Effectiveness of bottle brush (Callistemon lanceolatus DC.) extracts against diamondback moth (Plutella xylostella L.) and mealy bug (Phenacoccus manihoti Matile-Ferrero)
Abstract:
The insecticidal activity of hexane, acetone, and ethanol extracts obtained from bottle brush (Callistemon lanceolatus DC.) against diamondback moth (Plutella xylostella L.) was evaluated in laboratory conditions. The oral test, inhibiting growth and anti-feedant were performed by using leaf dipping methods. The various concentrations of extract as 0 (5% tween-20 in water) 1, 2, 3, 4, 5% (w/v) were applied and the larval mortality was checke at 24 and 48 hours, where the percentages of anti-feedant were observed at 24 hours. Then, survival larvae were reared with treated leaved remained until they developed to pupal and adult stages. The result showed that different extracts of bottle brush gave rather high efficiency in killing capacity against the diamondback moth, when all extracts at a concentration of 5% presented 38.9-61.1 and 61.1-72.2% mortality at 24 and 48 hours, respectively. Interesting result was found when the hexane extract from bottle brush showed extremely anti-feedant effect with 100%. When survival larvae reared with remaining leave treated acetone extract of bottle brush until they developed to pupal and stages, this extract presented high inhibiting growth at 16.7-33.3 and 0.0-16.7%, respectively. The deltamethrin insecticide at recommendation and double rates caused the insect mortality for 38.0 and 50% as well as at 24 and 48 hours, respectively with 38.0 and 58.0%. It could inhibit the insect development from larvar to pupae at 40.0 and 36.0% and inhibit pupae to be adult at 38.0 and 28.0%, respectively. The field experiment of using 1% acetone extract of bottle brush to control the diamondback moth was made and compared with possite control, deltamethrin insecticide at recommend rate and negative control (5% tween-20 in water). The insect number was checked before and after the application. The result showed that acetone extract could reduce the number of insect at 1, 3, 5 and 7 days for the average numbers of 2.3, 2.3, 1.0 and 0.7 insects/plant, whereas, of insecticides with 5.7, 5.7, 2.7 and 1.7 insects/plant, respectively. Beside, there hexane, acetone and ethanol extracts of bottle brush were also tested to the nymph of mealy bug (Phenacoccus manihoti Matile-Ferrero) to evaluate their insecticidal performance. Then, the insect mortality repellents capacities activities in terms of killing and repellency by using leaf dipping method. The extracts at the concentration of 1, 2, 3, 4 and 5% as well as control group, 5% tween-20 in water and imidacloprid insecticide were applied. Then the insect mortality was observed at 24 and 48 hrs Whereas, the repellent index (%RI) was calculated at 24 hrs. observation. The result showed that acetone extract from bottle brush at 2-5% concentrations were rather highly effective in killing the nymph of mealybug when 27.9-71.4 and 43.9-44.4% mortality with the LC50 at 24 and 48 hrs. as 3.543 and 2.275%, were found, respectively. While ethanol extract of bottle brush at 2-5% concentrations showed very strong effect against the nymph of mealybug with 78.9-100%RI. imidacloprid insecticide at recommendation and double rates expressed the mortality of mealy bug nymph with 39.2-68.5 and 88.3-100% at 24 and 48 hrs, respectively. Therefore, the acetone and ethanol extract of bottle brush leaf contained highly insecticidal activity against nymph of mealy bug in laboratory, then the experiment of filed conditions was developed. The acetone and ethanol extracts of bottle brush extracted at 3% as well as water and imidacloprid (control groups) were applied. The acetone extract showed greatly reduction of mealy bug nymp, there for, at 0, 1, 3, 5, and 7days, it was found with 375.2, 92.5, 66.2, 65.0, and 65.9 insects/plant, respectively. Similar result was appeared in ethanol extract when it showed 325.0, 233.5, 73.2, 67.5 and 60.0 insects/plant. Contrary result was found on imidacloprid insecticide treatment when insect numbers of 493.0, 287,5 235.0, 225.0 and 225.0 insects/plant was observed, respectively.