MANAGING POTATO LEAFHOPPER IN ORGANIC ALFALFA

Evaluation of glandular-haired, potato leafhopper
resistant alfalfa for organic farming systems

Wooster, OH - In the northern and eastern portions of the U.S., the primary insect problem in alfalfa is the potato leafhopper (PLH). A piercing-sucking insect, the leafhopper secretes toxic saliva into the plant, which interferes with phloem transfer. This injury results in leaves that are yellowed (known as "hopperburn") and plants that are often greatly stunted.

This study evaluated the potential of glandular-haired, PLH resistant alfalfa varieties in an organic system. Objectives were to determine whether glandular-haired, PLH resistant alfalfa can be produced organically in areas with significant PLH pressure; whether PLH resistant alfalfa can reduce PLH density; and to demonstrate the ability of glandular-haired, PLH resistant alfalfa to produce a higher yield of alfalfa with less PLH injury to organic growers. Three varieties of alfalfa were compared: Great Harvest (PLH susceptible), Doebler Predator (moderately PLH resistant) and Pioneer 54H91 (highly PLH resistant).

Above: Alfalfa variety Great Harvest which is susceptible to "hopperburn", showing extreme yellowing (80-90%) due to potato leafhopper (PLH).

Below: Alfalfa variety Pioneer 54H91 showing significant resistance to PLH, with only slight yellowing (5-10%).

Results and practical applications:
This study showed the ability of advanced generation, glandular-haired potato leafhopper alfalfa to produce a much better crop than regular, non-resistant alfalfa. This improvement was demonstrated by the near total lack of leafhopper injury (yellowing) on resistant alfalfa in a season of extreme leafhopper pressure, and plants attaining between 25 and 30 inches in height (the normal height at harvest), while the non-resistant alfalfa was very stunted, at best 15 inches in height, and nearly entirely yellowed. The study provided evidence that PLH resistant alfalfa is suitable to organic production.

For a detailed project summary (2 pages), link to: Hammond_04f14_PLH resistant alfalfa_summary.pdf

For Ronald Hammond's complete project report (7 pages), link to: Hammond_04f14.pdf