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Competency Area 4: Seeding Factors

PO 18. Know the factors that influence alfalfa variety selection in the Northeast.

Variety choice – the bottom line
Requires appropriate testing data and knowledge of producer’s particular needs.  What’s important to the grower is performance (yield, quality, etc.) in her/his environment! Use the best data available for the grower’s location or similar areas.

Select varieties with appropriate winter hardiness (fall dormancy ratings of 2 to 4) to minimize winter injury and winter kill. Select varieties with maximum resistance to diseases common in the Northeast (see pest management section of this manual). Also select quality, high yielding cultivars based on the closest alfalfa variety trial sites. Another factor to look for in a variety is fast recovery.

Alfalfa is a multi-year crop, so survival through winter and over time is important. When selecting a variety, first for disease resistance to verticillium wilt, phytophthora root rot, anthracnose (Hudson Valley only in NY), bacterial wilt (all modern varieties are resistant), maybe also fusarium wilt (not typically an economic problem in NY). Don’t worry about aphanomyces (in WI, not a problem in NY yet)

Alfalfa Ratings for Disease Resistance
Alfalfa varieties are genetically variable, so you almost never find all plants uniformly resistant diseases are rated by this scale:

HR = highly resistant, 50% or more of plants are resistant
R = resistant, 31-50% of the plants are resistant
MR = moderately resistant, 15-30% of the plants are resistant
LR = low resistance, 5-15% of the plants are resistant
S = susceptible, 0-5% of the plants are resistant

Individual plants may show disease symptoms even in R or HR varieties, but enough plants will be resistant to keep disease damage to a minimum. In choosing varieties, aim for R or HR ratings on all important diseases