5.21.15 Disease report, May 21: Mummy Berry Season is Winding Down, Frost and Botrytis
Mummy Berry Disease in Hancock and Washington Counties
The reports I have from around Washington county are there are drying up cups and no new viable pinheads being produced. Only a couple of sites have reported still seeing drying up cups. I think we are near the end of the mummy berry cup period this year in most fields. If you have a slower wetter field you may still have some mummy berry cups around for tomorrow when rain is forecast. I think most areas are going to have no or low risk of any further infection.
Frost Warning
NOAA has forecast low temperatures that may cause frost on Friday night in most blueberry growing areas. I have seen minimal frost damage on some leaf clusters on the lowest parts of the stems. Please see pictures below.
Botrytis
I have not heard any reports of Botrytis blossom blight this year so far. In most areas, we have not had long enough wet periods to have Botrytis infection. Where Botrytis infection is found in a given year is highly variable and dependent upon local inoculum in the field. In most fields, this varies every year. Fields with very heavy damage in a crop field one crop cycle may have none or very little infection 2 years later. Whether this fungus is a problem can be detected in by looking for infection of early blooming clones from which the fungus can then be spread with wet weather to other clones. I do not recommend protective fungicide sprays for Botrytis unless you are absolutely sure you have symptoms in your field and a lot of wet weather is forecast for your field during bloom. Spraying fungicides during bloom should be avoided if at all possible.
Botrytis kills almost open (pink stage) and open flowers. There may be only a few flowers in a cluster or a few clusters of flowers on a stem that are infected. The characteristic sign of the fungus is black hairs (often with gray spore masses at their tips) sticking out from the dead flowers. Please see pictures.
Mummy Berry
Monilinia, the fungus that causes mummy berry disease, typically kills flowers before they open. There may be a few or a cluster of closed flowers that are killed per stem. There is a characteristic gray powder at the base of the dead flowers and NO hairs.
Frost damage typically hits all flowers in a cluster or part of a stem and is more likely to occur to open flowers. Open flowers are more likely to be damaged by frost than closed flowers. You can also have some of the youngest tissues of leaf clusters can get damaged by frost. The leaves will appear as a cluster tight to the stem of the plant and the innermost leaves will die.