Anthracnose
Anthracnose can be very destructive on cantaloupe, cucumber and watermelon. Pumpkin and squash are rarely affected, except where overripe fruit is left in the field or garden. Losses of fruit in storage or shipment can occur when freshly harvested fruit becomes infected.

Symptoms
All above-ground portions of the plant may be affected, although the symptoms vary somewhat on different cucurbits. Brown, angular to roughly circular spots develop on a vein and expand rapidly. The spots sometimes become as large as 1/4 to 1/2 inches. Spots developing on watermelon are black and, when numerous, can give the leaf a scorched appearance. Expanding leaves may be distorted and entire leaves arc killed when large numbers of spots coalesce.
Lesions developing on the petioles and stems are elongated, shallow and tan. As these lesions enlarge and darken on cantaloupe, the girdled vines lose their leaves and die.
When infection occurs on cucurbit fruits approaching maturity, circular, sunken, water-soaked areas develop. These lesions may enlarge to 2 inches in diameter on watermelon. Often the fruit spots contain fungal fruiting bodies that appear as black specks in the diseased tissue. Salmon pink spore masses ooze from the fungal bodies in humid weather.

Spread
The causal fungus (Colletotrichum lagenarium) survives between crop seasons in infected plant debris as well as on and in cucurbit seed. The disease develops rapidly when moisture is high, and the spores are spread from plant to plant by splashing rain, cultivating tools, clothing and insects. The spores can infect any exposed part of the plant and symptoms usually develop within a few days.

Control
1.Use commercially produced, disease-free seed.
2.Rotate cucurbits with unrelated crops.
3.Clean up cucurbit fields at the end of the growing season by removing and destroying or plowing under crop debris.
4.Apply approved fungicides to the crop at regular intervals. You can get current spray recommendations from your Cooperative Extension office.
5.Use resistant varieties (like Charleston Gray watermelon) whenever they are available.

Bacterial Wilt
Bacterial wilt is a common, often destructive, disease of cantaloupe and cucumber. This disease can cause nearly complete losses of a planting before the first harvest. Squash and pumpkin are also susceptible, but damage to them is usually less severe.

Symptoms
The term "wilt" perfectly describes this disease. Individual leaves become dull green and wilt soon after infection. These first symptoms are often associated with insect feeding damage. As the disease progresses, more leaves wilt and eventually the entire vine is affected. Finally, the leaves and vines shrivel and die. Even the fruit on affected vines shrivels.
Field diagnosis of bacterial wilt can be confirmed using a simple "bacterial ooze test." With a sharp knife, cut through a wilted vine near the crown. Touch the edge of the knife to the surface of the cut end and then slowly pull the knife away from the stem. If the bacterial wilt organism is present, fine thread-like strands of a sticky bacterial slime can be drawn out of the cut end. The bacterial ooze test works well for cucumber and cantaloupe but is less reliable for squash or pumpkin. For these crops, place pieces of stem into a glass of water. if this disease is present, bacterial ooze will flow into the water.

Spread
The bacterial wilt organism (Erwinia tracheiphila) is of special interest because it overwinters in the bodies of both the striped and spotted cucumber beetles. The adult striped cucumber beetle is 1/5 in. long and is yellow-green with 3 black stripes down its back (Figure 1). The larvae, cream colored with a dark head, feeds on the plants' root system and can cause extensive damage. Spotted cucumber beetles are 1/4 in. long with 12 black spots on their back.
The beetles hibernate through the winter under leaf litter and in other protected sites, becoming active again once temperatures stay above 55°F in the spring. They are active for about 6 weeks, so you need to spray weekly to control new insects flying onto the plants. As soon as cucurbits begin to break through the ground, the beetles move in and feed on young leaves, cotyledons and tender shoots. While feeding they deposit the bacterial wilt organism into the plant tissues.
Once the bacteria invade the plant's water conducting vessels (xylem), they can spread to other parts of the plant. The slime produced by the wilt bacterium is thought to stop water movement in the xylem vessels, thus causing the wilt symptoms.
Further spread of the disease occurs when beetles feed on diseased plants and then feed on nearby healthy plants. Bacterial wilt tends to be less severe during rainy seasons since wet weather restricts beetle movement. The bacterium cannot survive in infected plant debris from one season to the next. In fact, the causal organism is completely dependent on the insect for survival.
A second generation of the striped cucumber beetle comes later in the summer. While this generation is not very important in disease spread for the current year, the adults overwinter and are active in the spring.
Note: Single vines on otherwise healthy plants may wilt because of the squash vine borer's tunneling activity. These whitish caterpillars with brown heads may be found inside the wilted vines. A wet, sawdust-like material may be found along infested runners. While the symptoms resemble bacterial wilt, the damage is usually not as widespread. Be careful not to confuse these two very different problems.

