Potato/tomato psyllid, Bactericera cockerelli
Order: Hemiptera
Family: Triozidae
Description
The potato/tomato psyllid is distributed throughout the central to western United States. This species is most problematic in northeastern parts of Colorado and is less prevalent in southeastern regions and the San Luis Valley due to high summer temperatures and the restricted flight path of migrating psyllids.
Adults of the potato psyllid resemble a miniature cicada but are about 2 mm (<1/10 inch) long and will readily jump when disturbed. They are dark gray or black insects with two prominent vertical white bands on the abdomen and horizontal stripes on the thorax. At rest, adults hold their wings tent-like over the body. The nymphs are wingless and have flattened oval-shaped bodies and red eyes. While they resemble immature soft scales or whiteflies, the nymphs of potato psyllids can move when disturbed. They are dull yellow or orange after hatching and become progressively greener as they feed and develop. The orange-yellow eggs are supported by small stalks and are only slightly larger than the hairs of a potato leaf. A hand lens capable of 10x or greater magnification is necessary to see the eggs.
Quick Facts
- Potato psyllid is the most damaging insect to potatoes and tomatoes in Colorado.
- Injury is caused by toxic saliva introduced when the insect feeds. This can produce a serious disease known as “psyllid yellows”.
- Psyllids can also transmit a bacterial pathogen which causes zebra chip disease.
- Potato psyllid does not survive outdoors in Colorado through winter. New infestations occur annually from migrations that originate in Texas and northern Mexico.
- Early detection and treatment of potato psyllid is important to prevent damage.
Adult potato psyllid on a pepper leaf. Note the two white bands on the abdomen. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Characteristic of sugar excrement on tomato plant. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Various stages of psyllid nymphs. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org.
Leaf symptoms of psyllid yellows. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Potato tuber produced above ground due to psyllid yellows. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Life history and habits
The potato psyllid is a phloem-feeding insect. This species does not survive the cold winter temperatures in many parts of Colorado. Rather, overwintering populations migrate from southern areas such as Texas and northern Mexico in May or early June. Overwintering hosts in certain parts of the Rocky Mountains include bittersweet nightshade (Solanum dulcamara) and matrimony vine (Lycium spp.). As temperatures warm the following spring, egg laying often occurs on the margins of leaves. Nymphs emerge within about a week after eggs are laid, then settle on the leaf and begin to feed. A single female can produce over 1,000 eggs, although this depends on environmental conditions and the host plant. Nymphs of the potato psyllid tend to concentrate on the underside of leaves lower on the plant. They develop through four or five instars and research suggests that development time is faster on tomatoes and potatoes compared to eggplants and peppers. As the nymphs feed on sugar-rich phloem, they excrete pellets covered in wax. Survival and development are optimal at temperatures between 24-27°C (75-81°F). Significant reductions in egg laying, egg hatch, and survival are observed at temperatures exceeding 30°C (86°F). In Colorado, four or more generations are produced each growing season.
While this species can occur on a variety of plants, reproducing populations are primarily associated with plants in the Solonaceae family such as potato (Solanum tuberosum), tomato (Solanum lycopersicum), pepper (Capsicum spp.), and eggplant (Solanum melongena). Other plant hosts include species of nightshade (Solanum spp.), groundcherry (Physallis spp.), matrimony vine (Lycium spp.) and other weeds and ornamentals. This pest can also feed and reproduce on certain species in the Convolvulaceae family, such as sweet potato (Ipomoea batatas), and field bindweed (Convolvulus arvensis). In potatoes grown in the central and western United States, populations tend to peak shortly before harvest.
Injury
Psyllid saliva has toxic properties and can cause psyllid yellows, which is evident in yellowing of leaves starting at the margins. The exact appearance of symptoms depends on the host plant. In white and russet potato varieties, leaf coloration often changes to yellow or yellow to green. In red and blue potato varieties, feeding of the potato psyllid can result pale shades of pink and purple on foliage. Areas of the potato stem can also swell, and small tubers may form on parts of the plant that are above ground. Psyllid yellows can reduce yield by decreasing the size and quality of tubers, which become misshapen and sprout prematurely. Outbreaks of psyllid yellows are typically associated with nymphs and can be particularly destructive in potatoes grown in the western United States.
On tomatoes, new growth can be stunted and have slight pink or purple coloration. Psyllid yellows can also reduce the size of fruits. The tomatoes of diseased plants may also have duller skin and less flavor. No significant effects on yield or quality due to psyllid yellows have been observed on eggplant or peppers grown in Colorado, although significant injury to peppers occurs in California.
