Management of Early Blight Disease in Tomato Plants (Lycopersicon esculentum) in White Nile State

Abstract

The presents study was carried out to investigate prevalence, spatial spread, incidence level and management of the fungus Alternaria spp. that causes early blight disease (EBD) in tomato crop in the White Nile State. The investigation about the spread and incidence level of disease was conducted in four locations (North, Central, Eastern and Western of South), where the disease constitutes a serious obstacle to the production of vegetable crops in general and tomato crops in particular. Accordingly, comprehensive surveys were conducted within three successive seasons (2017/2018–2018/2019–2019/2020) to investigate the spread and the level of incidence of the disease. Determination of the level of incidence of the disease was based on calculating the number of plants showing typical and apparent symptoms of the disease in selected plants as mean percentage of the total number of plant inspected in each of the three sites selected in each of the four locations surveyed in the State. This was in addition to isolation and microscopic identification of the pathogen. To manage the disease, the study involved the investigation of the effect of different concentrations of natural products formulations and fungicide, Seed Star 42, on the incidence of the disease under natural infection conditions for two successive seasons. Three concentrations were tested from each of the natural products e.g. Neem oil, aqueous extracts of plants leaves of argel, Neem and usher plus mesquite plant fruits extract, as follow; 2.5, 5 and 10 ml/l and 25, 50 and 100% for each of the extracts respectively. This in addition to argel 5gm powder per hole and the fungicide seed star 42 at the rate of 5 gm/Kg seeds as seed dressing plus the control. The assessment of the treatments effects on the pathogen was recorded as percentage disease incidence. Likewise, six varieties of tomato were screened for their resistance to early blight disease under natural infection conditions namely, Castle Rock, Strain B, B286, Hiraihry, Goal, Domestic (Local one)). The results of the surveys showed the prevalence of the disease in all the surveyed locations but at variable levels. The data showed invariable differences in the levels of incidence of the disease between the locations rather than the seasons. In fact, there was high rate of disease infection in the North of the State with an average of (15.11), followed (7.78), (6.0) and (0.89) in the South East, Center and South West of the State respectively. Moreover, within the South of the State, There was remarkable increase in percent disease incidence in the Eastern location of South (7.78) than in the Western location of it (0.89). The results of the investigation of the effect of natural products and fungicide on disease incidence reflected the positive effect in controlling early blight disease of tomato but their effects were variable. The result showed an invariably high effect on disease incidence obtained by the concentrations of Neem oil at 5ml/l, argel at 5gm/hole and seed star 42 at 5 gm/Kg seeds which gave almost 100% disease control where the percent was 0.0, 0.0, 1.0 at the forth count respectively compared to control which was 16.33. It is noteworthy that those encouraging results were confirmed by the same experiment repeated the season after. However, the effect of Neem leaves extracts at the three concentrations, 25, 50 and 100% was the lowest in disease control, at the forth counts; 8.67, 9.67 and 10.33% respectively, compared to the other treatments and this was an indication of inefficacy. Beneficial effects expressed as reduction in percent of fruits infected were also recorded due to application of these three treatments. Apparently, there was also obtained a high yield gains in this study upon treatments of tomato with those three products. The yield was almost doubled by application of the forgoing products giving a total of 41.6, 46.0 and 36.0 Kg per treatment respectively compared to control 23.1 Kg. The results of the screening of tomato varieties for resistance to early blight disease under natural infection attest the high level of resistance of the domestic variety to the disease (33.3%) followed by strain B (55.6%) and B286 (77.8%) compared to other varieties where the percent of disease incidence range from 88.9 to 100% infection. Nevertheless, this comparatively low level of disease incidence in these two varieties was coupled with high productivity in comparison to other varieties. The current results were considered promising and encouraging to carry out a photochemical analysis of Argel plant using different solvents so as to determine the bioactive ingredient in the plant. Obviously, the present study is presenting for the first in Sudan the highly effective method for control of early blight disease in tomato using argel powder at planting time.