Magnified Psyllid Nymphs (65864 bytes)

Tomato / Potato Psyllids

By Carl Wilson, Horticulturist, Denver Cooperative Extension

Psyllids ["Sill' lids"] are little recognized but devastating insects to gardeners growing tomatoes or potatoes. The insect causes tomato fruit to stop forming or ripening, and many small potato tubers to develop and sprout prematurely before harvest. Pepper and eggplant may be infested although no damage is done.

Psyllids are not year-round Colorado residents. They annually migrate from southern states and infestations vary from year to year. The aphid- sized adults migrate on weather fronts. They lay orange-yellow eggs on the backs of leaves.

The nymph stage that hatches is most often seen by observant gardeners turning over leaves to look for insect pests. Look for flat, yellow-green discs about 1/4 inch in size. The nymph stage does not move and lasts for 2 to 3 weeks. Four to 7 generations are produced per year.

Tomato plant damaged by psyllids (87034 bytes)

Tomato plant damaged by psyllids

Leaves on the tops of tomatoes yellow along the midveins and leaf edges. Leaf veins may turn purple. Growth is checked and new leaves remain small, narrow and stand upright producing a feathery appearance. Potato leaves become thickened and curled. Waxy beads of sugary waste from nymphs can be observed on the plants.

Spray at the first sign of infestation. The spray must thoroughly cover leaf undersides and be repeated weekly. Sulfur has been the most consistently effective treatment according to research at Colorado State University. Heed the label precautions to avoid sulfur sprays in hot temperatures for they can damage plants. Control with permethrin/esfenvalerate has been O.K. to fair in trials.

Soap spray results have been disappointing and neem has not worked. Do not use carbaryl (sevin) which apparently kills predators and does nothing against psyllids.

This insect is very tough to control with anything. Research into a variety of control alternatives including pyrethrin/canola oil combinations and kaolite clay sprays continues at Colorado State. This message will be updated as new information is learned.

Photos: Judy Sedbrook

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Date last revised: 01/05/2010