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McDaniel- Apple, rarely on other fruit trees.
Twospotted- Pear, stone fruits.
Leaves- For apple and stone fruits, speckled when lightly infested; bronzed and covered with webbing when heavily infested; injured leaves may fall. For pear, leaves turn black and drop off.
Fruit- Mite feeding can affect size, colour and subsequent fruit set of apple and pear if mites are numerous for a long period; little effect upon mature stone fruit.
Egg- Spherical, translucent to opaque.
Immature- Similar to adults but often lacking black spots, initially with six legs, later with eight.
Adult female- Oval, with eight legs, red or orange in winter, yellow to green in summer with two black spots on each side. McDaniel has additional smaller black spots toward the rear (Fig. 1) compared to the twopsotted spider mite (Fig. 2).
Adult male- Smaller than female, abdomen narrows toward rear.
|Figure 1. McDaniel spider mite life stages. (AA-FC)||Figure 2. Twospotted spider mite life stages. (AA-FC)|
Red to orange-coloured adult females overwinter beneath bark or in trash at the base of trees. In early spring they move up the tree trunk to leaves near the main limbs. They spread throughout the tree and produce several generations depending on temperature. Overwintering females appear in September.
Examine leaves throughout the orchard to assess average numbers of active spider mites and predatory mites. Inspections every week or two are desirable to evaluate population trends and tree response. Numbers of both plant-feeding and predatory mites may be determined either by hand lens examination or through one of the mite counting services.
Apple trees can tolerate the moderate numbers of spider mites that normally occur when predatory mites and insects are present. Pear cannot tolerate the level of spider mites needed to support populations of predatory mites. Chemicals applied for controlling other pests and diseases on apple may upset the ratio of plant feeding to predatory mites, reducing the effect of biological control. Refer to the table – Relative Toxicity of Insecticides/Miticides to Common Beneficial Mites and Insects – as an aid to selecting least disruptive control products.
Healthy, well-maintained trees will tolerate higher mite populations than weak or stressed trees.
Chemical control on apple is not required if predatory mites are present to keep McDaniel and twospotted spider mites at low to moderate levels. See chemical control of European red mite for recommended summer sprays if required to control spider mites.
Because pear is more susceptible to spider mite damage, early detection and control is often necessary to prevent losses. A petal-fall application of Apollo SC will provide season-long control. Apply when mite populations are mainly in the egg stage and there are fewer than 3 mites per leaf. Use Envidor, Nexter or Nealta for summer control of mites. Envidor controls all stages of spider mites and also controls any pear rust mite present. Do not apply more than once per season. Kanemite 15 EC will control all stages of spider mites. Apply Kanemite before economic thresholds are reached. Nealta will control all life stages of spider mites.
Pesticide resistance management - It is important to alternate products from different chemical classes or with different modes of action to avoid the development of resistance. Select miticides with different Group Numbers (see product label or Spray Schedules) to rotate as part of a resistance management program.