Aphids

• Aphids are tiny, pear-shaped insects that suck the sap from tomato leaves, stems and buds. Although aphid infestations are rarely fatal, heavy infestations can cause curled leaves, stunted growth and sun-scalded fruit. Aphids excrete a sticky substance known as honeydew, which promotes sooty mold growth. Two types of aphids are common tomato plant pests. The green peach aphid is yellow-green with a dark spot on the back. The potato aphid is pink, pink and green mottled, or green with a dark stripe.
  
  Natural predators that feed on aphids include ladybugs and syrphid larvae. Control measures include insecticidal soap, neem oil, or chemical pesticides such as permethrin, bifenthrin and malathion.
  
  

Flea Beetles

• Two species of flea beetle attack tomato plants. The dark brown potato flea beetle and the yellowish-brown tobacco flea beetle both measure 0.1 inch long. You may notice these tiny dark beetles when they jump. Flea beetles eat holes in leaves and fruit. These insects can completely destroy leaves in young plants under 6 inches tall. Infestations in mature plants usually do not affect yield. Insecticidal soap, horticultural oils, neem oil, pyrethrin, carbaryl, and bifenthrin are all effective against flea beetles.
  
  

Stink Bugs

• The stink bug, which is common in the southern United States, is one of the easiest pests to identify. This insect has a shield shape and foul odor when disturbed. Green stink bugs have a light green color with a length of 9/16 to 3/4 inch; the brown stink bug is light yellowish-gray and slightly smaller in size. Both species chew tiny holes in tomato fruit, causing yellowish tough spots that make the fruit unmarketable. According to the University of Kentucky College of Agriculture, the brown stink bug is the more destructive type. Effective control methods include horticultural oil, permethrin, bifenthrin and cyfluthrin.
  
  

Tomato Hornworm

• You can easily notice the tomato hornworm if it has infested your tomato plant. This green and white caterpillar grows up to 3 inches long and has a distinctive horn on its back end. Beginning in midsummer, hornworms eat tomato leaves and sometimes the surfaces of fruit. These pests can quickly defoliate a tomato plant and leave scars on the fruit.
  
  Colorado State University Denver County Extension notes that although tomato hornworms have a startling appearance, they are relatively easy to control. The braconid wasp deposits eggs on the hornworm, and the parasitic larvae feed on the caterpillar. You can even remove the caterpillars by hand. Bacillus thuringiensis, pyrethrin, spinosad, neem oil, carbaryl, and bifenthrin are effective control methods.
  
  

Whiteflies

• The greenhouse and silverleaf whiteflies are tiny winged insects found in warm, humid greenhouses and tropical and subtropical climates. Adults and wingless nymphs feed on the undersides of leaves. The yellowish silverleaf whitefly's length is 1/32 inch, and its wings that fold at a sharp angle over the body. The slightly larger greenhouse whitefly is white and has wings that fold over the body. Yellowed leaves and stunted growth, as well as sticky honeydew and sooty mold are telltale signs of whitefly infestation.
  
  According to the Colorado State University Cooperative Extension, the most effective control is insecticidal soap. Other measures include horticultural oils, cyfluthrin, and bifenthrin.