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Spider Mite

Spider Mite

Tetranychus urticae

mite

In a Nutshell

    White or yellow-red speckles on the leavesEggs and insects on the underside of the leavesWebbing that covers parts of the plantWithered, torn leavesBald shoot tips and growth of side shootsFruits are few and low-quality

Hosts: %1$s

· Grape · Raspberry · Blueberry · Gooseberry · Bean · Capsicum & Chili · Eggplant · Carrots · Turnip · Pea · Cucumber · Pumpkin · Zucchini · Tomato · Cabbage · Lettuce · Potato · Gram · Cotton · Soybean · Additional · Spinach · Chard · Onion · Garlic · Leek · Almond · Maize · Strawberry · Blackberries · Currant · Radish · Citrus · Peanut

Symptoms

The spider mites feeding causes white to yellow speckles to form on the upper surface of the leaves. The eggs stick on the leaves undersides. The spider mite itself is located there, nesting in a cocoon resembling webbing. As infestation become more severe, leaves appear bronzed or silvery first and then become brittle, rip open between the leaf veins, and finally fall off. The mites spin a web that can cover the surface of the plant. Shoot tips can become bald and side shoots start to grow. In cases of heavy damage, the quantity as well as quality of fruits is reduced.

Trigger

The adult female is 0.6 mm long, pale green with two darker patches on its oval body, and long hairs on the back. Overwintering females are reddish. In spring, the females lay globular and translucent eggs on the underside of the leaves. The nymphs are pale green with darker markings on the dorsal side. The mites protect themselves with a cocoon on the underside of the leaf blades. The spider mite thrives in dry and hot climates and will produce up to 7 generations in one year in these conditions. There is a wide range of alternative hosts, including weeds.

Biological Control

In case of minor infestation, simply wash off the mites and remove the affected leaves. Use preparations based on rapeseed, basil, soybean and neem oils to reduce populations of T. urticae. Also try garlic tea, nettle slurry or insecticidal soap solutions to control the population. In fields, employ host-specific biological control with predatory mites (for example Phytoseiulus persimilis) or the biological pesticide Bacillus thuringiensis. An array of biological solutions are commercially available.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. The spider mite is very difficult to control with acaricides because most populations develop resistance to different chemicals after a few years of use. Choose chemical control agents carefully so that they do not disrupt the population of predators.

Preventive Measures

    Plant resistant varieties availableMonitor your field and remove affected plantsRemove nettles and other weeds from fieldsControl the use of insecticides to allow beneficial insects to thrive