Dan Egel

Clinical Engagement Associate Professor
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103 articles by this author

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I have observed this disease in scattered commercial pumpkin and squash fields across Indiana. Bacterial leaf spot of pumpkin is perhaps the most serious disease of pumpkin in Indiana today. 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 is 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[Read More…]


Figure 5. Breakdown and death of older cantaloupe leaves caused by manganese toxicity.

Manganese toxicity is a common problem for cantaloupes growing in sandy soils across southwestern Indiana. Because symptom of manganese toxicity can easily be confused with foliar diseases, growers may misdiagnose the problem and waste fungicides by spraying for nonexistent diseases. As we now know that manganese toxicity is a nutrient related disorder caused by low soil pH, it is important for growers to learn the symptom and address the problem in right directions. Manganese toxicity can develop on both cantaloupes and watermelons. But the symptom is more often observed on cantaloupes as they are more sensitive to acid soil conditions than are watermelons. The symptom on cantaloupes is first noticed when light green to yellow color shows between the veins on older leaves (Figure 1). Look at the leaves toward the sun and you will notice the chlorosis is formed by numerous tiny light green to yellow pin-hole type spots growing[Read More…]


I have observed very few foliar diseases of cucurbits this season. However, I have had several worried phone calls about these diseases, so here is an update. Alternaria leaf blight-this disease is caused by a fungus that survives in crop residue. It usually is not an important disease. However, Alternaria can cause brown lesions with a ring-like structure in them. This disease is more important on cantaloupe. I have not observed this disease in 2017. Anthracnose-after some effort, I have been able to start this disease in my own plots. Look for jagged, brown lesions on leaves and stems and pitted lesions on fruit. Except for my own experiments, I have not observed this disease in 2017. Gummy stem blight-this disease does not seem to occur as often as anthracnose. However, this disease showed up uninvited in my research plots. I have not observed this disease in commercial fields. The[Read More…]


Since we are well into fungicide application time, 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 good idea. The normal[Read More…]


White mold or timber rot of tomato causes a light brown area on the stem and a wilt of the plant.

White mold has a large host range including tomatoes (where it may be referred to as timber rot), cucumbers, lettuce and snap beans as well as many more. In this article, I will concentrate on white mold on tomatoes in a greenhouse situation. Although white mold will occur in a field situation, this disease is more common in a greenhouse due to the higher relative humidity than in a field situation. Perhaps the most common symptom of white mold of tomato is the light brown area on the lower stem (Figure 1 and 2). This brown area is essentially dead and will result in the wilt and death of the plant above that point. Either on the outside of this dead area or inside the stem, dark, irregularly shaped fungal bodies can usually be found. These fungal bodies (known as sclerotia) are diagnostic of white mold. Recently, I had a complaint of severe[Read More…]


Cantaloupe, watermelon and pumpkin growers can use information in the Midwest Vegetable Production Guide for Commercial Growers (ID-56) to help determine what fungicides to apply. The MELCAST system (see accompanying article in this issue) can be used to help to decide when fungicides should be applied. I have developed two fungicide schedules that I hope will help growers determine the sequence of fungicides. One fungicide schedule is for cantaloupe and watermelon growers and the other one is for pumpkin growers. Growers who are interested in obtaining a copy of these fungicide schedules should contact Dan Egel using either the email or the phone number listed above. I look forward to getting feedback about the usefulness of these schedules.


Many cantaloupe and watermelon growers have transplanted seedlings to the field. Soon, these growers will have questions about what and when to apply fungicides. The article below in this issue of the Vegetable Crops Hotline will address what fungicides to apply (Fungicides schedules for cucurbits). This article discusses when to apply fungicides with the MELCAST system. MELCAST (MELon disease foreCASTer) is a weather-based disease-forecasting program for cantaloupe and watermelon growers developed By Dr. Rick Latin at Purdue University. Instead of using a calendar based fungicide application program where one applies fungicides every 7 to 14 days, the MELCAST program lets growers apply fungicides when the weather is most conducive to disease. The diseases for which MELCAST may be used for are: Alternaria leaf blight, anthracnose and gummy stem blight. Details are listed below or in the extension bulletin, Foliar Disease Control Using MELCAST, BP-67-W. Download the bulletin at http://www.extension.purdue. edu/extmedia/BP/BP-67-W.pdf or[Read More…]


Figure 3: Mottling of a tomato leaf caused by tomato spotted wilt virus.

Tomato spotted wilt virus can cause stunting (Figure 1), necrotic ring spots (Figure 2), mottling (Figure 3) or chlorosis (Figure 4). In Figure 5, a pepper plant is shown with a ring-like lesion due to tomato spotted wilt virus. Figure 6 is a photo of a pepper transplant with mottled lesions due to impatiens necrotic spot virus. Both TSWV and INSV can cause symptoms on many hosts including ornamentals. Figure 7 is a photo of INSV symptoms on begonia. For more information about the biology and management of these diseases see here.


A tomato leaf with necrotic rings caused by tomato spotted wilt virus.

While many virus diseases affect pepper and tomato plants, in the Midwest, the most common virus diseases of these two crops are tomato spotted wilt virus (TSWV) and Impatiens necrotic spot virus (INVV).  These diseases are usually observed in greenhouse or high tunnel situations. The two viruses, TSWV and INSV are closely related. In fact, at one time, they were both considered TSWV. Therefore, the symptoms, biology and management of these two diseases are similar. This article discusses the symptoms, biology and management of these two diseases. Both TSWV and INSV affect many hosts, including vegetables and flowering ornamentals. Symptoms vary according to host, stage of plant affected and environmental conditions. Both diseases can cause stunting, yellowing, necrotic rings, leaf mottle and more. Figure 1 shows a tomato leaf with necrotic rings caused by TSWV. Figure 2 shows a pepper transplant with ring spots caused by INSV. Additional symptoms may[Read More…]


Another update has been added for the Midwest Vegetable Production Guide for Commercial Growers 2017.   Under Root maggot controls for rutabagas, please substitute the information below for the existing information on page 211. Lorsban 15G at 3.3 fl. oz per 1000 linear ft. of row at planting or Lorsban 4E/Advanced at 1 fl. oz/1000 linear ft. of row at planting.