Beauveriabassiana, a Biocontrol Agent against the Red Palm Weevil, RhynchophorusFerrugineus Larvae under Laboratory and Field Conditions.

Document Type : Original Article

Abstract

The presented study was carried out to assay the efficacy of a Beauveriabassiana(Balsamo) Vuillemincommercial formulation (Newfar) and its isolates against larvae of the red palm weevil Rhynchophorusferrugineus(Olivier). Bioassay experiments took place to estimate theLC50, LC90, LT50 and LT90values. By Newfar treatment, theLC50’s against the 1st, 5th and 10th larval instars of R. ferrugineus were 0.078, 0.192 and 0.406 g/ml, respectively. LC90 values were 0.610, 2.030 and 4.547 g/ml, respectively for the 1st, 5th and 10th instarafter 25 days of treatment. Also, the LT50values after using the concentration 1x108 CFU’s / 100mlwere 14.549, 16.167 and 21.022, days, respectively, while those of LT90 were23.374, 31.196 and 99.344 days, respectively.Whereas,1 x 108 CFU’s / 100ml caused 95% mortality for 1st instar, 85% for 5th instar, and 65% for 10th instar, 25 days after treatment. The concentration 28 x 106 conidia / 100ml caused 85% 65% and 55%mortality for1st, 5th and 10th instar, respectively 25days post-treatment. Additionally, five concentrations of both commercial formulation and isolates of conidial spores (1 x 108CFU’s / 100ml and 28 x 106 conidia / 100ml) were evaluated against the 1st,5th and 10th larval instars of red palm weevil under laboratory and field conditions. The results revealed that mortalities among treated larvae were significantly different than control, where no larva died among the control treatments. The current study confirmed that the lethal action of B. bassiana was directly proportional to the spore's concentration. This study further confirmed that the earlier larval instars was more affected by B. bassiana treatments than older ones.
The field study showed that infested date palm trees injected by New far formulation (B. bassiana) at the site of infestation by the red palm weevil caused 80% recovery from infestation after 25 days from treatment.

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