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Apple replant disease (ARD) is a common problem typified by stunted growth and reduced yields in successive plantings of apple (Malus ×domestica Borkh.) in old orchard sites. ARD is attributed to biotic and abiotic factors; it is highly variable by sites, making it difficult to diagnose and overcome. In this experiment, we tested several methods of controlling ARD in a site previously planted to apple for >80 years. Our objective was to evaluate practical methods for ARD management. We compared three different experimental factors: four preplant soil treatments (PPSTs) (compost amendments, fumigation with Telone C-17, compost plus fumigation, and untreated soil); two replanting positions (in the old tree rows vs. old grass lanes); and five clonal rootstocks (`M.26', `M.7', `G.16', `CG.6210', and `G.30') during 4 years after replanting. The PPSTs had little effect on tree growth or yields during 4 years. Tree growth was affected by planting position, with trees planted in old grass lanes performing better than those in the old tree rows. Rootstocks were the most important factor in overcoming ARD; trees on `CG.6210' and `CG.30' grew better and yielded more than those on other rootstocks. Rootstock selection and row repositioning were more beneficial than soil fumigation or compost amendments in controlling ARD at this orchard.
Meadow vole (Microtus pennsylvanicus Ord) populations, feeding activity and damage to young apple (Malus ×domestica Borkh.) trees were monitored for several years in a New York orchard by direct observation, trap counts, and a feeding activity index in various groundcover management systems (GMSs). Meadow vole population density differed among GMSs, with consistently higher densities and more trees damaged in crown vetch (Coronilla varia L.), hay-straw mulch, and red fescue (Festuca rubra L.) turfgrass tree-row strips. Vole densities were high in autumn and low in spring each year. Anticoagulant rodenticides and natural predation did not adequately control voles in GMSs providing favorable habitat. Groundcover biomass per m2 was weakly correlated with vole densities in 2 of 3 years, while the percentage of soil surface covered by vegetation was not significantly correlated with vole populations. Applications of thiram fungicide in white latex paint were better than no protection, but less effective than 40-cm-high plastic-mesh guards for preventing vole damage to tree trunks. A combination of late-autumn trapping, close and consistent mowing of the orchard floor, trunk protection with mesh guards, contiguous habitat for vole predators, and herbicide applications within the tree rows provided effective control of meadow-vole damage to trees at this orchard during 3 years without applications of rodenticide baits. Chemical names used: Tetramethylthiuram disulfide (thiram)
Field studies were conducted in 2000 and 2001 to rate the efficacy and longevity of four pesticide treatments against corn earworm (Helicoverpa zea) larvae (CEW) in sweet corn (Zea mays). The four treatments used were 1) corn oil, 2) Bacillus thuringiensis ssp. kurstaki (Bt), 3) oil + Bt, and 4) an untreated plot. All treatments were applied on silk day 5. Silk day 1 was the first day that more than 50% of the ears had 2.5 cm (1 inch) or more silks emerging from the husk using a hand-held pump applicator. Two first-instar CEW larvae were placed directly into silk channel of selected ears on 6 different days (days 3, 6, 9, 12, 15, and 18 after first silk). The same six ears were then harvested 4 days later. Untreated ears had more live CEW and higher levels of feeding damage than the other three treatments ears for all harvest days in both years. The number of CEW found per ear was lower when Bt was included in the treatment. The use of corn oil gave the lowest damage ratings on almost all harvest days in both years. Treatments which contained oil had the highest number of marketable ears in both years, but also the highest percentage of underdeveloped kernels at the tip of the ear (6% to 9%). The oil and Bt treatments appeared to control CEW for at least 17 days, from silking through maturity. This treatment regime appears to be a promising alternative for growers to conventional pest management methods.
The influence of pecan [Carya illinoinensis (Wangenh.) K. Koch] leaflet bronzing, a discoloration of the lower surface, on foliar physiology and nut-meat yield is unknown. Field investigations indicate that bronzing can adversely affect foliage by reducing net photoassimilation (A), stomatal conductance (sgw ), and transpiration (E) while also altering stomatal aperture and cellular structure, and increasing temperature. Kernel weight and fill percentage are also reduced. Research indicated that foliar A declined in proportion to degree of bronze coloration, with negative A exhibited by heavily bronzed foliage. A by bronzed foliage did not increase as light levels exceeded ≈250 μmol·m-2·s-1. Within the same compound leaf, nonbronzed leaflets adjacent to bronzed leaflets exhibited greater than normal A. Bronzed leaflets also exhibited lower sgw to water vapor, less transpirational H2O loss, and higher afternoon leaf temperature. Light micrographs of bronzed foliage indicated abnormal epidermal and spongy mesophyll cells. Weight and percentage of kernel comprising the nut declined on shoots supporting foliage bronzing in July to August, but was unaffected when bronzing occurred in September to October. Bronzing of pecan foliage can therefore be of both physiological and economic significance.
