Plant Disease Management Handbook

Cause Botrytis cinerea, (teleomorph: Botryotinia fuckeliana), a fungus that is pathogenic on many plants. This organism can survive on many hosts or on plant debris. It is an opportunistic pathogen and its spores (conidia) easily invade weak, damaged, or senescing tissue when wet.

See:

Bean, Dry (Phaseolus vulgaris) - White Mold (Sclerotinia Rot)

Cause Bremia lactucae, a fungus-like microorganism of which there are at least three strains. The pathogen overwinters on wild hosts and weeds. It is serious in field-grown winter crops as well as in greenhouses and is worse in damp, foggy weather and between 43°F and 53°F.

Cause Pythium ultimum or Rhizoctonia solani, fungus-like and fungal microorganisms that live in soil and attack seedlings of many different crops. As seedlings mature, they become resistant to attack. The disease can be a serious problem in cool, wet soils.

Cause Rhizoctonia solani, a fungus. The disease is widespread, occurring most often on muck soil. It commonly attacks 'Big Boston' types of head lettuce.

Cause This viral disease is soilborne and transmitted by the oomycete, Olpidium virulentus (formerly known as O. brassicae).

Cause Microdochium panattonianum (formerly Marssonina panattoniana), a fungus that overwinters on crop refuse or in soil as microsclerotia, surviving in soil as long as 4 years. It also can be harbored in weed hosts such as prickly lettuce (Lactuca serriola). The disease is important only in prolonged periods of wet weather when it may cause heavy losses.

See:

Onion (Allium cepa) - Iris Yellow Spot

See:

Lawn and Turf - Downy Mildew (Yellow Tuft)

Host Bluegrass, bentgrass, and annual bluegrass have shown infections.