Plant Disease Management Handbook

Damage by freezing or below freezing temperatures when plants are actively growing. See also winter injury.

Plant tissues are injured when freezing temperatures precede or follow daytime warming by the sun. Can also be considered winter injury or called southwest injury.

See:

Wheat (Triticum aestivum) - Septoria tritici Blotch

Cause Macrophomina phaseolina is a soilborne fungus that is favored by dry and warm soil conditions. Although the pathogen has an extensive host range, this form of the fungus is specific to strawberry. Disease development is enhanced by high temperature, soil water deficit, strawberry monoculture, and sandy soils. The fungus produces microsclerotia for long-term survival and dispersal in the soil.

Cause This is a physiological disorder. High fertility and high temperatures aggravate the disorder. Research indicates it is caused by an imbalance of calcium. Water stress followed by a period of excessive growth and dry soil conditions favors development of tip burn.

See:

Fir, Douglas and True - Stem Decays (Heart Rots)

Cause The fungi Gloeosporium sp. has been found in Oregon and Colletotrichum sp. was found in Washington. These pathogens generally overwinter in leaf litter; therefore, infested debris can serve as an important source of initial inoculum. Prolonged periods of leaf wetness can also favor disease development.

See:

Greenhouse Plants, Ornamental - Pythium Seed Rot, Damping-off, and Root Rot

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Pear (Pyrus spp.) - Fire Blight

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Cherry (Prunus spp.) - Prunus Necrotic Ringspot

Peach (Prunus persica) - X-Disease