Michigan alfalfa scouting report and cutting schedule

Michigan alfalfa scouting report and cutting schedule – May 18, 2017

Phil Kaatz<kaatz@msu.edu>, Michigan State University Extension - May 18, 2017

Growing degree-day data confirms rapid development of alfalfa.

Crop development

The time to cut alfalfa for much of Michigan’s Lower Peninsula will be here within the week due to warm weather over the past several days. The timing of first cutting is a crucial factor in determining the quality of your alfalfa crop. Using the Michigan State University Enviroweather alfalfa cutting model, growers have a guide as to when they should cut their first cutting crop. The table below provides a regional report on alfalfa growing degree-days (GDD) for the next week. Producers in south central Michigan have started harvesting and are reporting yields above last year’s crop with excellent quality.

MSU Enviroweather stations have been placed across the state to monitor local conditions for temperature and rainfall accumulations. To access the nearest weather station information, go to MSU Enviroweather.

Regional GDD averages for alfalfa
Region location	Current GDDs (May 17, 2017)			Predicted GDDs (to May 23, 2017)
Region location	Average	Max.	Min.	Average	Max.	Min.
South central	593	673	544	746	826	700
East central (without East Lansing and Haslett)	491	565	390	638	728	524
East Lansing and Haslett	594	661	555	638	816	702
Southeast	533	679	442	697	854	606
Southwest	600	699	522	751	846	671
Northwest	325	372	200	439	495	314
North central	346	365	337	455	475	446
Upper Peninsula	192	260	146	258	345	197

The current recommendation for producers using bunk silos is to begin cutting at 680 GDD Base 41 degrees Fahrenheit corresponding to a value of about 38 percent neutral detergent fiber (NDF). Using GDDs is an important tool that should only be used for first cutting. The recommendation for an upright silo should begin harvesting at 750 GDD for alfalfa with 40 percent neutral detergent fiber plus/minus 3 percent most years.

Alfalfa weevil

Reports of alfalfa weevil have been confirmed in Michigan’s Thumb with approximately 11 percent of the tips showing light feeding at several locations. Consider early cutting rather than spraying to preserve natural enemies. To sample or scout for alfalfa weevil before first cutting, sample 20 stems in five different locations of the field and look for larvae and damage. MSU Extension’s recommended threshold for alfalfa weevil before first cutting is 40 percent of stems damaged plus live larvae present; after first cutting is 25 percent or more of new tips damaged, or six to eight larvae per square foot of regrowth.

Alfalfa weevil growth and maturation corresponds closely with temperatures. Enviroweather uses an alfalfa weevil development model. This model predicts when damage from alfalfa weevil is expected based on degree-day accumulations calculated from data recorded at Enviro-weather stations. Degree-day accumulations base 48 F begin Jan 1.

Egg hatch is expected to begin at 300 GDD and small larvae (first and secondinstar) are expected to feed between 301 and 438 GDD, producing light leaf feeding.

Major leaf feeding occurs as larvae grow and is expected when third and fourth instars feed (between 439 and 595 GDD).

For more information, contact me at 810-667-0341 or kaatz@msu.edu.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).