By D. Bruce Bosley

Extension Agent/Cropping Systems

Colorado State University Cooperative Extension

Psyllids are little recognized but devastating insects for tomatoes or potatoes crop producers. CSU Extension has found them to be infesting these crops earlier and more severely all across the High plains this year. Psyllids cause tomato fruit to stop forming or ripening, and many small potato tubers to develop and sprout prematurely before harvest.

Psyllids are not year-round Colorado residents. They annually migrate from southern states, so 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 growers by turning over leaves to look for insect pests. Look for flat, green discs about one-quarter inch in size. The nymph does not move and this stage lasts for only two to three weeks. Four to seven generations are produced per year.

The mid-veins and edges of leaves on the tops of tomatoes turn yellow, or 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 crystals of waste from nymphs can be observed on the plants.

Spray at the first sign of infestation to avoid psyllid injury to potatoes and tomatoes. Sulfur, lime sulfur, Esfenvalerate, and Permethrin are effective. Spray must thoroughly cover leaf undersides and be repeated weekly. Peppers and eggplants may also be infested, but psyllids do no damage to them.

It also appears that corn rootworm beetles are coming on heavier this year as well, so check crop levels for them as silks begin to emerge. As corn approaches the tasseling growth stage, scouting should also include looking for Western bean cutworm and spider mites. Consider all corn pests in a field when making a pest management decision. Do this to avoid flaring spider mite or other non-target pest populations because some insecticides can backfire by killing beneficial predator insects and allowing the non-target insect populations to grow unchecked. In fact, one insecticide actually increases the rate at which mites reproduce.

Sunflower fields are reaching the critical heading phase of growth for insect scouting. Many of the persistent insect pests cause most of the crop economic injury during early to mid flowering and therefore, treatment decisions should be made when a sunflower crop is at or just following full flowering.

Finally, the CSU Extension precision farming team will be hosting a site specific farming field day near Greeley on Wednesday, Aug. 3. It's important to keep abreast of new agricultural information tools and the practical uses for them in order to profitably fit them into your farming operation in a timely fashion. The first adopters are nearly always the ones to profit when a change comes to agriculture. Participating in this type of program is a small but effective commitment to your Ag business's future.

Date: 7/20/05