Striped Cucumber Beetle
Control
1.Start your insect control program early. Doing so is critical to protecting very small plants from beetle feeding and, ultimately, from bacterial wilt. Start applying an approved insecticide as soon as plants begin to crack the soil. Repeat applications at weekly intervals until the vines begin to run. Contact your Cooperative Extension office to see which insecticides are currently recommended in Kentucky.
2.Use resistant varieties. Refer to the current edition of Cooperative Extension publication, Vegetable Cultivars for Kentucky Gardens, (HO-58), for the names of resistant varieties that have performed well in Kentucky.

Belly Rot
A common soil-borne fungus, Rhizoctonia sp., causes belly rot of cucumber. This rot develops where the fruit comes in contact with the soil. Young fruit have a yellowish brown, superficial discoloration which later develops into sunken irregular spots on fruit undersides. Large water-soaked decayed areas may develop on mature fruit.

Control
1.Use a black plastic mulch. Doing so can help but may not eliminate the problem.
2.Grow cucumbers on raised beds (up to 2 ft high). This method is often more effective than using plastic mulch.
3.Start a fungicide spray program when the cucumber plants begin to vine. Contact your Cooperative Extension agent for the currently recommended fungicides.

Choanephora Wet-Rot
Choanephora cucurbitarum commonly causes a fruit rot of summer squash. This fungus infects wilted blossoms and then spreads to the attached fruit. Infected fruits decay rapidly, becoming soft and watery. The Choanephora fungus looks like many small black-headed pins sticking out of a pincushion. Its presence on rotting tissue is diagnostic for wet rot.

Control
1. Use fungicides to reduce fruit rot problems. Contact your Cooperative Extension agent for the currently recommended fungicides.

Fusarium Wilt
Cantaloupe, cucumber and watermelon are susceptible to Fusarium wilt.

Symptoms
The cotyledons of infected seedlings droop and turn yellow. Fusarium wilt may also result in damping-off of seedlings. On older plants first the older leaves wilt and yellow, then individual vines progressively wilt. Finally, the entire plant wilts and dies. Cracks and brown streaks often appear on the stem near the crown. A red-brown exudate is often associated with these lesions. If you examine the cut ends of infected vines, you see a brown discoloration of the water-conducting tissues.

Spread
Three species of fungi are responsible for the disease: Fusarium oxysporum f. sp. cucumerinum (cucumber), F. oxysporum f. sp. melonis (cantaloupe) and F. oxysporum f. sp. niveum (watermelon). These fungi are easily spread via infected soil on equipment and tools, in infected plant debris, with windblown soil and in irrigation water.

Control
1.Plant in areas where Fusarium wilt has not been a problem.
2.Use a long term rotation to help reduce fungal populations in infected fields. Because the Fusarium fungi can survive in the soil for many years, only extended rotations help control this disease.
3.Using resistant varieties is the most effective means of control.

Gummy Stem Blight and Black Rot
Gummy stem blight can be a serious problem on cantaloupe, cucumber and watermelon. On squash and pumpkin fruit, this disease is called black rot.

Symptoms
When emerging seedlings are infected, circular tan to black spots appear on cotyledons and stems. If the stems become girdled, damping-off results and seedlings die.
When stem infections occur on older plants, water-soaked lesions result. These lesions become dry, cracked and tan. Large lesions girdle the vine, resulting in wilt. A gummy reddish-brown exudate is usually associated with the cankers. Foliar infections cause formation of necrotic spots on the leaves or leaf edges. These necrotic areas may progress over the entire leaf, but they primarily occur along the veins. Tiny black fungal bodies (pycnidia) develop in the dead tissue of older stem lesions and leaf spots.
Black rot symptoms can develop on pumpkin and squash fruit in the field or storage. Initially, small water-soaked spots develop on the infected fruit surface. As they enlarge, the spots become sunken, discolored and irregularly-shaped. Pycnidia appear as black specks in the infected areas.

