After wetting periods of 16 hr May 30-31(0.13 in. rain) and 20 hr June 1-2 (1.2 in. rain), we have recorded almost continuous wetting 47 of 56 hours since 10 PM June 2. (It is still wet at the time of this post).
As fruits enlarge, they become more resistant to scab than the youngest leaves, so that at five weeks after petal fall, they require about double the length of wetting period at a given temperature than growing shoot tip leaves. But the several extended wetting periods the past week have easily surpassed the requirement for fruit infection. It is important to maintain protective residue now, to prevent fruit scab infection as well as early sooty blotch/flyspeck SBFS development.
Lower elevation orchards in central Virginia have passed the 250-hr accumulated wetting for SBFS. Also, we have confirmed Alternaria leaf blotch symptoms on Red Delicious leaves in Rockingham County.
Disease management information directed mostly to the Frederick County Virginia tree fruit industry, updated as needed throughout the growing season. Keith Yoder, Virginia Tech Agricultural Research and Extension Center, Winchester, Virginia
About Me
- Keith Yoder
- Professor Emeritus of Plant Pathology, Virginia Tech Ag. Research and Extension Center, Winchester, VA
