May 2012 Newsletter (vol.7)   >>   Insect Alert: Spider Mites

Spider Mite

We’ve heard from several growers that spider mites are appearing a tad earlier than last year. If the warm, dry weather sticks around we’re bound to see increased populations appear in what feels like overnight. What may seem like a slight infestation can explode into a severe problem. Scout regularly and react as soon as you see signs of damage. Spider mites reproduce and develop at an extremely fast rate, so it is important to stay alert!


There are several signs of spider mites to look for when scouting your plants. Many spider mites especially in high populations will produce webbing to provide shelter from enemies and protection for their eggs. Symptoms of injury include small spots creating a speckled appearance on the leaves, discoloration (bronzing), scorching of leaves, eggs which are normally laid near the veins of leaves, and defoliation. If not detected, spider mites will cause serious stress to the plant if not killing it completely.


If your scouting has proved an infestation is present, there are two control options either chemical or biological.


Chemical control options
Be sure to read the labels to ensure they are right for your application. It may be necessary to repeat applications at 3-5 day intervals to interrupt their life cycle.
Akari controls all stages of mites and provides residual control for 21-28 days.
Abamectin or Avid safe to use with beneficial insects.
Floramite 3-day knockdown of all stages and residual control for 28 days.
Judo affects all stages and provides residual control for 21-30+ days.
M-Pede OMRI listed.
Ovation kills eggs on contact and sterilizes females. Great in combination with Sanmite.
Sanmite controls all stages and lasts up to 28 days. Works well with Ovation.
Shuttle O rapid knockdown and long-term residual.
Tetrasan sterilizes eggs and controls all stages.


Biological control options
Neoseiulus fallacis predatory mite for prevention and low-infestation management.
Phytoseiulus persimilis the fast action predatory mite
Stethorus punctillum the spider mite destroyer


Cultural Practices
Be cautious and only apply insecticides when needed.  Some common active ingredients such as imidacloprid and carbaryl can destroy natural enemy populations of spider mites thus contributing to increased infestations. Sufficient watering of plants in the warmer months can limit plant susceptibility to mites since populations peak during these months. 


There are several things that you can do in addition to chemical or biological control to temporarily control an infestation.  The first is to try rinsing the plants with a strong jet of water. This would physically remove and possibly kill some of the mites.  Another attempt to disrupt spider mites once they are detected is to clean off any webbing that is present. This may delay egg laying temporarily until you are able to spray, although new webbing will be created rather quickly during the prime season.


Spider mites may be quite a nuisance, but at one time or another every grower has dealt with them.  Knowing how to properly identify and treat the pest is the key to having healthy plants. Remember stay alert and react fast!