In 2012, reports on aphids feasting on peanut pegs were
confirmed in many areas, including the panhandle of
Florida. It is likely that drought contributed to the infestation
and lack of adequate control of the minute pest.
Although many species of aphids have been recorded on
peanuts, adult aphids found had a black shiny body; nymphs
were smaller and light gray in color. Preliminary identification
indicated them to be cowpea aphids, A. craccivora, a common
pest species on alfalfa, cotton, cowpea, wheat and many other
crops. Common weed species for aphids include dandelion,
lambsquarter, pepperweed, pigweed and others.
Dense Feeding Clusters
Aphids were found on the pegs in dense colonies consisting
of adults and nymphs feeding together. Pull back the peanut foliage
and examine pegs closely for one or more black aphids. At
the location in Santa Rosa County on sandy soil, aphids were
found in masses of 25 to 30 adults and nymphs feeding.
Aphids will start dispersing if touched, and populations are
highly clustered in some parts of the field, so scout randomly
throughout the field and not just one location. Also look for the
white molted skin on plant parts.
Aphids primarily feed by sucking plant sap with their needlelike
mouthparts. Cowpea aphids inject a toxin in the plants.
There will be darkening and deformation of peanut pegs when
aphid numbers are high. Cowpea aphid is also a known vector
of the peanut mottle virus and peanut stripe virus.
Pest pressure can be estimated based on the number of damaged
pegs and area affected. Populations generally stay in check
from the presence of natural enemies, but outbreaks can happen
by use of contact insecticides that eliminate natural enemies.
Scout for insects and make insecticide treatment decisions
based on proper identification, economic thresholds, weather and
crop growth conditions.
In general, imidacloprid (insecticide class 4A) is effective
against aphids, leafhoppers and whiteflies. Some products that
are labeled on peanuts for aphid control include Sherpa, Loveland
Products, and Admire, Bayer CropScience.
Admire, with 21 percent imidacloprid, can be used early in
the season as an in-furrow spray below the seed. Sherpa, with
17 percent imidacloprid, can be a directed spray to the foliage
or base of the plant and seems to be a cost-effective product.
At the field site examined for aphid outbreaks, two applications
of Sherpa at 3.5 ounces per acre reduced aphid infestations
Scout crops two to three days after application to see if you
need a second spray. Imidacloprid will not affect caterpillars
and mites, so keep scouting for those pests. If you find deformed
peanut pegs but no live aphids, then the damage is already
done, and rescue treatment may not do much.
Identification Is Critical
Seek assistance from Extension personnel, providing insect
samples, for correct identification, which is key for effective integrated
pest management. For insect images, subscribe to the
Alabama Peanut IPM Project on Facebook. To subscribe to the
Alabama IPM newsletter, email firstname.lastname@example.org.