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

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.


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 water soaked area of the stem near the seed leaves (Figure 1). (A water soaked area near the soil line is more likely to be damping-off.) The water soaked 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. The fungus that causes gummy stem blight (Didymella bryoniae) may survive in crop debris, thus overwintering in the field[Read More…]


: These lesions of bacterial speck of tomato were observed on a tomato transplant for sale to homeowners at a retail outlet. Tomato transplants should be inspected for disease symptoms during production or at delivery.

Many Indiana growers may have tomato transplants growing in a greenhouse for field or greenhouse/high tunnel production. The three most likely diseases are bacterial spot, bacterial speck and bacterial canker. This article describes symptoms for these diseases and some management options. While these bacterial diseases thrive in transplant production where plants are often overhead watered, these diseases are not common on tomatoes grown to maturity in greenhouses or high tunnels. This is because, for the most part, tomatoes grown to maturity in a greenhouse or high tunnel do not have the necessary leaf wetness required for these diseases. Bacterial canker is occasionally observed in greenhouse/high tunnel situations since this disease may become established in transplants and becomes systemic in plants. Once bacterial canker is systemic in the plant, it ‘spreads’ within each plant even if it does not spread from plant to plant. Bacterial speck and spot – The symptoms produced by these two diseases are[Read More…]


Figure 2: We often observe Fusarium wilt in transplant trays in a clustered distribution. We believe that Fusarium wilt may spread from plant-to-plant within a transplant tray, perhaps by soil splash or spores that have been observed on diseased seedlings.

Fusarium wilt is one of the most serious diseases of watermelon in the Midwest. The disease often causes a one-sided wilt 2-3 weeks after transplanting. Whether a plant is affected, and to what degree, depends on the population of the long-lived spores in the soil that the roots contact. However, Fusarium wilt of watermelon is not known to spread from plant to plant in the field. This is in contrast with a disease such as anthracnose which can spread from plant-to-plant rapidly in one season. Occasionally, Fusarium wilt can be observed affecting commercially produced watermelon transplants in new trays and virgin soilless mix. The most likely explanation for such outbreaks is the introduction of Fusarium wilt on seed. The distribution of Fusarium wilt from seed should appear random. However, we often observe a clustered distribution of affected seedlings as seen in Figure 1. We conducted an investigation to determine whether[Read More…]


This backpack sprayer has three nozzles on a boom and a hand-pump that can be worked constantly.

The use of tractor drawn pesticide sprayers is not practical for many smaller growers. Two alternatives are garden-sprayers or backpack sprayers. I will argue here that garden-sprayers are not suited for most commercial pesticide use. The typical garden sprayer that may be found at a garden shop or hardware store usually has a 1 or 2-gallon capacity and a nozzle whose output may be manually adjusted from stream to spray (Figure 1).  Such sprayers use air pressure generated by a hand pump. Some models have a valve to quick-release air pressure. While such sprayers may be useful for cleaning tasks, they are not appropriate for commercial pesticide applications for the reasons stated below. Let’s start off discussing the adjustable nozzles on garden sprayers. These nozzles may be inadvertently moved to provide a different stream or spray. That is, the output may be changed from a full spray to a more[Read More…]


The following updates have been made to the Midwest Vegetable Production Guide for Commercial Growers 2017 (ID-56) since it was published in December. These updates have been made to the PDFs published on-line at mwveguide.org.  If you have a hard copy of the ID-56, please note these changes. Page 59-Additional plant families and example crops have been added to Table 22. Page 82-Dual Magnum entries under asparagus weed control have been updates to include Michigan only language. Page107-Velum Prime has been added to powdery mildew control for cucurbits; 6.5-6.84 fl. oz/A. May cause a mild yellowing of leaf margin.  May be applied through drip. Page 116- Velum Prime has been added to root knot nematode control for cucurbits; 6.5-6.84 fl. oz/A. May cause a mild yellowing of leaf margin.  May be applied through drip. Page 117-Entry for Luna Sensation should read “All cucurbits” under comments. Page 190- Velum Prime has[Read More…]


Small vegetable growers may find pesticide applications with a tractor driven sprayers impractical. Such growers may turn to hand sprayers. In a separate article, I argued that garden sprayers are not appropriate for most commercial pesticide applications.  In this article, I will discuss the use and calibration of a backpack sprayer, an excellent alternative to a garden sprayer for small growers. The remainder of this article will discuss one method of calibrating a backpack sprayer. Most pesticides are labeled for use on an area basis, typically an acre. Therefore, the first task in calibration is to measure the area to be treated. Let’s say that tomatoes are grown in a greenhouse where the production covers 30 X 100 feet = 3,000 square feet. For our staked tomato example, we will use a volume-based method of pesticide measurement. For this method: Determine the volume of water required to cover the fully-grown crop[Read More…]


Vegetable Crops Hotline - Department of Horticulture and Landscape Architecture 625 Agriculture Mall Dr. West Lafayette, IN 47907

© 2018 Purdue University | An equal access/equal opportunity university | Copyright Complaints | Maintained by Vegetable Crops Hotline

If you have trouble accessing this page because of a disability, please contact Vegetable Crops Hotline at guan40@purdue.edu.