This investigation, concerning the effects of electricity on nematodes, was conducted in order to find a method of controlling the root-knot nematode in the tobacco field by the use of electricity. The output of a simple induction coil (p. 13 and 37), a 220 Volt 60 cycle current (p. 44), and a 27.12 megacycle transmitter (p. 55) were used to treat the nematodes. Since the nematodes are microscopic, they were treated in the mediums of soil, tap water, distilled water, and distilled water filtered through tobacco soil. The width of the treated area varied trom ½ inch to 12 inches, and the time of treatment varied from 10 seconds to 120 seconds. Two methods were used to determine whether or not the nematodes were killed by the treatments. In the first method (p. 13), the treated soil was planted with okra and tomato seeds which would quickly develop a root system large enough to determine whether or not root-knot infections were present. In the second method (p. 34), the nematode was separated from the and observed in water under a microscope. Results of the treatments were determined more readily by the second method. However, this method required much patience by the operator, and an adequate technique to carry out the second method has not as yet been completely developed. By exposing the nematodes to heat (p. 47) and by comparing the effect of heat alone on the nematodes with the effects of other electrical treatments, it was shown that the heat generated by the electrical treatment provided the lethal effect on the nematodes. An analysis was made of an induction coil showing its output to be AC. An investigation was made to find the conductivity of Granville sandy loam tobacco soil at different moisture levels. The equation Y: 47 x 10⁴ X^-1.29 (10) Y: resistance in ohms X: % of moisture content of the soil shoving the relationship between conductivity and per cent moisture was determined from this test. Because of the scope of this problem of controlling nematodes by electrical means, the author had to conduct only preliminary investigations. However, it is the author's belief that the only way to control nematodes by electricity, and not heat the soil appreciably, is to ionize the chemical in the living cells of the eelworm. To ionize chemicals in the living cells of the nematode would necessitate the application of electrical energy with a frequency high enough to produce x-rays or gamma rays. / M.S.

Five potential resistance-inducing chemicals were applied to two sugarcane varieties (N12 and N27) in a pot trial with the aim of inducing resistance to nematodes in naturally-infested soil. BION® (acibenzolar-S-methyl), methyl jasmonate, cis-jasmone and 2,6-dichloroisonicotinic acid (INA) were applied as a foliar spray and suSCon® maxi (imidacloprid) applied to the soil. All chemicals were tested at two rates and plants were sprayed one week prior to being harvested at 7, 9 and 11 weeks of age. Meloidogyne and Pratylenchus infestation of sett and shoot roots was determined at each harvest. The activity of four pathogenesis-related proteins was examined at 7, 9 and 11 weeks using separate assays, these enzymes where chitinase, β-1,3-glucanase, peroxidase and polyphenol oxidase. Methyl jasmonate treatment produced significant increases in β-1,3-glucanase, chitinase and peroxidase activity. All other elicitor treatments showed little difference in enzyme activity from the Control. The effect of each treatment on plant growth was examined by recording the dried root and shoot biomass of each plant. No significant differences were seen (p<0.05; Holm-Sidak test). However, root and shoot dried biomass was highest in the N12 variety treated by suSCon® maxi. The infection of sugarcane with Ustilago scitaminea (sugarcane smut) is commonly identified visually by the presence of a smut whip. Identification of sugarcane smut infection can be determined prior to whip development by staining tissue sections with lactophenol cotton blue and examining plant tissues microscopically. This allows for a rapid determination of smut infection which can aid breeding programs. Smut infection is achieved in vitro by soaking sugarcane setts in smut spores collected from infected whips. Four methods of inoculation were examined. The method that most consistently caused infection involved allowing setts to germinate for 24 hours, before puncturing a bud with a toothpick, followed by submerging the sett in 1x10⁸ smut spores per mℓ. An elicitor of systemic acquired resistance called BION®, and an insecticide with resistance-inducing properties called Gaucho® (imidacloprid) were used as a sett soak treatments to induce resistance to sugarcane smut. The effect of each treatment at three concentrations on plant germination and growth was examined in the NCo376 variety. Smut spore germination on agar was examined in the presence of both treatments at three concentrations. Sugarcane setts were treated with a concentration that did not significantly reduce the germination of smut spores or sugarcane setts. Plants were infected with smut post treatment and allowed to grow for approximately one month until plants were between 8 and 10 cm in height. Smut infection was assessed by cutting longitudinal sections through the base of the shoot and staining each section with cotton blue lactophenol. Treatment with BION® and Gaucho® did not reduce smut infection. / M.Sc.Agric. University of KwaZulu-Natal, Pietermaritzburg 2013.