CCA Pest Diagnostics and Disease Management 1 — Questions and Answers
Question 1: Which pathogen causes common corn smut, characterized by large galls on ears and tassels?
- Ustilago maydis (Correct answer)
- Puccinia sorghi
- Exserohilum turcicum
- Fusarium graminearum
Correct answer: Ustilago maydis
Ustilago maydis is the fungal pathogen responsible for common corn smut, forming distinctive tumor-like galls on infected tissue.
Question 2: Soybean sudden death syndrome (SDS) is caused by which pathogen?
- Phytophthora sojae
- Fusarium virguliforme (Correct answer)
- Sclerotinia sclerotiorum
- Diaporthe sojae
Correct answer: Fusarium virguliforme
Fusarium virguliforme causes sudden death syndrome in soybeans, with foliar chlorosis and necrosis appearing due to toxins produced in colonized roots.
Question 3: Wheat streak mosaic virus is primarily transmitted by which vector?
- Aphids
- Leafhoppers
- Wheat curl mites (Correct answer)
- Thrips
Correct answer: Wheat curl mites
The wheat curl mite (Aceria tosichella) is the primary arthropod vector responsible for transmitting wheat streak mosaic virus.
Question 4: Northern corn leaf blight (NCLB) lesions are best described as:
- Small, circular tan spots with dark borders
- Large cigar-shaped grayish-green lesions parallel to leaf veins (Correct answer)
- Yellow halos surrounding brown necrotic centers
- Purple streaks running lengthwise on leaves
Correct answer: Large cigar-shaped grayish-green lesions parallel to leaf veins
NCLB caused by Exserohilum turcicum produces large, elongated, cigar-shaped grayish-green lesions that run parallel to leaf veins.
Question 5: Frogeye leaf spot in soybeans is caused by which pathogen?
- Cercospora sojina (Correct answer)
- Phakopsora pachyrhizi
- Septoria glycines
- Colletotrichum truncatum
Correct answer: Cercospora sojina
Cercospora sojina causes frogeye leaf spot, producing circular lesions with pale gray centers and reddish-brown borders that resemble a frog's eye.
Question 6: Which symptom pattern is most characteristic of bacterial leaf blight in soybeans caused by Pseudomonas savastanoi?
- White powdery coating on upper leaf surface
- Water-soaked angular lesions that turn brown with yellow halos (Correct answer)
- Circular lesions with tan centers and purple borders
- Dark, sunken lesions on pods and stems
Correct answer: Water-soaked angular lesions that turn brown with yellow halos
Bacterial leaf blight produces water-soaked angular lesions that turn brown and are surrounded by yellow halos, a typical bacterial disease symptom pattern.
CCA Pest Diagnostics and Disease Management 1
Which pathogen causes common corn smut, characterized by large galls on ears and tassels?