By Wesley Everman... I have received a number of questions lately about a couple of weeds in alfalfa that are becoming more common and difficult to control. Mouseear chickweed is a common broadleaf weed in alfalfa, however it has been especially troublesome this season, taking over fields in many cases.

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By Wesley Everman... Although many people are still concerned about getting their corn and soybeans planted, the first alfalfa cutting is soon approaching. The cool, wet weather early this season kept many people from making herbicide applications to dormant alfalfa, leading to a greater incidence of winter annual weeds in their fields making postemergence in-season applications necessary.

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By Christina DiFonzo... Looking back at my Field Crop CAT Alert articles from 2008, I feel like I’m repeating myself…which I am. At this time last year, I was stumbling around in newly planted corn fields covered with heavy mats of dying chickweed, warning folks about black cutworm.

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By Christina DiFonzo... As in the previous article, I feel like I am repeating myself. Alfalfa weevil is making a comeback as an alfalfa defoliator. An introduced non-native pest, alfalfa weevil was found in the eastern United States in the 1950s. Although insecticides were first used to manage the weevil, a successful biological control program found and introduced several parasitic wasp species that kept the weevil population below damaging levels for many years.

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By Richard Leep and Doo-Hong Min... Significant areas of alfalfa winterkill are now evident in Michigan. The worst areas are in southern Michigan from Lapeer County on the east side of the state to Ottawa County on the west side. Most of the damage is from saturated fine textured soils that heaved resulting in alfalfa crowns that were exposed to cold temperatures after heaving.

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By Fred Warner -- A few years ago, as we experienced a cool, wet spring in Michigan, a sample collected from an alfalfa field on campus was submitted to MSU Diagnostic Services. The plants were stunted and had very short internodes. High numbers of stem nematodes, Ditylenchus dipsaci, were recovered from the leaves and stems of these plants.

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By Richard Leep, Tim Dietz, and Doo-Hong Min --  Heaving, or the pushing of plants out of the ground, has been reported in several Michigan alfalfa fields, most notably in the Central and Southern Michigan area. A photo of a field of heaved alfalfa in Central Michigan is below.

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Richard Leep and Doo-Hong Min...Because of excessive rainfall in many areas of Michigan this past week, many newly seeded alfalfa fields may show poor growth in wet or poorly drained fields which may be due to several diseases. Seedling diseases should be suspected when emergence is poor or there are stunted, discolored, or dead seedlings.

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Christina DiFonzo...For those of you in the northwest part of the state, I have received multiple reports of armyworm in both corn and alfalfa fields, and visited a big infestation personally in Mason County. Judging by the time of the year, this is second generation armyworm. In some cases, the caterpillars are moving out of alfalfa and into corn. I assume these are alfalfa/grass fields, since the grass component is attractive for egg-laying.

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Tracy Aichele...Growing degree days are an effective measure for harvesting alfalfa fields at peak quality.  In years with adequate rainfall, Allen et al. recommend: “Begin cutting alfalfa at 750 GDD (base 41 degrees F) for upright silos and 680 GDD (base 41 degrees F) for horizontal silos. Start even earlier for horizontal silos if it takes more than a week to finish harvesting.

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Wes Everman...Winter annual weeds can be problematic and reduce forage quality and yield in alfalfa during the spring of the year. The best method for weed management is good stand establishment and to control weeds in the fall or spring with herbicide applications to dormant alfalfa. Several herbicides are labeled for control of grass weeds, broadleaf weeds, or both when applied to dormant alfalfa.

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David Hillger...The United States District Court in Northern California has ruled that until a formal Environmental Impact Statement (EIS) is prepared by the USDA- Animal and Plant Inspection Service (APHIS), no additional plantings of glyphosate resistant alfalfa can be made. Furthermore, current stands of glyphosate-resistant alfalfa will have to follow new guidelines to minimize the risk of pollen movement into non-resistant conventional and organic alfalfa stands.

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Christina DiFonzo...Reports of heavy alfalfa weevil feeding are coming in from southern Michigan, and cutting is seven to 14 days away. The easiest scouting method uses tip injury. Survey across the field and not just on one side or on an edge. Check tips of 100 stems for feeding. Treat if 40 percent of stems show damage and the field won’t be cut for at least seven days.

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Richard Leep...The warm temperatures in late March may have gotten the alfalfa into trouble. Fortunately, while the weather progression from a warm, dormancy-breaking late March to a bone-chilling early April has provided reasonable cause for concern; early field observations are providing some comfort, at least for the moment.

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David Hillger...As some of you are likely aware, a U.S. District Court in California has issued a temporary injunction that prohibits the planting of Roundup Ready alfalfa after March 30, 2007. This injunction was in response to arguments made against the procedures the USDA followed prior to deregulating glyphosate-resistant alfalfa in June 2005.

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David Hillger and Jim Kells...Establishing productive Roundup Ready (RR) alfalfa stands require close attention to details, especially when the plants are young. An early-season application of glyphosate will significantly help alfalfa establishment in two ways. First, glyphosate will remove many of the weed seedlings competing with the new alfalfa seedlings for nutrients and space. By targeting weeds when they are small, excellent control can be expected for almost all weed species.

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