S. K. Braman

Grass Species and Endophyte Effects on Survival and Development of Fall Armyworm (Lepidoptera: Noctuidae)

Abstract Grass selections including 10 zoysiagrasses, 18 paspalums, 34 Bermuda grasses, tall fescue, creeping red fescue, and perennial ryegrasses with and without endophyte were evaluated for potential resistance to fall armyworm, Spodoptera frugiperda (J. E. Smith), larvae. Laboratory evaluations assessed the degree of antibiosis among >70 grass lines to first-instar fall armyworms. When all parameters measured were considered, the trend in resistance to fall armyworm among endophyte-infected (E+) and endophyte-free (E-) cool season grasses from greatest to least was: ‘Dawson’ E+ > APR 1234 > ‘Dawson’ E- > ‘Rosalin’ E+ > Lp 5425, ‘Rosalin’ E-, ATF 480 > ‘Tulsa’ or: E+ slender creeping red fescue > E+ turf- type perennial ryegrass > E- slender creeping red fescue > E+ forage-type perennial ryegrass > E- forage-type perennial ryegrasses, and E+ tall fescue > E- turf-type tall fescue. Among warm season grasses larval weight gain was reduced on all zoysiagrasses. Larval weight gain also was lower on the Bermuda grasses ‘Tifsport’, ‘Tifgreen’, 97–4, 97–14, 97–22, 97–28, 97–39, 97–40, 97–54, 98–15, 98–30, and 98–45 than when larvae were fed ‘Tulsa’ tall fescue or the diet control. Only APR1234 and ‘Dawson’ creeping red fescue reduced larval survival to the same extent that was observed for zoysiagrasses. Survival on Bermuda grasses was least on 97–8. Seashore paspalums were only rarely less susceptible to fall armyworm than tall fescue, although pupal weights were consistently lower on ‘Temple 1’ and ‘Sea Isle 1’ paspalums than that on ‘Tulsa’ tall fescue. Genetic resistance to key grass pests can reduce insecticide use and simplify management of these cultivars.

Management strategy, shade, and landscape composition effects on urban landscape plant quality and arthropod abundance.

Abstract Intensity and type of management, the cultural variable shade, and the combination of woody and herbaceous annual and perennial plants were evaluated for their effect on key landscape arthropod pests. Azalea lace bugs, Stephanitis pyrioides (Scott), and twolined spittlebugs, Prosapia bicincta (Say), were most effectively suppressed in landscape designed with resistant plant species of woody ornamentals and turf. Landscapes containing susceptible plant counterparts were heavily infested by these two insect species in untreated control plots. A traditional management program of prescribed herbicide, insecticide, and fungicide applications effectively suppressed azalea lace bug and produced a high-quality landscape. Targeted integrated pest management with solely horticultural oils resulted in intermediate levels of azalea lace bug. Neither program completely controlled twolined spittlebug on hollies or turf. Carabidae, Staphylinidae, Formicidae, and Araneae were not reduced by any management strategy. Lace bugs (Stephanitis) were more common in plots with 50% shade than those in full sun. Spittlebugs (Prosapia) were more common in the shade during 1996 and in the sun during 1997. Spiders and ants were more often collected in full sun plots. Carabids, staphylinids, and spiders were more commonly collected from pitfall traps in turf than in wood-chip mulched plant beds, whereas ants were equally common in both locations. The addition of herbaceous plants to the landscape beds had little effect on pest insect abundance.

Evaluation of turfgrass species and cultivars for potential resistance to twolined spittlebug (Hemiptera: Cercopidae).

Abstract Potential resistance to the twolined spittlebug, Prosapia bicincta (Say), was evaluated among 56 turfgrass genotypes. Greenhouse, laboratory, and field bioassays identified differences in spittlebug survival and development, host preference and damage levels, and turfgrass tolerance to and ability to recover from pest induced injury. All centipede grasses demonstrated high levels of susceptibility, followed by bermudagrasses, seashore paspalums, and zoysiagrasses. Average nymphal survival to the adult stage ranged from 1.5 to 78.1%. Development required 38.1–62.0 d under greenhouse conditions, depending on plant taxa. Among seashore paspalums, nymphal survival to the adult stage was lowest and duration of development was longest on HI-1, ‘Sea Isle 2000’, 561-79, and ‘Mauna Kea’. Reduced spittlebug survival and increased developmental times were also observed on the bermudagrasses BERPC 91–15 and ‘Tifway’. Although zoysiagrasses supported spittlebug development and survival to the adult stage, developmental times were extended on the zoysiagrass cultivars ‘Emerald’ and ‘El Toro’. Spittlebug preference varied with generation evaluated. First-generation spittlebugs inflicted the greatest damage on TC201 (centipede grass), ‘Primavera’ (bermudagrass), and ‘Emerald’ (zoysiagrass) in choice tests. In the fall, second-generation spittlebugs damaged TC201 (centipedegrass) and ‘Sea Isle 1’ (paspalum) most severely, whereas 561-79 (paspalum) and ‘Emerald’(zoysiagrass) were less severely affected. Among taxa included in field trials, HI-1, ‘Mauna Kea’, ‘Sea Isle 2000’,and AP-14 paspalums, ‘Tifway’ bermudagrass, and ‘Emerald’ zoysiagrass were most tolerant (demonstrated the best regrowth potential following twolined spittlebug feeding).