A system of intercropping cabbage (Brassica oleracea var. capitata L.) with Indian mustard [Brassica juncea (L.) Czern.] to reduce pesticide applications was evaluated over three cropping seasons. Insects were monitored in nonintercropped cabbage, cabbage plots surrounded by Indian mustard, and the Indian mustard intercrop. Insecticide applications were made to individual plots based on specific treatment thresholds for lepidopterous insects and accepted pest management practices for other insects. Intercropping had no significant effect on the number of lepidopterous larvae in cabbage. Indian mustard did not appear to preferentially attract lepidopterous insects, but was highly attractive to hemipterans, especially harlequin bugs [Murgantia histrionica (Hahn)]. In one season with heavy harlequin bug pressure, intercropping with Indian mustard eliminated two insecticide applications to cabbage. Intercropping cabbage with Indian mustard does not appear to be an economical pest management practice under normal pest pressures in West Texas.
The chinch bug, Blissus occiduus Barber, has been documented as a serious pest of buffalograss, Buchloë dactyloides (Nutall) Engelmann, and zoysiagrass, Zoysia japonica Steudel, turf grown in the Midwest. In addition to these two warm-season turfgrasses, several other warm-season grasses, including bermudagrass, Cynodon dactylon (L.) Pers., may also be at risk of B. occiduus infestations. This research evaluated selected bermudagrass and zoysiagrass cultivars for resistance to B. occiduus. Eleven zoysiagrass and four bermudagrass cultivars were evaluated for resistance to B. occiduus using no-choice studies under greenhouse conditions. Based on turfgrass damage ratings, the zoysiagrasses ‘Diamond’, ‘Zoro’, and ‘Emerald’, and bermudagrass ‘Mini Verde’ were identified as moderately resistant to B. occiduus. The zoysiagrasses ‘Zenith’, ‘Meyer’, and ‘Crowne’, and bermudagrasses ‘Tifway 419’ and ‘Tifsport” were characterized as highly to moderately susceptible to B. occiduus. These results provide the first report of resistance to B. occiduus in zoysiagrass and bermudagrass germplasm.
Abstract
Methods were compared for controlling volunteer horseradish (Armoracia rusticana Gaertn, Mey. & Scherb.) resulting from commercial horseradish production. The most effective treatment was glyphosate [N-(phosphonomethyl) glycine] (4.5 kg/ha) applied in mid-September 6 to 8 weeks after discing. 2,4,5-T [2,4,5-trichloro-phenoxy acetic acid] was also effective, while dicamba [3,6,dichloro-o-anisic acid] and a dicamba plus glyphosate mixture provided less control. Horseradish roots can sprout from 90-cm deep and still be susceptible to a mid-September glyphosate application.
When applied before crop emergence, soil amendments with mustard seed meal (MSM) control some weeds and soilborne pathogens. MSM applications after crop emergence (herein “postemergence applications”) might be useful components of agricultural pest management programs, but research on postemergence applications of MSM is limited. The overall objective of this investigation was to develop a method for postemergence application of MSM that does not cause irrecoverable injury or yield loss in chile pepper (Capsicum annuum). To accomplish this objective, we conducted a sequence of studies that evaluated different MSM rates and application methods in the greenhouse and field. For the greenhouse study, we measured chile plant photosynthetic and growth responses to MSM applied postemergence on the soil surface or incorporated into soil. For the field study, we determined chile pepper fruit yield responses to MSM applied postemergence using a technique based on the method developed in greenhouse, and we confirmed that the MSM rates used in our study (4400 kg·ha−1 and 2200 kg·ha−1) inhibited the emergence of the weed Palmer amaranth (Amaranthus palmeri) and the growth of the pathogen Phytophthora capsici, which are common problems in chile pepper production in New Mexico. Greenhouse study results indicated that MSM at 4400 kg·ha−1 spread on the soil surface caused irrecoverable injury to chile pepper plants; however, chile pepper plants were not permanently injured by the following three treatments: 1) MSM at 4400 kg·ha−1 incorporated into soil, 2) MSM at 2200 kg·ha−1 spread on the soil surface, and 3) MSM at 2200 kg·ha−1 incorporated into soil. For the field study, postemergence, soil-incorporated applications of MSM at 4400 kg·ha−1 suppressed emergence of Palmer amaranth by 89% and reduced mycelial growth of Phytophthora capsica by 96%. Soil-incorporated applications of MSM at 2200 kg·ha−1 suppressed emergence of Palmer amaranth by 41.5% and reduced mycelial growth of Phytophthora capsica by 71%. Postemergence soil-incorporated applications of MSM did not reduce chile pepper yield compared with the control. The results of this study indicated that MSM applied after crop emergence and incorporated into soil can be a component of pest management programs for chile pepper.
Contribution no. 4188 of the Clemson Univ. Dept. of Plant Pathology and Physiology. This work was supported in part by the South Carolina Agricultural Experiment Station and by the Integrated Pest Management Collaborative Research Support Program, U
1 Research Geneticist. 2 Research Plant Pathologist. The technical assistance of F.P. Maguire. M.M. Hulsey, and E.L. Corley, Jr. is gratefully acknowledged. This work was supported, in part, by the Integrated Pest Management Collaborative