The Red spider

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Journal of the Department of Agriculture, Journal of the Department of Agriculture, Western Australia, Series 3 Western Australia, Series 3

Volume 4

Number 2 March-April, 1955 Article 4

3-1955

The Red spider - Tetranychus telarius (L)*

C.F. H. Jenkins

Follow this and additional works at: https://library.dpird.wa.gov.au/journal_agriculture3

Recommended Citation Recommended Citation

Jenkins, C.F. H. (1955) "The Red spider - Tetranychus telarius (L)*," Journal of the Department of Agriculture, Western Australia, Series 3: Vol. 4: No. 2, Article 4.

Available at: https://library.dpird.wa.gov.au/journal_agriculture3/vol4/iss2/4

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Tetranychus telarius (L.)*

rpHE red spider is a very common pest of vegetables, garden plants and some types of fruit trees during the summer. It should not be confused, however, with the red-legged earth mite (Halotydaeus destructor), which is such a serious pest of seed- lings, but during the winter season only.

The red spider was first described from Europe as long ago as 1761, and since then it has been recorded from most countries of the world.

Like the red-legged e a r t h mite, the red red spider is really a mite, not a true insect, but for all practical purposes, it may be included in the insect pest category.

GENERAL DESCRIPTION

The adult female is barely visible to the naked eye, being only about l/50th of an inch in length. The colour varies consider- ably, being often greenish brown or yel- lowish, but more generally rust or brick red. Darkish spots can usually be seen on the back with t h e aid of a strong mag- nifying lens. The male is smaller t h a n the female and usually reddish in colour.

Being true mites, both sexes have eight legs, and not the customary six charac- teristic of insects.

LIFE HISTORY AND HABITS The round, somewhat t r a n s p a r e n t eggs, which cannot be seen without the use of a hand lens, are laid on the under sides of the leaves of selected host plants. Each

Pig. 1.—Young Red Spider (X200).

(Univ. Flor. Exp. Stn).

female may lay from 70 to 100 eggs during her average life of two or three weeks, and usually lays from three to six daily. The

» Sometimes referred to as T. urticae.

145

Journal of agriculture Vol. 4 1955

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eggs a r e laid irregularly on t h e leaf surfaces a n d under favour- able conditions h a t c h in four or five days.

T h e young mites are almost t r a n s p a r e n t on first hatching, a n d have only six legs. They soon commence feeding a n d a c - quire a greenish tinge. Later they moult their first skin and become eight-legged like t h e adults. I n w a r m weather t h e mites may reach m a t u r i t y in a little over a week, so t h a t from egg-laying to adult may occupy less t h a n a fortnight. This rapid development explains how such swarms of red spiders can a p - pear a p p a r e n t l y from nowhere to plague our gardens during hot s u m m e r weather.

Although t h e normal life of t h e adult red spider, as already indicated, is only about a fort- n i g h t or t h r e e weeks, under cold conditions this period may be greatly lengthened. The females become inactive, shelter in s e - cluded situations, a n d in this m a n n e r spend t h e winter. With t h e arrival of spring they again become active, a n d lay eggs which give rise to t h e first spring generation of t h e pest.

The m o u t h p a r t s of t h e red spider a r e adapted for lacerat- ing t h e p l a n t tissue a n d sucking u p t h e oozing sap. T h e feeding injury causes pale spots to a p - ' pear on t h e infested foliage, and soon leaves acquire a mottled and unhealthy a p p e a r a n c e . A heavy infestation of t h e pest may cause t h e foliage to bleach a l - together a n d finally to shrivel.

The web-spinning habit so charac- teristic of t h e red spider increases the dis- figurement of t h e infested leaves. The t h r e a d s of t h e webbing are too fine to see w i t h t h e n a k e d eye, but t h e under side of a badly a t t a c k e d leaf often h a s t h e a p - pearance of having been dusted with fine powder. This impression is conveyed by t h e numerous cast skins and excreta of t h e feeding "spiders" sticking to the leaf.

Being quite devoid of wings or any other m e a n s of rapid progression, it may seem

Fig. 2.—Adult m a l e Red Spider (X200).

