Effect of aqueous leaf extract of cloves (Syzygium aromaticum) on growth and development of tobacco caterpillar (Spodoptera litura)

摘要

A study was conducted during 2008-09 to assess the biological activity of aqueous leaf extracts of cloves [Syzygium aromaticum (L.) Merr. Perry L.] against tobacco caterpillar (Spodoptera litura Fabricius) under laboratory conditions using 'leaf dip method'. Syzygium aromaticum extracts possess the insecticidal and juvenomimetic properties against S. litura, as total growth and development was reduced which will ultimately affect the future generation of the test insect. Leaf extracts of S. aromaticum inhibited the growth and development and affected the larval and pupal survival and adult emergence in a dose-dependent manner. It is clearly indicated that due to S. aromaticum extracts intoxicated food (20%) larvae died at early instars, hence the larval population could not reach the crucial late instar stage, which is actually responsible for crop damage. Consequently, the survival of the test insect (12.22%) was reduced in 15% concentration, whereas in control it was high (76.5%). Larval growth index and total development index of the test insect were drastically reduced 1.12 and 0.28 in S. aromaticum intoxication (15% concentration), whereas in control it was as high as 5.2 and 2.7, respectively. The leaf extracts of this plant also affected the fecundity and fertility of the test insect adversely as there was very less chance of the future generation.