Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Small Grains
In most years, the potential for overwintering insects to cause crop damage is a result of both winter and spring weather conditions. Despite the cold winter weather in 2014, cereal leaf beetle caused economic damage in a number of small grain fields last season. Although we did not see any beetles while sampling small grains this past week, we should begin to see adults emerging soon. Beetle adults do not leave overwintering sites until daily high temperatures are consistently above 60°F. Treatment thresholds are not based on adult beetle counts; however, detection of the first adults can give us an idea of when egg laying will begin. Treatment decisions are based on the number of eggs and/or larvae per 100 tillers. Please see the following link for more information on insect identification, sampling and treatment thresholds.
(http://extension.udel.edu/factsheet/cereal-leaf-beetle-control-in-small-grains/)
There is also very good information from North Carolina about when it may or may not pay to tank mix an insecticide with your nitrogen application. (http://entomology.ces.ncsu.edu/2015/03/tank-mixing-an-insecticide-for-cereal-leaf-beetle-in-wheat/?src=rss)
Timothy
Be sure to watch for an increase in cereal rust mites which are favored by cool temperatures. Symptoms can appear as retarded growth, leaf curling, stunting, and plant discoloration. Injured plants appear to be drought stressed even when adequate moisture is available for plant growth. As a general guideline, treatment is recommended in fields with a previous history of cereal rust mites and/or when 25% of the plant tillers exhibit curled tips of the new leaf blades within several weeks following green-up. The use of a 20x-magnifying lens is often necessary to find mites on leaves. The only effective and labeled material on timothy is Sevin XLR Plus. Be sure to read the label for information on the number of applications per season as well as the days to harvest. For effective rust mite control, the use of the higher labeled rate and at least 25 gal/acre of carrier to get good coverage of leaf surfaces generally results in better control.