February 2022 - 14

dr. bugs
BY RAYMOND A. CLOYD
Aphids
Question: Aphids are always a problem early in the growing season.
Can you provide information on how to manage aphid populations?
Answer: Aphids are major insect pests of greenhouse-grown
horticultural crops such as vegetables and ornamentals.
Species encountered in greenhouses include green
peach aphid (Myzus persicae), cotton or melon
aphid (Aphis gossypii), potato aphid (Macrosiphum
euphorbiae), foxglove aphid (Aulacorthum solani)
and/or chrysanthemum aphid (Macrosiphoniella
sanborni).
Aphids are 1.0 to 2.5 mm long, and green to black
Raymond A. Cloyd
is professor and
Extension specialist
in horticultural
entomology/
plant protection
at Kansas State
University. He
can be reached at
rcloyd@ksu.edu.
or yellow to pink depending on the host plant fed
upon. In addition, aphids have cornicles (tailpipes)
protruding from the back of the abdomen (Figure 1).
All aphids in greenhouses are females with each
female producing up to 100 live female nymphs within
30 days. Their high reproductive potential allows
aphid populations to build up quickly on horticultural
crops in greenhouses.
Aphids use piercing-sucking mouthparts to feed on
new growth and leaf undersides (Figure 2), withdrawing plant
fluids from the food-conducting tissues. Feeding by aphids
results in leaf yellowing, distorted leaves and plant stunting.
During feeding, aphids excrete honeydew, a clear, sticky liquid
that serves as a growing medium for black sooty mold. The
presence of black sooty mold on leaves inhibits the ability
of plants to produce food by means of photosynthesis. The
presence of white molting skins on plants (Figure 3) indicates
that you are dealing with an extensive population of aphids.
Aphid management strategies include: scouting, cultural
and physical practices, insecticide applications and releasing
biological control agents.
Scouting: Scouting for aphids involves inspecting plants,
especially those susceptible to aphids, at least once per week
during the growing season. Be sure to check new growth and
leaf undersides where aphids tend to reside.
Cultural and Physical Practices: Do not overfertilize
plants with water-soluble, nitrogen-based fertilizers because
overfertilizing plants encourages soft, succulent growth
that is easy for aphids to penetrate with their mouthparts.
Furthermore, young plants contain an abundance of essential
amino acids, which are the components of proteins necessary
for aphid reproduction and population growth. Weeds or
undesirable plants located within the greenhouse and around
the greenhouse perimeter should be removed because many
weed species serve as hosts for aphids. Plants heavily infested
with aphids should be disposed of immediately by placing them
(Photos: Raymond Cloyd, KSU)
14 FEBRUARY 2022 GPNMAG.COM
Figure 1. Close-up of aphids. Note the cornicles (tailpipes)
protruding from the back of the abdomen.
Figure 2. Aphids feeding on leaf underside.
Figure 3. Plant heavily-infested with aphids. Note the white molting
skins on the stems and leaves.
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February 2022

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