Spider Mites

Two-Spotted Spider MitesTwo-spotted Spidre Mites
(Gilles San Martin)

Spider MitesSpider Mites

Spider Mite Stippling DamageSpider Mite Stippling Damage


  • Hemp
  • Legumes
  • Root crops
  • Solanaceae crops
  • Cucurbits
  • Many weeds and ornamentals


Tiny, with a yellowishclear body and two dark spots on either side of its back. Eggs are very small, spherical, translucent initially, and turn opaque as they age. All life stages most frequently occur on the undersides of leaves. 


 Egg | Larva | Nymph | Adult.
  • 8 or more generations per year.
  • Overwinter as adults in ground cover and weed residue.
  • Adults become active in spring, feeding on weeds and laying eggs.


Leaves become stippled (small yellow spots) and may turn bronze as infestation increases. Generalized bronzing or reddish discoloration on leaves and stems as infestations progress. Leaf margins, and whole leaves in severe cases, may turn brown and die. Plant vigor may be reduced, and premature leaf drop can occur on heavily infested plants. Plants often appear dirty or dusty, especially when webbing is present. 


  • Keep plants healthy; reduce drought
  • Prevent dust from settling on foliage
    as this promotes spider mite survival.
  • Approved pesticides are available. 
Time for Concern:  Anytime weather conditions are hot and dry

When and Where to Scout: Monitor for injury symptoms (leaf stippling) during hot, dry conditions. Check the undersides of leaves for tiny black specks of debris and slowmoving mites with a hand lens. Shake stems over paper or cloth tray and watch for tiny moving dots (spider mites). Webbing and a dirty appearance indicates the presence of heavy populations. 

Threat Level: High for indoor-grown hemp and moderate for field-grown hemp.

Occurrence in Utah: Two-spotted spider mites are common in Utah, but have only occasionally been found in fieldgrown hemp