Psyllids
Pest Common Name
- Potato/Tomato Psyllid (Bactericera cockerelli)
- Potato
- Tomato, pepper, eggplant, other crops and weeds in the nightshade family
- Bindweed
Adult psyllids are approximately 5/64-1/8 in (2-3 mm) in length, about the same size as an aphid. In form, adults resemble small cicadas. Newly emerged adults are light brown to yellow green in color, but they darken significantly in just a few hours.
Adults can be distinguished from aphids by their lack of cornicles, the small, rear-facing, “tailpipe” like appendages near the end of the abdomen of aphids. Furthermore, they tend to jump when disturbed. In Idaho, potato psyllids can be differentiated from other psyllids by the presence of a white margin on the top, front of the head. They also have clear wings with a two-branched (not three-branched) split in the wing venation toward the base of the wing (Figure 1). A 10x lens is useful in differentiating psyllids from aphids, and for differentiating potato psyllids from other species.
Psyllid nymphs go through five growth stages (instars), ranging from about 1/64-5/64 inches (0.5-2 mm) in length. They have flattened, oval shaped bodies, no wings, and range in color from light brown to yellow green (Figure 2).
Eggs are orange-yellow and elevated off the leaf surface on fine stalks but are so tiny as to be barely visible with the naked eye.
Biology
Psyllid eggs are laid on stalks attached to leaves of host plants. After about a week, nymphs emerge from the eggs and begin to feed. Nymphs most often feed on the undersides of leaves located on the upper third of the plant. Though their small size, greenish coloration and general lack of movement can make them hard to see, infestations can sometimes be detected by looking for “psyllid sugar.” These tiny, waxy pellets are excreted by psyllid nymphs and accumulate on leaves under locations of heavy psyllid feeding.
Damage
Psyllid feeding can directly cause damage to plants when abundance is extremely high. Damage from feeding is called “psyllid yellows” and manifests as chlorosis (yellowing) and upward curling of new leaflets. This damage is thought to be caused by the toxic saliva that psyllids inject into the plant while feeding. However, psyllids are most often of concern due to their ability to transmit diseases, most notably zebra chip (ZC).
Zebra chip is caused by the bacterium Candidatus Liberibacter solanacearum. Aboveground symptoms in potato are minimal, with some yellow or pink-red discoloration in foliage, and often are easily mistaken for nutrient deficiencies. Symptoms within tubers are more severe, with light brown, necrotic striations forming in the flesh. These striations become significantly darker when the potato is fried.
Monitoring
The University of Idaho, in collaboration with crop consultants, maintains a potato psyllid and ZC monitoring network in commercial potato fields across the state. Traps are collected weekly, and psyllids are counted and tested for the presence of the bacterium that causes ZC. Results and recommendations are posted on the monitoring website throughout the season.
If you would like to monitor for potato psyllids, consider using yellow sticky cards. These traps, which capture adults, should be deployed no later than mid-May in Idaho and collected on a weekly basis. To deploy traps, place lath stakes about 10 feet (3 m) from the field edge. Remove wax paper from both sides of yellow sticky card and binder clip it to the stake just at the top of the canopy. Remember to move traps up or down to ensure they remain at the top of the canopy as plants grow or senesce. When retrieving traps, re-adhere waxy side of the paper covering to the card face.
To monitor for nymphs and eggs, collect 10 mature leaves from the upper third of 10 different plants located in outer rows of the field. Use a hand lens to look for nymphs and eggs on the undersides of the leaves.
Management
Primary Management Tactics
Control options for potato psyllids are limited. There is evidence that use of some insecticides that suppress natural insect predators cause psyllid populations to grow. Nevertheless, management of psyllids and ZC in potatoes is currently heavily reliant upon insecticides.
Biological
- Limiting the use of broad-spectrum pesticides can protect natural insect predators of potato psyllids, such as minute pirate bugs and damsel bugs
- In greenhouse production some fungi, notably Isaria fumosorosea and Beauveria bassiana, may infect and help control potato psyllids
Chemical
- Spinosad and horticultural oils can provide some control of potato psyllids, when applied thoroughly and repeatedly
- Recommendations for pesticides to use in the management of potato psyllid can be found on the PNW Pest Management Handbooks website
Pesticide Warning
Always read and follow the instructions printed on the pesticide label. The pesticide recommendations in this University of Idaho webpage do not substitute for instructions on the label. Pesticide laws and labels change frequently and may have changed since this publication was written. Some pesticides may have been withdrawn or had certain uses prohibited. Use pesticides with care. Do not use a pesticide unless the specific plant, animal or other application site is specifically listed on the label. Store pesticides in their original containers and keep them out of the reach of children, pets and livestock.
Trade Names — To simplify information, trade names have been used. No endorsement of named products is intended nor is criticism implied of similar products not mentioned.
Groundwater — To protect groundwater, when there is a choice of pesticides, the applicator should use the product least likely to leach.
- Erik J. Wenninger, University of Idaho
Desiree Wickwar, Entomologist, IPM Project Manager
Erik J. Wenninger, Professor of Entomology, IPM Coordinator
2023