Potato/tomato psyllid (Bactericera cockerelli Sulc)
Pest description and crop damage Adult psyllids resemble miniature cicadas, while the immature stages are scale-like and mostly sedentary (much more sedentary than aphids) and look like white fly nymphs. Feeding at immature stages sometimes causes a physiological foliage disorder known as "psyllid yellows" in potatoes. Symptoms of psyllid yellows are very similar to those caused by phytoplasmas transmitted by leafhoppers.
No laboratory test can confirm psyllid yellows; rather, symptomatic plants that test negative for phytoplasmas often are assumed to have psyllid yellows. Potato psyllid transmits a bacteria-like organism (Liberibacter) that causes a syndrome called "zebra chip" (ZC), named after the characteristic discoloring of the tuber flesh in affected plants. This disease has been most severe in the Southwest US and in Mexico, Central America, and New Zealand. In 2011 this disease was found for the first time in many potato fields in Oregon, Washington, and Idaho. It appears that ZC is now an annual pest issue for PNW potato growers, but its severity may vary substantially between years.
Biology and life history Potato psyllid is normally found in potatoes east of the Cascade Mountains beginning in early June. It is known to overwinter in many growing regions of the PNW, in association with bittersweet nightshade (Solanum dulcamara), morning glory (Ipomoea violacea), and related weeds It may also migrate from more distant areas, but more research on this question is required. Because of its late arrival in the crop, potato psyllid is rarely a direct pest in PNW potatoes, but the damage caused by ZC in 2011 showed that the PNW potato industry should be vigilant for early and severe psyllid populations each year. The ZC pathogen is acquired by psyllids during feeding, and once infected a psyllid can potentially remain infective throughout its life, and females can transmit it to their offspring via eggs. Most psyllid populations have a low infection rate - far below 10%, with a range of 1-2% being more typical.
Scouting and thresholds The most commonly used scouting method for psyllids is yellow sticky traps. Psyllid adults are active flyers and are attracted to yellow, but traps must be placed 5-10 feet inside crop fields. This differs from monitoring beet leafhoppers, which feed and reproduce outside potato fields. It is recommended that sticky cards are set 10-20 feet from potato field edges. Several other non-pest psyllid species are routinely caught on yellow sticky traps in the PNW, so knowing how to recognize potato psyllid is important. For detailed information on monitoring psyllids using yellow sticky traps, see: http://www.nwpotatoresearch.com/pr/Insect-Trapping-Guides.cfm .
Since nymphs are essentially sedentary, they likely are fed upon by a wide range of predators like Geocoris, Orius and Nabis. There has been little research or observation on psyllid biocontrol in the PNW.
Management-chemical control: HOME USE
- azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
- Beauvaria bassiana-Some formulations are OMRI-listed for organic use.
- plant essential oils (peppermint, rosemary, etc.)-Some formulations are OMRI-listed for organic use.
- pyrethrins (often as a mix with other ingredients)-Some formulations are OMRI-listed for organic use.
- spinosad-Some formulations are OMRI-listed for organic use.
Note: Pyrethroid (Group 3 in Tables 1-2) applications make aphid management more difficult and can lead to outbreaks of spider mites.
Management-chemical control: COMMERCIAL USE
Pyrethroid insecticide (Group 3 in Tables 1-2) applications make aphid management more difficult and can lead to outbreaks of spider mites.