Twospotted Spider Mite

Family: Tetranychidae

About the Twospotted Spider Mite

Reproduction and Life Cycle

Female twospotted spider mites will overwinter as adults on tree bark or ground litter near a host plant. In the spring they emerge and begin mating. The then lay their eggs on silken webbing that they spin on the underside of foliage, laying about 2 to 6 eggs each day and up to 100 in their lifetime, as females can live for up to 4 weeks. The eggs will take about 3 days to hatch into larvae. After the larvae stage of development has been completed, they will go through 2 nymphal stages, and then become an adult. If they are presented with optimum weather temperatures, about 80 degrees Fahrenheit, the entire process from egg to adult should take between 5 and 20 days. There will be numerous generations each year that overlap.

Twospotted Spider Mite Identification and Habitat

Identification

This pest is a tiny 0.5mm in length and has 2 defined body parts: the idiosoma (abdomen, thorax, and head) and the gnathosoma (the mouthparts). The abdomen has spines that sparingly cover it. As an adult, the twospotted spider mite has 4 sets of legs. They also have 4 sets as a nymph; just not during the larvae stage when they have only 3 pairs. The adult is oval shaped, and can be anywhere from brown to orange to green to yellow; however, a yellow-green is most common. They often take on a near translucent colouration. The females have 12 dorsal setae pairs. When the females overwinter, they tend to take on a more orange-red colour. On the sections of the mite where the body’s wall is translucent, you can see dark spots from within. These spots are a buildup of waste in the body and are often quite large in size; new mites will be spotless since their bodies have not yet created waste. Male mites tend to be slightly smaller in size than the females. The eggs are very small, white and round in shape. The larvae are similar to the adult other than the 1 less set of legs.

Habitat

The twospotted spidermite originated from Europe and can now be found throughout the United States, often in greenhouses where they can survive unfavorable weather conditions. They prefer temperate zones, with hot and dry summers. This mite will feed on numerous different plant types, such as flowers, trees, fruits, vegetables, and shrubs. They have mouthparts that will pierce the plant tissue and then suck the juices out of it. They typically feed from leaves undersides, creating silken webbing on the plant as they do this. If the plant has been fed on for a long period of time, the foliage will appear to have a fine cobweb on its surface. Due to the fact that they are so tiny and feed in areas that are hard to see, you may not notice they have infested your crops until the damage they have caused is significant. The damage they cause is seen by the leaves yellowing. Foliage my fall off before it should. If the mites were feeding on flowers, they will brown the petals and cause them to wither.

Twospotted Spider Mite Management and Control Methods

Cultural Control

It can be challenging to spot this pest; a magnifying glass is often necessary. Or instead, you can place a white sheet of paper underneath the foliage you think may be infested and shake the plant. If you see tiny black dots moving on the paper, you will know that your plant has mites. To help control this pest, you should ensure that weeds are destroyed near and in your fields, either in the fall or right at the beginning of spring. Sprinkler irrigation overhead can also help relieve your plants from mites for a short time.

Chemical Control

Miticides have proven to be effective on this pest. It is important that you try and apply it before the infestation has become too significant. Treatment often needs to be reapplied every 7 to 10 days, until the infestation has been contained, especially because the eggs are immune to sprays. Also, it is important to note that this mite can acquire a resistance to different types of chemicals, so be sure to change the chemical used every 3 applications. Additionally, sometimes when an insecticide is used, it can actually increase the mite’s population as it will kill off many of their predators. Therefore, if you are spraying plants that are at risk of a mite outbreak, mix a miticide in with the insecticide when spraying the plants. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy.

Latin / Alternative Twospotted Spider Mite Names

• - Tetranychus urticae
• - Red spider mite
• - Glasshouse spider mite

Sources