Correct answer. Northern corn leaf blight is caused by the fungus Exserohilum turcicum.

Correct answer. Brown spot of peas is caused by the bacterium Pseudomonas syringae.

Correct answer. White mold of pepper is caused by Sclerotinia sclerotiorum.

Correct answer. The most important disease of hemp is gray mold, caused by the fungus Botrytis cinerea. Crown gall of hemp is caused by Agrobacterium tumefaciens.

Correct answer. Wheat yellow leaf virus is a wheat, barley, rye, and oat pathogenic virus of the family Closteroviridae. The virus proliferates in the phloem of its host plants, interfering with the plant's ability to produce sufficient chlorophyll (chlorosis), causing the leaves to yellow and the plant to die.

Correct answer. Citrus canker is a disease affecting citrus species that is caused by the bacterium Xanthomonas axonopodis.

Correct answer. Gumming disease of sugarcane is caused by the bacterium Xanthomonas axonopodis.

Correct answer. Early blight of potato caused by the fungus Alternaria solani. Phytophthora infestans is an oomycete that causes the serious potato disease known as late blight of potato.

Wildfire of tobacco is caused by Pseudomonas syringae, a rod-shaped, Gram-negative bacterium with polar flagella. Symptoms of wildfire of tobacco include yellowish green spots on leaves. It causes losses in seedlings and field plants and occurs worldwide.

Correct answer. Downy mildew of rice is caused by the fungus Sclerophthora macrospora. Red rot disease of sugarcane is caused by the fungus Colletotrichum falcatum.

Correct answer. Powdery mildew of cucurbits is caused by two fungi, Sphaerotheca fuliginea (syn. Podosphaera xanthii) and Erysiphe cichoracearum (syn. Golovinomyces cichoracearum).

Correct answer. Soybean rust, also known as Asian soybean rust, is a disease that affects soybeans and other legumes. It is caused by two types of fungi, Phakopsora pachyrhizi and Phakopsora meibomiae.

Correct answer. Agrobacterium radiobacter is an effective, commercially applied, biological control agent for the prevention of crown gall disease caused by many virulent strains of Agrobacterium tumefaciens and A. rhizogenes. Trichoderma harzianum is an effective biocontrol agent against several fungal soil-borne plant pathogens.

Correct answer. Loose smut of barley is caused by Ustilago nuda. Covered smut of barley is caused by the fungus Ustilago hordei. Loose smut of wheat is caused by the fungus Ustilago tritici. Bunt of wheat (also known as covered smut of wheat) is caused by Tilleta laevis.

Correct answer. Wheat leaf rust is a fungal disease that affects wheat, barley and rye stems, leaves and grains. Puccinia triticina causes 'black rust', Puccinia recondita causes 'brown rust' and Puccinia striiformis causes 'yellow rust'.