How to Manage Pests
UC Pest Management Guidelines
Lettuce Root Aphid
Scientific Name: Pemphigus bursarius
In this Guideline:
Lettuce root aphids can be distinguished from other aphids found on
lettuce by their short antennae (less than one-third body length) and
undeveloped cornicles. They are found on lettuce roots in clustered colonies covered
with a white powdery wax. Where lettuce or related weeds are not available,
these aphids overwinter in the egg stage on the bark of Lombardy poplar. They
develop to adults and
reproduce once on poplar before
migrating to lettuce. On lettuce they begin to feed and reproduce; winged
adults develop that can spread from field to field. Lettuce root aphid is a serious
pest mostly where lettuce is planted near Lombardy poplars.
Plants heavily attacked by this aphid may wilt during the day. The
developing heads remain soft, fail to develop
and yields are reduced. Extremely heavy aphid populations over a prolonged
period can cause collapse and death of the plant. Individual rootlets turn
brown and die. Masses of white,
woolly material and aphids are present on roots.
Remove Lombardy poplars, the overwintering host of the root aphid, in
the vicinity of lettuce fields to reduce the severity of root aphid
infestations on lettuce. Some varieties of lettuce are resistant to this aphid.
Plant these varieties in fields with frequent root aphid problems.
If infested lettuce grows rapidly, a
satisfactory crop may often result. Avoid stressing plants and maintain optimum
water levels. To help reduce an infestation, eliminate cracks where aphids enter
the soil and attack plant roots.
If an infestation occurred on the
previous crop, work the soil deeply and allow it to dry thoroughly before
replanting to lettuce. Tilling or discing an infested crop will not eliminate
the population before replanting.
Cultural controls are organically acceptable.
An application of imidacloprid banded under the seedline at planting time
may prevent infestation by the lettuce root aphid. No insecticides are
available to control the root aphid after the lettuce crop is already infested.
|When choosing a pesticide, consider information relating to the impact
on natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
||MODE OF ACTION GROUP NUMBER1: 4A
||COMMENTS: Placement is critical to successful control; see label for details. Do not apply more than 0.38 lb a.i. Admire Pro/acre/year.
||1.2 fl oz/1000 ft/row
||MODE OF ACTION GROUP NUMBER1: 1B
||COMMENTS: When used at maximum rates under adverse conditions,
disulfoton may cause some delay in emergence, stunting of seedlings, or reduction of stand. Such damage may be more pronounced in light sandy soils.
UC IPM Pest Management Guidelines: Lettuce
UC ANR Publication 3450
Insects and Other Arthropods
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgment for contributions to Insects and Mites:
W. E. Chaney, UC Cooperative Extension, Monterey County
N. C. Toscano, Entomology, UC Riverside
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