Spread
The causal fungus (Didymella bryoniae) survives from season to season on infected crop debris and weeds. This fungus can also be carried in or on seed. Disease development is favored by temperatures between 61-75°F.
Wounds, such as those resulting from picking, pruning or insects, are important for the fungus' entry into older stems and leaves. Uninjured leaves are less prone to gummy stem blight infections. The feeding of striped cucumber beetles can increase the plant's susceptibility to infection. Powdery mildew and melon aphids may also predispose cucurbit leaves to infection. Apparently, late summer foliar symptoms on cantaloupe and cucumber result from an interaction between insects, powdery mildew and the Didymella fungus.

Control
1.Rotate with crops other than cucurbits.
2.Plow under plant debris soon after harvest so it can completely decompose.
3.Use fungicides to control this disease. Contact your Cooperative Extension office for the chemicals currently recommended.
4.Control insects and powdery mildew in the field.

Powdery Mildew
Powdery mildew commonly occurs on cantaloupe, cucumber, pumpkin and squash, both in home gardens and commercial fields. It is also the principal disease problem on cucumbers in greenhouse culture.

Symptoms
Tiny white surface spots appearing on leaves and stems are the first indication of powdery mildew. As they enlarge, the spots look powdery or cottony. Entire leaf and stem surfaces may eventually be covered by the powdery white growth. The disease first appears on the older leaves since they are more susceptible. When conditions are ideal for disease development, leaves may die and drop prematurely. Powdery mildew normally does not appear in Kentucky until near the middle of the growing season, so it generally has little effect on early cucumber production. Cantaloupes, on the other hand, have a longer growing season and are damaged when powdery mildew infections reduce fruit quality.

Spread
Most of the powdery mildew on cucurbits in Kentucky results from Erysiphe cichoracearum infections. This fungus produces two spore types: the white powdery spores present on the plant surface are called "conidia" while those produced in tiny round black fruiting bodies (cleistothecia) are called "ascospores."
Conidia are carried from plant to plant or from field to field by air currents. These spores begin new mildew infections if the humidity is high and temperatures are near 80°F. The fungus overwinters on or in perennial weeds. As the growing season approaches, the powdery mildew fungus produces conidia which are then wind blown to susceptible plants. It may take only 3 to 7 days for powdery mildew to appear following infection. Since great numbers of spores can be produced and then carried by the wind, an entire field may appear white from mildew within a week of infection.

Control
1.Apply approved fungicides regularly at the first signs of the disease. Fungicide applications are especially necessary for plants grown under greenhouse conditions. Contact your Cooperative Extension office for information on the fungicides currently recommended for Kentucky.
2.Control weeds near fields and gardens to help reduce the overwintering population of the powdery mildew fungus.
3.Use resistant varieties that are being developed. They may help in control until different races of the fungus become a problem.

Virus Diseases
Several viruses can affect cucurbits, including cucumber mosaic, watermelon mosaic and squash mosaic.

Symptoms
Distinguishing one virus from the other based on symptoms alone can be difficult. In general, typical virus symptoms include dwarfing of the vine internodes, mosaic patterns on fruit and leaves, warty malformations on fruit and gross distortions of leaves and fruit. Viruses seriously reduce yields and damage fruit quality while severe infections may stunt or even kill plants.

Spread
Cucurbit viruses generally overwinter in nearby weeds or, in the case of squash mosaic, on infected seed. Insects, like aphids, transmit the viruses from weeds to healthy plants in the field. Spread within the field may occur as a result of insect activity, or when virus particles are carried on workers' hands or equipment.

Control
1.Control insect pests using an approved insecticide.
2.Control perennial weeds in and around cucurbit plantings.
3.Use barrier crops to help reduce virus spread into the garden or field.
4.Plant resistant varieties. Doing so is the most effective control.