Alfalfa weevil numbers are higher than normal.

Alfalfa weevil numbers are higher than normal. Areas that typically see a lot of weevils in the alfalfa are reporting numbers that need to be monitored as the second cutting starts to grow back. After harvest, check stubble and regrowth for signs of weevil feeding. If 50 percent of regrowth shows signs of weevil feeding, larvae are <3/8 inch long, and there are few or no weevil cocoons, the field may need to be treated with an insecticide.

Last fall’s management of alfalfa and grass had a large effect on stands this spring. If a farm took a late (October) cutting from their grass or alfalfa stands, they likely paid for it this spring. Although not limited to late cut fields, there was a lot of winter kill of alfalfa (root rot and heaving) which was exacerbated by aggressive cutting in the fall. Alfalfa builds carbohydrate root reserves in the fall. A cutting between mid-September and early October allows the alfalfa to start regrowing, sapping energy from the root. It is better to leave that last cutting or wait until after a frost so that alfalfa doesn’t start to regrow.

Late fall cut and poorly fertilized grass fields are lacking in density. October is an essential time for grass. It initiates the growth of new tillers for the following year. If a stand was not growing actively in the fall because a late cutting was taken or it was under-fertilized (especially with Potash), we can see it this spring.

A lot of farmers have been disappointed with their hay fields, especially when they compare them to what corn silage will yield. Taking care of stands correctly in the fall will help tremendously.

It has certainly been a perplexing year in every way. As I write this article on May 8th I look out the window and see snowflakes falling. Not more than ten minutes ago I answered questions from a farmer as he planted corn into 45 degree soils. I am afraid we are going to see a lot of chilling injury on corn that was planted this past week. I have also fielded calls asking when first cutting is going to be ready. I looked online for answers from Albany, but found none. Guess I will have to rely on the best information I have and my own experience.

Alfalfa and grass must be confused. March started out fairly warm and dry. Alfalfa, which very much develops according to heat, took off. Then April was cold and quite wet and things quit growing. May has been dryer but still cold with a few warmer days. Growth has been by stops and starts.

When will first cutting be ready? It depends. The variability from year to year on maturity for alfalfa can be considerable. Maturity depends on Growing Degree Days, micro-climate (elevation, closeness to lake), soil drainage, what grass is planted with it and to a lesser extent variety. Calendar date at 40 NDF can sometimes vary by two weeks between years and micro-climates.

Grasses don’t tend to fluctuate from the calendar date from year to year quite as much as alfalfa. However, maturity will depend on all of the above and also fall cutting management and fertilization. Grass cut late last fall will be later maturing than fields last cut in September. Fields with nitrogen applied in early April will likely mature quicker. Of course, orchard grass will be ahead of most fescues, Reed Canarygrass and Timothy.

When to mow is obviously a complex question with many variables. But don’t wait for your governor to tell you when to mow. It will be best for you and your crop advisor to monitor fields and consult the following table from Dr. Jerry Cherney of Cornell. From my experience, it is the best place to start in determining your window to mow.

Use this table by evaluating the height of the tallest alfalfa in different areas of the field and the percentage of grass in the stand.

Table – Estimated NDF of a mixed alfalfa-grass stand based on alfalfa height and the percent grass in the stand. Target NDF for each mixture is highlighted. Using the table below, a field with 40% grass and 60% alfalfa will be ready to mow when the tallest alfalfa stems in the field are 26” tall. For straight grass fields, look at the stage of maturity on the grass (boot stage is ideal) and the height of the tallest alfalfa in the area.