Atividade acaricida dos extratos de algarobeira (Prosopis juliflora) e de juazeiro (Ziziphus joazeiro) no controle de Tetranychus bastosi (Acari: Tetranychidae) em pinhão-manso

Abstract

Physic nut Jatrophas curcas L. is a common culture in the Brazilian Northeast, and its productivity has been limited by the attack of the mite Tetranychus bastosi. The control of this mite is done with synthetic acaricides, while the use of plant extracts is an alternative method. The acaricidal potential of mesquite (Prosopis juliflora DC) and juazeiro (Z. joazeiro Mart.) leaf extracts on T. bastosi was evaluated. On chapter I, the CL50 e CL90 of juazeiro extract were estimated to be used with the mesquite extract in experimental tests. The extracts toxicity was evaluated in the concentrations of 0%, 5%, 10%, 15%, 20%, 25% e 30% on T. bastosi females in physic nut leaves arenas impregnated with these concentrations. After 48 hours, the number of dead individuals was counted.in each treatment. To evaluate the ovicide effect, 25 T. bastosi eggs were disposed in Physic nut leaves arenas, followed by the pulverization of the extract. Every 24 hours, the number of hatched eggs was observed, during ten days. The extracts effect on the T. bastosi females progeny exposed to the CL50 e CL90 of the extracts was also evaluated. 5 arenas containing 60 T. bastosi females were submitted to the application of the extracts. After 48 hours, 15 females/treatments who survived the extracts action were individualized and, on a daily basis, the number of eggs/female, the viability and the survival of the subsequent stages were counted. The lethal concentrations obtained for the juazeiro extract were CL50 = 11,87% (m/v) and CL90 = 54,96% (m/v). Both extracts in the tested concentrations reduced the viability of T. bastosi eggs, featuring the CL90. The T. bastosi females submitted to mesquite and juazeiro extracts presented a reduction on the viable eggs percentage, showing values next to 75%. There wasn’t any effect in the mite’s larval phase, but there was a reduction on at least 50% of the nymphs survival. On chapter II, the toxicity and repellency of CL50 e CL90 of the mesquite and juazeiro watery extracts on T. bastosi was analyzed. The toxicity was evaluated on females disposed in physic nut leaves discs arenas, impregnated in the extracts lethal concentrations (CL50 ou CL90). After 48 hours, the alive and dead individuals in each treatment were counted. For the repellency test, the phsic nut arenas were interconnected by a coverslip. One disc was treated with one of the extracts in the lethal concentrations, and the other with destilled water (witness). 10 adult female mites were released in the central area of each arena, and after 48 hours, the alive mites in each disc were counted. The mesquite and juazeiro leaves watery extracts in both concentrations (CL50 ou CL90) presented different levels of toxicity, varying from highly toxic to slightly toxic. They presented repellent effect, except the juazeiro extract in CL50, and control efficiency in CL90, in which T. bastosi mortality was over 80%, representing promisisng results for the control of the mite.