The spores are transported through the air, infected seed and through vegetative waste left in the planting site. Use our feedback form for questions or comments about this publication. Rind necrosis on a triploid watermelon. Control and prevent the problem by cleaning up leaf debris, not using overhead watering systems, planting disease-free seed, rotating crops and using preventative fungicides such as copper. Once in the field, high temperature, humidity and wet weather favor spread of the disease. In cantaloupe, dead tissue may extend into the flesh of the fruit. Environmental factors detirmine how serious a threat is posed to subsequent crops by bacteria that survive in volunteers, rinds and weeds. Matsum & Nakai) fruit are affected by a number of preharvest disorders that may limit their marketability and thereby restrict eco-nomic returns to growers. Fortunately, there’s precautions one can take to assure those watermelons make from the garden to your plate. Generally occurs in either cantaloupe or watermelon as dead, hard, dry reddish-brown to brown spots or patches of tissue in the fruit rind. Disease cycle. In watermelon, symptoms are not visible from the outside and are rarely found in the flesh. In: Isakeit, T. 1999. The watermelon plants eventually suffer leaf drop and decline. If symptoms are observed, copper hydroxide should be applied immediately after planting on a 7- to 10-day schedule. Develops during hot summer weather when fruit are suddenly exposed to direct sunlight. Fruit can be infected at an early age. High temperatures and humidity are requisites for development of BFB. The last thing any gardener wants to see is their plants or fruit affected by disease, which can decimate a crop and your months of waiting wasted. When grown under preferred conditions, watermelons usually aren’t plagued with disease problems. Diseases that affect watermelons are similar to those of pumpkins. Try to segregate triploid seedless varieties and seed lots from diploid seeded varieties in the greenhouse. Seedling transplantsWater-soaked, "oily" areas on the underside of the cotyledons or seedling leaves often paralleling the veins with a yellow halo are characteristic symptoms. Follow all label recommendations for any pesticide application. Chlorotic rings, mottling, crinckling on leaves are seen, on stunted plants. It’s spread through diseased seed, unsanitized growing area, or rain splashed upon plants. Triploid seedless watermelons are less susceptible to BFB than seeded diploid melons. Tan lesions develop usually on the edges of older foliage, expanding to the veins and stems. Diseased fruit decays and infected seeds and cucurbit weeds (e.g., citron) are hosts for the BFB pathogen. Lesions on watermelons become apparent shortly before the fruit ripens. The greenhouse is an excellent environment for spread of BFB. Generally occurs in either cantaloupe or watermelon as dead, hard, dry reddish-brown to brown spots or patches of tissue in the fruit rind. A few infected seedlings threaten all others. Remove any weeds growing in the greenhouse. Control measles by reducing irrigation frequency and duration as fruit approach maturity in fall-harvested crops. Cracks in internal watermelon fruit flesh can occur due to accelerated growth in response to ideal growing conditions. Proper identification of BFB is essential, because other less harmful bacteria can produce identical symptoms on seedling plants. It’s most severe during warm, humid conditions. The infected areas dry up and become elongated, angled, black, necrotic patches. Watermelon Spacing -- Give Them Room to Grow! Melon sunscald. It’s most severe during warm, humid conditions. Infected seedlings with inconspicuous lesions are transplanted to the field. If no symptoms are observed but BFB is suspected, copper hydroxide should be applied when the first male flowers appear. If transplants are confirmed to have BFB, destroy all transplants from that seed lot. JavaScript seems to be disabled in your browser. Type 2 or more characters into the input search below for suggested results, use up and down arrow keys to navigate through suggest box. For the best experience on our site, be sure to turn on Javascript in your browser. Watermelons perform best with a soil pH of 6 to 6.5. These spots turn brownish black, and leaves become brown and distorted. Minimize by maintaining strong vine growth to ensure the fruit is covered. A pathogen is introduced with a contaminated watermelon seed. Overhead irrigation disperses the pathogen throughout transplant facilities. Bacteria spread to neighboring plants in the field. Avoid drought stress in melon. Water plants evenly in early morning or by afternoon. Measles spots occur where a guttation droplet had formed. Copper hydroxide fungicides can be tank mixed with most fungicides used to control fungal diseases. The disorder occurs sporadically and is thought to be associated with bacteria that may be present in fruit, but the reasons for symptom development are not understood. Watermelon plants have competition from weeds growing in the planting site, which reduces the plant’s intake of moisture and nutrients. Help improve lives, communities and economies throughout the state. Local sources of inoculum: volunteer seedlings from seeds of infected fruit, buried infested rind, cucurbit weed hosts. 5-day postharvest interval; Apply at 14-day intervals. (Courtesy of Gerald Holmes), Pumpkin sunscald. These spots also may occur on leaves and stems. 1993. Associated with environmental conditions favoring guttation. Anthracnose is a fungal disease that affects all portions of the watermelon plant including the fruit and can negatively affect yield, if not controlled. Circular, water-soaked depressions also develop on the cantaloupe fruit surface. Purchase watermelon seed that has been tested negative for bacterial fruit blotch in a seedling grow-out test. At present, there is no complete varietal resistance to BFB. Avoid watermelon varieties with a tendency to exhibit hollow heart. Texas Agricultural Extension Service Publication L-5222, Latin, R. X. There is a genetic component to this disorder, but growing conditions can account for much of the variation observed. .If suspicious symptoms are observed, remove infected plants and have them diagnosed immediately for bacterial fruit blotch. TWO BACTERIAL DISEASES OF WATERMELON I. BACTERIAL FRUIT BLOTCH OF WATERMELON Bacterial fruit blotch of watermelon, caused by the bacterium Acidovorax avenae subsp. Cucurbit Physiological Fruit Disorder occurs when there are adverse environmental conditions for all of the crops in the cucurbit plant family: squash, pumpkins, watermelons, melons, and cucumbers. Transplants from other varieties in the same house should not be planted in the field. The site navigation utilizes arrow, enter, escape, and space bar key commands. Alternate planting sites every year and use disease-free seed or a resistant cultivar. Infected fruits exude an orange substance, with the areas becoming sunken and turning dark.