76 articles tagged "Plant Disease Management".

​Since the season of applying fungicides to vegetable crops has arrived, below I have listed 10 rules that will help vegetable growers apply fungicides effectively and safely. Apply fungicides prior to the development of disease. Although many fungicides have systemic (“kick back”) action they will not completely eradicate diseases after they have started. And by the time a single disease lesion is observed in the field, many more lesions too small to observe are already working at your crop.  Most systemic fungicides move less than an inch toward the tip of the plant or may just move from the upper to the lower side of the leaf.  Use shorter spray intervals during weather conducive to plant disease. Each plant disease has its own “personality” and thus prefers different weather. However, most plant diseases require leaf wetness. Therefore, during periods of rain and heavy dews, more frequent fungicide applications are a[Read More…]



While the hard copy of the Midwest Vegetable Production Guide for Commercial Growers 2015 (ID-56) has been available since early January, the on-line version is updated as needed. Below I outline the latest changes. Page 40, Table 16. Several insecticide products were added to the “Insecticide Labeling for Greenhouse Use” table. Page 100, Cucurbit chapter. Luna Privilege® was removed from the lists of suggested products for Alternaria leaf blight control and gummy stem blight/black rot control. While Luna Privilege® is labeled for these uses, it is not available yet. Page 100, Cucurbit chapter. The rates for Presidio® for downy mildew and Phytophthora blight control were modified by the manufacturer. Page 109, Product/Disease Rating for All Cucurbits. Several products were deleted, added, or modified in the Product/Disease Ratings for All Cucurbits table. These include Luna Experience®, Actigard®, Revus® and Presidio®. Page 125, Fruiting Vegetable Chapter. Ridomil Gold SL® was added to[Read More…]


Bacterial spot of tomato is one of the most serious diseases facing tomato growers in Indiana. As described at Vegetable Diseases in Greenhouses (PDF), bacterial spot is more of a problem for field tomatoes than for greenhouse tomatoes. Symptoms and management of bacterial spot are described briefly at Bacterial Spot of Tomato and Pepper (PDF). A more detailed version of this article is found at An Update on the Use of Copper Products for Managing Bacterial Spot of Tomato (Blog Post). This article will discuss why copper products have become less useful in the control of this important disease and options for managing bacterial spot of tomato. Copper products have been used for many years to help control bacterial spot of tomato. However, some strains of the bacteria that cause this important disease are resistant to copper—that is, the bacteria have mutated to a form that is no longer sensitive to copper. Some of[Read More…]


Lesions of bacterial fruit blotch on watermelon seedlings are easily confused with angular leaf spot. Check with a diagnostic lab to be sure. (Photo by Dan Egel)

Bacterial fruit blotch is a disease that can affect most cucurbits (see Figure 1). However, the symptoms are most often observed on watermelon. A brief description of this disease and some photos can be found here. This article will introduce new recommendations for this disease in Indiana. Details of these recommendations can be found in the Midwest Vegetable Production Guide for Commercial Growers 2015 (ID-56). Hard copies of the ID-56 are available from Purdue University now for $10. A free on-line version of the ID-56 will be available soon at mwveguide.org. Copper products such as those with copper hydroxide or copper sulfate are often recommended for management of bacterial fruit blotch (BFB).  However copper products applied too often can cause yellowing of leaves and even yield loss (phytotoxicity). Since BFB is mostly caused by rare contaminated seed lots, I have been reluctant to recommend copper products routinely for watermelon growers. However, the last few years I have[Read More…]


Bacterial spot of pumpkin often causes scab-like lesions on pumpkins. In this photo

The title of this article is pretty scary. But it isn’t entirely accurate. Pumpkins won’t really rot from the inside out. In this article, I will describe one way in which pumpkins can seem to rot from the inside out. Recently, I was asked to visit a field of pumpkins where the pumpkins were soft and rotting. Some of the pumpkins had already burst. Some were soft and when prodded, the insides flowed out. I set out to try to understand how this could happen. Although it seemed that the rotted pumpkins were healthy on the outside, upon closer examination, I found lesions of bacterial spot on the outside of affected pumpkins. More information about bacterial spot can be found in Vegetable Crops Hotline No. 586. Most lesions of bacterial spot on pumpkin are scab-like on the surface of the pumpkin (see Figure 1). Occasionally, however, such lesions will become[Read More…]


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