Wednesday, August 5, 2015

High Humidity Encourages Turf Diseases

Image of disease development of turfgrass infected with Bipolaris
Turfgrass infected by Bipolaris sp. - these photos are the same turfgrass
area photographed 10 days apart (Photos: NMSU - PDC)
Summer rain is a welcome occurrence in the desert, however it can also create a favorable environment for diseases. Recently, conditions have been especially favorable for a few common turfgrass diseases. Leaf spot, melting out and brown patch, have been identified in a number of samples submitted to the plant clinic over the past several weeks. These diseases are caused by common soil-borne fungi that are favored by wet, humid conditions. They can be especially severe when heavy rains follow periods of drought or dry conditions. Leaf spot and melting-out diseases are caused by a group of pathogens that used to be grouped together in the fungal genus Helminthosporium. Two fungi in this group, Bipolaris sp. and Curvularia sp., have been isolated from turfgrass samples in New Mexico. Brown patch is caused by Rhizoctonia solani. Similar environmental conditions favor these diseases and it is not uncommon to find more than one of these pathogens in the same sample. When
environmental conditions are highly favorable for disease development, these diseases can spread rapidly resulting in large areas of blighted turf.

Read on for more information on leaf spot and melting out diseases

Read on for more information on brown patch

Image of Curvularia spores
Curvularia spores
(Photo: NMSU - PDC)
Image of fungal leaf spots on turfgrass caused by Bipolaris
Leaf spots
caused by
(Photo: NMSU-PDC)
Image of Bipolaris spores
Bipolaris spores
(Photo: NMSU - PDC)

Image of brown patch caused by Rhizoctonia solani on turfgrass
Brown patch caused by Rhizoctonia solani
(Photo: NMSU - PDC)
Image of Rhizoctonia solani hyphae (fungal strands)
Characteristic hyphae of Rhizoctonia
(note the right angle branching)
(Photo: NMSU - PDC)

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