Watermelons are among the most popular fruits in the world. They are grown in many countries due to their delicious taste, beautiful color and nutritious value. The varieties of watermelon include Hortensia, Sugar Baby, Crimson Sweet, Charleston Gray, Moon and Stars, Yellow Doll and Casaba to name a few. The fruit is juicy and sweet with a mild flavor that adds to its popularity.
Watermelons grow best in warm climates where the temperature ranges from 60 degrees Fahrenheit to 80 degrees Fahrenheit. They require plenty of sunshine for proper growth and development of fruits. Watermelons also need an adequate amount of water for good production. If your soil is sandy or clay-like then you should add some organic matter before planting so that it will retain moisture throughout the growing season.
The major pests of watermelon are aphids, spider mites, whitefly, and leafhoppers. The most common pest is the aphid. Aphids are small insects that suck the sap from watermelon leaves. To control aphids, apply insecticidal soap to the plants during the growth stages. If you have a large infestation of aphids, use a stronger chemical insecticide such as carbaryl or malathion to control them.
To keep watermelons healthy and disease-free, learn about common pests and diseases. These include Whitefly, Cucumber beetle, Root-knot nematode, and Melon aphid. Follow these tips for pest control. Once you’ve mastered them, you’ll be ready to tackle the most difficult problems. Use our helpful pest control guides to make the most of your watermelon harvest.
Whitefly
Several studies have examined the relationship between whitefly infestation and TYLCV (the tomato yellow leaf curl virus) severity. Infections with the virus increase in density and severity in a hot field, affecting fields within 1.5-3 miles. Studies have also evaluated the effects of silver plastic mulch and insecticide on the development of WVD. A whitefly-resistant pollenizer called SqVYV has also been shown to have some efficacy against the virus.
Several insects attack watermelon, reducing yield potential and reducing quality. Proper identification of these pests is essential in selecting an appropriate control strategy. Many pests of melons are controlled with chemical and cultural management strategies. To control the emergence of new pests, it is important to monitor and identify outbreaks of these pests in a growing area. Some insecticides are effective against both types of insects.
In the summer of 2009, scientists conducted a smaller field study in four 0.6-acre watermelon fields. This study aimed to characterize the spatial distribution of whitefly and viral outbreaks, establish effective control strategies and quantify virus association. Researchers used yellow sticky cards to count whitefly populations and leaf spots each week. This study also aimed to determine whether higher temperatures exacerbate whitefly infestations and disease severity.
Cucumber beetle
Control measures are an important part of the fight against these destructive pests. In our study, combined cucumber beetle-repelling plants were planted at intervals of two feet along a 3-ft-long row. Along the outer border of the companion plant rows, we also planted ‘Summer Cross No. 3’ daikon radish plants. Then we monitored and measured the numbers of trapped beetles for a full year.
During the summer, growers should apply a contact insecticide to prevent and control cucumber beetles. Applying a contact insecticide such as Admire or Platinum after transplanting can provide near-season-long protection. Repeated applications of contact insecticides are necessary to protect muskmelon plants from the disease caused by bacterial wilt. Watermelon plants do not typically contract wilt, so protection should be limited to small plants or when beet populations are high.
The western spotted cucumber beetle is a 0.25-inch insect with eleven black spots on its wing covers. Adults feed on the roots and stems of newly-emerging plants. Infested plants are severely stunted, and the plant’s growth is drastically slowed. Moreover, they transmit the bacterium Erwinia tracheiphila, which causes bacterial wilt.
Aphids are another pest of cucurbits. These insects feed on the contents of individual leaf cells. They cause significant damage to seedlings and young plants. They can also carry disease-causing agents, such as aphid-borne mosaic viruses. While the impact of specific insects depends on their location and crop, their presence on a particular crop is a significant factor in crop production. In northern Florida, for example, melon thrips and root maggots are more common pests while pickleworm rarely attacks watermelon.
Root-knot nematode
The root-knot nematode, or RKN, is an important plant pest, causing severe damage to watermelons and cantaloupes. This disease has evolved to become a serious problem, particularly in high-value crops like melon. This pest can cause yield loss of 15 to 20% in some years, so effective management is crucial to prevent damage.
The nematode can be controlled by grafting susceptible watermelons onto resistant vegetable rootstocks. In other countries, grafting is a popular method to overcome disease problems, and it has been successful for watermelons. Grafted watermelons, known as Carolina Strongback, were found to be resistant to Fusarium wilt and southern root-knot nematode.
