The Tomato Magazine
Tomato Psyllids Cropping Up in Southern California
Tomato psyllids are spreading across the country, devastating crops in
Colorado, Montana, Washington, and Ontario, Canada. In Baja, Mexico,
growers lost more than 85 percent of their fresh market tomatoes in 2001.
California populations originated from Mexico, but are now surviving yearround
in San Diego, Orange and Ventura counties. Entomologists John Trumble,
and Richard Stouthamer from the University of California, Riverside, studied
the annual pattern of immigration of tomato psyllids into California tomato
production areas using visual surveys and molecular techniques. Their
results indicate how many psyllids it takes to cause crop damage and can
help to estimate when and how much insecticide to use to control them.
The tomato psyllid can attack species in 20 plant families, but prefers
to feed on tomato, potato, pepper, and eggplant. The name tomato psyllid
is commonly used, but the pest is also known as potato psyllid when it
feeds on potatoes.
The psyllid is now a major problem on tomatoes and peppers in California,
and potatoes and tomatoes in Texas, says Trumble. Currently,
yellow sticky cards can be used as an early indicator of psyllid movement
into an area, and plants on the field margins can be visually checked
for eggs and nymphs.
Female tomato psyllids can lay up to 1,000 eggs, and they inject a toxin
that results in a condition called psyllid yellows that reduces photosynthesis
and also reduces the level of nitrogen in tomatoes. It also causes the
plants leaves to curl, and it produces smaller fruit. Researchers
estimate that about 15 to 20 psyllids per plant during the course of a
week cause stunting, from which most plants never recover.
Researchers found that for some tomato varieties, psyllids laid eggs
on plants previously infested by nymphs far more than on uninfested control
plants. This suggests that for some cultivars there is a physiological
change in plant attractiveness following psyllid feeding.
Tomato psyllid density showed a strong correlation to the number of yellowing
leaves and leafl ets and distorted leaves. This discovery allows scientists
to do simple visual surveys of yellowing leaves to estimate psyllid populations.
Initial data suggests that about 18 nymphs per plant feeding for 7 to
10 days will cause psyllid yellows on tomatoes exposed during the first
three weeks after transplanting.
The psyllid uses its piercing mouth parts to extract plant juices from
foliage. Excess sugar, which the insect ingests, is excreted as small
waxy beads of psyllid sugar (resembling granulated sugar).
The adult psyllid is a small insect that has white or yellowish markings
on the thorax, clear wings, and lines on the abdomen that separate segments.
The lack of information on reliable monitoring techniques makes early
detection of these insects very diffi cult, leading growers in many areas
to apply pesticide treatments.
Relatively few reports are available on control using chemicals
other than organophosphates or pyrethroids, says Trumble. We
know that use of these materials in California causes a loss of biological
control agents, resulting in outbreaks of secondary pests such as leafminers
and spider mites. Imidacloprid is often injected through drip lines in
California, a practice that fits our IPM program because
it doesnt affect beneficial insects, yet provides additional control
in the field.
Trumble and his team are working to find new strategies for controlling
the pest. The UC Exotic/Invasive Pests and Diseases Research Program funded
this three-year project. The program targets research on exotic pests
and diseases in California. Its aim is not only to improve our knowledge
and management of pests that are already here, but also to reduce the
potential impact of those pests and diseases that pose a threat to the
state. The program is collaboration between the UC Statewide Integrated
Pest Management Program and the UC Riverside Center for Invasive Species
Research. U.S. Department of Agriculture, Cooperative State Research Education
and Extension Service, funds the program.
© 2006 Columbia
>> Return to top
Columbia Publishing & Design | 1-800-900-2452