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

Bacterial spot can cause mostly light colored angular lesions on pumpkin leaves.

I have observed this disease in scattered commercial pumpkin and squash fields across Indiana. Symptoms: Bacterial spot causes ⅛-¼ inch angular leaf lesions that are white to light brown in color (Figure 1). These leaf lesions may be accompanied by yellowing (chlorosis). The more important symptom are the lesions on fruit that are scabby to raised, round and a light brown in color. These lesions are often less than ⅛ inch in diameter and do not extend into the surface of the fruit. However, lesions may become secondarily infected in which case lesions can become an inch or more in diameter. Such lesions may grow into the flesh of the fruit (Figure 2). Any type of fruit lesion can ruin the marketability of the fruit. Biology: Leaf lesions, while unimportant economically, are important in diagnosing bacterial spot before fruit is present. This head start allows growers to begin preventive measures.[Read More…]


Southern rust pustules on corn leaf, and chlorosis on the underside of the leaves. Pustules generally form and erupt on upper surface. (Photo Credit: A. Sisson, Iowa State University

This article is modified from Darcy Telenko’s article about field corn in a recent Purdue Pest and Crop newsletter. Southern rust of corn is normally a disease of tropical areas. During summer months, however, the fungus which causes southern rust, Puccinia polysora, may move into Indiana or other Midwestern states.  Southern rust has officially been confirmed in Posey and Vigo County. If you think you have this disease contact me or submit a sample to the PPDL https://ag.purdue.edu/btny/ppdl/Pages/Submit-A-Sample.aspx Southern rust pustules generally tend to occur on the upper surface of the leaf, and produce chlorotic symptoms on the underside of the leaf (Figure 1). These pustules rupture the leaf surface and are orange to tan in color. They are circular to oval in shape. We are seeing a lot of common rust as well and both diseases could be present on a leaf. Common rust will form pustules on both sides[Read More…]


Downy mildew of cucumber can be recognized by the yellow angular lesions on the top of the leaf.

Cucurbit downy mildew has been observed on cucumber in the southwest corner of Michigan, just across the border from La Porte County and LaGrange Counties, Indiana. All cucurbit growers in Indiana should be scouting for downy mildew. Cucurbit growers in northern Indiana should be managing for downy mildew. The organism that causes downy mildew of cucurbits doesn’t overwinter in Indiana. It has to be blown in every year. It is common for downy mildew to start the season in the Gulf States and migrate north with the cucurbit crops. Downy mildew apparently overwinters in northern Michigan/southern Ontario in greenhouses where cucumbers are grown year round. Therefore, downy mildew is often found in Michigan before it is found in Indiana. In most years, the downy mildew fungus will blow from southern Michigan to Ohio before it tracks south. Many cucumber varieties have some resistance to downy mildew. For susceptible cucumber varieties or[Read More…]


Vegetable growers are used to scouting for pests such as spider mites and aphids. Growers have come to recognize the yellow leaves caused by spider mites and the curled leaves caused by aphids. Growers understand that even after spider mites and aphids are dead, the symptoms of the damage may remain on the affected leaves. Whereas, a leaf distorted by aphids remains distorted even after the aphids are dead, a leaf with symptoms of a foliar disease such as anthracnose of watermelon or early blight of tomato typically contains viable spores even after repeated fungicide applications. So, what is the purpose of fungicide applications? Contact fungicide applications with active ingredients such as chlorothalonil (e.g., Bravo®, Echo®, Equus®, Initiate®) or mancozeb (e.g, Dithane®, Manzate®, Roper®, Penncozeb®) are used to coat the surface of the leaf so that when spores land on a leaf, they are neutralized. While it is true that[Read More…]


Anthracnose of garlic, a new disease to Indiana, may cause sunken, orange lesions on scapes.

