Laboratory and field evaluations of camptothecin sodium salt against phytophagous mites.
BACKGROUND
Camptothecin (CPT), a monoterpene indole alkaloid from Camptotheca acuminate (Nyssaceae), is toxic to some insect pests but insoluble in water. Here we show that an aqueous CPT-Na(+) solution can kill the phytophagous mites Tetranychus urticae (TU), Acaphylla theae (AT) and Brevipalpus obovatus (BO) under laboratory and field conditions.


RESULTS
Modelling of 10 day time-concentration-mortality responses of female adults to 2 mL tower sprays of three CPT-Na(+) dilutions generated LC50 and LT50 values that decreased over post-spray days and sprayed amounts respectively. CPT-Na(+) sprays required to kill 50% BO, TU and AT were 35, 41 and 124 µg mL(-1) on day 1 post-spray, but rapidly decreased to 2.2, 2.5 and 3.6 µg mL(-1) on day 5, and to 0.69, 0.77 and 1.17 µg mL(-1) on day 7 respectively. In summer field trials, a spray rate of 7.5 g CPT-Na(+) ha(-1) provided better control efficacy against TU (81-85%) on cotton or AT (90-93%) and BO (83-88%) in tea gardens than aramite (commercial acaricide) at the labelled rate of 56.25 g ha(-1) . Half of the CPT-Na(+) rate controlled the mites as effectively as aramite.


CONCLUSIONS
Water-soluble CPT-Na(+) is a promising plant-sourced acaricide to combat wide-spectrum pest mites.
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
Sen-Miao
SM
Tong
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
Ming-Guang
MG
Feng
D056810:Acaricides; D000818:Animals; D002166:Camptothecin; D005260:Female; D007928:Lethal Dose 50; D008925:Mites / Q000254:growth & development; D009758:Nymph / Q000254:growth & development; D012964:Sodium; D040102:Tetranychidae / Q000254:growth & development
D056810:Acaricides; D012964:Sodium; D002166:Camptothecin
Acaphylla theae; Brevipalpus obovatus; Tetranychus urticae; acaricidal activity; camptothecin sodium salt; mite pest control; time-concentration-mortality response