Published Article / This study focuses on trials conducted on plots in the Leratong and Mpho vegetable gardens in the Eastern Free State. The aim was to investigate the possible impact of soil compaction on the growth of carrots planted on loosened (treated) and unloosened (untreated) soil. Aspects such as sprouting, vegetative length after 14 days of sprouting and diameter, as well as the length and mass of carrots after harvesting, were observed and compared between the treated and untreated carrot plots. Although there was no significant (P>0.05) difference between the two soil management practices applied in all locations, as well as the vegetative growth in the locations, a significant (P<0.05) difference between the length of carrots from the treated and the untreated plots was observed.

Mini-dissertation submitted in partial compliance with the requirements of the Master’s Degree in Technology: Homoeopathy, Durban University of Technology, 2012. / Lettuce is a cool season crop and requires an optimum growing temperature of 18°C. Lettuce is popular in summer as a salad ingredient but supply cannot always keep up with demand due to high spoilage rates, because of bolting and tip-burn as a result of heat stress while growing (Maboko &Du Plooy 2007). Heat stress reduces oxygen availability. This study sought to demonstrate that administration of homoeopathic Ozonum to hydroponic nutrient solution in a nutrient film technique design improves the growth ability and quality of lettuce during the summer season by increasing or improving its ability to absorb oxygen. The research was conducted at the Agricultural Research Council – Vegetable and Ornamental Plant Institute (ARC-VOPI) facility at Roodeplaat (near Pretoria), South Africa. The trial was conducted in a 40% shade net structure in the summer months of February to April 2012. Purpose The general aim was to measure the effect of homoeopathic Ozonum 6CH, Ozonum 15CH and Ozonum 30CH compared to a placebo control (96% alcohol only) on the growth and yield of leafy lettuce, Lollo Bionda Lobi cultivar grown in a closed hydroponic system in South African summer climatic conditions. Objectives:  Determine the increase in growth and yield of leafy lettuce as affected by Ozonum concentration in terms of: (i) leaf fresh mass; (ii) leaf dry mass; (iii) number of leaves; (iv) leaf area; (v) chlorophyll content; (vi) root fresh mass; (vii) root dry mass;  Determine the impact of heat stress in terms of bolting and tip-burn;  Determine the differences in specific plant leaf mineral content between the experimental groups and control group; and,  Determine the differences between dissolved oxygen (DO) concentrations in the nutrient solution of the verum group and control group. Methodology This was a placebo controlled randomized plant experiment. A total of 384 plants were laid out in a randomized complete block design with 4 treatments (Ozonum 6CH, Ozonum 15CH Ozonum 30CH and a control) and replicated 4 times. The total number of plants per plot was 24 and the middle 8 plants were selected as data plants while other plants were regarded as border plants. Thus, data was gathered from 96 plants per treatment in total. Leafy lettuce seeds of cultivar Lollo Bionda Lobi, were sown in polystyrene trays. The seedlings were transplanted 28 days after sowing into a gravel-film technique hydroponic system. Ozonum and the placebo was added to the nutrient solution on the first day and every 6 days thereafter, at the same time as the nutrient solution was changed. Various daily measurements were recorded. Plants were harvested 27 days after transplanting when final measurements of nutrient content and growth were made. Data Analysis Data was collected over time as repeated measurements; the time factor was included as a sub-plot factor in the analysis of variance (ANOVA). All data items collected were subjected to an appropriate analysis of variance using the GenStat statistical system (VSN International, 2011). The residuals were examined for deviations from normality and outliers causing skewness were removed. Fisher’s protected t-LSD (Least Significant Difference) was calculated to compare treatment means of significant effects (Snedecor & Cochran, 1980). Results The results for (i) lettuce yield criteria, (ii) DO concentration, (iii) leaf chlorophyll content and (iv) specific mineral content of lettuce leaves (Appendix B) indicate that there was no significant difference between Ozonum treatments and the control. The incidence of bolting was not observed in lettuce plants among the treatment or control groups. Results showed a reduced tendency in tip-burn percentage for treatment Ozonum 30CH although not significantly different to Ozonum 15CH or the control. Conclusion The conclusion derived from this study is that homoeopathic Ozonum was not effective at improving dissolved oxygen levels in the nutrient solution, or in stimulating growth in lettuce under South African summer climatic conditions (February to April). Further research is needed to explore the effect Ozonum 30CH may have on tip-burn.

No description available.

Several studies were conducted in the spring and fall 2001 to evaluate a number of neonicotinoid compounds (Admire, Calypso, Actara, Platinum and dinotefuron) for whitefly control in spring and fall melons. The results of these studies demonstrate that several insecticide products are being developed that offer melon growers management alternatives for controlling whiteflies. The new foliar neonicotinoid Calypso (thiacloprid), shows excellent promise as a foliar, post-planting spray with 14-21 day residual. Further, no consistent negative interaction was detected between Platinum and fertilizer, 10-34-0 and UN 32, applied together as at-planting or side dress soil treatments. These treatments provided good whitefly control, but further research is needed to replicate these effects as Platinum has been labeled at lower rates than the manufacturer initially anticipated. At planting applications of Platinum at 8 oz (current labeled rate) did however provide acceptable residual control of whiteflies on fall melons under heavy population pressure.

