Prospects of fungal endophytes in the control of Liriomyza leafminer flies in common bean Phaseolus vulgaris under field conditions

Field trials were carried out for two seasons in two sites (Sagana and Naromoru, Central province of Kenya) to evaluate the prospects of endophyte isolates of Beauveria bassiana (Balsamo) Vuillemin G1LU3 and Hypocrea lixii Patouillard F3ST1 for the control of Liriomyza leafminer in common bean Phaseolus vulgaris L. crops through seeds inoculation. Autodissemination device (AD) treated with conidia of Metarhizium anisopliae (Metschnikoff) Sorokin ICIPE 20 was also added as a treatment. Leafminer infestation was not significantly different during the first season but was higher in the controls than in endophtyte treatments at both sites during the second season. Three key Liriomyza species [(L. huidobrensis Blanchard, L. sativae Blanchard and L. trifolii (Burgess)] and six parasitoid species [(Opius dissitus Muesebeck, Phaedrotoma scabriventris Nixon, Diglyphus isaea Walker, Neochrysocharis formosa Westwood, Hemiptarsenus varicornis Girault and Halticoptera arduine (Walker)] were identified during the trials. Leafminer infestation, number of pupae, leafminer flies and parasitoids emergence and yield were the parameters evaluated. Both isolates successfully colonized different parts of P. vulgaris plants, although the colonization was higher with H. lixii F3ST1 than B. bassiana G1LU3 at both sites. The mean number of pupae from the infested leaves varied between 141-252 and 331-416 in endophyte and control treatments, respectively, during the first season and from 110-223 to 366-523, respectively, in endophyte and control treatments during the second season. There were no significant differences among the treatments in the number of parasitoids that emerged from pupae. Higher yield of P. vulgaris seeds was obtained in endophyte than in control treatments. The inclusion of AD treatment did not have significant effect on all the parameters evaluated, except yield. Results of the present study suggest that both fungal isolates hold potential for pest management and could be considered for the control of leafminer flies. However, there is the need to confirm these results on large-scale trials.