Page 18 - Griffin Gazette Issue 1 - 2019

Root Aphids:

A Hidden Threat

By Moriah LaChapell, CEA GGSPro Technical Specialist

Root aphids are a widespread pest that can devastate controlled
environment agriculture (CEA) crops, such as lettuce, herbs and
cannabis. Root aphids are difficult to control and detect, since they
feed below the soil line, out of easy sight. Root aphids cause decreased
plant health and crop yield. Scouting for root aphids, selecting the
correct chemical control strategy and preventing introduction of this
pest is key to maintaining plant quality.

UNDERSTANDING ROOT APHIDS

Understanding the life cycle and distinguishing features of root aphids is a critical step
for correct identification. Root aphids vary in color and are similar in size to standard
aphids. Normally, they reproduce by parthenogenesis. This is a fancy way of saying that
root aphid reproduction is entirely asexual: No males are produced and females give
live birth to genetically identical daughter aphids. Periodically, winged aphids develop
and disperse to other plants. These winged adults are more easily seen and can be
trapped on sticky cards and plant structures, such as developing flowers or leaf hairs.
Root aphids may be confused with mealybugs because they're often covered with white
wax. However, they're generally smaller than mealybugs, have cornicles and are pear-
shaped. In comparison, mealybugs lack cornicles and are oval-shaped. Mealybugs
also sometimes have long tail hairs.
Root aphids are often introduced to a facility on incoming plant material. Winged forms
of root aphids can also find their way in through greenhouse vents and open warehouse
doors during warmer months. The best way to prevent root aphids is to isolate all
inbound plant material in a quarantine area separate from the normal production
spaces. Plants in quarantine should be heavily scouted, including inspection of the
root systems, and treated for any suspected issues prior to commingling with existing
crops.
Root aphids don't spread as rapidly as foliar aphids. They move from plant to plant
via drainage holes in pots or through irrigation water. It's critical to find root aphids
early. If severe root aphid infestations are detected, remove the infested plants. Manage
lighter infestations with the correct insecticides, maintaining tight drench intervals until
the aphids are no longer detected. Keep good scouting records and use preventative
treatments when historic patterns suggest increased risk of infestation.

Image captions
(Top Left) Aphid Cornicles, (Bottom Left) Waxy Residue from Pemphigus Root Aphid Infestation,
18 | GRIFFIN GAZETTE 2019 (Bottom Right) Root Aphids Feeding on Plant Roots