Dan Egel

Clinical Engagement Associate Professor
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The wilted and dead leaves of the watermelon transplants in Figure 1 could have several causes. Above ground symptoms such as wilts and leaf death may be caused by problems underground.  When I investigated the plants in Figure 1, I found that many of the plants had a root rot. The dark area at the base of the stem (technically, the hypocotyl) is caused by a fungus that is growing in the plant (Figure 2). The fungus also can be found on the roots of the plant. This disease is known as black root rot of watermelon. The fungus that causes this disease is Thielaviopsis basicola. This fungus causes a similar disease on carrot, tobacco, pansies and many more crops. The dark area on the base of the stem is actually a ‘sign’ of the disease since the fungus that causes the disease is visible. The wilting and decline of[Read More…]


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This disease has been observed in southern Indiana. Symptoms often begin with dark, wet-looking lesions on the stem (Figure 1). These lesions may extend up the stem and result in the wilt and death of the plant (Figure 2). Occasionally, opportunistic microorganisms invade the stem and produce a disagreeable rotten odor. The conditions that may favor aerial blackleg include dense canopies and warm, wet weather. Overhead irrigation can also be a factor in promoting aerial blackleg. The bacteria which cause aerial blackleg are Dickeya and Pectobacterium spp. These bacteria are often introduced by infected seed potatoes. The bacteria may then spread into the soil and be splashed into wounds or leaf scars.  Conversely, the bacteria have been reported to survive 2 years or less in crop debris. It is important to note that while symptoms of aerial blackleg do not include rot of the seed piece, blackleg may start on[Read More…]


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Below, I will briefly discuss a few of the diseases that I have observed on tomatoes recently. Powdery mildew of tomato – Powdery mildew of tomato is not usually a common problem in Indiana. However, in recent years, there have been more reports of this disease than usual. Powdery mildew is more often observed in a greenhouse situation than in a field. The key symptoms of this disease are the talc-like lesions on the upper and lower leaf surfaces (Figure 1). It is important to note that the location of the upper and lower lesions do not correspond with each other. When the lesions are young, it may almost seem as if the lesions can be ‘wiped off’. Few varieties exist with good levels of host resistance, although growers may notice some difference in susceptibility between varieties. It may not be necessary to treat tomatoes affected with powdery mildew with fungicides. If[Read More…]


Figure 1. A cucumber plant grown in a high tunnel died because of bacterial wilt.

Bacterial wilt is one of the most destructive diseases in high tunnel cucumber production. The reason bacterial wilt is so important is because, like other wilt diseases, it ties up with the entire vascular system of a plant, causing systemic effects (Figure 1). The relatively less important roles that other cucumber diseases play also make bacterial wilt the major limitation for high tunnel cucumber production in Indiana. For example, common cucumber diseases such as angular leaf spot, anthracnose and Alternaria leaf blight seldom occur in a high tunnel scenario; improved resistance to powdery mildew was observed in some of the newly developed cucumber varieties; downy mildew in general does not occur in Indiana until end of the high tunnel cucumber production season. The causal organism for bacterial wilt of cucumbers is Erwinia tracheiphila. After the bacteria enter the plant vascular system, it multiplies quickly. As a result, it interferes with[Read More…]


The Purdue MELCAST system allows growers to apply foliar fungicides according to weather conditions instead of using a calendar-based system.

MELCAST is a weather-based disease-forecasting program that helps growers schedule foliar fungicides. MELCAST stands for MELon disease forCASTer. This program, designed by Dr. Rick Latin, Professor of Plant Pathology at Purdue University, keeps track of weather conditions so that cantaloupe and watermelon growers can apply foliar fungicides to their crops when they are most needed. The foliar diseases that MELCAST was designed for are Alternaria leaf blight, anthracnose and gummy stem blight. In a typical year, MELCAST will save growers 2 to 3 foliar applications of fungicides without sacrificing yield. MELCAST works by having growers apply fungicides at specific Environmental Favorability Index (EFI) values instead of using a calendar-based schedule. The extension bulletin “Foliar Disease Control using MELCAST” BP-67 describes this program in more detail. To use MELCAST, follow these steps: Apply your first foliar fungicide application when vines first touch within a row or earlier. Find a MELCAST site[Read More…]


