''Pythium violae'' is a plant pathogen infecting carrots. It is a soil-borne

oomycete Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the resul ...

that causes the

cavity spot This article summarizes different crops, what common fungal problems they have, and how fungicide should be used in order to mitigate damage and crop loss. This page also covers how specific fungal infections affect crops present in the United St ...

disease of carrots. '' Pythium sulcatum'' also causes a less serious form of this disease. ''Pythium violae'' causes elliptical shaped brown

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classif ...

s surrounded by a thin yellow halo on the surface of the

taproot A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plants, such as the carrot, the taproo ...

. These lesions cause a blemished aesthetic appearance on the carrot, reducing their market value while maintaining yield. The lesions are, on average, less than half an inch in diameter and appear near harvest, but can grow as the carrot matures and grow larger on processing varieties of carrots. Low density hyphae are present in early formation of the lesions, but there is little to no presence of ''Pythium violae'' spores in the mature lesions making it difficult to diagnose in the field. This disease can be instigated by excessive rainfall, poor soil drainage, cool temperatures, and low Soil pH. ''Pythium violae'' has been shown to infect and produce similar necrotic lesions on other hosts such as alfalfa,

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

, and

broccoli Broccoli (''Brassica oleracea'' var. ''italica'') is an edible green plant in the cabbage family (family Brassicaceae, genus ''Brassica'') whose large flowering head, stalk and small associated leaves are eaten as a vegetable. Broccoli is cla ...

. However, no economic loss has been reported from these alternate host infections.

References

External links

Index Fungorum

USDA ARS Fungal Database
Water mould plant pathogens and diseases Carrot diseases violae {{plant-disease-stub