Browsing by Author "Jonathan R. Schultheis, Committee Member"

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • No Thumbnail Available
    Growth regulator Effects on Watermelon Chilling Resistance, Flowering, and Fruiting
    (2008-08-22) Oh, Jiyoung; Jonathan R. Schultheis, Committee Member; Todd C. Wehner, Committee Chair; James D. Burton, Committee Member
  • No Thumbnail Available
    Testing effects of alternative diets on reproduction rates of the small hive beetle, Aethina tumida.
    (2002-10-22) Keller, Jennifer June; Jonathan R. Schultheis, Committee Member; Beulah M. Parker, Committee Member; John T. Ambrose, Committee Chair
    The small hive beetle, Aethina tumida was exposed to several alternative food sources to test their ability of producing successive generations while exposed to these diets. Once it was determined that they could successfully produce successive generations while on these diets, further tests were performed to examine the effect of these alternative diets on rate of reproduction when compared to the more typical diet of honey bee resources. This was accomplished by counting the eggs produced per day on each of the given food sources. Beetles consistently produced greater numbers of eggs when exposed to the typical diet and lower numbers when exposed to an alternative diet. Because there were significantly greater numbers of eggs produced when exposed to the typical diet, it was determined that this diet was superior to any of the alternative diets but the beetles were able to successfully reproduce on alternative diets of banana, cantaloupe, pineapple, mango, and an artificial 'manduca' diet. Previous research has shown that small hive beetles can successfully be reared on the contents of bumble bee colonies (at least in laboratory settings) and adult beetles can at least sustain themselves on various fruits. This research confirms that the beetles are also capable of producing successive generations on fruit diets as well as artificial diets. These findings provide additional insight as to how the beetles may have entered the United States and their subsequent spread, as well as possible control measures.
  • No Thumbnail Available
    Tillage and Cover Crop Management Influence Weeds, Insects, Soil and Crop Nutrients, Crop Development and Yield in Organically Managed North Carolina Sweetpotato Ipomoea batatas (L.) Lam. Systems.
    (2005-09-22) Treadwell, Danielle Dion; George G. Kennedy, Committee Member; Greg D. Hoyt, Committee Member; Jonathan R. Schultheis, Committee Member
    In 2004, North Carolina supplied 46% of the nations' sweetpotato and generated 79 million dollars for the state but of the 16,000 ha in production that year; only 405 ha were managed according to federal organic standards. A three-year field experiment was initiated in 2001 to evaluate organic sweetpotato 'Beauregard' production systems that varied in cover crop management and tillage. Three organic systems including 1) compost and no cover crop with tillage (Org-NC), 2) compost and cover crop incorporated prior to transplanting (Org-CI), and 3) compost and cover crop with reduced tillage (Org-RT) were compared to a conventionally managed tilled and chemical control (Conv) production system using a randomized complete block design with six replications. All sweetpotato tissue macro and micronutrient concentrations were within sufficiency ranges defined by North Carolina Department of Agriculture & Consumer Services. Sweetpotato N (4.6%), P (0.5%), and K (4.3%) tissue concentrations were greater in Org-CI compared to remaining systems at 60 DAP in 2004. Monocot and dicot weed density and biomass were similar between Org-NC and Org-CI each year, and with few exceptions were similar to Conv. In Org-RT, high monocot weed density limited sweetpotato vine above ground biomass (154 g m⁻²) and total yield 11.2 Mg ha⁻¹) in 2002. In 2001, the percentage of No. 1 grade roots was at least 19% greater in Org-CI (65 %) and Org-NC (62 %) than Conv (50 %). In 2002, the percentage of No. 1 roots was similar among Org-CI (74 %), Org-NC (71 %) and Conv (67 %) and similar among systems in 2004. Root quality was assessed based on degree of insect damage by wireworm-Diabrotica-Systena (WDS) complex. In 2001, Org-RT had the highest percentage of marketable roots (68 %) compared to remaining systems (19-43 %). The number of marketable roots was similar among systems in 2001 and 2004, but reduced in Org-RT (1.3 Mg ha⁻¹) compared to remaining systems. Means of wireworm (Melanotus and Conoderus spp.) densities per trap were significantly correlated with degree of root damage. Overall, organic systems performed as well as the conventionally managed system in at least one or more areas.