Azalea lace bug (Stephanitis pyrioides) is the most serious pest on azalea. Both evergreen and deciduous azaleas are susceptible, though more resistance has been observed in the deciduous. To identify genes for resistance, fourteen deciduous azalea species, three deciduous azalea cultivars derived from complex hybrids, and one evergreen cultivar were planted in a randomized complete-block design under mixed deciduous trees in the fall of 1994. Each block was replicated 12 times. In the spring and summer of 1995, azalea lace bugs were introduced onto branches of six plants of each of the taxa. One month later, and again in the fall of 1996, the percentage of infected shoots per plant was measured. Very little damage from azalea lace bug was observed on the R. canescens, R. periclymenoides, and R. prunifolium plants, while `Buttercup', `My Mary', R. japonicum, and R. oblongifolium had the greatest damage. The cranberry rootworm, Rhadopterus picipes, damages many woody ornamentals, including some azalea species. The injury appears as elongated cuts on the leaves, and is most severe on plants growing under dense canopies. The cranberry rootworm has been observed in this azalea field plot. Plants were evaluated for damage in June 1995 and 1996. Cranberry rootworm damage was most severe on `Buttercup', R. japonicum, R. prinophyllum, and R. calendulaceum, while the evergreen azalea `Delaware Valley White' was the most resistant.
Carol D. Robacker and S.K. Braman
Carol D. Robacker and S.K. Braman
Azalea lace bug, Stephanitis pyrioides (Scott), is a major pest on azalea. Adults and nymphs feed and oviposit on the underside of the leaves, causing a stippled appearance when viewed from above. Previous field and laboratory screenings of 17 taxa of deciduous azalea, including representatives of 11 species, have identified a range of resistance to lace bug. One of the most resistant plants observed was of the species R. canescens. The interveinal region on the underside of the leaves of this plant is highly pubescent. This plant was crossed to a susceptible plant of R. viscosum (formerly R. serrulatum), which was glabrous on the lower leaf surface. The resulting seeds were planted in 1996, and the seedlings were transplanted to the field in 1998. In Sept. 1999, a laboratory bioassay was conducted to determine the resistance levels of these progeny. Five cuttings, each with two leaves, were collected from each plant, including the parental genotypes. Two female lace bugs were transferred onto the leaves of each cutting and the leaves were enclosed in a plastic cup with mesh for ventilation. After 5 days, the number of live bugs and number of eggs per cutting were counted. The percent damage from feeding was estimated. To determine whether pubescence was correlated with lace bug resistance, two terminal leaves were collected from each plant, and interveinal leaf hair density was calculated. Results from the laboratory bioassays revealed a high degree of susceptiblity to lace bug among these seedlings. Most of the progeny were pubescent, indicating no relationship between leaf hair density and resistance.
Yuefang Wang, Carol D. Robacker, and S.K. Braman
Azalea lace bug is the most serious pest of cultivated azalea. Though deciduous azaleas are generally considered to be more resistant to lace bug than are evergreen azaleas, some variation in resistance has been reported. The identification of the genetic and physiological basis of resistance is important to eventual development of resistant cultivars of both the deciduous and evergreen azaleas. The first step in this program is to evaluate a wide range of deciduous azaleas for level of resistance. Laboratory evaluations were conducted on nine species and two hybrid cultivars of deciduous azalea and a known susceptible cultivar of evergreen azalea, `Delaware Valley White'. Oviposition rate, rate of egg hatch, number of nymphs surviving, and percent damaged leaf area were evaluated for each of the tested genotypes. Results indicated a wide range of susceptibility, with R. canescens and R. periclymenoides plants highly resistant to infection, while R. atlanticum and R. viscosum were highly susceptible.
