Infection and Colonization of Several Bermudagrasses by Ophiosphaerella korrae.

Bermudagrass (Cynodon spp.) is the most commonly used turfgrass in the southern United States where it is severely affected by spring dead spot (SDS) caused by Ophiosphaerella herpotricha, O. korrae, and O. narmari. In this study, infection of bermudagrass roots and stolons by O. korrae was characterized using a transformant that expressed the red fluorescent protein tdTomato. Roots of interspecific hybrid cultivars Midlawn and Tifway 419, C. transvaalensis accessions Uganda and 3200, and C. dactylon cultivar U3 were inoculated and observed from 2 to 14 days postinoculation (DPI) while stolons were observed from 2 to 22 DPI. For all five cultivars tested, a similar level of root colonization was observed; however, differences were observed in the rate of necrosis development. Necrosis of Tifway 419 and Midlawn tissues was evident at 2 DPI, in Uganda and 3200 at 8 DPI, and in U3 necrosis was often absent as late as 14 DPI. The fungus rapidly penetrated the root epidermis and colonized the cortex of all cultivars by 4 DPI. Colonization of stele tissues by O. korrae was rare in hybrid cultivars but common in C. transvaalensis and C. dactylon accessions. On intact stolons, the fungus did not penetrate the epidermis 22 DPI though epidermal necrosis was evident on the surface of only the hybrid bermudagrasses. Wounded stolons became necrotic in all cultivars. Infection and colonization of various bermudagrasses by O. korrae was found to be similar to that by O. herpotricha, suggesting that host genetic resistance may be used for effective management of SDS caused by both species.

Species composition and seasonal occurrence of Phyllophaga (Coleoptera: Scarabaeidae) infesting intensely managed Bermudagrass in Oklahoma.

Larvae of Phyllophaga spp. (Coleoptera: Scarabaeidae) are important turfgrass pests in many regions of the United States. However, not all of the species associated with turfgrass are known, including species most likely to be of economic concern in Oklahoma turfgrasses, especially Bermuda grass. This study documented the species composition and seasonal occurrence of Phyllophaga associated with high maintenance Bermuda grass turf in Oklahoma over a 2-yr period. In 2005 and 2006, adult Phyllophaga spp. were collected with blacklight traps from selected golf courses throughout Oklahoma Phyllophaga larvae were obtained from Bermuda grass stands at selected sod production facilities adjacent to or near the light traps. We collected 20 species of Phyllophaga beetles in light traps, and nine species of Phyllophaga larvae from turfgrass. Peak flight periods for most species occurred in May and June, but some were captured as early as mid-April and others as late as September. The cytochrome c oxidase I (COI) gene from adults and larvae was amplified using polymerase chain reaction, sequenced, and then used to compare larval DNA against DNA from identified adults. These results confirmed the validity of using COI sequences to identify species of some Phyllophaga larvae. The identifications will aid in optimizing the timing of insecticide applications against Phyllophaga white grubs as discussed.