Bionomics of Tetranychus urticae Koch on Eggplants under Various Nitrogen Regimes in Controlled Environment
2008
Kim, J. (Jeollabuk-Do Agricultural Research and Extension Services, Iksan, Republic of Korea), E-mail: [email protected] | Lee, S.K. (Chonbuk National University, Jeonju, Republic of Korea) | Kim, J.M. (Jeollabuk-Do Agricultural Research and Extension Services, Iksan, Republic of Korea) | Kim, T.H. (Chonbuk National University, Jeonju, Republic of Korea) | Moon, H.C. (Jeollabuk-Do Agricultural Research and Extension Services, Iksan, Republic of Korea) | Choi, K.H. (Jeollabuk-Do Agricultural Research and Extension Services, Iksan, Republic of Korea) | Choi, D.C. (Jeollabuk-Do Agricultural Research and Extension Services, Iksan, Republic of Korea)
Development of T. urticae was studied on the leaves of eggplant grown in hydroponics with nitrogen contents of 5 mM, 10 mM, 30 mM, and 60 mM. As the nitrogen level in hydroponics increased, it also increased in the plant whereas that of K, Ca, and Mg decreased. More nitrogen in hydroponics resulted in increased contents of water and crude protein, and decreased ash, carbohydrates, and fibers within the plant. Biomass was the heaviest as 989.5 g at 10 mM and the lightest at 60 mM. Leaf thickness and the content of chlorophyll increased as the content of nitrogen increased. Laboratory leaf disc tests obtained from plants grown at various nitrogen levels revealed that feeding and oviposition preferences of T. urticae were high at 30 mM and low at 5 mM. Ratio of damaged leaf by naturally occurring T. urticae on eggplants of 99 days post-transplant in the greenhouse was the highest as 98% at 60 mM. Degrees of damage on eggplants with and without T. urticae infestation turned up more as the differences in the levels of nitrogen in the hydroponics get bigger. No definite differences in the rate of T. urticae development was found between nitrogen treatment levels but, mortalities in immature stages dropped as the nitrogen levels went up. Adult longevity was the longest of 11.9 for female and 6.9 days for male at 60 mM. Oviposition period was also the longest as 11.7 days at 60 mM and shortened as the level of nitrogen decreased. The number of eggs oviposited was the most as 144.4 at 60 mM while it was the least as 41.0 at 5 mM. Sex ratio was 0.75 in favor of female at 10 mM. R∧o and T increased, no trends were detected in r∧m and λ, while Dt decreased as the levels of nitrogen went up.
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