Summer disease pressures have increased in the past two weeks. At our AREC in Winchester, we recorded three extended wetting events since the last post Jul 6: Jul 5-6 (13 hr wet at 73° with 0.06 in. rain; Jul 8 (7 hr wet at 73° with 0.12 in. rain); and Jul 11 (8 hr wet at 79° with 0.63 in. rain). Infection by the bitter rot and white rot fungi will occur quickly with wetting and temperatures in the 70s.
The image below, sent to me from the Winchester area, suggests increasing rot pressures.
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| Rots with mummies. (Photo by W. Mackintosh). |
The proximity and distribution of the spots to the mummies suggests that they are developing rots. Some spots were described as having droplets on them. The explanation is that it is probably droplets splashed off the mummies, carrying
spores and other dark juicy material. Some droplets carrying spores may incite rot infection and others may not, or some might stay latent for a period of time. Some rots might just be growing
slower than others so they get over run by the faster growing organism.
For purposes of predicting the development of the sooty blotch and flyspeck (SBFS) fungal complex, we record accumulated wetting hours from rainfall or dew, starting 10 days after petal fall. This year we chose May 2 as the petal fall date for Winchester, so the start of wetting hour accumulation (ACW) was from May 12. Wetting hour accumulation in July has brought the total ACW to 273 hr, (past the 250-hr action threshold). ACW at Roanoke remains similar to Winchester at 269 hr, but with only 0.36 in. rainfall in July.
Other areas of Virginia with (ACW total) and rainfall in July are: Staunton (452 hr, 1.40 in.); Rappahannock County (Gadino Cellars, 362 hr, 3.06 in. rain); Red Hill (878 hr, 0.24 in.); Lynchburg (552 hr, 1.54 in,); Floyd (362 hr, 1.66 in.); Danville (649 hr, 2.53 in. rainfall).
