High susceptibility of Tetranychus merganser (Acari: Tetranychidae), an emergent pest of the tropical crop Carica papaya, towards Metarhizium anisopliae s.l. and Beauveria bassiana strains

Abstract

Background The mite Tetranychus merganser is considered to be an emerging pest of various crops in tropical countries. It is one of the most detrimental pests in the papaya orchards of some regions of México. The current field control of Tetranychus spp. involves the extensive use of chemicals that have some degree of toxicity to humans or the environment and may cause selective resistance. The use of biological alternatives such as parasitoids and mite predators have limited effectiveness. In order to find effective but non-toxic alternatives for mite pest management, bio-products that are able to be mass produced and applied to large production areas have been sought, including the entomopathogen fungi. B. bassiana and M. anisopliae s.l. are the fungi most extensively used for the biological control of insect pests. Although they do not cause natural epizootic diseases in mites, there are reports that show that they infect T. urticae, and should be evaluated for use in the biological control of papaya’s mite pests. Methods A T. merganser colony was established and the susceptibility of adult females to 30 entomopathogenic fungi strains was evaluated under laboratory conditions with an in vitro mass screening bioassay. Ten strains of Metarhizium anisopliae sensu lato (s.l.), eleven of Beauveria bassiana, nine of Lecanicillium sp. and one of Hirsutella thompsonii var. sinematosa were tested. The infectivity of adult females was evaluated calculating the percentage of mortality. To calculate the LC50 and LT50 of the most virulent strains, a bioassay was performed using serial concentrations (1×104–1×108 conidia/mL) for each strain. Strains showing ability to infect eggs laid were evaluated with a novel egg-infectivity bioassay. The internal transcribed spacer (ITS) region of the more lethal strains were sequenced. Results T. merganser and T. urticae were found in orchards of Carica papaya (Maradol variety and Tainung hybrid) in Campeche, México. All tested strains of M. anisopliae s.l. and B. bassiana were infectious to the adult female of T. merganser at a concentration of 1×108 conidia/mL. Six strains of M. anisopliae (Ma002, Ma003, Ma004, Ma005, Ma014 and Ma034) caused 100% mortality, and one of B. bassiana (Bb016) caused 95% mortality. The most virulent was Ma034, with an LC50 of 1.73×106 conidia/mL followed by Ma005 and Ma003. Ma005 and Ma034 were the fastest strains to reach LT50,achieving this in less than 3.7 days. Additionally, Ma034 and Ma014 strains were infectious to more than 70% of the eggs. Conclusions T. merganser and T. urticae are present in the papaya orchards of Campeche, México. The high susceptibility of T. merganser adult females and eggs toward several M. anisopliae s.l. or B. bassiana strains suggests that these fungi are a viable alternative to control this emergent pest. The most virulent strain, Ma034, was also infective to eggs, and is the most promising to be tested in the field.

Impact of Operational Parameters on Droplet Distribution Using an Unmanned Aerial Vehicle in a Papaya Orchard

“…Papaya production is at risk, given that the reduction in cultivated areas is a result of phytosanitary problems [2] since the crop is susceptible to pest and disease attacks [4][5][6][7][8]. The main pests include the white mite (Polyphagotarsonemus latus), the spider mite (Tetranychus urticae), among other tetranychid mites, aphids Aphis gossypii and Myzus persicae, and mealybugs, such as Aonidiella comperei and Coccus hesperidum.…”

Life Table Parameters of Tetranychus merganser Boudreaux (Acari: Tetranychidae) on Five Host Plants

“…It is found in China, Mexico, the United States, and Thailand [ 5 ]. The red spider mite is considered an emerging pest in Mexican agriculture due to the recent increase in the range of its host plants and geographic expansion [ 6 ]. The feeding habits of T. merganser destroy the epidermal tissue, the parenchyma, and the chloroplasts of the leaves, causing the host plant to fail to grow, develop, and reproduce [ 7 , 8 ].…”

“…They cause a minimal environmental impact, including predator mites ( Neoseiulius californicus McGregor and Amblyseius swirskii Athias-Henriot (Gamasida: Phytoseiidae)) [ 8 ], botanical extract ( Moringa oleifera ethanol extract) [ 11 ], and entomopathogenic fungi ( Metarhizium anisopliae s.l. and Beauveria bassiana ) [ 6 ].…”