Small plot studies were conducted from 1999-2001 to examine the population abundance and control of the lettuce aphid on winter and spring head lettuce crops. In each year, Seven, 0.25 acre planting of head lettuce were established beginning in Sep-Oct with final harvest occurring in April. Replicated plots within several planting were treated with an Admire treatment at planting, a side dress application of Platinum post-planting or allowed to remain untreated. Lettuce aphids were first detected in our experimental area in December in PD 3 in 2001, but in 2002 first occurred in lettuce almost 2 months later (Feb 21). Similarly, lettuce aphid abundance was much greater in 2001 than in 2002, probably a result of temperature difference. Temperature had an important influence upon lettuce aphid development based on our field observations. Population appeared to increase in early March when the average daily temperature was about 65 E F. We observed a sharp decline in population abundance in April where daytime highs exceeded 90E F. Insecticide treatments also influenced seasonal abundance. Under heavy aphid pressure in 2001, lettuce treated with Admire in the early planting dates appeared to prevent lettuce aphids from significantly infesting lettuce heads at harvest. However, lettuce aphids in the last 3 planting dates were able to colonize plants and infest a larger proportion of heads at levels not considered commercially acceptable. Under lighter pressure in 2002, lettuce aphids did not significantly colonize Admire treated lettuce. Green peach aphid, potato aphid and foxglove aphids were also present in both years, but seldom reached economic levels, and where completely controlled in plots treated with soil, systemic insecticides.

Three separate field trials over two years were conducted to evaluate the comparative knockdown and residual efficacy of several conventional, Reduced risk and biopesticide compounds against western flower thrips in romaine lettuce. These trials consistently demonstrated that both Lannate-pyrethroid combinations and Success provided significant knockdown and residual control of thrips adults and larvae when compared to the other spray biopesticide treatments. Unfortunately, the biopesticide alternatives at best provided poor to marginal efficacy against western flower thrips. The implication of these results on desert lettuce production and resistance management programs is discussed.

A field study was conducted in Yuma, Arizona during the late fall 2001 growing season to determine the optimum postemergence (POST) timing of glyphosate application on glyphosate- tolerant Lactuca sativa (head lettuce) for weed control. Head lettuce cv. Raider demonstrated excellent tolerance and no injury was observed on the crop after any glyphosate application at the 2, 4, 6, or 8 leaf stage of growth. A single application of glyphosate at 1.0 lb AI/A at the 4 or 6 leaf stage of lettuce growth was optimal for providing near complete control of Portulaca oleracea (common purslane), Chenopodium album (common lambsquarters), C. murale (nettleleaf goosefoot), Physalis wrightii (Wright’s groundcherry), volunteer cantaloupe (Cucumis melo), and Echinochloa colonum (junglerice). An early application at the 2 leaf stage resulted in few new weeds emerging after the application. A later application at the 8 leaf stage resulted in reduced yields of lettuce fresh weight due to weed competition. POST applications of glyphosate on lettuce offered superior weed control compared to soil-applied preemergence (PREE) herbicide treatments.

Success®, Proclaim®, and Confirm® treated lettuce exhibited no beet armyworm (BAW) larvae at 3 days after treatment (DAT). Avaunt®, Intrepid®, and S-1812 (Valent) treated lettuce had no medium-sized larvae but 0.3 to 0.5 small larvae were observed. At 7 and 10 DAT, BAW populations diminished significantly in all of the lettuce and no larvae or eggs were observed in any lettuce.

The effect of three different release rates (1x, 10x, and 20x the recommended rate of 10,000/acre) of Eretmocerus eremicus, a whitefly parasitoid, on sweet potato whitefly populations in cantaloupe were evaluated against populations in untreated control plots. Parasitoids were released from a point source in the center of each of nine treatment plots. All stages of whitefly development were monitored within a 10-m annulus surrounding each release point in all 12 plots, as were rates of parasitism. This occurred over a 52-d period from July 21 through September 11, 2001. The rates of sweet potato whitefly population increase during this time were equivalent and independent of the parasitoid release rate. Whitefly densities were not controlled in any of our treatment plots, nor in the controls. Moreover, rates of parasitism did not increase with time in any of the treatment plots and did not differ among the three release rates (22.0 ± 16.2%). Hence, Eretmocerus eremicus, by itself, is not efficient as a means to control whitefly populations in melon crops in the Southwest US. The ineffectiveness of E. eremicus to control whitefly populations in the field may be due to its propensity to dispersal at low host densities.

Studies were conducted in the field and laboratory to investigate how the addition of spray adjuvants to Success affected its insecticidal activity against leafminers, thrips and lepidopterous larvae. Studies were also designed to evaluate the knockdown and residual mortality of Success against worms when applied with a buffer to produce an acidic spray solution. Results indicated that Success applied without an adjuvant appeared to provide the most consistent adult mortality of Liriomyza leafminers. In contrast, the addition of a penetrating surfactant (crop oil concentrate) resulted in significantly greater larval mortality consistent with the leafminer feeding behavior. Efficacy of Success against lepidopterous larvae and western flower thrips was not improved using a spray surfactant. However, addition of buffering agents to Success spray solutions significantly affected efficacy against beet armyworm and cabbage looper. Lab bioassays and field studies showed that knockdown mortality was not affected, but residual efficacy was significantly reduced when Success was applied in an acidic (pH 4.2) spray environment.