Toxicity of Bacterial Isolates on Adults of Zaprionus indianus (Diptera: Drosophilidae) and Parasitoids Trichopria anastrephae (Hymenoptera: Diapriidae) and Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae)

Abstract

Bacillus thuringiensis (Berliner) has demonstrated potential use in insect pest management. We evaluated the toxicity and sublethal effects of formulations of toxic baits composed of bacterial isolates (Bt) B. thuringiensis var. oswaldo cruzi (Bto), B. thuringiensis var. israelensis (Bti), B. thuringiensis var. kurstaki (Btk), and B. circulars (Bc) in combination with three food attractants 50% grape juice, 7% sugar cane molasses, and 7% hydrolyzed protein on adults of Zaprionus indianus (Gupta, 1970), the main pest of fig fruit (Ficus carica) in Brazil. Likewise, we evaluated the toxicity on the parasitoids Trichopria anastrephae Lima, 1940 and Pachycrepoideus vindemmiae (Rondani, 1875) in ingestion bioassays. Adults of Z. indianus showed high susceptibility to Bacterial isolates. However, the Bto isolate (1013 CFU. ml−1) caused adult mortality of 100%, in 72 h after exposure, with LT50 values of ≈20 h. By using the lethal concentrations (LC90) of the Bto isolate, estimated via the concentration–response curves with the food attractants, a significant reduction (40 to 50%) in the total fecundity and in the embryonic viability of eggs from females fed with the toxic baits was observed. The food attractants + Bto (80 × 108 CFU. ml−1) did not cause significant mortality of T. anastrephae and P. vindemmiae adults (mortality < 20%). The bacterial isolates Bti, Btk, Bc, and Bto are considered promising for the formulation of toxic baits, because, besides providing toxic effect on adults of Z. indianus, they showed no toxicity on T. anastrephae and P. vindemmiae adults.

Toxicity of Bacillus sp. (Bacillales: Bacillaceae) on the fungus gnats, Bradysia aff. ocellaris larvae (Diptera: Sciaridae)

“…Considering that the toxin acts in the digestive system (Ben-Dov 2014), the greater the exposure to the toxin, the greater the consumption of food contaminated with the bacteria, and therefore, the greater should be the impact on the larvae metabolism (Taylor et al 2007). The susceptibility of larvae of dipteran species to B. thuringiensis isolates has been demonstrated in several studies (Aboussaid et al 2010;Molina et al 2010;Ilias et al 2013;Shishir et al 2015;Buentello-Wong et al 2015;Cossentine et al 2016;Geisler et al 2019;Martins et al 2018), however, for sciarids and some mosquitoes, such as Aedes, Culex, and Anopheles, it is known that some endotoxins are more specific and effective in control (Ben-Dov 2014). Nevertheless, they act similarly to what occurs in lepidopterans.…”

“…Studies have shown that several species of dipterans are susceptible to B. thuringiensis, such as Anastrepha ludens (Loew) (Toledo et al 1999;Buentello-Wong et al 2015), Bactrocera oleae (Gmelin) (Alberola et al 1999;Ilias et al 2013), Ceratitis capitata (Wiedemann) (Aboussaid et al 2010), Bactrocera cucurbitae (Shishir et al 2015) and Anastrepha fraterculus (Wiedemann 1830) (Diptera: Tephritidae) (Martins et al 2018), Drosophila suzukii (Matsumura) (Cossentine et al 2016), Zaprionus indianus (Diptera: Drosophilidae) (Geisler et al 2019), Bradysia sp nr. coprophila (Cloyd and Dickinson 2006) and Bradysia difformis (Wang et al 2020).…”

Pest categorisation of Zaprionus indianus

“…(Marchiori et al, 2003, Marchiori and Silva, 2003, Silva et al, 2004. Bacterial isolates are considered promising for the formulation of toxic baits (Geisler et al, 2019). Epsky et al, 2014Epsky et al, , 2015Renkema et al, 2018), as well as different traps (Pasini and Link, 2011;Renkema et al, 2018;Lasa et al, 2020).…”

“…Various hymenopteran parasitoids have been documented parasitising Z. indianus in Brazil, though with low levels of parasitisation (2–4%) (Marchiori et al., 2003, Marchiori and Silva, 2003, Silva et al., 2004). Bacterial isolates are considered promising for the formulation of toxic baits (Geisler et al., 2019).…”