Arthropod Predator Occurrence and Performance of Geocoris uliginosus (Say) on Pest-Resistant and Susceptible Turfgrasses
Abstract Interactions between host plant resistance and biological control may be advantageous or disadvantageous for pest management. Turfgrass cultivars have rarely been tested for extrinsic resistance characteristics such as occurrence and performance of beneficial arthropods on plants with resistance to known turf pests. Among six turfgrass cultivars tested, the bigeyed bug, Geocoris uliginosus (Say) nymphs varied in ability to reduce numbers of fall armyworm, Spodoptera frugiperda (J. E. Smith), larvae. The six grasses tested (Sea Isle 1 and 561-79 seashore paspalum, Paspalum vaginatum Swartz; TifSport and TifEagle bermudagrass, Cynodon dactylon [L.] x C. transvaalensis [Burtt-Davy]; and Cavalier and Palisades zoysiagrass Zoysia japonica von Steudel and Z. matrella [L.] Merrill) represented a range in resistance to S. frugiperda. In the laboratory, the greatest reduction in S. frugiperda larvae by a low density of G. uliginosus occurred on the resistant Cavalier zoysiagrass. A 7-fold difference in weight of 10-d-old larvae between those feeding on susceptible versus resistant grasses suggested that on the resistant grass larvae remained for a longer period in a size range susceptible to predation. Results of laboratory studies were not directly translated to the field, in which a diverse predatory arthropod community varied in composition depending on turfgras cultivar. In the field, the greatest reduction in S. frugiperda larvae by a low density of G. uliginosus occurred on Sea Isle 1 and 561-79 seashore paspalum grass. In the field, vacuum samples indicated that predaceous Heteroptera were most abundant in paspalum grasses and bermudagrasses, while Carabidae, Staphylinidae, and Araneae were more common in zoysiagrasses. In contrast, pitfall traps indicated that carabids were more common in bermudagrasses, Araneae and Staphylinids were similar among grass taxa, and Cicindellidae were most common in paspalum grasses and bermudagrasses. Predation was never significantly decreased on resistant turfgrass cultivars in any of the experiments described in this work, indicating no negative tritrophic interactions.
Short-Term Effects of Insecticidal Applications on Predaceous Arthropods and Oribatid Mites in Kentucky Bluegrass Turf
Chlorpyrifos, bendiocarb, trichlorfon, and isofenphos were applied as surface sprays to Kentucky bluegrass turf, and effects on nontarget arthropods were measured. The most abundant families of predaceous Insecta, Araneida, and Acari were Staphylinidae, Erigonidae, Parasitidae, and Eupodidae. Chlorpyrifos and isofenphos had the greatest impact on predaceous arthropods, with some taxa significantly reduced for at least 6 weeks. Effects of bendiocarb and trichlorfon were generally less severe and more temporary. Oribatid mite populations were apparently unaffected by the insecticides. Bendiocarb increased trap catches of ants for up to 2 weeks after application.
Preference of Twolined Spittlebug for Ilex Species, Hybrids and Cultivars
Abstract Preference of twolined spittlebug, Prosapia bicincta (Say), for holly species and cultivars was evaluated in the laboratory using detached leaf assays. Field evaluations of spittlebug preference confirmed the high level of susceptibility of holly taxa with Ilex cassine L. or I. opaca Ait. parentage. Taxa observed in the field were rated as highly preferred (10 taxa), moderately (15 taxa), slightly (49), or not preferred (63) based on number of spittlebugs found infesting plants and degree of damage apparent during the two-year study. Increased production and use of pest-resistant plant material reduces the need for pesticide use and provides a good foundation for integrated pest management efforts.