We spent lots of time this past week looking at grazing and small grain crops. This photo of triticale above is real common in many fields. Stripes indicate nitrogen deficiency between former layby rows. This time last year, we were also seeing affects of barley yellow dwarf virus (BYDV) which is vectored by aphids. Last season, aphids were very bad early (November and December). The earlier planting of small grain/forage crops is more likely to contract BYDV based on early aphid presence. The issue is that we must plant our grazing earlier so they are established.
The presence of aphids were low early this season – opposite of last year. Following Christmas, however, I noticed evidence of aphid feeding was showing up in all small grains. We are now seeing symptoms of BYDV in some fields. The difference in cold injury, BYDV, phosphorus, and nitrogen and potash deficiency can be difficult to tell. Additionally, all elements depend on all other elements – if one is deficient, the whole thing collapses. UGA Extension Forage Agronomist Dr. Dennis Hancock sums up some of the issues we are seeing in the field:
Discoloration can mean different things in different situations. Yellow tips and leaf margins usually mean K deficiency, if N is sufficient. Yellow to tan tips but not leaf margins usually mean cold injury. Purpling tips usually means cold injury, but if temps have been mostly mild and we are dealing with susceptible species (oats, wheat, etc.), then it could also mean BYDV – especially if yellowing extends all the way to the base. Purpling at the base of the plant can also be cold temperature related or it could mean P deficiency. Usually in those situations, it is actually P deficient because of the cold (which slows down mycorrhizal fungi that assist the plant in absorbing P and Zn).
Fields have been wet the past 2 weeks, and anaerobic conditions could also be causing problems. Growers have been sidedressing when fields have been dry enough. Looking over the past month, some fields are looking better.