Impact of initial densities of the convergent lady beetle on tobacco

H. Mohd. Norowi and P. J. Semtner

Abstract

Field cage studies were conducted to determine the impact of various initial ratios of the convergent lady beetle (CLB), Hippodamia convergens Guerin- Meneville, to tobacco aphid (TA), Myzus nicotianae Blackman, on CLB and TA populations and cured leaf yield in flue-cured tobacco. Initial ratios of CLB:TA (1:25,1:50,1:100:1:200 and 1:300) were established on the flue-cured tobacco confined under field cages. The initial CLB:TA ratios were compared to uninfested tobacco and tobacco infested with TA but with CLB excluded' CLB suppressed TA population development, specially during the first 40 days after TA became estabtished. The initial CLB:TA ratios did not influence the ovipositional rate of CLB, but the lower ratio of 1:300 in 1.985 and 1:200 in 1986 may have shortened the development period for CLB. CLB reduced the economic damage caused by TA at some ratios, but control was inadequate at all ratios. The effect of cages on TA population development and tobacco growth are discussed.

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