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Endophytic colonisation of tomato by the entomopathogenic fungus Beauveria bassiana: the use of different inoculation techniques and their effects on the tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae)

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Allegrucci N., Velazquez M. S., Russo M. L., Perez E., Scorsetti A. C.

Journal of Plant Protection Research

2017

tom 57

nr 4

Fungal entomopathogens can naturally regulate populations of various insects. The entomopathogen Beauveria bassiana (Bals.- Criv.) Vuill. is also able to endophytically colonize different plants. Endophytic colonization by entomopathogens may provide a source of indirect interactions between fungi and insects and has been associated with the ability of the fungus to control insect pests. The tomato leaf miner, Tuta absoluta (Meyrick) is considered one of the most devastating pests of tomato (Solanum lycopersicum L.) and its difficult control is due to its miner habit, short life cycle, and high reproductive capacity. The aims of this study were: (i) to use three different techniques, i.e. leaf spraying, seed immersion and root dipping, for the endophytic inoculation of B. bassiana in tomato plants; and (ii) to assess the effect of B. bassiana on tomato leaf consumption and mortality of T. absoluta after inoculation. The percentage of colonization by B. bassiana was assessed 7, 14 and 28 days after inoculation. All inoculation techniques employed allowed the recovery of B. bassiana, although our results showed significant differences between techniques. Leaf spraying was the most effective, with the highest percentage of colonization recorded 7 days after inoculation. We also evaluated (i) the effect on the mortality of T. absoluta by direct contact with conidia of B. bassiana, and (ii) the effect on tomato leaf consumption and mortality by indirect contact through ingestion of inoculated plant tissues with B. bassiana. Mortality bioassays showed that B. bassiana infected T. absoluta, either by direct contact or indirectly, via ingestion of inoculated tomato leaves. Direct contact showed a higher percentage of mortality and a lower median survival time (MST) than indirect contact. Significant differences in the mortality percentages of T. absoluta after exposure with B. bassiana were found among the treatments and the control. Our results suggest that the endophytic inoculation of B. bassiana in tomato crops provides the basis for further investigation, which should focus on the virulence of the endophytic B. bassiana against T. absoluta.

Interactions between the entomopathogenic fungus Beauveria bassiana and the Neotropical predator Eriopis connexa (Coleoptera: Coccinellidae): Implications in biological control of pest

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Scorsetti A. C., Pelizza S., Fogel M. N., Vianna F., Schneider M. I.

Journal of Plant Protection Research

2017

tom 57

nr 4

Aphids (Hemiptera: Aphididae) are serious pests of crops causing direct damage by feeding and indirect by the transmission of plant viruses. The use of conventional insecticides for controlling aphids has caused different problems and insecticide resistance. Accordingly, there is more interest in alternative control methods such as biological control by natural enemies for sustainable agricultural management. Among biological control agents, entomopathogenic fungi are one of the most significant microbial pathogens of insects. Also, Coccinellidae, as a major group, is a serious natural enemy. Both larval and adult stages of Coccinellidae feed on different soft-body pests, such as aphids. Eriopis connexa (Germar) (Coleoptera: Coccinellidae) is a common species in agroecosystems of the Neotropical region where it is considered to be a potential control agent. Pathogens and arthropod natural enemies may contribute to the control of phytophagous pests; however, it is important to assess potential interactions within biological control agents that share hosts (intraguild interaction) to evaluate their combined use for pest control. Therefore, the aim of this study was to evaluate the compatibility and interaction (lethal and sublethal effects) between E. connexa and the entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) Vuill. (Ascomycota: Hypocreales). Both are important biological control agents of aphids. The pathogenicity of B. bassiana against larvae, pupae and adults of the predator E. connexa was evaluated, and results showed, that B. bassiana infected the coleopteran. On the other hand, interaction between B. bassiana and the predator was evaluated through infected-prey. The effects of fungus on larvae survival were significantly different when we analyzed the accumulated survival (from first larval instar to adulthood). The daily fecundity was significantly reduced at five days compared to control group. By contrast, no significant differences were observed between the five oviposition days in the rate of hatched eggs. This study shows that despite having received a single dose of the fungus in its life cycle, the population parameters of the predator E. connexa are affected. More studies would be necessary to help identify interactions between microbes and natural enemies to increase and enhance opportunities and further develop biological pest control programs.

Ograniczanie wyników

2 Journal of Plant Protection Research

2 Scorsetti A. C.

1 Allegrucci N.

1 Fogel M. N.

1 Pelizza S.

1 Perez E.

1 Russo M. L.

1 Schneider M. I.

1 Velazquez M. S.

1 Vianna F.

2 2017

Wyniki wyszukiwania

Endophytic colonisation of tomato by the entomopathogenic fungus Beauveria bassiana: the use of different inoculation techniques and their effects on the tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae)

Interactions between the entomopathogenic fungus Beauveria bassiana and the Neotropical predator Eriopis connexa (Coleoptera: Coccinellidae): Implications in biological control of pest