49 articles tagged "Watermelon".

Vegetables such as this watermelon may become sunburned if lack of foliage cover exposes the fruit to excess sun and heat. (Photo by Dan Egel)

​Loss of foliage due to poor growing conditions or disease can cause fruit to be exposed to the sun. Hot temperatures and direct sunlight can lead to areas of the fruit that appear bleached or sunburned. Sunburned fruit may not be marketable. To reduce the probability sunburned fruit, every effort should be made to maintain foliage throughout the season. Early wet weather encouraged foliar disease and recent hot, dry weather may have restricted foliar development. Orienting vegetable plantings to minimize damage from the prevailing winds and providing windbreaks such as strips of rye or wheat may help to reduce sunburn. Several products are available that are labeled for use as a preventive for sunburn. These products may be broken into two groups: kaolin (clay) based products and calcium carbonated based products. Kaolin based products include Surround®. Some Surround® products are labeled for use as sunburn protection, while others are not. For example,[Read More…]


Downy mildew of watermelon causes dark brown or black lesions often surrounded by a yellow halo.

This disease has been observed on watermelon in Knox County. The following article will discuss the symptoms, biology and management of downy mildew of cucurbits. Symptoms. The symptoms of downy mildew vary depending on the host.    On watermelon, the lesions start out as chlorotic (yellow) areas that become round and necrotic (brown/black) areas surrounded by a chlorotic halo. Lesions may be limited by veins (Figure 1). Note that leaf lesions of gummy stem blight may have dark fungal structures (pycnidia) present that are lacking with downy mildew. Also, whereas gummy stem blight will affect stems and petioles, downy mildew will not.  Pumpkin lesions also start out chlorotic and are often angular. Eventually, the chlorotic lesions become necrotic. Lesions may be more common along a vein. Lesions on muskmelon often have poorly defined margins and are not as angular as described above for pumpkin.   Cucumber lesions start out chlorotic and very[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…]


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…]


​For most insect pests, we have some viable options to manage them organically. For years we have been looking for an organic solution for striped cucumber beetle and bacterial wilt on melons and cucumbers. It appears that we now have a viable option. There is a relatively new product, Cidetrak D, manufactured by Trece, which is sold as a gustatory stimulant. The active ingredient is buffalo gourd root powder, which contains a high percentage of cucurbitacin, which causes cucumber beetle to compulsively feed once they have tasted it. Years ago, there was a product available called SLAM, which contained buffalo root gourd and carbaryl, which we tested extensively and found to be quite effective. There were difficulties in applications, so the product never really took off with growers. More recently, my colleague in Kentucky, Dr. Ric Bessin, has tested Cidetrak D in conjunction with Entrust, which contains the active ingredient[Read More…]


In December 2014, I described the ‘Yearbook of Agriculture, 1928”. In that blog, I wrote about processing tomato production in 1925 and 2013 (the ‘Yearbook of Agriculture, 1928’ lists data back to 1925). Today, I would like to discuss cantaloupe and watermelon production. Unfortunately, yields posted in the “Yearbook” are in different units than in use today. However, I can compare acreage in 1925 and 2015. Cantaloupe production in Indiana in 2013 was at 2,100 acres. This compares to 4,820 acres in 1925. Part of the reason for the drop in acres might be that cantaloupe requires a lot of postharvest handling. Buyers want cantaloupe, also known as muskmelon, to be washed and cooled. Food safety concerns require growers to invest in specialized equipment and wade through reams of regulations. In 1925, Indiana was number 6 in the US in cantaloupe acreage, behind California and Arizona (of course) as well[Read More…]


Lesions of bacterial fruit blotch on watermelon seedlings are easily confused with angular leaf spot. Check with a diagnostic lab to be sure. (Photo by Dan Egel)

Bacterial fruit blotch is a disease that can affect most cucurbits (see Figure 1). However, the symptoms are most often observed on watermelon. A brief description of this disease and some photos can be found here. This article will introduce new recommendations for this disease in Indiana. Details of these recommendations can be found in the Midwest Vegetable Production Guide for Commercial Growers 2015 (ID-56). Hard copies of the ID-56 are available from Purdue University now for $10. A free on-line version of the ID-56 will be available soon at mwveguide.org. Copper products such as those with copper hydroxide or copper sulfate are often recommended for management of bacterial fruit blotch (BFB).  However copper products applied too often can cause yellowing of leaves and even yield loss (phytotoxicity). Since BFB is mostly caused by rare contaminated seed lots, I have been reluctant to recommend copper products routinely for watermelon growers. However, the last few years I have[Read More…]


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Over the past few weeks, I have observed several watermelon fields with relatively large areas of wilted plants.There can be several reasons for such symptoms.In the article below, I will discuss late season Fusarium wilt of watermelon.In a separate article, I will discuss mature watermelon vine decline.In a separate article/blog I discussed root knot nematode.All of these diseases can cause wilt and decline of relatively large areas of cucurbits. Fusarium wilt of watermelon is often observed when the vines are just starting to touch each other within a row. Sometimes, however, Fusarium wilt of watermelon does not show up until later in the season when the plants are near maturity. Fusarium wilt at this point in the season may cause a few vines to wilt (Figure 1). The distribution of affected plants is due to the distribution of the Fusarium fungus in the soil. Often well drained areas of the[Read More…]


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