Earlier this summer, sunken lesions were observed on garlic scapes on a small farm in east central Indiana. Lesions started out a cream or tan color (Figure 1), however under rainy or humid conditions, spore production caused lesions to turn orange (Figure 2). Larger lesions resulted in the collapse of the scapes. It is estimated that 45 to 50 percent of scapes were affected. Lesions ranged from ¼ to ½ inch long. Samples of these scapes were sent to the Purdue Plant and Pest Diagnostic Laboratory in West Lafayette where they were diagnosed as anthracnose of garlic, a new disease to Indiana. This new disease is caused by the fungus Colletotrichum fiorinae. This fungus has also been reported on elephant garlic in New York. Reports from New York suggest that onion is unaffected. In the US, C. fioriniae has also been reported as an Apple post-harvest decay, causing bitter rot on[Read More…]


The 2019 production season started with above-normal rains. The wet conditions affected agriculture production, including watermelon and cantaloupe. In this article, we will review some of the watermelon and cantaloupe problems that are often associated with wet conditions. Manganese toxicity– This nutrient disorder occurs more often on cantaloupe that is grown in soils with pH lower than 5.5. Although liming before planting is a common practice, it is not unusual that we see soil pH that has dropped below 5.5 in sandy soil, especially during wet years. Manganese exists in soil solution as either reduced (Mn2+) or oxidized (Mn3+) form. Plants take up manganese in the reduced form (Mn2+). The proportion of exchangeable Mn2+ increases dramatically as soil pH decreases, and this reaction is promoted in waterlogged soils with low oxygen condition. As raindrops fall through the air, they dissolve CO2 and form enough carbonic acid to lower the pH of[Read More…]


Anthracnose of strawberry causes sunken lesions.

At the Southwest Purdue Ag Center, we are studying annual strawberry production on plastic mulch. Our hope is to gather information on the best methods and varieties to use for annual strawberry production in Indiana. As we learn about insect and disease problems, we will pass this information on to producers. This article is about the diseases we have observed in our strawberries which were planted in March 2019. Strawberry leaf spot-Lesions on leaves start out purple. As the lesions enlarge, the center becomes gray-brown (Figure 1). Under rainy conditions, lesions may coalesce across leaves and cause large necrotic areas. Lesions on stems and petioles may cause dieback. Yield or fruit quality loss can be caused by leaf spot under severe conditions. Although leaf spot symptoms are spread throughout our trial, this disease has not become serious for us. There are several cultural methods of managing leaf spot. Host resistance[Read More…]


Figure 1: A cantaloupe plant surrounded by striped cucumber beetles that have died after feeding on a plant treated with an imidacloprid product.

I know this may not come as a surprise to most of you, but it is rare that we get to observe the effectiveness of insecticides in such a dramatic way as we encountered when visiting a melon grower in southern IN recently. And in this case, the decision to apply an insecticide at transplant was a good one. In the photo below (Figure 1), one can see an accumulation of dead striped cucumber beetles that have fed upon a cantaloupe seedling that was treated with an imidacloprid soil drench (Trade names include: Admire Pro®, Macho®, Midashe Forte®, Montana®) at transplant 14 days prior to the photo being taken. The beetles are dead because they fed upon the cantaloupe plant and ingested the imidacloprid. Therefore, the plants were protected from defoliation by the beetles, but what about bacterial wilt? Did the act of feeding, however brief, cause bacterial wilt to[Read More…]


Seed Corn Maggot in cucurbit stem. Photo credit John Obermeyer.

In addition to delaying much of our fieldwork, the cool set spring has wreaked havoc on some of the plants we have been able to squeeze in during brief dry periods. We have received reports of damage caused by seedcorn maggots (Figure 1) and wireworms (Figure 2). In preparation of this article I browsed the Vegetable Crops Hotline archives and came across eight articles published by Rick Foster. What do they have in common? Associations with weather and limited strategies for control. Capture LFR® remains the only product labeled and for wireworms only. Rick Foster did some work with this product and had some promising results. Seedcorn maggots typically lay their eggs in organic matter and feed on seed in the soil, however, they can also cause damage in cucurbit transplants. The adults are active in April and May laying eggs in the field. When soil temperatures reach 70°F the[Read More…]


Figure 1. Watermelon seedlings planted in a week

In the past week, we have observed a few cases where newly planted watermelon seedlings were severely damaged or dead (Figure 1). In some fields, we observed rotted roots and lower stems caused by fungal pathogens. However, such diseases were in response to the cold soils and would not normally cause problems in warm soils. Most of the dead plants had intact stems, although growers did report seedcorn maggot and wireworm in the stems of a few dead plants. The same thing happened in May 2016. Coincidentally, rain, cloudy days, and lower than normal temperatures were observed in the same period in both years. Since early May, We have had consecutive days with the lowest temperatures in the 40s°F. There was no risk of frost damage, however, this temperature was low enough to cause chilling injury on young cucurbit plants.  This article ‘Protect Early Planted Warm-Season Vegetables from Low Temperature’[Read More…]


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