| dc.description |
The insecticidal efficacy of 10%, 5% and 1% w/v of Tephrosia vogelii, Croton
dichogamus and Syzygium aromaticum aqueous plant extracts were assessed against larvae of
Plutella xylostella and Trichoplusia ni on Brassica oleracea var. capitata crop field. Synthetic
organophosphate pesticide (Chlorpyrifos) was used as a positive control and the negative controls
were water and water plus soap. It was revealed that, aqueous plant extracts significantly (P ≤ 0.05)
controlled the number of P. xylostella and T. ni larvae compared to negative controls. The 10%
concentration of aqueous plant extracts showed significant higher efficacy in terms of reducing the
insect population and their damage than 1% and 5 % concentration. The population of P. xylostella
larvae per B. oleracea in five weeks of treatment applications at 10% w/v of T. vogelii, C.
dichogamus and S. aromaticum aqueous plant extracts were 0.08, 0.15, 0.13, 0.05 and 0.08; 0.08,
0.20, 0.15, 0.13 and 0.18; 0.03, 0.05, 0.15, 0.18 and 0.13, respectively which was significantly (P ≤ 0.05)
lower than in water (1.13, 1.68, 2.28, 2.20 and 3.28) and water plus soap (0.75, 1.60, 2.58, 1.83
and 3.30) negative controls respectively. The number of T. ni larvae per B. oleracea in five weeks of
treatment applications at 10% w/v of T. vogelii, C. dichogamus and S. aromaticum of aqueous plant
extracts were 0.00, 0.03, 0.05, 0.03 and 0.00; 0.03, 0.08, 0.05, 0.08 and 0.08; 0.05, 0.03, 0.00, 0.05
and 0.03, respectively which was significantly (P ≤ 0.05) lower than in water (0.50, 0.63, 0.60, 0.48
and 0.78) and water plus soap (0.30, 0.48, 68, 0.65 and 0.80) negative controls. The percentage
damage of B. oleracea in five weeks of treatment applications at 10% w/v of T. vogelii, C.
dichogamus and S. aromaticum aqueous plant extracts were 10.0, 6.3, 7.5, 7.5 and 5.6; 11.3, 11.3,
186
AIMS Agriculture and Food Volume 6, Issue 1, 185–202.
11.3, 11.3 and 12.5; 8.8, 8.1, 6.9, 8.1 and 9.4, respectively compared with water (33.8, 33.1, 38.8,
45.0 and 70.6) and water plus soap (30.0, 31.9, 41.3, 41.3 and 56.3). These pesticidal plants can be
recommended for smallholder farmers to significantly control P. xylostella and T. ni larvae in B.
oleracea crop |
|