52 articles tagged "Watermelon".

Downy mildew has been observed in LaPorte County in northern Indiana on cucumber. In addition, downy mildew on cucumber has been reported in southern Kentucky and on watermelon in the Kansas City area of Kansas. Growers in northern Indiana should manage for downy mildew on valuable cucurbit crops (Figure 1). Growers throughout the state should scout for the disease. Note that the Kansas report is directly west of us and could, eventually, blow this way. Growers should assume that all cucurbit crops may be affected. The cool, foggy mornings we have had recently are conducive for downy mildew. The organism that causes downy mildew of cucurbits doesn’t overwinter in Indiana. It has to be blown in every year. It is common for downy mildew to start the season in the Gulf States and migrate north with the cucurbit crops. Downy mildew apparently overwinters in northern Michigan/southern Ontario in greenhouses where[Read More…]

About half of the watermelon fields in our area are not equipped with supplemental irrigation. Watermelon production in these fields is therefore dependent exclusively on rainfall. In fields where supplemental irrigation is available, drip irrigation under black plastic mulch is the most commonly used system. Overhead irrigation through central pivot is also used in some fields. Irrigation management is complex in our area because of significant but unpredictable rainfalls during the watermelon production season. Supplemental irrigation is profitable because it avoids water stress during periods of drought, thereby increasing and stabilizing yields. However, there is always a question whether supplemental irrigation is required for watermelon production in our region; if so, how much water should be applied; if not, what would be the consequence if there was an extended drought period. I do not have a straightforward answer to all the questions. But here are a few facts that I[Read More…]

Root knot nematode

On a sandy hillside in a watermelon field, we noted vines that, from a distance, appeared undersized compared to the vines in the flats. Upon closer inspection, some of the vines had either wilted or a portion of the plant had wilted. The wilted vines had discolored vascular tissue. These vines were affected by Fusarium wilt of watermelon. The roots of many of the plants had galls caused by root knot nematodes. That is, many of the vines were infected with both Fusarium wilt and root knot nematode. This article discusses root knot nematode on watermelon. Root-knot nematodes are small, colorless roundworms that dwell in the soil. They penetrate into plant root in the juvenile stage. Once they find a favorable location in plant tissues, they stop moving. Infested root cells start swelling and form galls that are the characteristic symptom of root-knot nematode infestation (Figure 1). Infested roots fail[Read More…]

Contact herbicide

What is causing the spots on the watermelon leaf? A) anthracnose B) early blight C) a contact herbicide   The answer is that the leaf above has been affected by a contact herbicide. The herbicide caused lesions upon contacting the leaf. However, there was no growth of the lesion and no yellowing of the leaf since the herbicide caused no effect after the initial contact. While the distribution of the lesions in the photo above appears like a disease, the lack of ridges and yellowing in the leaf above is why it is not a disease. In the photo below, which is anthracnose of watermelon, the lesions have many ridges caused by growth of the lesion. Plus, there is a bit of yellowing of the lesions.

Watermelon is best grown at temperatures around 80-90°F. Temperatures above 90°F reduce the growth rate; above 105°F may cause plant injury. Temperatures below 42°F result in watermelon chilling injury; below 32°F will kill watermelon plants. Extended cool days that lead to soil temperatures dropping into lower 50°F can also kill watermelon seedlings. Using low tunnels is one strategy to avoid chilling injury and encourage early plant growth. How does the plastic covered low tunnels modify temperatures in early watermelon season? Figure 1 shows the air temperature comparison between low tunnel (1 mil plastic film, perforated) and without low tunnels. The data was taken from April 24 to May 25, 2020 in a watermelon field at Southwest Purdue Agricultural Center. During the time period, the recorded minimal temperatures were below 40°F for 5 nights. Low tunnels increased the minimal temperature from 0-4.5 degrees (Table 1). Table 1. Minimal air temperatures with and[Read More…]

In the last issue of the Vegetable Crops Hotline, I wrote an article about common diseases of cantaloupe and watermelon transplants. Based on the samples I have received over the last few days, I would like to write about a disease that is not usually a problem: angular leaf spot. Angular leaf spot affects all cucurbits. In this article, I would like to concentrate on angular leaf spot on cantaloupe and watermelon. Symptoms of angular leaf spot on cantaloupe often consist of brown, necrotic lesions on the margin of true leaves and seed leaves (Figure 1). On watermelon leaves the lesions may appear darker (Figure 2). Under cool, wet conditions, the disease can be quite severe, resulting in hotspots where seedlings are rendered useless for field transplanting. Angular leaf spot may be seed borne. I suspect that the pathogen may also survive on transplant trays and on greenhouse surfaces. Therefore,[Read More…]

Figure 1. A common symptom of gummy stem blight of watermelon is a watersoaked area where the seed leaves attach to the stem.

1. What caused the water-soaked stem of this watermelon transplant? A-damping-off B-gummy stem blight C-Lightening strike Correct Answer: B 2. Is this problem likely to spread to other transplants? Yes 3. Will this problem likely spread in the field? Yes More information about gummy stem blight can be found in the article Cantaloupe and Watermelon Transplant Diseases in this issue.

This is a newly released video about when to plant watermelons. https://youtu.be/tHT2mAnNRWk Watermelon, cantaloupe, cucumber plants are very sensitive to low temperatures. Even when frost has passed, soil temperatures below 60°F can result in transplant establishment failure. Check soil temperatures before planting. The rule of thumb is to plant watermelon, cantaloupe and cucumber transplants when soil temperatures at the root zone are stable above 60°F. Ideally, watermelon, cantaloupe, and cucumber grow well when soil temperatures are above 70°F.

Dear Watermelon Growers, At our past winter technical meeting, several growers suggested fertilizer recommendations need to be reevaluated for watermelon production in our area. This suggestion is timely and critical. We plan to initiate a project for the 2020 watermelon production season to reevaluate the fertility and irrigation practices used in Indiana.  We will identify 7-10 watermelon fields with different irrigation and fertility practices. We will collect soil samples and plant tissue samples at different crop growth stages. Lab results will be shared with growers immediately after they are received. Growers who wish to closely watch the nutritional status of the watermelon plants may want to take this free opportunity. As part of this project, we will collect information about fertilizer and irrigation application, and approximate yield of the evaluating field from growers. Summarized results of this project will be shared at the next Southwest Indiana Vegetable and Melon Growers[Read More…]

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