Cucurbit Downy Mildew Early Warning Scouting Program Project Report October 2007

Size: px

Start display at page:

Download "Cucurbit Downy Mildew Early Warning Scouting Program Project Report October 2007"

Blaze Bennett
5 years ago
Views:

1 Cucurbit Downy Mildew Early Warning Scouting Program Project Report October 2007 Elaine Roddy, Vegetable Crops Specialist OMAFRA, Ridgetown During the summer of 2007, forty cucurbit fields across southwestern Ontario were intensively monitored on a weekly basis for early symptoms of cucurbit downy mildew. The distribution and locations of these sites was determined through consultation with the grower organizations, processing industry and agribusiness. Area Crop Number of Farms Number of Fields Aylmer/Bayham pickling cucumbers 4 6 pumpkins 1 3 Charlottesville/Windham pickling cucumbers 6 6 pumpkins 3 3 Dover/Chatham pickling cucumbers 5 8 Elgin/South Kent pickling cucumbers 2 2 pumpkins/squash 3 3 melons 1 1 Walsingham/Houghton pickling cucumbers 7 8 Total all vine crops Protocol and Communications Each location was visited weekly, starting at crop emergence (early June for most locations). Scouts were trained in disease and insect identification as well as basic production information, physiological disorders and phytotoxicity. Depending on the size of the field, scouts visually inspected 10 plants at each of 20 to 30 random locations across the field. Special attention was given to low-lying and sheltered areas. When necessary, samples were collected and taken back to the OMAFRA supervisor and/or the pest diagnostic clinic for identification. A weekly scouting report was sent to each of the participating growers. A full summary of the crop and disease status, as well as relevant crop protection recommendations, was provided to the cucurbit industry via OMAFRA s Cucurbit Crop Update. Thirteen Cucurbit Crop Updates were produced over the course of the 2007 growing season. The OMAFRA crop updates are a free service provided to growers, consultants, agribusiness, researchers and crop insurance. The Cucurbit Crop Update is distributed to approximately 300 recipients via fax, and the OMAFRA website. Printed copies

2 were hand delivered to the old order Mennonite and Amish communities each week and several key agri-businesses made copies available at their outlets. Sprayer Meetings OMAFRA hosted a series of sprayer workshops for cucumber growers during the week of May 22 nd, Meetings were held in Chatham, Vienna and Delhi. Approximately 60 growers attended these meetings. Topics included: fungicide recommendation updates water volumes and spray coverage new nozzle technologies nozzle comparisons Each participant was given a free sample of water sensitive paper for their own spray coverage assessment. General Observations The 2007 growing season was characterized by unusually dry weather from early June onwards. Many fields suffered considerable drought stress and dry-weather associated problems including fusarium, leafhoppers and thrips. Leafhopper and thrips feeding was largely incidental and is not associated with any yield loss. Fusarium infections caused significant yield losses in several cucumber fields in Fusarium is a stress disease. It normally appears during unseasonably wet or very dry years. Fusarium is soil-borne; the fungi enter the plant via the roots and eventually block the transpiration stream, causing the plant to wilt and die. There are no chemical controls for this disease. It overwinters in the soil and the only effective management tools are resistant varieties and a 3-5 year crop rotation. Fusarium infections are often exacerbated on soils with a ph lower than 5.5. The hot, dry conditions also resulted in low levels of phytotoxicity associated with the fungicide spray program. The damage did not appear to affect the plant s overall health, stress tolerance or yield. Downy Mildew Monitoring Results The greenhouse cucumber industry reported low levels of downy mildew in the greenhouse crop on June 6 th, It is not known weather the innoculum survived the winter in the greenhouse, or if the initial infection came from wind-borne southern US sources. According to the Downy Mildew Disease Forecast, run by North Carolina State University, several low pressure troughs did deposit air from Texas into the Great Lakes basin during mid-to-late May, so airborne transmission is a possibility. The first field outbreak of downy mildew was identified in a 3 ac slicing cucumber field near Aylmer on June 27, At this time 100% of the plants in the field were severely

3 infected with the disease. A conventional preventative fungicide program was not followed The field in question was produced from transplants kept under plastic row covers, until early June. The transplants were grown on the farm in a seasonal greenhouse used solely for the production of a variety of transplants for market garden crops. The initial infection of the transplants may have occurred from an airborne source of innoculum either in the greenhouse prior to transplanting or in the field while the plants were covered. Aylmer/Bayham Despite the early arrival of downy mildew in the immediate area, the first confirmed diagnosis in a commercial pickling cucumber field in Aylmer/Bayham did not occur until July 27, 2007, one month after the initial field diagnosis near Aylmer. The early infection levels were generally low, ranging from 1 to 10% of the canopy infected (1 to 3 lesions per leaf). The progression of the downy mildew disease in this area was relatively slow. At the conclusion of scouting on August 17, infection levels ranged from 5-70%. Aylmer/Bayham Downy Mildew Incidence CDM-07-04A Straffordville 27-Jul-07 80% 27-Jul-07 80% CDM Straffordville 27-Jul-07 10% 17-Aug-07 55% CDM Springfield 27-Jul % 17-Aug-07 27% CDM-07-06A Calton 2-Aug-07 7% 17-Aug-07 8% CDM-07-06B Calton 2-Aug-07 1% 17-Aug-07 5% CDM-07-04B Straffordville 3-Aug-07 10% 17-Aug-07 70% Charlottesville/Windham The first confirmed report of downy mildew in Charlottesville/Windham occurred near Vittoria on July 30, By August 7 the disease was confirmed at all of the regional monitoring sites in the area. Early infection levels ranged from 1 to 4% of the canopy infected with an average of less than 3 lesions per leaf. At the conclusion of the monitoring program on August 20 th, the levels of downy mildew ranged from 20-55% of the canopy severely infected (< 5 lesions per leaf). While the levels of downy mildew were generally low across the area, one regional monitoring site was severely impacted, with the levels exceeding 40% infection at the time of the initial diagnosis on August 6 th. Two weeks later, the infection at this location had increased to more than 80% of the field and the field was destroyed.