Evaluating Grower, Landscape Manager, and Consumer Perceptions of Azalea Lace Bug (Heteroptera: Tingidae) Feeding Injury

Abstract A survey using modified azalea stems was used to establish a “tally threshold value” for assessing azalea lace bug, Stephanitis pyrioides (Scott), feeding injury to azalea shrubs. Consumers and green-industry professionals, represented by ornamental growers, landscape architects, and landscape managers, recognized azalea lace bug injury when injured leaf area exceeded 2%. Purchase and treatment decisions of professionals and consumers were evaluated by surveying responses to Rhododendron indica variety alba ‘Delaware Valley White’ azaleas representing a range of damage. Survey participants also provided a brief biographical background and answers to questions regarding pesticide use, ability to identify diseases, pests, and beneficial organisms, and willingness to consider pesticide alternatives. Professionals and consumers expressed a strong interest in limiting urban pesticide use. The 2 groups indicated a hypothetically acceptable level of 6–10% plant damage by arthropod pests. A 2% injury threshold was used to determine the level of proportional damage (the percentage of leaves displaying 2% or more lace bug leaf feeding injury) resulting in either the rejection of plant purchase or initiation of treatment. A nonlinear curve was fit to treatment and no-purchase responses of professionals and consumers using a modified 3-parameter Mitscherlich nonlinear growth function. Half of the surveyed professionals and consumers indicated that damage proportions >10% (1.03% actual injury) were sufficient to reject an azalea for purchase. Proportional damage levels >43% (3.3% actual injury) would be necessary to prompt 50% of the respondents to initiate treatment of damaged azaleas to control lace bugs.

Influence of Plant Parameters on Occurrence and Abundance of Arthropods in Residential Turfgrass

ABSTRACT The effect of taxa [common Bermuda grass, Cynodon dactylon (L.); centipedegrass, Eremochloa ophiuroides Munro Hack; St. Augustinegrass, Stenotaphrum secundatum [Walt.] Kuntze; and zoysiagrass, Zoysia spp.], density, height, and weed density on abundance of natural enemies, and their potential prey were evaluated in residential turf. Total predatory Heteroptera were most abundant in St. Augustinegrass and zoysiagrass and included Anthocoridae, Lasiochilidae, Geocoridae, and Miridae. Anthocoridae and Lasiochilidae were most common in St. Augustinegrass, and their abundance correlated positively with species of Blissidae and Delphacidae. Chinch bugs were present in all turf taxa, but were 23–47 times more abundant in St. Augustinegrass. Anthocorids/lasiochilids were more numerous on taller grasses, as were Blissidae, Delphacidae, Cicadellidae, and Cercopidae. Geocoridae and Miridae were most common in zoysiagrass and were collected in higher numbers with increasing weed density. However, no predatory Heteroptera were affected by grass density. Other beneficial insects such as staphylinids and parasitic Hymenoptera were captured most often in St. Augustinegrass and zoysiagrass. These differences in abundance could be in response to primary or alternate prey, or reflect the influence of turf microenvironmental characteristics. In this study, Simpsons diversity index for predatory Heteroptera showed the greatest diversity and evenness in centipedegrass, whereas the herbivores and detritivores were most diverse in St. Augustinegrass lawns. These results demonstrate the complex role of plant taxa in structuring arthropod communities in turf. An increased understanding of how turf species and cultivars help shape pest and beneficial arthropod communities will enhance predictive abilities and further pest management objectives.

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.

