Control Efficiency and Mechanism of Spinetoram Seed-Pelleting Against the Striped Flea Beetle Phyllotreta Striolata

The striped flea beetle (SFB, Phyllotreta striolata) is an important pest of the cruciferous crops in Asia. SFB is regarded as the most destructive pest of cruciferous crops in China due to the severe crop loss and frequent infestation incidents. As no SFB resistant cultivar is available at present, therefore, application of insecticides is the primary method of SFB control. On the contrary, the exploitation of chemical insecticides causes severe environmental issues and is not cost-effective. The use of a seed-pelletized coating of spinetoram effectively reduced SFB feedings on the flowering cabbage seedlings, whereas in combination with the insect-proof net, it controlled the SFB infestation throughout the cabbage growth period. The analysis of the pesticide residues in soil and different cabbage parts indicated the degradation dynamics of spinetoram. Furthermore, estimation of the half-life of spinetoram revealed that via seed-palletized application spinetoram half-life was found to be 2.82 days in soil, 4.21 days in the root, 5.77 days in the stem, and 3.57 days in the leaf, respectively. Both the lower pesticide residues and the half-life of spinetoram in soil and cabbage parts suggested it to be a promising environment and food-safe pesticide in controlling SFB. Moreover, the seed-pelletized coating ensured a sustainable release of spinetoram that can reduce the pesticide application frequency and be cost-effective and pocket-friendly for the farmers.

Evaluation of the Efficacy of Chemical Insecticides and Biopesticides against Flea Beetle in Cabbage (Brassica oleracea var. Capitata)

Aims: This study aimed to evaluate chemical insecticides and bio-pesticides against flea beetle in cabbage. Study Design: The experiment was laid out at a randomized complete block design with three replications. Place and Duration of Study: Experimental farm of Sher-e-Bangla Agricultural University, Bangladesh during the period from October 2017 to March 2018. Methodology: The experiment consisted of nine treatments viz. T1(Sevin 85 WP @ 2g/L of water), T2 (Decis 2.5 EC @ 1.0 ml/L of water), T3 (Voliam flexi @ 0.5 ml/L of water), T4 (Ripcord 10 EC @ 1.0 ml/L of water), T5 (Dursban 20EC @ 1 ml L-1 of water), T6 (Tobacco leaf extract @ 3 g L-1 of water), T7 (Neem seed kernel extract @ 3 g L-1 of water), T8 (Bioneem plus 1 EC @ 1 ml L-1 of water) and T9 (Untreated Control) were used at 7 days interval. Results: Stripped flea beetle(Phyllotreta striolata) and white-spotted flea beetle (Monolepta signata), these two species of flea beetle were found in the experimental field. Among all the treatments T4 (Ripcord 10EC)performed the best in managing flea beetles based on the lowest percentage of leaf infestation (5.84%), lowest no. of holes per plant (6.13), lowest percentage of head infestation by number (18.04) and highest percentage of infestation reduction over control on all parameters at vegetative stage of plant. Again, the lowest leaf infestation intensity (5.73%), lowest number of holes per infested head (14.00), lowest percentage of infestation of head by number (6.69) were achieved at harvesting stage from the same treatment (T4) whereas the highest values of all these parameters were achieved from untreated control treatment (T9). T4 treatment provided the best performance in yield where yield was increased (112.51 %) over control, giving maximum yield 75.76 tons ha-1. Bioneem plus 1 EC (T8) performed the best among the biopesticides while the neem seed kernel extract showed less effectivity against flea beetle. Conclusion: It is concluded that in case of chemical insecticides Ripcord 10EC while in case of biopesticides Bioneem plus 1 EC would be effective for flea beetle management.

Full length sequencing reveals novel transcripts of detoxification genes along with related alternative splicing events and lncRNAs in Phyllotreta striolata

The striped flea beetle, Phyllotreta striolata (Fabricius), damages crops in the Brassicaceae. The genetic data for this pest are insufficient to reveal its insecticide resistance mechanisms or to develop molecular markers for resistance monitoring. We used PacBio Iso-Seq technology to sequence the full-length transcriptome of P. striolata. After isoform sequence clustering and removal of redundant transcripts, a total of 41,293 transcripts were obtained, and 35,640 of these were annotated in the database of gene products. Structure analysis uncovered 4,307 alternative splicing events, and 3,836 sequences were recognized as lncRNAs. Transcripts with the complete coding region of important detoxification enzymes were further classified. There were 57 transcripts of P450s distributed in CYP2, CYP3, CYP4, and Mito CYP clades, 29 transcripts of ESTs from 4 functional groups, 17 transcripts of GSTs classified into 5 families, 51 transcripts of ABCs distributed in 6 families, and 19 transcripts of UGTs. Twenty-five lncRNAs were predicted to be regulators of these detoxification genes. Full-length transcriptome sequencing is an efficient method for molecular study of P. striolata and it is also useful for gene function analysis.