4 Charlottesville/Windham Downy Mildew Incidence CDM Vittoria 30-Jul-07 2% 20-Aug-07 40% CDM Vittoria 6-Aug-07 2% 27-Aug-07 55% CDM Vittoria 6-Aug-07 40% 20-Aug-07 80% CDM Vittoria 6-Aug-07 5% 20-Aug-07 30% CDM Simcoe 7-Aug-07 2% 28-Aug-07 30% CDM Simcoe 7-Aug-07 2% 28-Aug-07 20% Dover/Chatham Downy mildew levels in the early planted crop were universally low in Dover/Chatham. Six of the nine regional monitoring sites had less than 10% infection on the final date of harvest. The first field identification occurred on July 24, Infections developed in the lateplanted crop during the first week of August. The late crop was severely impacted by a combination of drought stress and high disease pressure due to heavy dews. Dover/Chatham Downy Mildew Incidence CDM Wallaceburg 24-Jul-07 2% 7-Aug-07 0% CDM-07-16A Chatham 7-Aug-07 6% 21-Aug-07 48% CDM-07-16B Chatham 7-Aug-07 10% 14-Aug-07 1% CDM Wallaceburg 14-Aug-07 8% 21-Aug-07 78% CDM Chatham 21-Aug-07 9% 21-Aug-07 9% CDM-07-16D Chatham downy mildew not present at last field visit (17-Jul-07) CDM-07-16C Chatham downy mildew not present at last field visit (30-Jul-07) CDM Dresden downy mildew not present at last field visit (7-Aug-07) Elgin/South Kent Downy mildew was found in approximately 35% of the canopy in a field near Dutton on July 25, Within two weeks the disease had severely infected over 85% of the canopy. Severe drought stress was a compounding factor in the progression of the disease at this site. Downy mildew levels at the regional monitoring site near Ridgetown were less than 5% during the final week of harvest (August 1, 2007). Walsingham/Houghton This area was perhaps the hardest hit by downy mildew in The infection first appeared in low levels (1 lesion per leaf) at the edge of one field on July 11, The infected area was clearly the result of the spray boom having been turned off prematurely at the end of a row. The grower continued with an aggressive spray program and one month later, less than 40% of the canopy was infected.

5 A second field was identified on July 13 th, The initial level of infection in this field was 70%. The field was destroyed shortly thereafter. Downy mildew was confirmed at the remainder of the regional monitoring sites in this area between July 19 th and August 9 th. Infection levels in late August ranged from 5% to 50%, with the late planted crop being the hardest hit. Walsingham/Houghton Downy Mildew Incidence 2007 CDM Walsingham 11-Jul-07 5% 15-Aug-07 40% CDM-07-26A Glen Meyer 13-Jul-07 70% 13-Jul-07 70% CDM Frogmore 19-Jul-07 3% 16-Aug-07 50% CDM-07-26B Glen Meyer 20-Jul-07 15% 17-Aug-07 85% CDM Houghton 26-Jul-07 2% 16-Aug-07 15% CDM Glen Meyer 27-Jul-07 10% 17-Aug-07 50% CDM Langton 1-Aug-07 5% 22-Aug-07 5% CDM Frogmore 9-Aug-07 5% 16-Aug-07 5% Spore Traps Following the confirmation low levels of downy mildew in commercial cucumber greenhouses, a spore trap was set up in the Leamington area in co-operation with Dr. Mary Hausbeck at Michigan State University. Spore reels were changed weekly from June 14 th to August 10 th and sent to MSU for analysis. The number of spores caught by the trap were low (0 to 50 spores per m 3 per day) throughout the season. Two short periods of activity were noted from July 3-10 and from July At the Michigan trapping locations spore numbers were also low throughout the season, with the exception of Munroe County, the location of the first field outbreak in Michigan. In Michigan the 2007 peak catches (excluding Munroe County) ranged from 140 to 5,000 spores per m 3 per day. In Munroe County spore counts were elevated throughout much of late July and August. Peak catches exceeded 64,000 spores per m 3 per day. While spore trapping is a valuable research tool, it does not provide an accurate, inseason assessment of the risk of downy mildew infection in a given area. For more information on the MUS spore trapping project visit:

Final Report Aphid monitoring and virus testing in strawberries

Final Report Aphid monitoring and virus testing in strawberries 15 February 2017 Prepared for: Horticulture Nova Scotia 32 Main St Kentville, NS B4N 1J5 Prepared by: Jennifer Haverstock Small Fruit Specialist