49 articles tagged "Watermelon".

Figure 2. Wilt cucumber plants in a high tunnel

  Last week, we were called by a few watermelon growers who reported their newly planted watermelon seedlings were dead (Figure 1 ). After closely inspecting the affected plants, we did not find any pathogens. This reminded us of what happened to our cucumbers back in early April in our high tunnel. We will review the cucumber story first, and rethink what might have happened to the watermelons. Cucumbers were planted on March 30 in a high tunnel located at Southwest PurdueAgricultural Center (SWPAC), Vincennes, IN. The lowest air temperature after planting was recorded at 37.5°F inside the high tunnel, which should not be low enough to cause frost damage. However, we lost 40% to 80% of the newly planted cucumbers depending on varieties. The symptoms were similar to water deficiency-caused plant wilt (Figure 2 ). Most of the dead plants had intact stems, however, we did find wire worms[Read More…]


The cool, wet weather we are experiencing is perfect for the root and seed maggots, namely cabbage maggot, onion maggot, and seedcorn maggot. One way of avoiding damage from these pests is to wait until the soils warm up to 70o F before planting, but that is not always possible. The use of row covers early in the season can physically prevent the flies from being able to lay their eggs on the soil near the base of the plants. There are some insecticides available, which vary by crop. Lorsban®, for the crops on which it is labeled, is probably the most consistent of the available insecticides. Capture LFR® has shown decent efficacy on melons and other crops. Melon growers who are putting Admire Pro® or Platinum® on as a soil drench at planting should not expect any control of seedcorn maggots from those applications.


Gummy Stem Blight – this fungal disease causes dark brown leaf spots, however, the diagnostic feature of this disease is the water soaked lesion that is often formed under one of the seed leaves (cotyledons). Such lesions often start at the point where the seed leaf joins the stem (hypocotyl) and do not extend to the soil line (Figure 1). In time, these lesions turn a light brown in color and appear ‘woody’. If one inspects the woody stem closely, it is possible to see dark specks imbedded in the stem—these are fruiting bodies of the fungus and will exude numerous spores when wet. Gummy stem blight affects both cantaloupe and watermelon. The fungus that causes gummy stem blight may be seed borne. The fungus may also survive on the residue left on contaminated transplant trays, the greenhouse floor or bench. Gummy stem blight may spread rapidly from plant to[Read More…]


Every year since 1980, we have conducted watermelon and cantaloupe variety trials at Southwest Purdue Agricultural Center. In 2016, our variety trials include 44 standard seedless watermelons, 12 cantaloupes, 4 mini-sized seedless watermelons, and 5 seeded watermelon varieties. Seeds have already been planted in the greenhouses and our target date for transplanting in the field will be the week of May 9th. The fruit will become ripe around the middle of July. If you are interested in observing how each variety performs during the season, don’t hesitate to come to visit us and witness the plots first hand. We will continue to present the results of our variety trials, as in the past, at the annual meeting held at the Southwest Purdue Ag Center in late November or early December but don’t miss the opportunity to visualize them during the growing season. In the winter meeting, we will discuss yield[Read More…]


I have never had as many questions about how to use MELCAST as I did in 2015. The interest in this program is growing both here in Indiana and nationally. Read on to find out how to apply fungicides according to the weather and perhaps save money in the process. 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 contact Dan Egel for a[Read More…]


Anthracnose on watermelon fruit, caused by Colletotrichum orbiculare, is typically round and sunken. (Photo by Dan Egel)

​Late in the 2015 season, I observed some unusual symptoms of anthracnose on watermelon fruit. I wanted to discuss these symptoms, but first a little background of cucurbits. An extension bulletin on this subject may be found at https://www.extension.purdue.edu/extmedia/bp/bp-180-w.pdf. Anthracnose of cucurbits, caused by Colletotrichum orbiculare, is responsible for lesions on leaves, stems and fruit. Crops affected include cucumbers and cantaloupe, however, watermelon is the host most often affected in Indiana. Although lesions on leaves and stems can cause significant loss, it is the lesions on fruit that cause direct yield losses. Lesions on watermelon fruit tend to be close to the ground where the fruit tends to stay wet. These lesions are typically round, sunken and orange to salmon colored (Figure 1). However, the lesions I observed toward the end of the 2015 season differed from the typical. Instead of regular round lesions, the symptoms I observed on the bottom of affected watermelon were[Read More…]


​Downy mildew has been confirmed on jack-o-lantern pumpkins in Daviess and Jasper Counties and on acorn squash in LaPorte County. These are the first confirmed reports of this disease on Cucurbita pepo in Indiana in the 2015 season. There are unconfirmed (but reliable) reports of downy mildew on pumpkins in Parke,  Washington, and White Counties. This disease has also been observed on butternut squash (Cucurbita moschata) in Knox and LaPorte Counties and on giant pumpkins (Curbita maxima) in LaPorte County. Read more about this disease at ag.purdue.edu/arp/swpap/VeggieDiseasesBlog/Lists/Posts/Post.aspx?ID=48.


On July 22, I announced that downy mildew had been observed on watermelon in Knox County in southwestern Indiana. This article in the Vegetable Crop Hotline issue 603, https://ag.purdue.edu/hla/Extension/VegCropsHotline/Pages/Latest-Articles.aspx?article=118, describes the outbreak and management options. Downy mildew has now been reported on cucumber and cantaloupe in Knox and cucumber in La Porte County Indiana and pumpkin in Jasper County. Downy mildew has been observed on pumpkins in Mason County in central Illinois. In addition, several counties in Kentucky and Michigan have reported downy mildew, primarily on cucumbers. You may follow the development of downy mildew of cucurbits on this website http://cdm.ipmpipe.org/.


(Photo by Dan Egel)

​We have received a number of reports of outbreaks of spider mites, primarily in watermelons and in high tunnels. The problems in high tunnels are not unexpected because one of the primary causes of mortality in mite populations is rainfall washing them off the plants and, of course, that is lacking completely in high tunnels. With all the rain we have had, it’s a little surprising that we are seeing problems in watermelons, but the older I get, the less I’m surprised by how infrequently arthropods behave the way we expect them to. In both scenarios, we don’t really have treatment thresholds for mites. Generally speaking, if populations are increasing, they need to be controlled. Once the decision to treat has been made, that’s where things get very different. In watermelons, we have a variety of pesticide choices. See page 115 of the Midwest Vegetable Production Guide (ID56) for the[Read More…]


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…]


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