Update on Alfalfa Insect Pest Management

Ayman Mostafa
Aphids, a key pest complex of alfalfa, are mostly controlled by broad-spectrum insecticides such as organophosphates and pyrethroids, leading to devastated natural enemy populations, other negative environmental impacts, and posing risks to insecticide applicators. It is therefore urgent to investigate the efficacy of lower-risk, selective insecticides against aphids.
The University of Arizona Cooperative Extension has started a project addressing the development and implementation of IPM practices directed at economically important pests of alfalfa hay. We wish to identify effective and environmental solutions that could improve current insect pest management practices in the low elevation desert southwest. One objective of this project is to investigate the efficacy of various insecticides for the control of alfalfa aphids. Lower risk, selective insecticides are available for sucking insects such as aphids in other crops, but their efficacy against alfalfa aphid complex has not been investigated.
Currently, we are conducting two trials to study the efficacy of new and currently registered compounds at the University of Arizona Maricopa Ag Center. Several active ingredients are being tested in these trials, either as premixes or in tank mixes: dimethoate, malathion, chlorpyrifos, lambda-cyhalothrin, zeta-cypermethrin, chlorantraniliprole, and thiamethoxam, and experimental chemistries like: sulfoxaflor, flonicamid and flupyradifurone.
PCAs and growers have expressed to me the many challenges in managing the aphid complex in alfalfa over the last two seasons. Many PCAs have reported different levels of control for the same product or tank mix. It is fair to say that our current arsenal of remedies to combat alfalfa aphids contains many old, broad-spectrum chemistries of diminished, declining or otherwise insufficient efficacy against today’s populations. The introduction of new products, like Transform® and Sivanto® for alfalfa would be welcomed; however, the actual date for the availability of these products remains uncertain. The alfalfa aphidicide trials we are conducting could help facilitate future special EPA emergency exemption requests (i.e., Section 18) in case they are needed for next year.
In order to learn more about the current situation of pest management in alfalfa and future opportunities, we would like to hear from more of our clientele: PCAs, growers, ag professionals and ag industry representatives. We will have a breakout session during the upcoming Desert Ag Conference (DAC) on May 8, 2014, , 3:00 – 4:30 pm to communicate with each other regarding the issues of alfalfa pest management this season.
As always, feel free to contact me with any questions, suggestions, comments or feedback about this issue.