Wild, Wacky Winter Weather

Weather’s effect on alfalfa and forage fields Alfalfa

Author: Mike Rankin, Hay & Forage Grower

The weather geeks at the National Oceanic and Atmospheric Administration (NOAA) tell us that 2016 was the second warmest year for the U.S. in the 122 years of record keeping. It was the 24th wettest year, but we also had double the record number of inland flooding events.

What’s done is done, but 2017 is not exactly starting out as anything close to normal in many U.S. regions. The impact on the forage industry, especially alfalfa, looms heavy; it almost always does in matters concerning weather.

Let’s begin in the West where Dan Putnam, extension forage specialist for the University of California-Davis, recently reported that some fields in northern California are flooded from relentless rains. It was needed moisture, for sure, but Putnam points out that there can be consequences to long-term ponding on alfalfa fields.

“The extent of either (plant) death or damage depends upon temperature, drainage, alfalfa growth status, and duration of flooding,” Putnam notes in a recent Alfalfa & Forage News blog.

He explains that dormant alfalfa varieties under cool or cold conditions may tolerate winter flooding more so than the green, actively growing plants in the warmer, desert regions. This is because plant respiration rates are much slower, somewhat buffering the effect of anaerobic (no oxygen) conditions caused by flooded or waterlogged soils.

In addition to the impairment of the plant to “breath,” Putnam notes that flooded alfalfa plants may suffer root damage in the form of fine root hair death, pruning, and weakened nitrogen-fixing nodules. Saturated soils also impair the uptake of micronutrients and predispose plants to disease infections. New seedings planted last fall are especially susceptible to damage.

A warm and wet Midwest

Some early December snow set the stage for a desired winter groundcover in most of the Upper Midwest. It didn’t last long as temperatures warmed with the new year and were accompanied by volumes of liquid precipitation in many areas. Temperatures in the 40s and 50s are not normal for January, but they have been this year, even in the northern states.

Many fields contain standing water with thawed or thawing saturated soils. Given that winter is far from the finish line, the concern now turns to ice formation if the water doesn’t infiltrate the soil before colder temperatures return.

“A solid layer of ice restricts air diffusion and suffocates alfalfa plants,” says Dan Undersander, University of Wisconsin extension forage agronomist. “Solid ice is more devastating than ice that is cracked or where plant stems are sticking above the ice layer,” he adds. As with water, the duration of ice cover plays a large role in determining the potential for damage.

Undersander doesn’t recommend any remedial practices when ice forms over alfalfa fields. Practices such as pulling a disk across the field to break the ice or applying fertilizer to melt the ice are generally of little consequence and often can cause more damage than if fields were left alone.

The waiting game

It’s never easy to predict damage incurred to alfalfa during winter. Be it water or ice, the effects of damage, or lack thereof, are usually not known for weeks and sometimes months into the future.

Past history tells us that the spectrum of potential damage is wide, ranging from total death to slightly weakened plants. In the latter case, both Putnam and Undersander suggest conservative management during the upcoming growing season. Let plants reach 10 percent bloom to build carbohydrate reserves before taking the initial cutting. Also, be vigilant to ensure adequate soil fertility and control pests. Insects often prefer stressed plants. Where possible, also try to control weeds.

Though nothing can be done at this time, it doesn’t hurt to develop a backup plan if the worst-case scenario comes to fruition. Think about alternative crop rotations, possible interseeding strategies for new seedings, annual forages that could fill a short-term feeding need, and when or where new seedings might be established in 2017. Then hope none of those plans will ever be needed.

Full article shared from Hay & Forage Grower website.

Butterflies May Signal Future Alfalfa Problems

Alfalfa caterpillars, the larvae of butterfly eggs, can cause reductions in yield and quality Butterflies-Alfalfa

Author: Mike Rankin, Hay & Forage Grower

Butterflies in alfalfa fields may be free and make for a good photo opportunity, but they also can indicate future alfalfa worm-feeding issues. That’s the warning coming out of Central California where alfalfa fields are awash with yellow and white butterflies this summer.

“Some alfalfa fields appear more yellow and white than green with outbreaks of alfalfa caterpillar butterflies in the Sacramento and San Joaquin Valleys,” notes Rachael Long, an extension farm advisor in the region. “In certain cases, the populations have been massive,” she recently reported in the University of California extension’s Alfalfa & Forage News.

It’s not that the butterflies do any direct damage, but the eggs they lay soon develop into larvae known as alfalfa caterpillars. The yellow butterflies, sometimes referred to as sulfur butterflies, are cyclical, occurring in large numbers every few years. According to Long, contributing to high populations are factors such as slow and uneven alfalfa growth, a lack of predator insects such as the parasitoid wasp, and hot, dry weather.

The alfalfa caterpillar worm is green with a white stripe along each side. “They consume entire leaves and strip a plant, causing significant reductions in yield and quality if numbers are high enough,” Long notes. In severe cases, plants can be completely stripped of the high-value leaves.

Sulfur butterflies and the associated alfalfa caterpillar are not confined to California. The species can be found throughout the United States. According to the “Compendium of Alfalfa Diseases and Pests” (Third Edition), this pest does the most damage in the southwestern U.S., usually on irrigated fields. In southern regions, up to seven generations can occur, whereas in northern locations there may be as few as two.

The economic threshold for controlling alfalfa caterpillars is 10 healthy, nonparisitized caterpillars per sweep of the net. California specialists recommend scouting for the pest in conjunction with armyworms. They have produced a video that helps growers and consultants identify the worms, their natural parasite enemies, and how to differentiate a healthy worm from one that is parasitized.

If treatment thresholds are reached and the field is not close to harvest maturity, there are several chemical control options available for spraying alfalfa. Products containing the bacteria Bacillus thuringiensis (Bt) are also an option. Long reports that a number of fields in Central California have already required chemical applications to control their worm outbreak.

Full article shared from Hay & Forage Grower website.