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

This watermelon transplant has a water soaked area just under the seed leaves

Most watermelon growers are in the process of placing transplants in the field. I have received several commercial samples of transplants still in trays prior to out-planting. The two diseases I have observed so far are gummy stem blight and bacterial fruit blotch. Below, I discuss these two diseases as well as management options. Gummy stem blight on transplant seedlings may be recognized by the watersoaked area of the stem (botanical term:  hypocotyl) as shown in 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 (Figure 2). The true leaves of watermelon transplants may also be affected. The fungus that causes gummy stem blight (Didymella bryoniae) may survive in crop debris, thus overwintering in the field from year to year. This fungus may also survive in seed. It is also possible for the fungus to[Read More…]


​Many cantaloupe and watermelon growers have planted transplants in the field or will soon. A question many growers often have is when and how should one apply fungicides.  Applying fungicides according to a weather-based system is easy for cantaloupe and watermelon growers. MELCAST was developed at Purdue University by Rick Latin to allow growers to apply foliar fungicides to control Alternaria leaf blight, anthracnose and gummy stem blight. When MELCAST is followed, fungicides are applied when they are most needed depending on leaf moisture and temperature. Details are listed below or in the extension bulletin, Foliar Disease Control Using MELCAST, BP-67-W. Download the bulletin at www.extension.purdue.edu/extmedia/BP/BP-67-W.pdf or contact Dan Egel for a copy.  The MELCAST program uses weather information from one of the 12 sites located around Indiana: Daviess County, Decker, Elkhart County, Gibson County, Jackson County, Oaktown, Richmond, Rockville, Sullivan, SW Purdue Ag Center, Vincennes, and Wanatah. MELCAST also[Read More…]


The tomato plants shown here are stunted

​Symptoms of this disease include tomato plants with lower leaves that become yellow (chlorotic) and die; plants that begin to wilt; a lesion on the lower stem at ground level (Figures 1 and 2). If tomato plants are removed from the soil and carefully split open from the ground level, a discoloration of the vascular tissue can be observed (Figure 3). It is important to note that this discoloration does not extend up the stem more than 6 to 8 inches. If the discoloration extends up into the plant canopy, the disease may be Fusarium wilt of tomato. Although growers may observe multiple plants begin to die of this disease over a period of days or even weeks, the fungus does not splash from plant to plant.  Therefore, there should be no plant-to-plant spread in the high tunnel. Temperatures from 68 to 72°F favor Fusarium crown rot and may explain why I observed this disease last week when[Read More…]


​This time of year, I receive many questions about what fungicides to apply. I get fewer questions about how to apply fungicides. Below, I will try to address how to apply fungicides. Many years ago, I was told that to successfully use fungicides on vegetables, one must use high spray pressures and hollow cone nozzles. However, I had trouble finding any research on this topic, just rumors. So, I did my own research. Dennis Nowaskie, Superintendant at the Southwest Purdue Agricultural Center (SWPAC) built a single row sprayer that could be used to vary nozzle types between flat fans and hollow cones and spray pressures from 30 to 150 PSI. We used the sprayer to conduct experiments on Alternaria leaf blight of muskmelon during three years of field tests. The fungicide we used to try to manage this disease was the contact product chlorothalonil (trade names include Agronil®, Bravo®, Echo® and Terranil®). Phillip Harmon, now[Read More…]


​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…]


​ Last year at the Southwest Purdue Agricultural Center (SWPAC) we conducted a tomato high tunnel trial described here. In this article, I would like to talk about the trial we will conduct in 2015, a repeat of the 2014 trial. In particular, I would like to talk about what we have done for fertility. Before deciding on a fertility scheme, it is critical to conduct a soil test each year. Our soil test from November 2014 showed that our high tunnels were low in sulfur, boron and moderately low in zinc. In fact, plant tissue tests conducted during the 2014 season were low for both sulfur and boron. As a result of these tissue tests, we added a 10% liquid boron product and ammonium thiosulfate (7%) to the fertigation during the 2014 season. However, the next set of tissue tests carried out during the 2014 season also came back[Read More…]


The tomato seedlings above exhibit downward curled leaves (red arrows) which maybe a symptom of ethylene damage and yellow seed leaves with lesions (red circles)

​This is the time of year when growers often call to complain about tomato transplants that do not look right.  One possibility is that the seedlings suffer from heater problems.  In particular, tomato plants are very susceptible to damage from the gas ethylene.  In Figure 1, some of the seedlings have leaves that are curled down and stems that are twisted (epinasty in botanical terms). Epinasty is a common symptom of ethylene damage. Ethylene is a common by-product of incomplete combustion of several different types of fuel.  Incomplete combustion is often the result of heaters that are not working efficiently. Tomatoes are very sensitive to ethylene damage. A second clue is to take a closer look at the yellow seed leaves (Figure 1). Ethylene damage does not include yellowing. Furthermore, there is a spotting on the lower leaves that is not typical ethylene damage. I believe that the symptoms on seed leaves were as a result of a different compound,[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…]


In December 2014, I described the ‘Yearbook of Agriculture, 1928”. In that blog, I wrote about processing tomato production in 1925 and 2013 (the ‘Yearbook of Agriculture, 1928’ lists data back to 1925). Today, I would like to discuss cantaloupe and watermelon production. Unfortunately, yields posted in the “Yearbook” are in different units than in use today. However, I can compare acreage in 1925 and 2015. Cantaloupe production in Indiana in 2013 was at 2,100 acres. This compares to 4,820 acres in 1925. Part of the reason for the drop in acres might be that cantaloupe requires a lot of postharvest handling. Buyers want cantaloupe, also known as muskmelon, to be washed and cooled. Food safety concerns require growers to invest in specialized equipment and wade through reams of regulations. In 1925, Indiana was number 6 in the US in cantaloupe acreage, behind California and Arizona (of course) as well[Read More…]


White mold

In early March, I observed white mold of recently transplanted tomato plants in a greenhouse situation. I have described the symptoms, biology and management of white mold at https://ag.purdue.edu/arp/swpap/VeggieDiseasesBlog/Lists/Posts/Post.aspx?ID=18 . I have never observed white mold (a.k.a, timber rot) in February before. I have observed white mold of tomato transplants in April. However, the very small mushroom (smaller than a dime) that is part of the life cycle usually emerges in the spring after a cold period. The appearance of white mold in February may be as a result of the presence of the mushroom in the greenhouse that produced the transplants. To reduce severity of white mold of tomato, I recommend that tomato growers: Inspect transplants for stem lesions which may be a symptom of white mold. Bring questionable symptoms to my attention or send them to the Purdue Plant and Pest Diagnostic Laboratory (http://www.ppdl.purdue.edu/ppdl/index.html). Clean and sanitize greenhouses[Read More…]


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