Managing Windrow Disease In Alfalfa

Recently I received an email from Bruce Anderson about ‘windrow disease’ which I’ve noticed so thought I’d share his information in this week’s column. Windrow disease — that’s the name he gives to the striped appearance in fields where alfalfa windrows remained so long that regrowth was delayed.  Usually it’s due to rained on hay and sometimes, insects.

Windrow disease presents special challenges.  Weeds often invade, requiring spraying to maintain quality and protect stands.  During the next growth period, plants that were not smothered regrow rapidly, while plants underneath the windrow suffer delays.  Part of the field often will begin to bloom while windrow-stressed plants are still short and tender.  So when do you harvest?  When the first plants begin to bloom or do you wait until injured plants are ready?

Bruce suggests using two factors to tell you when you should cut — the health and vigor of your stand and the nutrient needs of your livestock.  For example, is your alfalfa healthy and re-growing well?  If not, wait to cut until stunted plants begin to bloom so you can avoid weakening them even more.

But, if your alfalfa is in good shape, then cut when it will best meet the needs of your animals.  Dairy cows need alfalfa that is cut early, so harvest when the first plants begin to bloom.  Regrowth of injured plants may be slow after cutting, but this sacrifice is needed for profitable milk production.  Beef cows, though, do not need such rich hay.  So if the hay will be fed to beef cattle, let stunted plants recover, and then cut when they are ready to bloom.

Hopefully, by next cut, growth will be more uniform, plants healthy, and production back to normal.


Alfalfa Weevil Adults on Regrowth

Bruce Anderson, UNL Extension Forage Specialist reminds producers that with late first cuttings of alfalfa, alfalfa weevil activity often increases when this occurs.  Anderson says that weevil larvae generally eat small holes in leaves at the growing tip of alfalfa plants.  As larvae grow, damage increases as the holes become larger.  Severely damaged fields have a grayish appearance because of the drying of skeletonized upper leaves and buds.

Most fields have not had enough damage to need spraying before first cutting.  After harvest, many larvae die when exposed to direct sunlight and high temperatures at the soil surface.  But will enough larvae survive to be a problem for regrowth?

Maybe more likely is survival of weevil adults.  These critters can be really hard on alfalfa regrowth by feeding on the developing crown buds, retarding growth and preventing fields from greening up after harvest.

Your first step in controlling weevil adults is removal of windrows and bales as soon as possible to expose these insects.  Then examine stubble frequently to see if adults are delaying greenup by feeding on new buds, especially where the windrow laid.

If damage is noticed, a threshold guideline has been developed that uses insecticide cost, hay value, and harvest management to help you determine when spraying may be desirable.  This guide, along with other tips to manage alfalfa weevil, is available from local extension offices.

Don’t let alfalfa weevil adults delay second growth of your alfalfa.  Keep a watchful eye on the stubble and spray, but only if necessary. Download our UNL Extension NebGuide for more information.