Now is a good time to discuss resources that might be used to help solve vegetable disease problems. This article will discuss online resources that may be useful for vegetable disease management.
Let’s start with my favorite resource: the Plant and Pest Diagnostic Laboratory. While it isn’t necessary to send in a sample to the PPDL each time you see a spot on a leaf, it makes sense to consider sending in a sample when new symptoms that appear to be spreading appear. Be sure to check the information on the PPDL website (https://ag.purdue.edu/department/btny/ppdl/) about how to submit a sample and/or call the number provided. The $11 cost for instate samples is very reasonable. You might also consider sending photos digitally to the PPDL. Some problems can be identified by photos alone, but others may require a physical sample sent as a follow-up. The sample fee covers both the photo sample and any physical follow-up that may be needed at no additional charge. The link to the PPDL submit samples page is https://ag.purdue.edu/department/btny/ppdl/submit-samples/submit-sample.html.
Another option for determining what disease might be present is to study the vegetable disease photos recently posted at https://ag.purdue.edu/department/arge/swpap/veg-disease-photos.html. These photos are of vegetable diseases that one may observe in a typical season in Indiana. Brief descriptions of each crop and disease are included. While viewing photos is not a substitute for sending in a sample to the PPDL, the photos may help you narrow the possible disease problems that might exist in a field.
The PPDL or the photos described above will help in disease diagnosis. Armed with a disease name, you can review the resources below for management options.
Beginning with the Midwest Vegetable Production Guide, which is available as a hard copy or as an online guide at https://mwveguide.org/. The first portion of the guide contains a narrative about many aspects of vegetable production. For disease management, most growers will want to visit the second portion of the guide. At the site, you will be asked to follow the prompts to select which crop and disease is of interest. Management options will include cultural and fungicide options (insect and weed pests are also included). Filters can narrow results, such as limiting recommendations to organically certified options or fungicides labeled for greenhouse use. Searches for a particular disease can be downloaded as PDFs. Be sure to check any fungicides listed on the label.
Fungicide schedules for cantaloupe and watermelon have been condensed into a document that can be found here. A pumpkin schedule can be found here. These links and many others can be found by going to the Southwest Purdue Ag Program page at https://ag.purdue.edu/department/arge/swpap/index.html. Visit resources, then click on cucurbit resources. These fungicide schedules should be used together with current recommendations from the Midwest Vegetable Production Guide described above.
The Southwest Purdue Ag Program cucurbit resource page also provides links to extension bulletins that describe anthracnose and gummy stem blight of cucurbits, Fusarium wilt of watermelon, and other subjects. These bulletins describe symptoms, biology, and management options. Other resources, such as for tomatoes and greenhouses, can also be found under resources on the Southwest Purdue Ag Program page. Note that several videos are posted on these pages, such as how to diagnose cucurbit downy mildew or bacterial wilt of cantaloupe. The banner menu on the Southwest Purdue Ag Program also has a link to this newsletter, the Vegetable Crops Hotline: https://vegcropshotline.org/.
Finally, when searching elsewhere online for vegetable disease information, websites that end in ‘.edu’ or ‘.gov’ are most likely to provide science-based information unrelated to sales. As you gather information, it’s helpful to compare and contrast advice given from multiple sources. Purdue specialists are always available to help sort through problems when management recommendations are unclear.