squash diseases
Squash is usually produced for retail markets, but occasionally for wholesale. Plants are usually produced as transplants on black plastic. Often produced as several successive crops.
Anthracnose
Anthracnose-Concentric lines of sporulation of the causal fungus may be observed in a large sunken lesion. I have only observed this disease in post-harvest.
Figure 1. Anthracnose of winter squash. 
Figure 2. Anthracnose of winter squash. 
Figure 3. Anthracnose of winter squash. 
Figure 4. Anthracnose of winter squash. 
Figure 5. Anthracnose of winter squash. 
Figure 6. Anthracnose of winter squash. Cross-section of squash is designed to exhibit depth of lesion into the flesh. 
Figure 7. Anthracnose of winter squash. Bacterial spot
Bacterial spot and black rot of squash-In the photos shown here, both bacterial spot and black rot can be observed on this spaghetti squash. The bacterial spot lesions are round, 2-3 mm in diameter and scabby. Lesions of black rot are large, brown, water-soaked area in Figure 2.
Figure 1. Bacterial spot of squash. Note scabby, light brown lesions with water-soaked margins. 
Figure 2. Bacterial spot and black rot of squash. Bacterial spot lesions are scabby and light brown lesions. Black rot lesions are not well defined and are a water soaked brown.
Bacterial wilt
Bacterial wilt-This disease is not common in squash since, as in pumpkins, only feeding of the cucumber beetle at or prior to the 5 leave stage results in disease.
Figure 1. Bacterial wilt of squash. 
Figure 2. Cucumber beetle feeding on squash. Cucumber beetle feeding is associated with bacterial wilt. Black rot
Bacterial spot and black rot of squash-In the photos shown here, both bacterial spot and black rot can be observed on this spaghetti squash. The bacterial spot lesions are round, 2-3 mm in diameter and scabby. Lesions of black rot are large, brown, water-soaked area in Figure 2.
Figure 1. Black rot of squash. 
Figure 2. Black rot of squash. choanephora rot
Choanephora rot-May result in the rot of the blossom end of the squash. Sporulation is usually obvious.
Figure 1. Choanephora rot of squash. Note sporulation of causal fungus on blossom end of squash. Phytophthora blight
Phytophthora blight-Symptoms similar to the same disease on pumpkin.
Figure 1. Phytophthora blight of squash. Note wilting on plant due to lesions on stems. 
Figure 2. Phytophthora blight of squash. Note lesion on stem. 
Figure 3. Phytophthora blight of squash. Necrotic lesions in the crown of plants has lead to overall wilting of the plant. 
Figure 4. Phytophthora blight of squash. Note white sporulation on lesion on fruit. 
Figure 5. Phytophthora blight of squash. Note white sporulation on lesion on fruit. Plectosporium blight
Plectosporium blight of squash-See pumpkins. Often occurs sporadically, but when it does appear, it can be lower fruit quality.
Figure 1. Plectosporium blight on squash. Powdery mildew
Powdery mildew-Not a common disease of squash—seen here in a high tunnel.
Figure 1. Powdery mildew of squash. High tunnel conditions may be very conducive for powdery mildew. Sooty mold and fly speck
Sooty mold and flyspeck-Symptoms are superficial, but may nevertheless, affect marketability.
Figure 1. Sooty mold and fly speck on squash. 
Figure 2. Sooty mold and fly speck on squash.