(Univ. Flor. E x p . S t n ) .

surprising t h a t t h e red spider is so wide- spread. I t has, of course, been carried from one country to another with intro- duced plants. Local dispersion would occur in t h e same way, but in addition it is known t h a t t h e creature may be borne by the wind for considerable distance, and t h a t it can also be swept from higher to lower ground by flood waters.

HOST PLANTS

A complete list of host plants would be too long to include, but some examples are peas, beans, cucumbers, marrows, cotton, tomatoes, tobacco, violets, carnations, geraniums, a n d strawberries, as well as many shrubs a n d deciduous fruit trees.

146

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CONTROL

The effective control of the red spider entails prompt action and thorough treatments especially to the under-surface of the leaves as soon as the pest is detected.

Chemical Control.

Sulphur dusts and sprays have been ex- tensively used for the control of the red spider but some of the newer miticides are now supplanting the old treatments.

Where sulphur is used care should be taken not to use it during a heat wave as scalding to foliage may occur. When sulphur dust is applied it should be diluted with equal parts of some carrier such as slaked lime.

Lime sulphur spray should generally not be used at a greater strength t h a n 1 part to 60 parts of water, and on delicate plants the dilution should be 1 to 100.

Colloidal sulphur and other forms of sulphur sprays should be used in accordance with the manufacturer's instruc- tions.

Parathion and HETP ("Hexone") are two new materials (known as organic phosphates) which are particularly effective against most types of mites and are widely used for red spider control. They should be diluted in accordance with the manufacturer's recommendations and used with considerable care. Gloves should be worn when handling the concentrate and should any material splash on the bare skin it must be washed off immediately.

Care should be t a k e n not to inhale the spray mist during application to the plants.

"Hexone" has little lasting effect and so must be thoroughly applied. Parathion.

o n t h e other hand, has some residual action and should not be applied to fruits or vegetables later t h a n a m o n t h before picking.

Special Miticides. P.C.P.B.S.1 and "Ovo- t r a n "2 types of miticides are quite recent

developments. These materials are very selective in their action and, although harmless to most insects, they are very toxic to the eggs and immature stages of certain mites. They should be applied

1. Parachlorophenyl benzene sulphonate = "Vallo- mite," "Elimlte," etc.

2. Parachlorophenyl para chloro benzene sulphonate

— "Ovomlte," "Ovobone," "Mltran," etc.

after the winter eggs of the red spider have hatched but before the summer population has had time to reach plague proportions. The general use of these new materials cannot yet be recommended under local conditions as some foliage injury may occur to susceptible plants under certain weather conditions. Some growers, however, may be interested to carry out their own tests.

Systemic Insecticides. Certain chemicals have recently been developed with systemic properties which means t h a t when applied either to the roots or foliage of a plant the insecticide is absorbed into the sap stream and renders certain areas of the plant toxic to sucking pests.

Fig. 3.—Tomato shoot showing discolouration due to Red Spider Injury.

Most of the systemic materials are toxic to the higher animals and can only be used under certain circumstances.

"Systox" is available on t h e local market and has given good results against aphis and red spider. "Systox" should not be applied to plants required for h u m a n con- sumption and the manufacturer's instruc- tions should be carefully followed.

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Biological Control.

T h e value of n a t u r a l enemies in com- bating the red spicier is well demonstrated by t h e fact t h a t the "spiders" increase rapidly following the use of DDT. Natural enemies, especially small ladybirds, are easily killed by the DDT but the red spider a n d various other mites can withstand strong DDT applications. Where there is danger of red spider attack, therefore, DDT should be used as sparingly as pos- sible.

Cultural Methods.

I t h a s been frequently shown t h a t t h e red spider thrives best under hot, dry conditions. Where plants can be kept well watered, especially with overhead sprinklers, t h e result is a definite drop in t h e "spider" population, and this means of control is adopted by m a n y gardeners.

As the red spider attacks a variety of weeds as well as cultivated plants, t h e necessity for clean cultivation will be self evident.

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of agriculture Vol. 4 1955