How to deal with Mites
Mites are not insects but small animals related to ticks, scorpions and spiders. They live in diverse habitats throughout the world and more than 30,000 species are known.
Many are less than 0.5 mm long and their elongated or circular bodies have no visible segmentation; there are no antennae and the mouthparts are often adapted for sucking as well as rasping - the mouth is surrounded by palps which may be sensory structures, or modified for grasping or piercing. Adults generally have four pairs of legs. Most species are capable of reproduction by simple cell division without fertilization. They feed on plant and animal material including fungi, birds, man and his domestic animals, and food products such as cheese. They can spread serious human diseases and plant viruses.
Of the species attacking plants, some, such as the two-spotted mite or red-legged earth mite, can just be seen with the naked eye.
A number of mites not visible to the naked eye, including the eriophyid mites, seriously damage plants and are quite common in gardens. If they feed on fully developed plant parts no distortion occurs, but surfaces may be roughened and the color changed, perhaps to deep gray, bronze or rusty red. Rough, corky areas may develop on fruit, stems or leaves.
In general, control of mites can be rather difficult. Mites have developed resistance to many miticides in certain areas, causing a serious problem in deciduous fruit orchards. Predarory mites of the family Phytoseiidae attack some pest mites and this biological control has been developed as an alternative to spray programs. Although insecticides such as dimethoate and maldison do kill many mites, these natural enemies of the spider mites can continue to attack the pest mites even when spraying has been carried out.
Sulphur sprays and dusts continue to kill mites efficiently and are extremely useful in the garden. Although some insecticides kill mites, the miticides are a better choice because they are designed to disrupt the physiology of pest mites and therefore rarely affect insects, many of which, like the small black ladybirds of Stethoms genus, are natural enemies of mites. In the absence of insect pests it is ecologically more desirable to. use a specific miticide such as dicofol.
Miticides, sometimes called acaricides, have a low toxicity to humans. They are usually contact poisons and must be applied so that the plant is thoroughly covered. Some miticides, such as sulfur, also have fungicidal action, especially against the powdery mildews.
Success depends on timing and frequency of sprays since miticides do not always kill all stages of the life cycle. Read the label and follow the advice given and check with your department of agriculture for latest advice.
Where mites have overwintering eggs, as with the red mite which attacks deciduous fruit trees, the eggs can be destroyed by a winter clean-up superior oil spray. For blister mite, leaf rust mite and bunch mite in grape vines, a spray of lime sulfur can be given in August.
Types of Mites
Bean spider mite
A serious pest of beans, cucurbits and some other plants and is often found in association with the very similar, two-spotted mite. Adults are a uniform red.
Infected leaves begin with a few yellow specks, gradually become mottled yellow all over, and finally wither and die. On heavily infested bean plants, mites congregate in masses of webbing on leaf-tips towards cop of plant as weather gets colder. Spray thoroughly with dicofol or use sulfur dust. Observe withholding periods.
Some very tiny mites feed around and in buds, flowers and young foliage, and remain undetected until flowers, fruit and leaves become twisted and distorted. This type of damage is produced by the broad mite on plants such as lemons, camellias, dahlias, chrysanthemums, cyclamen, begonias and delphiniums, where the leaves may appear bronzed and the young leaves become narrow and twisted with turned-down edges. Spray wirh dicofol, or werrable sulfur or use sulfur dust.
This attacks flowers, foliage and buds. Adult mites are very small and not easily seen. Foliage is distorted, cyclamen flowers are spotted or streaked. Spray with dicofol.
Can damage all grasses. As the mites feed, they scrape the surfaces of the leaves which dry out very quickly. The grass yellows in circles and damage spreads rapidly; large quantities of webbing are seen on plants. Most miticides give reasonable control.
Hydrangea spider mite
Mottles and deforms flowers and foliage. Cup-like blisters develop on young leaves and flowers are reduced in size. The pest thrives in warm, dry situations. Spray with dicofol or another specific miticide.
