The first signs of this pest to the uninitiated may seem like a nutrient shortage, as the leaves of the crop turn yellow and die. These moths generally choose the upper leaves first, where conditions are drier and warmer. The pest itself is not noticeable because it lives on the underside of the leaves and is very small. However, if you turn the affected leaves over and look at the undersides, in cases of severe infestation, small moving red dots can be seen, and quite often also spider webs (because mites are closely related to spiders; hence the term ” Red spider”). ).
Spider mites feed on plant cells and produce characteristic small, yellowish, speckled feeding marks. If you examine the leaves closely, this spot is quite obvious on the upper surface of the leaf, although the damage occurs below. Many insecticides have little or no effect in controlling them. Its small size, ability to exist near plant veins, spider webs, and being a different pest species than other insects make spray control extremely difficult.
Spider mites are sensitive to day length and are able to hibernate within cracks and crevices of plant structure. If you had spider mites last year, there’s a good chance it will still be a problem this year.
Spider mite populations can explode in conditions of high temperature (above 30oC or 85oF) and low relative humidity (below 60% RH). Temperature affects the rate of the life cycle, therefore the higher the temperature, the faster the growth rate of the spider mite population.
Temperature (C & F) – No days (from egg to adult)
60oF (16oC) …………………………..30
18oC (64oC)………………………………21
70oF (21oC) …………………………..14.5
32oC (90oF) …………………………..3.5
Predatory mites can be purchased in the US and some other countries, and are extremely effective at clearing spider mites. These predatory mites multiply almost twice as fast as spider mites and only feed on other mites and not plants.
Where it is not possible to buy predatory mites, it is possible to slow the development of the pests by increasing the humidity around the plants by watering their leaves.
Products such as fish emulsions sprayed on plant foliage are also known to be effective.
When the crop is finished, it is important to clean and destroy all plant debris to minimize the risk of transmission of these pests.