S.K. Braman, J.G. Latimer, and C.D. Robacker
Questionnaires on pesticide use and other aspects of integrated pest management (IPM) were mailed to 1678 lawn care and landscape maintenance firms in the 20 county metropolitan Atlanta area. The survey return rate adjusted for nonapplicable addresses and undeliverable mailings was 25.4%, yielding a total of 350 usable surveys. Responding lawn care and landscape maintenance professionals purchased a total active ingredient of 250,527 lb (93,447 kg) of herbicide, 35,416 lb (13,210 kg) of insecticide and 10,367 lb (3,867 kg) of fungicide during 1993. Most insecticides and fungicides were applied during June, July, and August. About one-third of herbicides were applied during March to May, one-third during June to August, and one-third during September to February. Key pests and plants were identified by survey respondents. Opportunities and impediments to implementation of IPM in the landscape as reported by respondents are discussed.
S.K. Braman, R.R. Duncan, and M.C. Engelke
Turfgrass selections including 21 paspalums (Paspalum vaginatum Swartz) and 12 zoysiagrasses (Zoysia sp.) were compared with susceptible `KY31' tall fescue (Festuca arundinacea Schreb.) and more resistant common bermudagrass (Cynodon dactylon Pers.) and common centipedegrass [Eremochloa ophiuroides (Munro.) Hack] for potential resistance to fall armyworm [Spodoptera frugiperda (J.E. Smith)], an occasionally serious pest of managed turf. Turfgrass and pasture grasses annually suffer sporadic damage by this pest, often severe in the Gulf Coast states. Resistant grasses offer an alternative management tool for the fall armyworm, reducing the need for pesticide use. Laboratory evaluations assessed the degree of antibiosis and nonpreference present among more than 30 turfgrass genotypes to first and third instar fall armyworms, respectively. Zoysiagrasses exhibiting high levels of antibiosis included `Cavalier', `Emerald', DALZ8501, DALZ8508, `Royal', and `Palisades'. Paspalum selections demonstrating reduced larval or pupal weights or prolonged development times of fall armyworm included 561-79, Temple-2, PI-509021, and PI-509022.
S.K. Braman, R.R. Duncan, W.W. Hanna, and W.G. Hudson
Bermudagrass (Cynodon sp.) and paspalum (Paspalum vaginatum) genotypes were evaluated in laboratory, greenhouse, and field experiments for potential resistance to the common turfgrass pests, tawny mole cricket (Scapteriscus vicinus Scudder) and southern mole cricket (Scapteriscus borellii Giglio-tos). Potential resistance among 21 seashore paspalums to both insects in an environmental chamber at 27 °C, 85% relative humidity, and 15 hours light/9 hours dark) revealed that Glenn Oaks `Adalayd' was least tolerant of cricket injury, while 561-79, HI-1, and `Excalibur' were most tolerant. Nymphal survival was not influenced by turfgrass type. Plant selections that maintained the highest percentage of their normal growth after 4 weeks of feeding by tawny mole crickets over three separate greenhouse trials were 561-79, HI-1, HI-2, PI-509018, `Excalibur', SIPV-1 paspalums, and `Tifeagle' and `Tifsport' bermudagrasses. Although none of the tested genotypes was highly resistant to tawny mole cricket injury, `TifSport' bermudagrass and 561-79 (Argentine) seashore paspalum were most tolerant.
S. Varlamoff, W.J. Florkowski, J.L. Jordan, J. Latimer, and K. Braman
A survey of Georgia homeowners provided insights about their use of fertilizers and pesticides. Knowledge of current homeowner practices is needed to develop a best management practices manual to be used by Master Gardeners to train the general public through the existing outreach programs. The objective of the training program is to reduce nutrient runoff and garden chemicals and improve the quality of surface water in urban water-sheds. Results showed three of four homeowners did their own landscaping and, therefore, fully controlled the amount of applied chemicals and the area of application. Fertilizers were primarily applied to lawns, but a high percentage of homeowners also applied them to trees, shrubs, and flowers. Insecticides were applied by a larger percentage of homeowners than herbicides. Control of fire ants (Solenopsis invicta) was likely the reason behind the frequent use of insecticides. The desire for a weed free lawn was the plausible motivation behind the use of herbicides, which were used mostly on lawns. Fungicide use was infrequently reported by Georgia homeowners. The pattern of fertilizer and pesticide use suggests that the developed manual should emphasize techniques and cultural practices, which could lower the dependence on chemicals, while ultimately assuring the desired appearance of turf and ornamental plants.