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Agronomic Crops > Crops Blog > Posts > How to identify and manage spider mites on vegetables

spider mite outbreak on vegetables 7-28-17.jpgWith summer comes hot and dry weather in the southeast. Many insect pests and mite species thrive in the hot weather. In many parts of the south east, spider mites can be a major nuisance throughout the crop production season whether it is open field crop or under high tunnels. Spider mites can cause direct crop injury and produce contamination, so timely detection and reduction are critical for producers. Here is some critical basic information about spider mites.

Mites are not insects. The most common species of mites in Alabama and adjoining states is the twospotted spider mite that is easily identifiable from the two spots on their oval body. Mites look like dust particles that move - use a magnifying lens when scouting for mites! Typically, producers will find spider mites along with numerous eggs under the webbing on lower surface of leaves. Twospotted spider mites have a very wide host range from row crops to horticultural plants. Russet mites are smaller than the twospotted spider mites and have elongate bodies. Infestations seem to start from lower leaves and these mites have a restricted host range. 

  • Damage symptoms: Twospotted spider mites cause leaves to curl up with extensive webbing in the late stages. Bronzing or discoloration of leaves is also very visible. Russet mites also cause severe leaf deformation. Usually, spider mites can be very difficult to control when there is extensive webbing under the leaves. 
  • Management:
    • Cultural control:  Get healthy mite-free transplants or grow transplants yourself. Spider mites like hot weather – be extra careful transplanting in dry weather. Remove plant stress by regular watering, especially the small plants. Do not mow grasses close to crops in drought conditions as mites will ride the wind and settle on the crop.
       
    • In dry conditions, avoid using synthetic pyrethroid insecticides repeatedly for caterpillar control. These insecticides are excellent for a broad range of pests but also destroy beneficial mites that result in pests to increase.
       
    • Conventional miticides:  There are many miticides for producer to choose from (after proper identification). Agri-Mek and Acramite are two popular products with a long history of effectiveness. They are different chemistries with adequate residual and short preharvest intervals. There are restrictions on how many sprays producers can do with these products – so follow the label closely and do not exceed recommendation use rates. Zeal is another relatively new material suitable for cucurbit crops; it kills eggs and molting of immature mites with long residual action. Portal and Oberon are unique rescue products suitable for extreme conditions/outbreaks; they stop mite feeding and reproduction with selective action to protect predatory mites.
       
    • Organic management:  Pest prevention is better than cure for organic farming. Organic miticides provide adequate control of the pest when populations are low and plants are fully covered with the material. Good mite control options for slowing down spider mites include paraffinic oils (Suffoil-X), insecticidal soaps, and biological extracts (Grandevo). Several applications may be necessary with organic insecticides/miticides – so scout repeatedly and note the effectiveness of the products. Rotate insecticides to avoid resistance and lack of control with any one product.

       For any further assistance, contact a regional extension agent at your county office or call this author at 251-331-8416.

Ayanava Majumdar

Extension Entomologist, ACES


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