TechNotes Aug. 15 – BTA, Spring Dead Spot, Soil Temps

BLACK TURFGRASS ATAENIUS. Black turfgrass ataenius (BTA) grubs are being observed throughout the transition zone and the Midwest.  This insect feeds on the roots of annual bluegrass plants primarily, but can attack other cool season turfgrasses.  The major damage usually occurs through the middle of July.  However, with the higher temperatures 2nd generation BTA are appearing.  If BTA is suspected as the cause of turfgrass decline, peeling back the sod should reveal the grubs.

SPRING DEAD SPOT. In the northern range of bermudagrass adaptation, spring dead spot is a potential problem on highly maintained turf. Multiple pathogens have been identified as the causal agent of spring dead spot including Ophiosphaerella narmari (Australia), Ophiosphaerella korrea (U.S., Australia), Ophiosphaerella herpotricha (U.S.), and Gaeumannomyces graminis (U.S.). These organisms tend to be active and infect when bermudagrass is growing slowly (50 to 70 F). Thus, autumn is the primary time when infection occurs. Disease symptoms appear as circular patches of white or bleached turf during the spring when bermudagrass begins to break dormancy. Spring dead spot is often associated with winter injury. Plants predisposed to this disease do not tolerate cold temperatures.

Culturally, severity of spring dead spot increases with delaying fall dormancy or reducing winter hardiness. Nitrogen fertilization should be decreased to the point that “it is used up” by autumn. Conversely, potassium levels should be increased to enhance winter stress tolerance. Raising the height of cut also provides some protection from winter injury.

SOIL TEMPERATURES.