In addition, the potato psyllid is a vector of the bacterial pathogen that causes zebra chip, Candidatus Liberibacter solanacearum. Adults are more effective at transmission of the bacterium than nymphs. In Colorado, zebra chip incidence is typically low, although the disease can infect significant amounts of plants. Potato psyllids acquire the plant pathogen as they feed on an infected plant, and infective adults can produce infective offspring. A potato plant can be infected in one to six hours, depending on the density of feeding potato psyllids. Research has shown that twenty adults can infect a potato plant within one hour.
Zebra chip affects the quality of the tubers and can render chipping potatoes unmarketable. The symptoms can go unnoticed until tubers are sliced, which exposes the brown striations that become more evident once the sliced potatoes are fried. On plant structures above ground, symptoms may be mistaken for nutrient deficiencies such as yellowing of foliage. Although zebra chip is a serious disease of potatoes in southwestern United States and Mexico, it is rare in Colorado. Rather, yield losses are typically due to the psyllid yellows.
Monitoring
Potato psyllid outbreaks occur irregularly and are unpredictable, so monitoring is important for effective management. In larger fields, sweep nets or yellow sticky traps are the most efficient way to detect adults, while vacuum and beet sheet sampling is recommended on alternative host plants. When using yellow sticky traps, five should be deployed on the field edges to detect immigrating potato psyllids. Later in the season, the sticky traps should be distributed evenly throughout the field. Insecticides can be applied when adults are captured in sweep net samples or yellow sticky traps in June or early July,
Since nymphs tend to prefer shade, leaves on the lower part of the plant can be inspected with a 10x hand lens. To sample for juvenile psyllids, ten mature leaves can be collected from the middle of each plant at ten separate locations in field’s the outer rows. The presence of nymphs on leaves indicates that the pest is established and increasing in numbers. It is worth noting that immature stages are more easily seen on pepper leaves than tomato or potato leaves, which tend to be hairier.
Cultural control
Delaying planting can reduce the densities of potato psyllid and the incidence of zebra chip. The use of mulches, UV-blocking screens, and mesh row covers can reduce psyllid densities in small fields. However, these approaches have not been shown to reduce the incidence of zebra chip.
Biological control
The most important natural enemies of the potato psyllid are predatory bugs, including damsel bugs (Hemiptera: Nabidae), minute pirate bugs (Hemiptera: Anthocoridae), lady beetles (Coleoptera: Coccinellidae), and the larvae of green lacewing (Neuroptera: Chrysopidae). However, these natural enemies are also susceptible to insecticides, which may limit their ability to suppress populations of potato psyllid.
Certain entomopathogenic fungi can infect potato psyllid and may provide some control in greenhouses. Formulations of Isaria fumosorosea and Beauveria bassiana are commercially available. High humidity is important for effective suppression of the psyllids using these fungal biocontrol agents.
Chemical control
Insecticide options for control of potato psyllid are limited, and resistance to a number of insecticides such as neonicotinoids, spinosad, and abamectin, has been documented in North America. The use of broad-spectrum insecticides can have negative effects on resident populations of natural enemies. Some alternatives include kaolin particle film and crop oils. It is worth noting that reducing the incidence of zebra chip is dependent on suppressing populations of the potato psyllid.
CSU Extension Fact Sheet
Download or view the CSU Extension’s PDF fact sheet for your reference.
References
USU. (n.d.). Potato Psyllid. Utah State University – Extension. Available https://extension.usu.edu/vegetableguide/potato/potato-psyllid#:~:text=All%20stages%20of%20potato%20psyllids,%2C%20smaller%2C%20or%20misshapen%20tubers.
USU. (n.d.). Zebra Chip Disease of Potato. Utah State University – Extension. Available https://extension.usu.edu/vegetableguide/potato/potato-psyllid#:~:text=All%20stages%20of%20potato%20psyllids,%2C%20smaller%2C%20or%20misshapen%20tubers.
Wenninger, E., and A. Rashed. 2024. Biology, Ecology, and Management of the Potato Psyllid, Bactericera cockerelli (Hemiptera: Triozidae), and Zebra Chip Disease in Potato. Annual Review of Entomology. 69: 139-157. Available https://www.annualreviews.org/doi/pdf/10.1146/annurev-ento-020123-014734