Oat mite (blue oat mite or pea mite)
Attacks many plants including cereals and grasses, various weeds, lucerne, clovers, peas, lupins, lettuce, stocks, snapdragons and lobelia. Adults are about 1 mm long and purplish blue to black with pale red legs; there is a small, oval, reddish patch on the back towards the end. Damaged leaves are mottled with grey or silver. These mites are only active in cool weather.
Control weeds or use dimethoate to kill this pest. Observe withholding periods and spray any nearby grass as well as the flowers or vegetables themselves.
Pear-leaf blister mite
Adults overwinter in the bud scales. When the weather warms up eggs are laid and the new generation feeds under the new leaves, gradually producing blister galls on the upper surface. More eggs are laid inside galls and feeding continues inside. Mites may leave the walls through small, central openings and form other galls nearby. Activity decreases during hot months. Depressed, russetted spots may be produced on the fruit which will be dwarfed and malformed if severely infested. Spray with oil and lime sulfur in lace July or early August.
Red-legged earth mite
Occurs mainly in cooler regions and damages many plants including lucerne, clovers, peas, lettuce, beetroot, silver beet, calendulas, snapdragons, stocks and chrysanthemums.
Weeds like capeweed, thistles and nettles harbour infestations. Damage often beg ins near the main veins and whitish or silvery bands gradually spread as mites keep feeding. Adults are about 1 mm long, velvety black with red legs. They feed at the cooler times of day during autumn, winter and early spring. Yellow or orange colored eggs are laid in clusters on the undersides of leaves touching the soil surface. There may be two or more generations, but when weather warms up activity ceases and the last batch of eggs is retained in the female.
These eggs are protected from the heat of summer by the dead female body and hatch in cool weather after autumn rains. Spray with dimethoate, including surrounding weeds and observe withholding period on edible crops. Increase moisture, keep crops weed free. Organic methods include using buttermilk, garlic, petroleum oil, quassia or derris sprays, or sulfur powder.
Is a serious, widespread pest during summer and autumn. Infestations are usually begun by a few of these microscopic mites moving from debris of the previous crop onto the lower parts of new plants. Large numbers quickly develop and feed on stems, fruit and undersides of leaves. Lower leaves go silver, droop and curl. Stems become smooth and bronzed or brownish and later develop corky patches.
Blossoms may be shed and any fruit which develops is reduced in size with rough, corky areas on the surface. Leaves at base of plant gradually die and infestation progresses up the plane. Spray with maldison, dimethoate or wettable sulfur.
Start when plants are only about 10 cm high if infestation has occurred in previous crop. Rotate crops and observe the withholding periods of the chemicals used.
Two-spotted mite (red spider)
A worldwide pest and the most serious spider mite in Australia. It attacks many plants such as deciduous fruit trees, vegetables, strawberries, dahlias, azaleas, roses, polyanthus and violets. The mites usually feed on the underside of the leaf where they pierce the surface and suck sap, causing yellow mottling or bronzing which gradually spreads. Leaves wither and fall prematurely, and infested plants are stunted. The characteristic fine webbing, especially around midribs and petioles, helps the mites move from place to place on a leaf. They also crawl from plant to plant, are blown by wind or spread by animals, machinery or wind-blown plant pares. Adults can just be seen with the naked eye; they are pale green or yellowish and females especially have a large, dark mark on each side of body. Each female lays about 70 eggs which hatch in a few days, so that in favorable, warm, dry conditions populations increase rapidly.
Sometimes in winter females turn orange-red and become inactive. Those attacking deciduous fruit trees shelter in leaf litter at base of tree and resume activity in spring.
Control should involve weed control and destruction of infested crop residues.
Overhead and frequent watering and removal of infested leaves, plants and weeds is sometimes enough because two-spotted mite prefers dry conditions. For small outbreaks there is wettable sulfur or sulfur dust, pyrethrum and all seasons oil, or dicofol. Spray on both leaf surfaces thoroughly. However, if you want to mail order predatory mites, particularly for food plants, watch the crop carefully and order as soon as you see the first sign of spider mites.
Take the advice of the supplier on the spray to use if mites are more than about 5 to 10 per leaf, before releasing predators.
Walnut blister mite
Causes swellings on the leaves of walnuts. Each has a dense, felt -like mat beneath. Spray with lime sulfur during winter.