4.13.12 Mummy Berry Forecast: Friday, April 13
By Seanna Annis
What does an “infection period” mean?
Once mature cups are present in your field, they will be actively producing and shooting off spores into the air that will land on your plants. The spores will be produced as long as there are mature cups in the field. The spores on the plants will not be able to infect unless there is an “infection period,” which is when there is a long enough time of wetness on the plants for the fungal spores to germinate and penetrate into the plant. The length of time the wetness is required for germination and penetration of the spores depends upon the air temperature, with cooler temperatures requiring longer wetness periods. Dew typically does not last long enough on plants; only rain or fog can produce infection periods.
Knox, Lincoln and Waldo Counties
Mature cups producing spores have been found in Liberty in a wet field. I suspect other fields will also have cups present in their fields.
Most plants are probably susceptible at this point. An Appleton field had approximately 75% of their plants at flower stage F2 or beyond on Thursday.
The scattered showers this past week did not produce an infection period for any of the locations monitored. The bit of rain that has fallen and the warm weather predicted this weekend is likely to get cups developing for next week.
The scattered showers predicted this weekend in this area is unlikely to cause wetness on the plants long enough for an infection period for the fungus to get in the plants.
Around Ellsworth, no cups have been identified in our two fields yet, but cups may be present in wetter fields. Since there are beginning of pinheads in Deblois, I think there may be earlier fields in this area that do have cups. There were borderline conditions for an infection period from Thursday around 7:00 to 9:00 p.m. to Friday morning from 4:00 to 8:00 a.m. The leaf wetness was just long enough to maybe cause an infection period. What was required at the average temperature at one location during that time was 12½ hours of wetness to get an infection period and we got exactly 12½ hours of wetness.
If you have a wetter field, you may have cups in your field and may have experienced an infection period last night.
The weather forecast for this weekend suggests it is unlikely there will be conditions for an infection period until the wet period next week. I expect mummy berry cups to be developing this weekend.
Hancock North and Washington Counties
Very young pinheads (not producing spores yet) have been found in Aurora and Deblois on Thursday evening and Friday. Plants were approximately 15% susceptible in fields in Deblois. With the warmer weather this weekend, I expect mature cups will be present next week.