Effect of age of Spodoptera litura larvae on the effectivity of Metarhizium anisopliae
2002
Prayogo, Y. | Tengkano, W.,Balai Penelitian Tanaman Kacang-Kacangan dan Umbi-umbian, Malang (Indonesia)
One of the most destructive insect pest of soybean, S.litura, can be found almost throughout Indonesia. Attention is focussed on the control of this pest by means of resistance breeding, improved cultural techniques, biological control by using NPV, and the application of insecticides. In the case of using the entomophagous M. anisopliae as a means of a natural control method of the larvae of S. litura at different age stages, it is important to determine the age of the larvae when they are susceptible for the fungal infection of M. anisopliae. The experiments was conducted in a completely randomized design with six different age levels of S. litura and five replications. Research was carried out in the laboratory of the Plant Protection Department of RILET, starting in December 2001 till March 2002. M. anisopliae was applied by spraying suspensions of spores 10 at the power of 7/ml water + Tween 20, and 0.05 percent sugar on the larvae of S. litura fed on the leaves of soybean in plastic boxes, 100 larvae in each box. On 2, 4, 6, 8, 10, and 12 days after the application of the M. anisopliae spores, observations were carried out to assess the mortality of S. litura caused by fungal spores. The results showed that 72 hours after application M. anisopliae infected on the larvae of S. litura start with the white fungal colonies, change to dark green. Two days old larvae were the most susceptible with 43 percent mortality occuring ten days after application. Larvae of 6 and 8 days old were more resistant to M. anisopliae with mortality level of 18 percent and 12 percent respectively. Based on the results of these experiments, it is suggested to apply M. anisopliae on younger larvae, less than 2 days, viz when the larvae are still massively lumped on the leaves of the soybean on the place where the eggs were deposited
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