceous bugs have modified front legs that can grasp and hold prey, and short, stout beaks that help them feed on prey. Their salivary glands produce poisonous or paralyzing secretions that subdue the prey.

These beneficial insects can be found worldwide. They are very efficient predators of aphids, scales and mites. Adult ladybird beetles are generally hemispherically shaped and brightly colored, although some, such as Stethorus punctum, are completely black.

Adults overwinter in sheltered locations such as tree holes and other natural hiding places. They become active in the spring and lay their eggs on the undersides of leaves that are usually near aphid colonies.

Eggs are yellow and spindle-shaped, and they stand on end. The larvae, which resemble tiny alligators, have well developed legs and are quite active. They are usually brightly colored, with various protuberances on the body segments. The larvae develop through four instars, then pupate on a leaf or branch by attaching the body to the leaf surface. The larval skin splits along the upper surface and is pushed to the bottom of the pupa. The pupa then stands erect on the leaf or branch until the adult emerges. The life cycle takes about one month. Depending on location, there are two or three generations a year.

Lacewings

These can be easily recognized because of their distinctive characteristics. Adults have lacy, net-veined wings, metallic golden colored eyes and a strong defensive odor. The predaceous larvae have long, sickle-shaped mandibles and rotund bodies. Lacewing larvae feed on aphids, mealybugs, leafhoppers, scales, mites and eggs of Lepidoptera. Lacewings are important predators of Oriental fruit moth eggs.

Mature larvae overwinter inside cocoons situated in bark cracks or on leaves on the ground. Adults become active in the spring, laying eggs on tree trunks and branches. Each oval egg is situated at the tip of a long, erect stalk. When larvae hatch, they climb down the stalks and seek out prey. The stalks offer protection from egg parasites and predators and help reduce cannibalism by newly emerged larvae.

Larvae often adorn themselves with the remains of their prey and other debris. The trash placed on top of their bodies is lost at each molt and a new accumulation is then started. The life cycle is completed in about one month. Depending on locations, two or three generations are produced a year.

Tachinids

This is a large group of flies that are nearly all parasitoids. They are valuable because they have a high biotic potential. This rapid increase in numbers can be effective in biological control. Tachinida commonly parasitize lepidopterous larvae and beetle larvae and adults.

Tachinid adults are medium to large flies with dull coloring and prominent bristles. Tachinids generally overwinter in the pupal stage in the soil or leaf litter. Adults emerge in the spring and feed on insect honeydew and flower nectar. After mating, the female seeks out hosts to parasitize.

The larvae feed internally in the host, often consuming all but the skin of the host. Only one larva usually develops in each host, but if the host species is large, more than one larva may successfully develop. When the larva completes feeding, it bores out of the host and pupates.

Some species of tachinids have only one generation a year, while others have multiple generations a year and require about a month for development of each generation.

Ichneumonid and Braconid wasps

These are large groups of wasps that closely resemble one another and parasitize beetle larvae and adults, fly larvae, lepidopterous larvae, sawflies and aphids. Most of the braconid and ichneumonid larvae develop inside the host's bodies. When the host is concealed, however – which may be the case for such pests as leafrollers or wood-boring beetles – the parasitic larvae may remain outside the hosts’ bodies, feeding externally. Eggs of many pests species are parasitized by very small wasps, most of which are from the trichogrammatid family. In some cases, up to 90 percent of lepidopterous pest eggs are parasitized.

Eulophid parasites

Under natural conditions, these egg parasites can have an almost 100 percent control effect on spotted tentiform leafminer.

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Created: June 20, 1999
Last modified: October 19, 2009