Spider mites Entering Diapause

Friday, 10 September 2010 15:42

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Spider mites are extremely successful at surviving winter temperatures and periods of heat or drought in the summer. This is because spider mites enter a period of rest, called diapause. During this time their bodies and behaviors change to facilitate their survival. Diapausing spider mites can be recognized by their orange-red color, not to be confused with predatory mites. Predatory mites are pear shaped. Diapausing mites have more fat deposits and their oxygen consumption is considerably lower. They are also less susceptible to chemical pesticides and feed very little before leaving the host plant in search of hibernation or resting sites. They tend to move downwards towards the floor area and away from light. Diapausing mites are more difficult for predatory mites to find because they hide in concealed places and since they do not feed, they do not release attractants that predatory mites use to find them.

Shorter daylength, cooler night temperatures promote diapause. Diapausing spider mites can hibernate in any crevices in the greenhouse structure. After a few weeks, the diapause condition ends and the mites remain dormant until favorable conditions return in the spring, when they will resume normal activities of egg-laying and feeding.

Because diapausing mites feed very little and are mainly concerned with finding hibernation sites, their populations will decrease on plants, however mites will remain a problem for growers. A high late-summer population means a high spring infestation if they are not managed before fall arrives. They will re-emerge during the spring and in the same locations they infested during the summer. It is important to reduce populations as soon as possible.

Contact materials such as horticultural oils and insecticidal soaps might be best at this time.  

Note, the new 2011-2012 version of the New England Recommendation Guide will be available at the Northeast Greenhouse Conference, (November 3-4) at a discounted price.

More information, photos: Impact of Fall Conditions on Spider Mites and Implications

Photo of predatory mites

Tina Smith, University of Massachusetts and Leanne Pundt, University of Connecticut

Spider mites are extremely successful at surviving winter temperatures and periods of heat or drought in the summer. This is because spider mites enter a period of rest, called diapause. During this time their bodies and behaviors change to facilitate their survival. Diapausing spider mites can be recognized by their orange-red color, not to be confused with predatory mites. Predatory mites are pear shaped. Diapausing mites have more fat deposits and their oxygen consumption is considerably lower. They are also less susceptible to chemical pesticides and feed very little before leaving the host plant in search of hibernation or resting sites. They also tend to move downwards towards the floor area and away from light. They are also more difficult for predatory mites to find because they hide in concealed places and since they do not feed, they do not release attractants that predatory mites use to find them.

Shorter daylength, cooler night temperatures promote diapause. Diapausing spider mites can hibernate in any crevices in the greenhouse structure. After a few weeks, the diapause condition ends and the mites remain dormant until favorable conditions return, when they will resume normal activities of egg-laying and feeding.

Because diapausing mites feed very little and are mainly concerned with finding hibernation sites, their populations will decrease on plants, however mites will remain a problem for growers. A high late-summer population means a high spring infestation if they are not managed before fall arrives. They will re-emerge during the spring and in the same locations they infested during the summer. It is important to reduce populations as soon as possible.

Contact materials such as horticultural oils and insecticidal soaps might be best at this time.  

Note, the new 2011-2012 version of the New England Recommendation Guide will be available at the Northeast Greenhouse Conference, (November 3-4) at a discounted price.

Tags: Content Type: Update Topics: Insects and Mites