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- Author or Editor: Philip A. Roberts x
The eastern subterranean termite, (Reticulitermes flavipes (Roller) has caused extensive losses in localized areas of young citrus in southwest Florida by girdling trees between the crown roots and planted soil line. Applications of insecticides provided only short term deterrence lasting only a few months, and granular formulations in general have been most effective. Since termites will not venture far from the protection of moist soil and their primary area of attack has been found to be the trunk cambium below the soil line and not the roots, shallow planting and/or removal of soil have been found to be effective controls. Removing the soil around the affected trees to expose the tops of the crown roots has almost always resulted in arresting termite attack and allowing the tree to recover. Planting trees shallow does not slow tree growth.
Many vegetable growers rely on methyl bromide or other soil fumigants to manage soil pathogens, nematodes, and weeds. Nonchemical alternatives such as solarization and organic amendments are as yet largely unproven, but do offer promise of more sustainable solutions. The objective of this study was to evaluate the effects of long-term organic amendments and soil solarization on soil chemical and physical properties and on growth and yield of pepper (Capsicum annuum L.) and watermelon (Citrullus lanatus [Thunb.] Manst.). Main plots consisted of a yearly organic amendment or a nonamendment control. Four subplots of soil sanitation treatments consisted of solarization, methyl bromide, Telone, and nonfumigated. Each subplot was divided into two sub-subplots, one with weed control and one without weed control. Plant biomass was higher in plots with organic amendments than in nonamended plots. There were no differences in marketable pepper and watermelon yields between organic amended and nonamended plots during the 1998-99 and 1999-2000 seasons, respectively. However, higher pepper yields were produced from organic amended plots in the 1999-2000 season. Soil pH and Mehlich 1-extractable P, K, Ca, Mg, Zn, Mn, Fe, and Cu were higher in organic amended plots than in nonamended control plots. Soil organic matter concentration was 3-fold higher in amended soil than in nonamended soil. Effects of soil sanitation and weed management varied with crop and season. The methyl bromide and Telone treatments produced higher yields than soil solarization. In general, weed control did not affect plant biomass and yield for any of the crops and seasons. The results suggest that annual organic amendment applications to sandy soils can increase plant growth and produce higher or comparable yields with less inorganic nutrient input than standard fertilization programs.
Blue mold of apples, incited by Penicillium expansum, causes extensive losses on stored apples worldwide. Despite the severity of this problem, apple breeders do not evaluate their crosses for resistance to this disease, because there has been little resistance to blue mold in the gene pool of the germplasm used. A new apple germplasm collection from the center of origin in Kazakhstan, maintained in Geneva, NY, and representing a much broader gene pool, was evaluated for resistance to blue mold. Apples were harvested from the Elite collection trees that were clonally propagated from budwood collected in Kazakhstan and from seedling trees originating from seeds of the same trees as the Elite budwood or from other wild seedling trees in Kazakhstan. Fruit from 83 such accessions were harvested at the preclimacteric to climacteric stage, wound-inoculated with P. expansum at 103, 104, and 105 mL−1 conidial suspension, incubated for 5 d at 24 °C, and evaluated for decay incidence and severity. Two accessions were classified as immune (no decay at 103 and 104 mL−1), four as resistant (no decay at 103 mL−1), 53 as moderately resistant (lesions less than 10 mm at 103 mL−1), and 24 as susceptible. There were positive correlations (r = 0.92, 0.86, and 0.91) between decay severity and all three inoculum levels. Our results indicate a greater genetic diversity among the Kazak apple collection than among cultivated apples as evidenced by their broad range of fruit maturity, quality, and disease resistance patterns. The immune and resistant accessions may serve as a source of resistance in breeding programs and can be useful in explaining the mechanism of resistance to blue mold in apples.
Cowpea (2n=2x=22) is a high protein, short-cycle, and essential legume food crop of the tropics, especially in the low input agricultural areas of sub-Saharan Africa, Asia, and South America. Lack of genetic diversity within breeding programs can limit long-term gains from selection. The cowpea gene pool is thought to be narrow and the genetic diversity within breeding programs could be even less diverse. Genetic relationships among 87 cowpea accessions, including 60 advanced breeding lines from six breeding programs in Africa and the United States, and 27 accessions from Africa, Asia, and South America were examined using amplified fragment length polymorphism (AFLP) markers with six near-infrared fluorescence labeled EcoR I + 3/Mse I + 3 primer sets. A total of 382 bands were scored among the accessions with 207 polymorphic bands (54.2%). Overall, the 87 cowpea accessions have narrow genetic basis and they shared minimum 86% genetic similarities. The data also show that the advanced breeding lines of different programs have higher genetic affinities with lines from the same program but not with lines from other programs. The results suggest that there is a need to incorporate additional germplasm of different genetic background into these breeding lines and to ensure the long-term genetic gains of the programs.
Competitive cover crop varieties are needed to reduce weed problems and herbicide use. Identifying specific crop traits related to competitive ability would provide breeders with useful information that could be used to develop an ideotype for highly competitive cover crop varieties. Cowpea varieties with different growth habits were grown with sunflower or purslane to determinate which growth habit (erect, semi-erect, and prostrate) is more likely to be most competitive with tall or short growing weeds. Regression models were used to analyze additive and replacement series experiments. The results showed that erect varieties were more competitive with weeds than semi-erect varieties and prostrate varieties. However, the simple regression models did not provide much information about competitive mechanisms helpful to breeders. An ecophysiological model, INTERCOM, was used to understand competitive mechanisms. Validated INTERCOM model provided us with more information about competitive cover crop traits, including competitive growth habit.