SPIDER MITES: Tetranychus (Tetranychus) spp., including CARMINE SPIDER MITE, T. (T.) cinnabarinus, and TWO-SPOTTED SPIDER MITE, T. (T.) urticae, Tetranychidae

ADULT: The mites are eight-legged,1/32 in. long, round to oval-shaped and range from whitish with spots to dark reddish-brown in color. They are often found in thin webs on the undersurface of leaves.

EGG: The round, white to tan eggs are deposited singly on the undersurface of leaves often beneath webs. Larvae emerge in 3 to 5 d.

IMMATURE STAGES: The larvae are six-legged and translucent. Most of the actual growth of the mite occurs during this stage. The following protonymph and deutonymph stages are eight-legged and begin to look more like adults in shape and color. The mite goes through periods of inactivity between each of these immature stages. It anchors itself to a leaf or webbing while its new cuticle is being produced beneath the old. It then molts and continues activity until ready to go through another inactive molting period.


DAMAGE: Mites feed by pushing their stylets into the plant tissue, creating tiny ports through which they feed on plant fluids forced through the holes by turgor pressure. Mite feeding damage appears as yellow stippling between veins on the lower leaves. Entire leaves can become yellow and then brown. By the time lower leaves are killed by mites, they are usually common on the upper leaves as well. Large, damaging populations can develop during hot, dry weather. Cool, wet weather retards population growth and they may enter an extended period of quiescence during periods of extremely high humidity. Potential damage is more prevalent in the central and north growing areas of the state during the summer.

CONTROL: Natural enemies and weather often keep mites from reaching damaging populations.  Pesticides are available for foliar applications.  Several applications at 4 to 5 d intervals will likely be required to kill larvae emerging from eggs deposited before the initial pesticide application.  Formulations, rates, and pre-harvest intervals of insecticides labeled for mite control in Florida are listed below for sweet corn (Table 1) and field corn (Table 2).

Table 1.  Chemical control of mites in sweet corn
Insecticide, formulation Rate/acre Min. days to harvest Application notes
cyhalothrin (Karate, Warrior) 1 EC 2.56 - 3.84 fl oz 1 spider mite spp.
diazinon (D-z-n) 50 W 1 lb 7 spider mite
diazinon (D-z-n AG500) 4 EC 1 pt 7 spider mite
diazinon (D-z-n AG600) WBC 12.75  fl oz 7 spider mite
ethyl parathion (Parathion) 8 EC 0.5 pt 12 spider mites
oil (Sun Spray Ultra Fine Oil) 98.8% 2 gal / 100 gal water    
oxydemetonmethyl (MetaSystox-R) 2 EC 1.5 - 2 pt 7 - 1 app., 21 - 2 app.  
phorate (Thimet) 20 G 6 oz / 1000 row- ft 30 banded at plant, not in-furrow
pyrethrins + rotenone (Pyrellin) EC 1 - 2 pt 12 hr  
soap, insecticidal (M-Pede) 49 % EC 2 gal / 100 gal water 0 spider mites

Table 2.  Chemical control of mites in field corn
Insecticide, formulation Rate/acre Min. days to harvest Application notes
dimethoate (Dimate, Dimethoate 400) 4 EC 0.67 - 1 pt 14 banks grass mite, two spotted spider mite
dimethoate (5 Lb Dimethoate) 5 EC 8.4 - 12.8 fl oz 14 banks grass mite
disulfoton (Di-Syston 8) 8 EC 1.2 fl oz / 1000 row-ft or 8 - 16 fl oz 28 banded at plant or injected post plant (not in-furrow) or foliar
ethyl parathion (Parathion) 8 EC 0.5 pt 12 spider mites
phorate (Thimet) 20 G 6 oz / 1000 row-ft 30 banded at plant, not in-furrow
propargite (Comite) 6.55 EC 2 - 3 pt 30 banks grass, two spotted spider mite
pyrethrins + rotenone (Pyrellin) EC 1 - 2 pt 12 hr  
sulfur (Sulfur) 6 L 0.67 - 2.5 gal   banks grass, red spider, and two-spotted spider mites