Predatory Potential of Geocoris spp. and Orius insidiosus on Fall Armyworm in Resistant and Susceptible Turf

ABSTRACT Predatory potential and performance of the predaceous heteropterans, Geocoris punctipes (Say), G. uliginosus (Say) (Geocoridae), and Onus insidiosus (Say) (Anthocoridae), were evaluated using fall army worm, Spodoptera frugiperda (J. E. Smith), as prey on different turfgrass taxa (resistant zoysiagrasses, ‘Cavalier’ and ‘Palisades’; moderately resistant Bermuda grass, ‘TifSport’; and susceptible seashore paspalum, ‘Sea Isle 1’) through laboratory and field studies. When background mortality was taken into account, in small arena trials in the laboratory, the greatest mortality by predators occurred on TifSport. The predator impact on TifSport by O. insidiosus was 92.6% above the mortality in the no-predator treatment on that grass. Predator induced mortality was rarely significant on the highly resistant zoysiagrass cultivar Cavalier because mortality, even in the absence of predators, was so high. Survival of larvae on TifSport Bermuda grass was significantly reduced by the addition of just two O. insidiosus per pot in laboratory pot trials. An increase in predator density to 4, 6, 8, or 10 further suppressed larval survival. O. insidiosus reduced larval survival on Sea Isle 1 at all densities. On Sea Isle 1, a density of two O. insidiosus resulted in >50% reduction in live fall armyworms compared with the no predator treatment in laboratory trials. However, addition of O. insidiosus did not significantly reduce survival of fall armyworm larvae on this cultivar in the field in the presence of alternative prey and predators. O. insidiosus densities of six or higher per 181.4 cm2 did significantly reduce larval survival on TifSport Bermuda grass by as much as 80% during a 5-d trial period in the field. Predator-induced mortality among all trials was most consistent on a grass of intermediate resistance, TifSport Bermuda grass.

Azalea Growth in Response to Azalea Lace Bug (Heteroptera: Tingidae) Feeding

Abstract The effects of azalea lace bug, Stephanitis pyrioides (Scott), feeding injury on azalea growth and development were investigated using ‘Girard’s Rose’ azaleas during a 2-yr field study in Georgia. Low, medium, and high injury treatments, which corresponded to 6, 8, and 14% maximum canopy area injury, were compared with control azaleas that received no lace bug infestation. Flower number, whole-shrub leaf and stem dry mass, and dry mass and size of new growth tissues were unaffected by treatments. In contrast, growth index measurements, a general measure of variability frequently used for horticultural differentiation, showed significant reductions for all treatments in comparison to control azaleas after 20 wk. Though not directly quantified, this apparent discrepancy may be explained as an artifact of lace bug feeding-induced leaf abscission. Growth index measurements had considerable variability and may not be the most reliable measurement of size. In July 1998, plant canopy densities among azaleas maintained in the high injury treatments were ≈15% less full than the canopies of control shrubs. Predaceous insects had a significant negative association with azalea lace bug number during the 2-yr study. Flower and new tissue production, measured destructively during two growing seasons, revealed azalea tolerance to 14% of maximum canopy area lace bug feeding-injury levels.

Using Aesthetic Assessments of Azalea Lace Bug (Heteroptera: Tingidae) Feeding Injury to Provide Thresholds for Pest Management Decisions

Abstract Research on consumer, grower, and landscape manager perception of azalea lace bug, Stephanitis pyrioides (Scott), feeding and on plant productivity parameters, including gas exchange and growth, has increased our understanding of the nature of feeding injury. These studies made it possible to develop decision-making guidelines for cost-effective maintenance of aesthetically pleasing azaleas. Criteria were considered for three management situations: a 0.41-ha (1-acre) nursery production system that may use either insecticidal soap, acephate, or imidacloprid to control lace bugs; a landscape planting of a group of 10 azaleas; or maintenance of a single azalea in the landscape. Lace bug thresholds were calculated using a hybrid economic injury level (EIL) formula. Pesticide application decisions were determined using survey-based data from grower, landscape manager, and consumer perceptions of unacceptably injured azaleas at point-of-purchase for the nursery situation. Additional landscape scenarios incorporated the perceptions of growers, landscape managers, and consumers for those levels of lace bug feeding-injury that prompted the desire for treatment. Hybrid EIL determinations are appropriate for lace bug management in landscape systems where landscape professionals manage large plantings of azaleas and as a component of pest management among nursery production systems. Aesthetic considerations are more appropriate in determining control thresholds among a few or individual azaleas in the landscape.

Whole-Plant CO2 Exchange Measurements on Azaleas Injured by Azalea Lace Bug (Heteroptea: Tingidae) Feeding

Abstract Whole-plant gas exchange was measured continuously for 24 h on rooted cuttings of Girard’s ‘Pleasant White’ azaleas. Azalea treatments were azalea lace bug, Stephanitis pyrioides (Scott), feeding injury levels that averaged 6, 13, or 31% leaf-area injury throughout the plant canopies. Gas exchange parameters, including net photosynthesis, dark respiration, carbon use efficiency, and growth, were compared with undamaged control plants. Responses of Girard’s ‘Pleasant White’ azaleas suggested that azaleas were tolerant of lace bug feeding injury levels above the aesthetic threshold. Azalea tolerance can be incorporated into an integrated management plan to reduce chemical inputs into the urban landscape.