Pests and Diseases Viewer

Red Spider



P_redspider1

Red Spider

Usually appear in

All Seasons


Back to Pests and Diseases


Caused By:-     Red Spiders Tetranychus urticae & Panonychus ulmi

Description

Two genus of pest have the common name Red Spider mite. One is the Fruit Tree Red Spider mite — Panonychus ulmi — which mainly attacks vine as well as fruit trees such as apple, pear, cherry, currant bush and cane fruits. This pest overwinters on the stem usually near the growing tip. The other red spider mite is also known as the Two Spotted Spider mite — Tetranychus urticae — and is more normally a pest of crops grown under glass, but can attack outside plants like Strawberries, hops, blackcurrants and cane fruits in hot, dry summers. Damage by infestation with either species is caused by them feeding on plant leaf tissue. The first symptom of attack is speckling of the upper leaf surface, where colonies of mites are feeding on the underside. As the population builds the foliage becomes dull, eventually turning a bronze colour followed by premature leaf fall. The leaves start to get speckled with white dots, which are caused by the cells dying where the red spider sucks the cells sap. The tiny spider is not bright red, but a light shade of red almost orange. They are very difficult to see with the unaided eye, but their effect on the leaves are almost unmistakable. As the population builds the foliage becomes dull, eventually turning a bronze colour followed by premature leaf fall. If left unchecked a web is spun around the leaves. When this is seen the plant is usually almost beyond saving. They blend in well with the soft hairy leaves of plants like the tomato. They spread extremely fast and can infest a large tree causing it to lose its leaves early, weakening it and allowing other diseases to kill it. This is the leaf of a Brugmansia (Angels Trumpet) the typical white spots are clearly seen. It is said that spraying with water regularly keeps them at bay, but it has never worked for me. Regular insecticide does work, but the best chemical attack is an organic one from The green Gardener called Savona, but they do not list it in their new catalogue. They sell a new product called invigoratorThe Green Gardener also sells biological control insects that controls red spider. I must try it sometime. I know that Kew Gardens use biological control on their plants and I have never seen red spider on their plants so it must work.


Control

The best control is to spray with a systemic insecticide, but this may not be possible as some insecticide are harmful to some plants. There are some organic insecticide like Savona, from the Green Gardener, which are very effective. They are also doing a new product called invigorator, which is supposed to be better. Another control is to spray the underside of the leaves every day with soapy water. Red Spider does not like humid conditions and regular spraying with water, especially soapy water, is said to be effective. Their life cycle is about every ten to 14 days depending on temperature. Therefore spraying regime must take this unto account as the eggs are not usually killed by most insecticides. If the temperature is high enough a biological control with red spider predator Phytoseiulus persimilis is quite effective.

P_redspider1 P_redspider2 P_redspider3 P_redspider4 P_redspider5

Click picture to see larger view and more information   



Back to top