In the scope of mitigating the negative impacts of pesticide use and managing greenhouse whiteflies, Trialeurodes vaporariorum sustainably, 16 endophytic fungal isolates from five different genera (Beauveria, Trichoderma, Hypocrea, Bionectria, and Fusarium) were screened for their ability to colonise two preferred host plant species, namely, tomato (Solanum lycopersicum L.) and French bean (Phaseolus vulgaris L.), through seed inoculation. Seven and nine isolates were endophytic to P. vulgaris and S. lycopersicum, respectively, where significant differences in the endophytic colonisation rates were observed among the fungal isolates in P. vulgaris and its plant parts, with a significant interaction between the isolates and plant parts in S. lycopersicum. Hypocrea lixii F3ST1, Trichoderma asperellum M2RT4, Trichoderma atroviride F5S21, and T. harzianum KF2R41 successfully colonised all the plant parts of both hosts and therefore were selected and further evaluated for their endophytic persistence, effect on plant growth, and pathogenicity to T. vaporariorum adults and F1 progeny. The four endophytes remained in both host plants for the 5-week assessment with varied colonisation rates related to the strong interaction with the time, isolates, and plant parts in both hosts. The effect of the same endophytes on the different host growth parameters varied in P. vulgaris and S. lycopersicum, with T. asperellum M2RT4 not boosting the growth in both host plants while T. atroviride F5S21 resulted in enhanced shoot biomass in S. lycopersicum. T. atroviride F5S21 and T. harzianum KF2R41 inoculated S. lycopersicum plants and H. lixii F3ST1, T. asperellum M2RT4, and T. harzianum KF2R41 inoculated P. vulgaris plants had significantly lower oviposition, while nymph development in both hosts was significantly prolonged in all the endophytically–colonised plants. The endophytes H. lixii F3ST1 and T. asperellum M2RT4 significantly reduced the longevity/survival of the exposed T. vaporariorum adults and the progeny in both S. lycopersicum and P. vulgaris. The findings demonstrate the attributes of the various endophytes in host plant growth promotion as well as their effects on the life-history parameters of T. vaporariorum and could consequently be developed as potential endophytic fungal-based biopesticides for the sustainable management of the pest in S. lycopersicum and P. vulgaris cropping systems.
The efficiency of an autodissemination technique in controlling adult whiteflies, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae) on tomato, Solunum lycopersicum was investigated with previously identified potent fungal isolates of Metarhizium anisopliae ICIPE 18, ICIPE 62 and ICIPE 69 under screenhouse or semi-field conditions. The autodissemination device was inoculated with dry conidia of the M. anisopliae isolates, while control insects were exposed to a fungus–free device. Sampling for conidia uptake, conidial viability and persistence, and insect mortality was done at 1, 2, 3, 5 and 8 days post–exposure, and collected insects were monitored for mortality over ten days. Overall, mortality was higher in insects exposed to ICIPE 18 (62.8%) and ICIPE 69 (61.8%) than in those exposed to ICIPE 62 (42.6%), with median lethal times, (LT50) ranging between 6.73–8.54 days. The control group recorded the lowest mortality rates (18.9%). A general linear reduction in conidial viability with exposure time was observed, although this was more pronounced with M. anisopliae ICIPE 62. Insects exposed to M. anisopliae ICIPE 69 also recorded the highest conidia uptake, hence selected for further evaluation with a T. vaporariorum attractant volatile organic compound, (E)–2–hexenal. The volatile inhibited fungal germination in laboratory compatibility tests, therefore, spatial separation of M. anisopliae ICIPE 69 and (E)–2–hexenal in the autodissemination device was conducted. The inhibitory effects of the volatile were significantly reduced by spatial separation at a distance of 5 cm between the fungus and the volatile, which was found to be more suitable and chosen for the subsequent experiments. Results showed that (E)–2–hexenal did not influence conidia uptake by the insects, while fungal viability and the subsequent mortality variations were more related to duration of exposure. The fungus–volatile compatibility demonstrated with spatial separation provides a basis for the optimisation of the volatile formulation to achieve better T. vaporariorum suppression with an excellent autodissemination efficiency when used in the management of whiteflies under screenhouse conditions.
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