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Agronomic Crops Network

Ohio State University Extension


Statewide Alfalfa Weevil Population Update #2

Alfalfa weevil has hit peak activity in terms of growing degree days (GDD) accumulated, for nearly the entire state. From now until after first cutting, alfalfa weevil will eat away at forage quality and quantity. Scouting alfalfa fields will allow for timely decision-making to limit the impact of an alfalfa weevil population.

The following table indicates the average alfalfa height and alfalfa weevil population for the couple of fields scouted in each county for the week of April 23rd-29th.


Alfalfa Height (inches)

Average Larvae Count per Stem
















Based on the current alfalfa height and average larval count per stem observed, none of the fields scouted across the state reached the economic threshold for either a spray control or an early harvest. The fields closest to the threshold were in Putnam County and Ross County both experiencing very different levels of GDD accumulation. To further highlight the importance of scouting your fields, there is a wide range of alfalfa development and larvae populations observed in the group of northwestern counties that have experienced very similar GDDs.

Each field's circumstances are different and scouting for alfalfa is a quick and easy process. To get started, reference the article written earlier this year “Scouting Early Alfalfa Weevil Activity” and this 5-minute forage team video “Alfalfa Weevil Scouting”. If control thresholds are met, options for control are an early harvest or insecticide usage, being mindful of the preharvest interval for insecticides as harvest gets closer.


Author(s): Kyle Verhoff, Nic Baumer, Ryan McMichael, Beth Scheckelhoff, Ryan Slaughter

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.