78 articles tagged "Plant Disease Management".

Boiler Hops Logo

​Burrs and Cones. Both of the trellises in the Boiler Hopyard have begun flowering and coning. The primary shoots were pruned at the top of the net on the dwarf trellis in order to promote lateral growth. The pruning took place on May 19 and again on May 28. The bines on the dwarf trellis have been flourishing with flowers and now cones. Out of the six cultivars in the hopyard, Galena was the first to reach the top of the dwarf trellis and begin flowering. The tall trellis began flowering in early June along with the dwarf trellis, but after adding the last dose of nitrogen the plants in the tall trellis began putting on more vegetative growth, including lateral branches. This appeared to delay flowering and allowed for more lateral growth development. The plants in the tall trellis are now in full bloom and appear to be several[Read More…]

(Photo by Dan Egel)

​Bacterial spot of tomato causes lesions on foliage and fruit of tomato. On leaves, the lesions begin as small water soaked areas and turn into brown lesions with a yellow halo. Lesions on stems often lack a yellow halo. Fruit lesions, which are responsible for direct loss of marketable yield, are often scabby in appearance (Figure 1).  Bacterial spot of tomato is favored by warm, wet weather. The causal bacterium survives on crop debris and may be seed borne. Volunteer tomatoes and peppers may also carry the disease. Transplant greenhouses should be cleaned and sanitized after each generation of transplants is produced. Management of bacterial spot of tomato has been covered in more detail here https://ag.purdue.edu/arp/swpap/VeggieDiseasesBlog/Lists/Posts/Post.aspx?ID=31. The Midwest Vegetable Production Guide for Commercial Growers 2015, also has recommendations.  In this article, however, I would like to discuss a new product that has recently been labeled for this disease. Quintec® has been labeled for[Read More…]

These lesions may be covered with a white mold during moist conditions. (Photo by Dan Egel)

​Most growers first notice this disease when large, soft areas develop on mature watermelon fruit. These lesions can be several inches across and are often covered with a white mold. The lesions usually form first on the bottom of the fruit, close to where the fruit comes into contact with the soil. Further development of the disease often results in lesions on the top of the fruit as well (see Figure 1). Conditions that favor Phytophthora fruit rot include warm, rainy weather such as occurred recently over much of Indiana. Water that stands in pools also favors severe disease symptoms. Overhead irrigation may help the disease to spread. Phytophthora fruit rot can spread rapidly when conditions are favorable. The organism that causes Phytophthora fruit rot of watermelon is Phytophthora capsici. This organism is more closely related to algae than to fungi. Therefore, P. capsici is sometimes referred to as a fungus-like[Read More…]

Shoots infected with downy mildew.

​Purdue University’s Boiler Hop Yard has started its second growing season with the hopes of providing Indiana growers with science-based recommendations for hop production in the Midwest. With summer rapidly approaching, hop bines are now climbing over 10 feet high in portions of Indiana, and the Boiler Hop Yard is no exception. Downy Mildew. One of the biggest threats to Indiana hop production is downy mildew. Downy mildew (Pseudopernospora humuli) can cause hop quality to depreciate, yield to be stunted, and sometimes even plant death. Downy mildew was identified in the Boiler Hop Yard in mid-April this year, and is present in other Indiana hop farms as well. Downy mildew overwinters in the crown of the hop plant, and appears in the early spring on newly emerged primary basal or aerial spikes as a sidearm (Figure 1). These spikes have irregular growth patterns and are undesirable in hop production. The[Read More…]

​Cabbage is the crop most often affected by black rot, however, other crucifers such as broccoli, cauliflower, mustard, kohlrabi or Brussels sprouts may be affected. The first symptom one is likely to notice is a ‘V’ shaped lesion on the margin of the leaf (Figure 1). However, the symptom on Brussels sprouts observed recently are irregular, jagged lesions on leaves (Figure 2). The plants represented in Figures 1 and 2 are different varieties of Brussels sprouts. The differences may be due to differences in susceptibility of the two cultivars or the cultivar in Figure 2 may have been infected at an earlier age than the one in Figure 1. Figure 3 shows two severely affected plants next to a relatively healthy plant. Black rot is most severe in wet, warm weather. The emergence of this disease during a rather cold spring may mean that the disease started in a greenhouse situation. The bacterium that causes[Read More…]

Pith necrosis of tomato may result in dark

​This disease has been reported in two different greenhouse situations. Although the disease is not usually economically important, a brief review of the disease is offered here to help tomato growers differentiate pith necrosis from more important problems. Tomato pith necrosis causes dark brown streaks on tomato stems and leaf petioles (Figure 1).  Often stems may appear twisted and distorted. When cut open, the stem may appear discolored and chambered (Figure 2). Eventually, the affected plant may become stunted and wilt. Tomato pith necrosis is usually found in greenhouses or high tunnels. Because the plant has a discoloration in the stem, it is sometimes confused with bacterial canker, a much more serious disease. A comparison of the two diseases can be found at https://ag.purdue.edu/arp/swpap/Documents/pith-necrosis%20.pdf.  It is not clear how pith necrosis spreads or enters the tomato plant, but it is probably best to remove affected plants and avoid using pruning equipment on diseased plants. When removing[Read More…]

​Blossom end rot of tomato has been showing up in some protected growing structures. This article reviews the disorder and summarizes preventive practices. Blossom end rot is a physiological disorder caused by a deficient supply of calcium to the developing fruit. It is a common problem on tomatoes, but can also occur on peppers, eggplants, and melons. Blossom end rot appears first as a small darkened or water soaked area, usually at the blossom end of the fruit. This spot darkens, enlarges and dries out as fruit matures. The area may be invaded by secondary decay causing organisms. Prevention is the best way to avoid losses from blossom end rot. Prevention strategies emphasize ensuring adequate supply and availability of calcium, and managing plant growth environmental conditions to promote movement of calcium to the developing fruit. If I could offer just one suggestion it would be to maintain a consistent water[Read More…]

​Samples in plug trays, as well as unrooted and rooted cuttings, and plants in pots require extra care when they are packaged for submittal to a diagnostic lab. Before you mail the next sample, please take a few minutes to review these suggestions for packaging and submitting samples. This will help preserve the integrity of the sample during shipment and increase the likelihood of a more accurate diagnosis. Plugs – keep them in the tray. If possible, do not remove the plugs from the plug tray. Submitting either an entire tray or cutting off a section of the tray helps maintain the integrity of the plants (Figure 1). Secondary decay often occurs when soil is allowed to come in contact with the foliage, interfering with accurate diagnosis. When possible, submit at least 5-10 cells with plugs. This provides the diagnostician with ample material for microscopic observation, culturing, and virus testing[Read More…]

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…]

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.