91 articles tagged "Cucurbits".

This disease is more likely to develop during periods of heavy rains in relatively poorly drained soils. June started out dry for many areas of Indiana, however recent rains increase the likelihood of Phytophthora diseases. Phytophthora fruit rot of watermelon causes large, soft areas to 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. The first application of a systemic fungicide for this disease should occur when watermelon are about softball stage. Since Phytophthora does not usually affect the foliage of watermelon, there is no need to apply fungicides for this disease until fruit are present. Applications to small fruit may include[Read More…]

We have received a number of reports of outbreaks of spider mites, primarily in watermelons in the field and cucumbers in high tunnels. Spider mite damage can be recognized by the chlorosis often observed on older leaves (Figure 1).  Plus, the underside of leaves affected by spider mites often appears ‘dirty’ due to the debris caught by the webbing (Figure 2).  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. In addition, the warmer temperatures present in high tunnels allow mites to complete generations faster so populations can build to high levels quickly. The hot weather recently is helping to drive population increases in fields as well. In both scenarios, we don’t really have treatment thresholds for mites. Generally speaking, if populations are increasing,[Read More…]

We sometimes hear that excessive nitrogen could delay fruit set, stimulate excessive vine growth, and depress overall yield of pumpkins, but it is often unclear how much nitrogen is too much. This article reviews research on nitrogen fertilizer rates for pumpkins, and discusses the potential factors that might affect the recommended nitrogen rate. In a study conducted in 1987 and 1988 in Kilbourne, IL, four nitrogen rates were compared: 50, 100, 150 and 175 lb N/acre. The first three rates (50, 100 and 150 lb N/acre) were applied through fertigation, while the highest rate (175 lb N/acre)  was applied preplant and about a month after seeding. The study found the highest early and total marketable yields were obtained with fertigation of 100 lb N/acre. The lowest total yield was associated with the lowest nitrogen rate (50 lb N/acre). Fertigation with 150 lb N/acre and dry-blend with 175 lb N/acre delayed[Read More…]

Figure 1. Aphids on tomatoes in a high tunnel (Photo credit Wenjing Guan)

We have begun to receive the first reports of aphid outbreaks in high tunnels on tomato, pepper, and cucumber (Figure 1). Aphids are a very common problem in high tunnels because the covering excludes rainfall, which is a major mortality factor for small insects like aphids. Some growers are interested in using biological control in their high tunnels because the ability to contain natural enemies within the tunnels increases the likelihood of achieving control. Based on our experience, we believe that lacewing larvae hold the greatest promise for successful biological control of aphids in high tunnels. Because they don’t fly, they are less likely to leave the high tunnel than many other biological control agents. There are a number of biological control suppliers who can provide lacewing larvae for growers. For growers interested in chemical control, some of the insecticides that could be expected to provide good control and are[Read More…]

thumbnail image

White mold of watermelon – Usually when I write about a vegetable disease it is because the disease may cause important economic loss. Once in a while, however, a disease I find is more a curiosity than a real problem. So, go ahead and read this article about white mold of watermelon. But please don’t worry about this disease. Simply, watch for these symptoms and let me know if you have questions. Readers may have heard me ‘talk’ about white mold of tomatoes. The fungus that causes white mold, Sclerotinia sclerotiorum, has a wide host range. Important hosts include bean, cabbage, potato, lettuce and sunflower in addition to tomato. More about the disease on tomato can be found here. If you have never heard me talk about white mold of watermelon, don’t feel left out. I don’t talk about white mold of watermelon since I have only observed the disease twice in 21[Read More…]

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…]

Figure 1. Striped cucumber beetles on melon plants

We found our first striped cucumber beetle on Friday, May 20 and several more on May 23 (Figure 1). Given the cool weather, this is a little earlier than we would have expected. As the temperatures warm up this week, it would not be surprising for cucumber beetles to become very numerous in our melon and squash fields. Striped cucumber beetles are more attracted to squash so growers with those crops should look there first to see if the beetles are active in their area. Growers who direct seeded crops treated with FarMore® insecticide can expect about 3 weeks of control of striped cucumber beetles from that treatment. Growers who grow transplants from seeds treated with FarMore® will receive no benefit from those treatments once plants are in the field because the 3 weeks of control have ended. Likewise, growers who treated at planting with Platinum® or Admire Pro® can[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…]

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.