The nematode’s life cycle is relatively long, with the most common symptoms involving yellowing leaves, wilting in the hotter parts of the day, and loss of vigor. Infested plants grow slowly and produce smaller leaves than healthy ones, and the symptoms often mimic those of a lack of water and nutrients. Watermelon pest and disease control methods may include insecticides, crop rotation with corn or sorghum, and weed-free fallow.
Despite the many pesticides and fungicides available for watermelon, it is still necessary to monitor root-knot nematode infestations. A recent study published in the journal of Applied Botany and the American Society of Plant Pathology suggests that the nematode is more widespread than previously thought, and that a specialized pest management program may be necessary for some areas.
Melon aphid
Melons are vulnerable to aphid attack, especially in autumn. This pest is known to attack a variety of other crops, including cotton, citrus, okra, pepper, muskmelon, squash, pumpkins, and asparagus. In addition to melon, aphids also attack a variety of vegetables, including zucchini, corn, potatoes, cucumbers, and eggplant. Despite being difficult to eradicate, you can control this pest by using cultural methods and natural enemies.
Aphids feed primarily on foliage and can cause chlorotic foliage. The pests secrete large quantities of honeydew, which reduces the plant’s ability to produce the sugars it needs for photosynthesis. Moreover, melon aphids can transmit several potyviruses, such as zucchini yellow mosaic virus and cucumber mosaic virus. They can even spread disease to other melons.
In the early spring and fall, aphids and leafminers are the most common pest problems. In addition, leafminers are often the source of disease in fields planted with alfalfa or cotton. In some cases, their absence may cause an outbreak. The presence of natural enemies and a lack of predators may make it difficult to detect if the infestations are widespread in a given area.
Yellow vine is a major problem for watermelons in Oklahoma. These vines often kill melons before harvest. Infested plants may be accompanied by squash bugs. Light brown discoloration is evident around the vascular core of affected plants. The phloem is responsible for carrying sugars and nutrients downward. The disease spreads through water and soil.
Cabbage looper
Natural enemies of the cabbage looper are responsible for controlling the pest. To preserve these insects, use insecticides that are less harmful to them. In some cases, cabbage looper can be controlled without any treatment by introducing adverse weather conditions or mixing in predatory insects. However, this method may not be effective in all regions. To improve the chances of success, check the pesticide label to make sure it is suitable for your location.
A cabbage looper infestation is most severe during the months of August and September. While cold, wet weather may reduce the larval population, moths blown from the south can increase the population of cabbage looper. Cabbage looper adults are nocturnal and lay white eggs on the undersides of leaves. The larvae of the cabbage looper are about one-half-inch in length, with white stripes running along their sides and a pattern of looping movements.
There are several products that provide excellent control of cabbage loopers and beet armyworms on melons. Exirel and Vetica both provide activity against sweet potato whiteflies and cabbage loopers. A variety of cultural controls are also available, including disking crop residue to reduce the attractiveness of the field for ovipositing flies. Proper incorporation of organic fertilizer and composted manures can also help reduce maggot problems.
Fusarium wilt
The problems that affect watermelon growers are numerous. These include disease and pests, as well as the pursuit of fruit uniformity. However, one new threat to watermelons has recently been identified by scientists from ARS and the University of Maryland in Salisbury. Fusarium wilt can damage watermelon at all stages of its growth, including young seedlings.
One management method that may reduce the risk of Fusarium wilt in watermelon is the use of vetch. Hairy vetch or the hybrid common vetch ‘Cahaba White’ can help suppress Fusarium wilt by stimulating beneficial microorganisms in the soil. Both vetch and hairy vetch can increase the yield of watermelons. But be sure to kill vetch with herbicide and then roll and diske it after covering the plant with plastic mulch. The five management practices differ in labor and efficacy. For more information and advice on which is best for your particular situation, contact your local Extension office.
Another cultural practice to control Fusarium wilt in watermelon is to adjust the planting date. Infestation rates are significantly reduced when watermelons are planted in soil that is 27 degrees Celsius or warmer. Planting later in the season can increase marketable yields, as long as the soil temperature is at least 27 degrees Celsius. In the past, farmers were able to grow watermelons that were 48% less susceptible to Fusarium wilt when they planted them on 8 April.