As August settles in, Southwestern Ontario and Norfolk County potato fields are seeing significant developments, with most fields having undergone top-killing. Dr. Eugenia Banks of the Ontario Potato Board shared the latest updates in her regular newsletter, shedding light on the current state of the potato crop and the challenges faced by growers.
Early Chipping Varieties Harvest
According to Mark Van Oostrum, the harvest of early chipping varieties for field frying is ongoing, with yields, quality, and size meeting expectations. However, the high temperatures during harvest pose a risk of soft rot. Growers are cautiously timing their digging efforts to when temperatures are below 25°C, a challenging task during the recent heat wave.
Crop Conditions and Disease Management
In the Melancthon area, fields exhibit various stages of growth, from beginning to bloom to past blooming with closed canopies. Notably, sprayer tracks are visible across many fields as growers intensify their efforts against late blight and other diseases such as early blight, brown spot, Botrytis, and white mold.
Fields in the Alliston area, which are past blooming, show signs of maturity and appear to be at least a week ahead compared to last year’s crop. The weather has been favorable for late blight, prompting growers to adopt preventive measures. Blight-specific fungicides are most effective when applied as protectants before infection signs appear. Factors such as soil type, location, and rainfall, in addition to timing and fungicide specificity, play crucial roles in infection rates.
Importance of Spray Coverage
Syngenta emphasizes the importance of thorough spray coverage. Syngenta notes that the active ingredient in Orondis penetrates the leaf surface and moves upward within the plant, protecting both existing leaves and new growth. However, insufficient coverage can leave the lower parts of the plants unprotected, creating a risk of late blight lesions that can serve as inoculum sources.
Tuber Protection
August marks a critical period for tuber protection. Phosphorous acid applications are recommended as the best defense against late blight for tubers. Dr. Banks highlights the importance of this practice to safeguard the crop during this vulnerable time.
Home Gardens: A Source of Inoculum
Home gardens, particularly tomato plants, have been severely impacted by late blight, posing a risk to commercial potato fields. Unfortunately, there are no effective treatments available in garden centers for home gardeners. Dr. Banks advises that infected tomato plants should be destroyed to prevent the spread of the disease to commercial crops.
As Ontario potato growers navigate the challenges of the season, diligent disease management and strategic harvesting practices remain paramount to ensure a successful harvest.
Contact:
Dr. Eugenia Banks
EugeniaBanks@onpotato.ca
Image: Potato field in the Melancthon area in Ontario, Canada. Credit Dr. Eugenia Banks
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