Analysis Of Pyrethrum Plant Extract And Its Anti-Aphid Effect On Growth, Yields, Chlorophyll And Phytonutrient Contents Of African Nightshades

ABSTRACT

African nightshades (Solanum scabrum) is one of indigenous vegetables widely consumed in Kenya. It is used for food, income and for medicinal purposes, but faces low yields due to severe damage by aphids. Yield losses due to aphids is estimated to about 84-96% in Kenya. Aphids have developed resistance to synthetic pesticides. There is need to search for ecofriendly alternatives such as the use of botanicals like pyrethrum which are cheaper. Pyrethrum extracts are known to control insect pests of most crops. Past studies have concentrated on the insecticidal effects of pyrethrum flower extracts on pests like Tribolium confusum and Costelytra zealandica but there is little information on anti-aphid effects of pyrethrum extracts on African nightshades. The objectives of this study were to determine the phytochemical constituents in pyrethrum flower, leaf and root parts, to determine the effect of different concentration levels of pyrethrum extracts on aphids affecting S. scabrum, to determine the anti-aphid effect of pyrethrum extracts on growth parameters and yields of S. scabrum and to determine the anti-aphid effect of pyrethrum extracts on chlorophyll and phytonutrient contents of S. scabrum. The study was conducted at Maseno University farm. A field experiment was laid in Randomized Complete Block Design with three replications. Five treatments consisting of 0%, 33% ,67% and 100% pyrethrum flower, root and leaf extracts and duduthrin were applied. Phytochemical screening of extracts was carried out. Solanum scabrum seeds were locally sourced from the Botanic Garden, Maseno University. Seeds were germinated and raised in 3m by 1m plots caged with mosquito net. After four weeks the seedlings were thinned to 9 seedlings per plot. Aphids (Aphis fabae) were obtained from International Center of Insect Physiology and Ecology- Nairobi were reared then introduced to every seedling (10 aphids) in all plots. Aphid population was determined on leaves and by use of yellow water pan traps and data collected weekly after treatment. Growth parameters including plant height, number of curled leaves, leaf area, fresh and dry weights, yield/ha, chlorophyll content and phytonutrients content was recorded. The data was subjected to analysis of variance and means were separated using Least Significant Difference at P ꞊ 0.05. The study revealed that pyrethrum extracts contained phenols, saponins, alkaloids, flavonoids, tannins, triterpenoids and phytosterols. Triterpenoids were absent in the leaf extracts. Phenols, flavonoids and triterpenoids were more in flowers than in root and leaf extract. The root exhibited more amounts of saponins, alkaloids and phytosterols. Aphid population was significantly (p≤0.05) reduced in all plant treated with pyrethrum extracts. Outstanding concentration were 100% and 67% pyrethrum flower and root extracts which recorded zero number of aphids on day 69th, 76th and 83rd day but leaf extracts showed a reduced effect. The highest concentration (100%) of pyrethrum extracts reduced aphid population significantly, leading to a high plant growth, yield, chlorophyll and phytonutrient content of S. scabrum as compared to control. This observation may have been attributed to the death of aphids. The use of 100% pyrethrum flower or root extracts is recommended to farmers in aphid control so as to realize improved yield and production of S. scabrum in order to reduce the overdependence on synthetic pesticides.