Flea Beetle (Coleoptera: Chrysomelidae) Populations, Effects of Feeding Injury, and Efficacy of Insecticide Treatments on Eggplant and Cabbage in Southwest Virginia

Flea beetles, are common pests of cabbage Brassica oleracea L. (Brassicales: Brassicaceae) and eggplant Solanum melongena L. (Solanales: Solanaceae), but little is known about the flea beetle populations in Virginia, their impact on yield, or the most effective control methods. This research investigates flea beetle populations and the impact of their feeding injury on cabbage and eggplant in Southwest Virginia and determines the most efficacious control methods. In Whitethorne, VA, cabbage and eggplant crops were vacuum sampled weekly throughout two summers (2015, 2016). Crucifer flea beetle, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), and striped flea beetle, Phyllotreta striolata Fabr. (Coleoptera: Chrysomelidae) were found on cabbage; whereas, eggplant flea beetle, Epitrix fucula (Crotch) (Coleoptera: Chrysomelidae), and the tobacco flea beetle, Epitrix hirtipennis (Melsheimer) (Coleoptera: Chrysomelidae) were found on eggplant. To evaluate the impact of flea beetle feeding on these plants flea beetle densities and defoliation were assessed weekly and individual plant, as well as whole plot yields, assessed at harvest. For cabbage, significant yield reductions were observed between 1 and 20% and >60% defoliation. Similarly, significant yield reductions were observed between 41 and 60% and >60% defoliation for eggplant. The efficacy of various insecticides was also evaluated. Soil application of the systemic neonicotinoid dinotefuran, imidacloprid, and the foliar-applied bifenthrin resulted in the fewest beetles, the least amount of leaf defoliation, and the highest yield in cabbage and eggplant. This research helps vegetable growers to better understand the severity of these pests and how to effectively combat them.

Two methods for rearing the striped flea beetle Phyllotreta striolata (Coleoptera: Chrysomelidae) under laboratory conditions

The striped flea beetle, Phyllotreta striolata (Fabricius) (Coleoptera: Chrysomelidae), is a major pest of canola (Brassica Linnaeus, Brassicaceae) on the Canadian prairies. The previously published methods to rear striped flea beetles under laboratory conditions are not sufficient to maintain laboratory colonies over a sustained period of time. Here, we describe two methods to rear striped flea beetles in the laboratory. The first method produces both immature stages and adult flea beetles using Napa cabbage (Brassica napa subsp. pekinensis (Loureiro) Hanelt) and canola as food sources. Beetles reared using this method produced an average of 9.7 ± 4.5 eggs, had a juvenile development period of between 26 and 33 days, and had an adult longevity between 17 and 55 days. Between 62% and 90% of the colony-reared eggs resulted in the successful development to an adult beetle. The second method uses canola as the only host, and facilitates easy access to high quantities of adult beetles. This method resulted in a six-fold to nine-fold increase in adult numbers per generation. Developmental time from adult to adult ranged from 25 to 30 days. Our two methods facilitated rearing striped flea beetles for several generations in the laboratory with or without hibernation.

Scanning electron microscopic observation of the infection process of a Metarhizium strain Ma6 highly pathogenic to Phyllotreta striolata

Background. Phyllotreta striolata is a worldwide pest that harms cruciferous vegetables. The use of pathogenic microorganisms to control pests is an important means of biological control. Using pathogenic microorganisms to prevent and control P. striolata has rarely been reported. Methods. In this study, the infection process of a Metarhizium strain highly pathogenic to P. striolata was observed by stereomicroscopyand scanning electron microscopy (SEM). Results.The results showed that the attachment of Metarhizium strain Ma6 to the body surface varied; the conidia distribution was greatest in the tibia of the posterior leg with thick bristles and in the intersegmental abdominal membrane, and the spore distribution occurred least in the smooth and hard portions of the insect’s body. At the start of the infection, Metarhizium strain Ma6 generally grew from the body parts with gaps or connecting spaces such as mouthparts and the thoracic leg base and joints, then the spores germinated with germ tubes and penetration peg, and the penetration peg penetrated the body surface. Ten days after inoculation, the mycelia divided into conidia, and many mycelia and spores covered the entire adult insect’s body. Discussion. Spore germination occurred on the 5th day after inoculation, and many hyphae and spores covered the entire adult insect body within 10 days after inoculation. And the invasion into tissue gaps from the weaker areas is more efficient than intruding from the body hard surface. This may be the reason for the Metarhizium strain Ma6’s high virulence. This study preliminarily clarified the infection ability and invasion approach of a Metarhizium strain against P. striolata, providing evidence for evaluating the strain’s insecticidal effect and application prospect.