| Abstract/Contents: | "Phyllophaga congrua (LeConte) white grubs commonly damage irrigated and unirrigated tall fescue (Festuca arundinacea Schreb.) in North Central Texas. The adult beetles have been observed to feed on tall fescue, unmowed creeping bentgrass (Agrostis palustris Huds.), and numerous spring weeds. Feeding by adults has not been sufficient to cause noticeable damage. This species of beetle has not previously been considered to be a significant turf pest in Texas. Larvae of Phyllophaga crinita (Burmeister) and Cyclocephala immaculata (Olivier) are recognized as significant turf pests in Texas (Crocker 1982). Both species of white grubs are broadly distributed throughout the state, and injure common and improved bermudagrasses (Cynodon spp.), St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze), buffalograss (Buchloe dactyloides (Nutt.) Engelm.), and tall fescue (Festuca arundinacea Schreb.). Both species have a 1-year life cycle, are strongly attracted to lights at night in the adult stage, and typically have reproductive flights in some portion of June-August (thus the term "June beetle" for some adults). In fact, flights of the two species tend to be highly synchronous at any given site. Most of the turf in Texas, and consequently most of the turf research, is divided among the so-called "warm-season" species (bermudagrass and St. Augustinegrass, with lesser amounts of buffalograss, centipedegrass (Eremochloa ophiuroides (Munro) Hack), and zoysiagrass (Zoysia). Increasingly, however, tall fescue is being used throughout North Central Texas, especially in heavily shaded landscapes. Additionally, creeping bentgrass (Agrostis pulustris Huds.) is being used more frequently on golf course greens. With increased use of "cool-season" grasses has come a sharpened awareness of problems associated with and perhaps peculiar to them. Reports were first received in 1984 of heavy damage to tall fescue lawns. Examination of soil samples disclosed white grubs that were neither C. immaculata nor P. crinita, although obviously they were some species of Phyllophaga. Taxonomic keys to the larvae of Phyllophaga do not cover many Texas white grubs, and many of the species descriptions are vague. Thus, firm diagnosis of the species as Phyllophaga congrua (LeConte) was withheld until larvae recovered from damaged turf could be brought through to the readily identifiable adult stage. Large numbers of P. congrua larvae also have been recovered from heavily damaged fields of wheat and barley that had been in tall fescue sod during the beetles' reproductive period, and from severely injured field space-plantings of experimental tall fescue accessions not under supplemental irrigation. Reported food plants of P. congrua adults are ash and walnut in Iowa (Travis 1934), oak in Arkansas (Sanderson 1944), and pecan, elm, and oak in Texas (Reinhard 1950). Luginbill and Painter (1953) listed as "host families" beech, elm, mulberry, pulse, rose, willow, grass, and walnut. Nocturnal observations of adult P. congrua have shown the beetle to feed on mowed and unmowed tall fescue and unmowed (but not mowed) creeping bentgrass leaves as well as various spring weeds. Feeding by adults has not been sufficient to cause visible damage to turfgrass, but the availability of food probably is what draws the beetles into a turf where they subsequently oviposit. The beetles emerge from the soil at dusk and climb or fly to plants where they feed and mate. Before dawn, the beetles burrow into the ground and lay their eggs. Larvae have not been recovered from bentgrass. It appears that adult preference for these cool-season turfgrasses comes from the fact that such grasses are actively growing during April and May, the period of adult activity; at that time warm-season grasses often are at least partly dormant and unattractive to foliage feeders. Bermudagrass and buffalograss also are fed on by P. congrua adults when warm-season grasses are active. It should be noted that Reinhard (1950) reported 96 Texas Phyllophaga species. Our knowledge of which Phyllophaga spp. commonly damage turf in various parts of the state certainly should not be considered complete at the present." |
|---|
