Control Potentials of Three Entomopathogenic Bacterial Isolates for the Carob Moth, Ectomyelois ceratoniae (Lepidoptera: Pyralidae) in Pomegranates

Abstract

Ectomyelois ceratoniae (Lepidoptera: Pyralidae) is the primary pest of pomegranates in Saudi Arabia and is mostly controlled using broad-spectrum pesticides. Providing environmentally sound choices to limit reliance on chemical management is a major challenge in the control of E. ceratoniae and, as a consequence, in the protection of pomegranate crops from its invasion. Entomopathogenic bacteria (EPB) symbiotically associated with entomopathogenic nematodes (EPNs) are well-known biocontrol agents of soil-dwelling or aerial pests. The bacterium symbiont (EPB) is the real insect-killing biocontrol agent, while the nematode (EPN) serves as a vector. We wondered whether the EPB vector, which is extremely vulnerable to adverse environmental conditions, like drought, high temperatures, and repellent soil microorganisms, could be omitted. We intended to evaluate the biocontrol potential of directly applied EPB cells and cell-free culture media (CFCM) on the larval instar E. ceratoniae. Xenorhabdus budapestensis DSM 16342 (EMA), X. szentirmaii DSM 16338 (EMC), and Photorhabdus luminescens ssp. laumondi (TT01) strains were used. After three days of exposure, the cells of EMA, EMC, and TT01 strains resulted in 100%, 88%, and 79.3% larval mortality rates, respectively. The applied EMA CFCM resulted in 53.7% larval mortality, indicating the presences of (at least) one extremely strong component produced by EMA. We concluded that the direct application of either the EPB cells or the CFCM must be a prospective alternative biocontrol of E. ceratoniae, especially to protect the important fruit (pomegranate, Punica granatum) cultivars. Especially, newly identified local EPB isolates could be applied as bio-pesticides for integrated management practices or organic pomegranate production.

Identification and environment-friendly biocontrol potential of five different bacteria against Aphis punicae and Aphis illinoisensis (Hemiptera: Aphididae)

“…Five bacterial isolates associated with EPN S. feltiae were identified. These findings are consistent with and add to those previously reported by ( Alotaibi et al, 2021 and Noureldeen et al, 2022 ), who isolated Xenorhabdus sp. and Photorhabdus sp.…”

“…S. tumulicola isolate either cells or filtrates, showed aphicidal activity against A. punicae and A. illinoisensis systematically or through direct contact, causing lethality to the adult stage of both aphid species, and the accumulative mortality approached 100% 48 h following treatment. These results were in accordance with those of ( Alotaibi et al, 2021 ) who observed that the two Xenorhabdus bacterial species EMA and EMC causing significant higher E. ceratoniae larvae mortality than that caused by the Photorhabdus species TT01. In a recent study conducted by Elbrense et al, (2021) , it was discovered that H. bacteriophora and its symbiont, Photorhabdus sp., were more virulent against Pieris rapae and Pentodon algerinus .…”

Isolation, Identification, and Biocontrol Potential of Entomopathogenic Nematodes and Associated Bacteria against Virachola livia (Lepidoptera: Lycaenidae) and Ectomyelois ceratoniae (Lepidoptera: Pyralidae)

“…on V. livia and E. ceratoniae larvae. These results are consistent with those of Alotaibi et al [ 48 ], who recorded that mortality of E. ceratoniae larvae caused by two Xenorhabdus bacterial species was significantly higher than that of Photorhabdus species. In contrast, a recent study by Elbrense et al [ 15 ] showed that H. bacteriophora and its symbiont, Photorhabdus sp., were more virulent than S. riobravis and its symbiont, Xenorhabdus sp.…”

“…Following methods by Alotaibi et al [ 48 ], pomegranate butterfly ( V. livia ) and carob moth ( E. ceratoniae ) larvae were collected from commercial pomegranate orchards located in Taif, Saudi Arabia, and then reared on a wheat bran diet (300 g of wheat bran, 50 g of sugar, 120 mL of water, 130 mL of glycerol, and 9 g of yeast), whereas adults were fed with a 10% honey–water solution. The rearing room was adjusted to 25 ± 1 °C, a relative humidity of 60% and a light–dark cycle of 16 L:8 D.…”

Type Strains of Entomopathogenic Nematode-Symbiotic Bacterium Species, Xenorhabdus szentirmaii (EMC) and X. budapestensis (EMA), Are Exceptional Sources of Non-Ribosomal Templated, Large-Target-Spectral, Thermotolerant-Antimicrobial Peptides (by Both), and Iodinin (by EMC)

“…A successful symbiotic complex needs to be able to kill the available insect prey more efficiently than other alternatives. For this, the EPB should produce toxins [ 87 , 88 , 89 , 90 , 91 ].…”