Predatory Mite Biology

Table of Contents

1. Introduction
2. Balastium putmani
3. Zetzellia mali
4. Amblyseius fallacis
5. Typhlodromus pyri

Introduction

Before synthetic pesticides were widely introduced at the end of the 1940s, mites were rare pests on fruit crops. They were almost completely regulated by their natural enemies, mostly beneficial mites and some insects, such as mullein bug.

A 1986 field survey of 112 Ontario apple orchards revealed that over 75% had beneficial mite populations surviving in them, but often in low number. A number of orchard pesticides that are toxic to these beneficials and not compatible with IPM, should be avoided to minimize harmful effects on predatory mites. Some examples are pyrethroids, Benlate, Zolone, and Carzol. Another pesticide, Sevin, even used at low rates as a fruit thinner, can be very toxic to some important predator mite species, but the benefit of using this material as a chemical thinner often outweigh the risks.

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Balastium putmani

The three most common species of predatory mites in Ontario apple orchards according to a 1986 survey, are Balaustium putmani, Zetzellia mali and Amblyseius fallacis.

Balaustium putmani is a large velvety-red, tick-shaped mite (Figure 1) that overwinters as a n egg underneath bark. Nymphs hatch in early May and begin feeding on mites, their eggs and other small soft-bodied insects.

They remain in fruit trees all season and are important early-season predators.

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Zetzellia mali

Zetzellia mali is a lemon-yellow mite, with a diamond-like shape (Figure 2). It overwinters under bark and may suffer heavy winter mortality in some parts of the province.

It becomes active early in the spring, feeding on overwintering European red mite eggs and rust mites. It can be fairly effective in controlling low-density pest mite populations.

Figure 2. Zetzellia mali feeding on European red mite egg.

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Amblyseius fallacis

Amblyseius fallacis, a phytoseiid mite, is a commonly found mite predator in Ontario, particularly in July and August (Figure 3).

It is a pale mite, the colour varying from off-white to brownish to reddish, depending on what the individual mite has been feeding on. It is tear-drop-shaped and extremely fast-moving.

Somewhat smaller than an adult female European red mite, it feeds on all stages of all three pest species of mites on apples. Alternate food sources include apple rust mites and pollen grains.

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Typhlodromus pyre

Typhlodromus pyre, another phytoseiid mite species, has traditionally been a more important mite predator in New York, Nova Scotia, and several other apple-growing areas. The life cycle of T. pyre sib similar to that of A. fallacis but I. pyre overwinter as mated females on the tree, under bark scales. Emergence occurs around the time first green tissue is present. New York reports three to four generations per year with populations building gradually through the season.

There have been several strains of T. pyri developed that are resistant to various pesticides. OMAFRA and AAFC have initiated several controlled field trials to test the feasibility of establishing pesticide resistant T. pyri populations in Ontario apple orchards.

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