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. 2022 Oct 25;12(1):17858.
doi: 10.1038/s41598-022-22229-6.

Chromobacterium Csp_P biopesticide is toxic to larvae of three Diabrotica species including strains resistant to Bacillus thuringiensis

Adriano E Pereira  1 , Man P Huynh  2   3 , Kyle J Paddock  2 , José L Ramirez  4 , Eric P Caragata  5 , George Dimopoulos  5 , Hari B Krishnan  6 , Sharon K Schneider  7 , Kent S Shelby  8 , Bruce E Hibbard  6
Affiliations

Chromobacterium Csp_P biopesticide is toxic to larvae of three Diabrotica species including strains resistant to Bacillus thuringiensis

Adriano E Pereira et al. Sci Rep. .

Abstract

The development of new biopesticides to control the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is urgent due to resistance evolution to various control methods. We tested an air-dried non-live preparation of Chromobacterium species Panama (Csp_P), against multiple corn rootworm species, including Bt-resistant and -susceptible WCR strains, northern (NCR, D. barberi Smith & Lawrence), and southern corn rootworm (SCR, D. undecimpunctata howardi Barber), in diet toxicity assays. Our results documented that Csp_P was toxic to all three corn rootworms species based on lethal (LC50), effective (EC50), and molt inhibition concentration (MIC50). In general, toxicity of Csp_P was similar among all WCR strains and ~ 3-fold less toxic to NCR and SCR strains. Effective concentration (EC50) was also similar among WCR and SCR strains, and 5-7-fold higher in NCR strains. Molt inhibition (MIC50) was similar among all corn rootworm strains except NCR diapause strain that was 2.5-6-fold higher when compared to all other strains. There was no apparent cross-resistance between Csp_P and any of the currently available Bt proteins. Our results indicate that Csp_P formulation was effective at killing multiple corn rootworm strains including Bt-resistant WCR and could be developed as a potential new management tool for WCR control.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Percent mortality, percent second instar, and dry weight of multiple WCR strains exposed to increasing concentrations (µg/cm2) of an air-dried preparation of Chromobacterium formulation, in 7-day diet overlay toxicity assays. Each time point in the bars is the average (± SE) of 10 replicates with eight neonate larvae per concentration per replicate.
Figure 2
Figure 2
Percent mortality, percent second instar, and dry weight of NCR and SCR strains exposed to increasing concentrations (µg/cm2) of an air-dried preparation of Chromobacterium formulation, in 7-day diet overlay toxicity assays. Each time point in the bars is the average (± SE) of 10 replicates with eight neonate larvae per concentration per replicate.
Figure 3
Figure 3
Longitudinal sections of 3-day old western corn rootworm midgut (WCR; Diabrotica virgifera virgifera LeConte) larvae reared on artificial diet overlaid with (A) sucrose (50 mg/ml) or (B) an air-dried Chromobacterium preparation at 80 µg/cm2. Untreated larvae have intact microvilli (MV) and a single layer of columnar cells (CC) surrounding the gut lumen. Treated larvae exhibit symptoms of muscle constriction from the clustering of muscle cells (MC). The CC are elongated at the posterior (PST) end of the midgut. The anterior portion of the midgut displays dissolved CC and MV and an increased abundance of stem cells (SC). The CC appear multilayered in some places in the treated insects. Cellular debris is visible within the gut lumen.
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