Late-Season Population Buildup Of The Threecornered Alfalfa Hopper In Alfalfa In Western Kentucky
POOJA GUMMAKONDA, FELIPE C. BATISTA AND DR. RAUL T. VILLANUEVA
UNIVERSITY OF KENTUCKY
The threecornered alfalfa hopper (TCAH), Spissistilus festinus (Hemiptera: Membracidae), is a native sap-sucking pest prevalent in the southern region of the United States. It can damage alfalfa, soybeans, peanuts, and other leguminous crops, and has gained economic relevance due to the injury it causes to plant stems. Population peaks usually occur during periods of vigorous vegetative growth, typically between June and September. However, in an alfalfa field at the UK Research and Education Center, we detected averages ranging from one to two insects per sweep from late September to mid-October (Figure 1). Although there is no established threshold level for TCAH in alfalfa to date, in Tennessee, an economic threshold of two adults or nymphs per sweep using a 0.38 m net is applied to established plants. This late-season population buildup of TCAH may have been influenced by the unusually warm conditions in Kentucky and the limited availability of alternative host plants.
Description & Life Cycle
The adult TCAH is about 1/4 inch long and has a distinct green, triangular, wedge-shaped body (Figure 2A). Nymphs are smaller than adults, wingless, and have a spiny, pale green body (Figure 2B). Adult females lay eggs in the stem tissues of their host plants, particularly in delicate petioles or stems. Under ideal conditions, the long, translucent eggs hatch after 7 to 10 days. Newly hatched nymphs pass through five developmental stages (instars), each lasting 3 to 5 days depending on temperature and food availability. The complete life cycle, from egg to adult, typically takes 30 to 40 days. The species overwinters as adults and may resume feeding in alfalfa fields during early spring.
Damage in Alfalfa Fields
Feeding by TCAH on alfalfa plants causes girdling, stem weakness, and lodging, which ultimately reduce hay quality and yield. Affected plants become yellow, stunted, and weakened. Severe infestations can reduce yields, particularly in young or newly seeded alfalfa stands. In addition, feeding wounds make plants more susceptible to opportunistic pathogens and secondary infections.
Management Strategies
Several practices are recommended to reduce TCAH populations in fields, including weed removal, proper fertilization and irrigation, avoiding mowing during periods of highest nymph activity, and harvesting early. Scouting with sweep nets should be routinely conducted to monitor TCAH population buildup. Insecticide applications are not recommended unless infestations exceed the economic threshold. Although neonicotinoids and pyrethroids can be effective, rotating chemical groups is advised to help prevent resistance development. ∆
POOJA GUMMAKONDA, FELIPE C. BATISTA AND DR. RAUL T. VILLANUEVA
UNIVERSITY OF KENTUCKY