This article provides more detailed information about this herbicide. How does Chateau® herbicide work Chateau® is a group 14 mode-of-action herbicide. Compounds in this group are most active on broadleaf weeds. Before Chateau® became available,  no other preemergence herbicide with the same mode of action was labeled for use in watermelons and cantaloupes. The active ingredient of Chateau® herbicide, flumioxazin, controls susceptible weeds by inhibiting propoporphyrinogen oxidase (PPO), an enzyme that controls chlorophyll synthesis. Because of chlorophyll production inhibition, a chain reaction occurs within the plant that causes cell membrane disruption. Chateau® herbicide can assist in the postemergence control of emerged weeds. It is taken up by roots, stems, or leaves of young plants. It kills weeds through direct contact. There is usually little or no translocation of the herbicide within plants. Foliage necrosis can be observed after 4 to 6 hours of sunlight following the herbicide application. Susceptible plants[Read More…]


One can hardly glance at the news recently without noticing an item about the health of bees and other pollinators. We can all agree on the importance pollinators play in the health of our planet and the critical role honey bees and bumble bees play in agriculture. There is no doubt that populations of honey bees in particular have been in decline over the last several years. The multiple reasons for the decline are not as clear. This article will address the role that fungicides may play in bee health. There are many possible reasons for the decline of bee populations. Pesticides have been implicated in bee declines. Most experts would agree pesticides may play a role in bee population declines. The type of pesticide that is most often implicated in bee declines are the insecticides. This makes sense: bees are insects. There is less known about the role that[Read More…]


Chateau SW® herbicide now has a 24(c) special local needs label for cucurbits. This product is produced by Valent, but the label is held by the Indiana Vegetable Growers Association (IVGA).  To obtain a label, one must be a member of the IVGA, pay an annual $100 processing fee, read and understand the ‘conditions for use’ and have the appropriate forms signed and notarized. One cannot use Chateau SW® without completing these forms and obtaining a label. This process must be repeated every year. Chateau® can only be used in row middles between raised plastic mulch beds that are 4 inches higher than the treated row middle. The mulched bed must be at least 24 inches wide. The application must be directed between rows with a shielded sprayer. Chateau® cannot be applied post-transplant. Do not apply more than 4 oz. of Chateau® per acre at a broadcast rate during a single application.[Read More…]


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I recently encountered some lesions of Tomato Spotted Wilt Virus (TSWV) that appeared relatively large and had a ring-like structure.  I was able to confirm the presence of the virus, but at first glance, the lesions could be mistaken for a very common tomato disease: early blight. This article will describe how the foliar lesions of these two diseases might be distinguished. First, a bit about the symptoms of these diseases. Early blight is perhaps the most common foliar disease of tomato in Indiana. One might first notice that the older leaves turn necrotic. If left uncontrolled, the diseased lesions appear to ‘move’ up the plant. A closer look at early blight lesions may reveal the bull’s-eye lesions of this disease (Figure 1). These lesions may also be described as having concentric rings similar to a target. (Early blight is not the only disease to have concentric rings.) I usually[Read More…]


The Midwest Vegetable Production Guide for Commercial Growers 2018 (ID-56) was printed in December 2017.  At the same time, the on-line version was posted at mwveguide.org.  As updates need to be made to the ID-56, I will make those updates to the on-line version. I will announce these updates in the Hotline as I post them. Consider the updates below and mark those updates in the hard copy of your ID-56 that will affect you. Briefly, Quadris Top® has been changed to silent on greenhouse use, Luna® products have been added to crops in the fruiting vegetable chapter, and RUP® has been added to Pounce 25WP® under sweet corn. My thanks to the several individuals who have suggested updates. Fungicide table, page 79-Change Quadris Top® from no to silent under the column for greenhouse use. Eggplant, page 134-under anthracnose, add Luna Sensation® at 7.6 fl. oz. per acre. 3-day PHI.[Read More…]