Vegetable Disease Update

W. R. Stevenson, Department of Plant Pathology, UW-Madison

Rain continues to be the biggest story or rather the lack of rain. Many growers pre-irrigated their fields just before planting to restore soil moisture after a dry spring. This likely paid dividends in terms of keeping seedpiece decay to a minimum. I have not received a single sample of rotting seedpieces this season. Compared with previous years of not so long ago when we were besieged with many rotting samples, this year must be some sort of record. By warming seedpieces before cutting, pre-healing the most decay-sensitive varieties, pre-irrigating fields and not irrigating the crop up, and trying to avoid large differentials in soil and seedpiece temperatures (<10°F differential is the goal) at planting, the industry has achieved a significant reduction in losses. Replanting fields due to seedpiece decay and stand loss used to be common, but it’s now a rare event.

We are now entering our fifth year without seeing late blight in our state. The last time we confronted the disease was mid-season 2002. I have the sense that no one really misses the disease and hopefully we can add to this fortunate string of non-appearances. Still, the industry must be on guard. We are starting the year with low relative humidity and infrequent rainfall. Periods of leaf wetness have up to this point been short. Growers have purchased seed from late blight-free areas and there have been no samples of suspicious seed. Cleanings and culls from last year’s storage are being properly disposed as well as slivers and chips remaining from the seed cutting and planting. It wouldn’t hurt to do a quick survey of your property and those adjoining your production fields just to be sure that there are no volunteers, culls, etc. that are potential sources of inoculum of a variety of pathogens.

Our potato research plots at Hancock have emerged and plots are planted at Spooner, Antigo, and Endeavor. We are also raising additional potatoes at Hancock so that with an early harvest in early August, we can conduct postharvest studies in the new Storage Research Facility at Hancock. It’s going to be a very busy summer, but results from these many activities will help in improving your comprehensive disease management programs.