Portal Strawberry Advisory (by E. Barclay Poling, Professor Emeritus, NC State University)
January 17, 2012
I returned from SE Regional Fruit and Vegetable Conference in Savannah (5-8, Jan.) feeling pretty excited abut a talk that had been delivered by colleague, Dr. Guido Schnabel, Plant Pathologist, Clemson, at the Strawberry Conference on Saturday, Jan. 7th. His talk title was, “Disease Forecasting for Fungicides and Developing Location-Specific Spray Programs for Grey Mold/Grey Mold Resistance.” Dr. Schnabel gave us an important “heads up” that he has identified grey mold resistance to several important fungicides, including the “single site inhibitor fungicide” thiophanate-methyl (Topsin M). Also, he has identified a serious grey mold resistance problem with pyraclostrobin + boscalid (Pristine). At the meeting in Savannah he suggested that strawberry growers should not rely on either Topsin M or Pristine for their grey mold (botrytis) spray programs during bloom in 2012, “unless you have a (grey mold) susceptible population according to the profile kit.”
Dr. Schnabel passed around a “profile kit” so that everyone could see what one of these kits looked like. In case you missed the advisory I sent out last December 7, 2011 about this whole resistance problem, here is what was shared with growers and agents in a DEC 7, 2011 Berry Alert:
“Follow-up on Botrytis Crown Rot (BCR) – Clemson Pathologist looking for NC and SC cooperators”
After sending out last week’s Berry Alert, I received a very important email from Dr. Guido Schnabel, Plant Pathologist, Clemson. Dr. Schnabel has done some very noteworthy work on Phytophthora cactorum isolates from strawberry and other hosts. Here is what he had to say to us the other day about BCR:
Hi Barclay,
I just read your e-mail notification for strawberry growers (Dec 2), and noticed you mentioned the early threat of Botrytis due to early flower development. I was wondering if you could help me make the following information available to our NC and SC strawberry growers. As you may know, we are developing a research and extension program to help southeastern strawberry growers make more informed decisions on fungicide use for gray mold control. We collected over 200 Botrytis isolates from SC and NC last season and were stunned to learn that many isolates were COMPLETELY resistant to various key fungicides (including Pristine). The occurrence of resistance was location dependent, which means that generalized recommendations will not be suitable any longer unless we are just recommending protectants such as captan for disease control. This will have significant implications on future spray program designs and I will give a talk about that in Savannah early January. In recent months we developed an assay to relatively quickly (within 4 days) determine fungicide resistance profiles and we are now ready to provide a service to growers. If growers are willing to send me ‘samples’, we will provide the resistance screening service FOR FREE.
The service will consist of a written report about the location-specific resistance profile based on the samples we received and a recommendation to optimize the spray program for that specific location.
A ‘sample’ is defined as a flower, stem, or crown showing symptoms or signs of gray mold disease. The more samples from one location we get, the more accurately we can determine the resistance profile. I would ask for a minimum of 10 samples per location and there is no maximum number of samples. They should be shipped or delivered to:
Guido Schnabel, Clemson University, School of Agricultural, Forest, & Environmental Sciences, 114 Long Hall, Clemson, SC 29634
My contact information for further questions is:
864 656 6705 (office) 864 643 7131 (cell)
PLEASE NOTE: Relatively dry samples from crowns, stems, flowers can be shipped in one plastic bag (for ease of sampling; Dr. Schnabel is not too worried about cross contamination when putting all samples in one bag). For wet samples (such as fruit) it would be best to swirl the cotton tip of a q-tip in the gray spore mass of the fungus until you see gray discoloration of the white cotton. Each sample would need a fresh q-tip. All q-tips from one location can be sent in one plastic bag to Dr. Schnabel
Dr. Schnabel told me in e-mail on December 2nd that, “I do really believe that this service will be an important contribution to produce a high quality crop. It will also teach growers a lot about fungicide performance, resistance, and efficacy and raise awareness about the resistance issue.”
This morning (1/17/12) he mentioned that, ” We are ready to roll in my lab and already received samples from SC growers. I can already tell you that resistance is still out there in 2012, even though we have not sprayed much yet.”
Tentatively, both Dr. Schnabel and I are making plans to participate in the “Upstate Strawberry Meeting” on Tuesday, February 28th from 3 till 6 pm at the County Extension office in Gaffney, SC. THIS DATE HAS NOT BEEN FIRMED UP YET. So, please be looking for a final program announcement from:
Philip (Andy) Rollins, Upstate Fruit and Vegetable Agent, 612 Chesnee Highway, Spartanburg, SC 29303 (864) 596-2993 ext. 115
Photos: Dr. Schnabel realizes that most of our growers are familiar with this disease, but for the newcomers he has attached a couple of pictures of tissue that qualifies as a ‘sample’:
