Dan Egel’s Veggie Disease Blog

Dan Egel is an extension plant pathologist with Purdue University who works with vegetable growers across the state of Indiana. This blog will highlight recent disease issues, management options, meeting dates and new publications relevant to vegetable growers. Dan is located just north of Vincennes at the Southwest Purdue Agricultural Center.

Contact Information

Dan Egel
Southwest Purdue Agricultural Program
4369 N. Purdue Road
Vincennes, IN 47591
Phone: 812-886-0198
Email: egel@purdue.edu

www.watermelondr.info

In the last issue of the Vegetable Crops Hotline, I wrote an article about common diseases of cantaloupe and watermelon transplants. Based on the samples I have received over the last few days, I would like to write about a disease that is not usually a problem: angular leaf spot. Angular leaf spot affects all cucurbits. In this article, I would like to concentrate on angular leaf spot on cantaloupe and watermelon. Symptoms of angular leaf spot on cantaloupe often consist of brown, necrotic lesions on the margin of true leaves and seed leaves (Figure 1). On watermelon leaves the lesions may appear darker (Figure 2). Under cool, wet conditions, the disease can be quite severe, resulting in hotspots where seedlings are rendered useless for field transplanting. Angular leaf spot may be seed borne. I suspect that the pathogen may also survive on transplant trays and on greenhouse surfaces. Therefore,[Read More…]


Figure 1:

Botrytis gray mold can cause disease on many different host plants, enabling the fungus to easily survive and disperse between crops. Host crops include flowers such as geraniums, vegetables such as green beans and fruit such as strawberries. The disease is favored by relatively cool temperatures and high humidity. We recently observed botrytis gray mold on tomatoes grown in a greenhouse and strawberry grown on a plasticulture system in the open field. Tomato: Gray mold of tomato is one of the more common diseases of greenhouse-produced tomatoes. Although it is often a minor problem, if left unchecked, gray mold can cause yield loss. Gray mold, or as it is sometimes called, Botrytis gray mold, may cause a light gray or brown necrotic lesion on leaves (Figure 1). The lesions on leaves are sometimes wedge shaped on the margin of the leaf. Stem lesions are a similar color and may encircle[Read More…]


In creating the new format of the Midwest Vegetable Production Guide for Commercial Growers 2020 (ID-56), I inadvertently left out the portion of the fruiting vegetable section that deals with Phytophthora blight of pepper. The new format allows me to update items easily; I have now added information on this important disease. Go to mwveguide.org to find the update. However, the hard copy of the Guide still lacks this information. Anyone who wants a hardcopy of the Phytophthora blight on pepper information should contact me. I apologize for any inconvenience or confusion. Please let me know of any comments or questions that you might have.


Figure 1. A common symptom of gummy stem blight of watermelon is a watersoaked area where the seed leaves attach to the stem.

1. What caused the water-soaked stem of this watermelon transplant? A-damping-off B-gummy stem blight C-Lightening strike Correct Answer: B 2. Is this problem likely to spread to other transplants? Yes 3. Will this problem likely spread in the field? Yes More information about gummy stem blight can be found in the article Cantaloupe and Watermelon Transplant Diseases in this issue.


Figure 3. Anthracnose lesions on watermelon often appear jagged.

Many cantaloupe and watermelon growers are either growing transplants in a greenhouse or are expecting delivery of transplants in the next few weeks. Either way, growers should inspect transplants for disease before planting in the field. Below I will describe several common transplant diseases of cantaloupe and watermelon as well as management options. Gummy stem blight on transplant seedlings may be recognized by the watersoaked area of the stem near the seed leaves (Figure 1). The watersoaked area may eventually turn brown and woody. A closer look at the woody area may reveal the small, dark fungal structures of the gummy stem blight fungus. Medium brown, irregular lesions may also be observed on true leaves. A watersoaked area near the soil line is more likely to be damping-off (Figure 2). More information about damping-off can be found in previous issue’s article Damping-off of Vegetables. The fungus that causes gummy stem[Read More…]



If it hasn’t happened already, vegetable growers will soon drop seeds into transplant trays in preparation for the 2020 season. Or, in a few weeks, vegetable growers may drop seed into the ground. In either case, it is possible that one of several fungi that survive in the soil may attack the seed or seedling as it emerges from the ground. This disease is known as damping-off. The symptoms of damping-off range from a poor stand of seedlings when the fungus kills the seedlings before it emerges from the soil to seedlings that have fallen over due to a lesion of the stem (Figure 1). There are several fungi which may cause damping off. These include Pythium, Rhizoctonia, Theleviaopsis, Fusarium spp. and many more. The identity of the culprit may seem unimportant, but if the problem persists, knowledge of the causal fungus may help one to know how to alter[Read More…]


As Indiana growers start the 2020 season, it is important to remember to clean and sanitize equipment and tools. In this article, I would like to discuss the importance of and how to sanitize. Bacteria and fungi that cause plant disease may survive on some types of equipment. Examples include: stakes, transplant trays, shovels, greenhouse benches etc. Equipment can be contaminated by diseased plants in close contact with the surfaces. For example, a tomato with bacterial canker may rub up against a wooden stake, transferring some of the bacteria to the stake. Such bacteria may cause disease problems next year. A transplant tray of cantaloupe with a damping-off problem may have the same disease next year if the tray is not properly cleaned and sanitized. It is important to clean the equipment of crop debris or soil prior to the use of one of the sanitizers described below. Equipment free[Read More…]


In a normal year, vegetable growers may drop samples by the SW Purdue Ag Center in Vincennes Indiana for problem identification. However, this is far from a normal year. Due to concerns about the coronavirus, SWPAC is closed to walk-in visitors. We do not know how long this situation may last. We have devised an alternative method of dropping off samples that will avoid face-to-face contact. Follow these instructions to drop off samples. Contact Dan Egel or Wenjing Guan before stopping by or attempting any drop off (see contact info below)! There will be a sign on the front door with instructions about how and where to drop off a sample. Do not try to enter the front door. When leaving the sample, include as much info as you can about the sample. You will be contacted as soon as possible about the sample by phone or email. Leave only[Read More…]


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While many growers use high tunnels to extend the growing period for warm-season crops such as tomatoes or cucumbers, it is also possible to grow cool-season crops such as spinach well into winter. The winter over much of Indiana has been rather mild; spinach and other cool-season crops should be doing well. However, disease and insect pests may be a problem. In the first week of March, I observed leaf spot on spinach growing in a high tunnel (Figure 1). Note that the lesions occur on a cluster of plants indicating possible spread of a fungus. A closer look shows that the center of the lesion may be dark with fungal sporulation (Figure 2). I was able to confirm the disease as Cladopsorium leaf spot of spinach. Little is known about the biology of the fungal pathogen. However, the disease is favored by rainy or at least moist weather. The[Read More…]


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