Insects

15 pages, 1526 KiB

Open AccessArticle

Bt Trait Efficacy Against Corn Earworm, Helicoverpa zea, (Lepidoptera: Noctuidae) for Preserving Grain Yield and Reducing Mycotoxin Contamination of Field Corn

by William Yancey Barton, George David Buntin and Micheal D. Toews

Insects 2024, 15(12), 914; https://doi.org/10.3390/insects15120914 - 22 Nov 2024

Abstract

The corn earworm, Helicoverpa zea (Boddie), causes persistent ear damage to corn grown in the southeastern United States region. Increased levels of ear damage have been associated with mycotoxin contamination in addition to yield loss. Corn hybrids expressing proteins from the Bacillus thuringiensis (Bt) may provide corn earworm control. A selection of hybrids expressing various Bt traits were evaluated in field experiments across Georgia over two years to assess their efficacy for corn earworm control, grain yield and quality protection, and grain mycotoxin mitigation. Ear damage was significantly reduced only by Bt hybrids expressing the Vip3Aa20 protein. The remaining Bt hybrids expressing Cry proteins provided only marginal control. Ear damage had a variable effect on grain yield and was not correlated with grain aflatoxin contamination. In contrast, grain fumonisin contamination was positively associated with earworm damage. These results indicate Bt hybrids that effectively reduce corn earworm damage may also assist in reducing fumonisin contamination and possibly yield loss. Full article

(This article belongs to the Special Issue Corn Insect Pests: From Biology to Control Technology)

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7 pages, 1669 KiB

Open AccessArticle

Diversity Survey of a Pine Leafhopper Genus Pinopona Viraktamath & Sohi (Hemiptera: Cicadellidae: Koebeliini: Grypotina) in Yunnan Province, with Description of Two New Species

by Lin Lu and Yalin Zhang

Insects 2024, 15(12), 913; https://doi.org/10.3390/insects15120913 - 22 Nov 2024

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Abstract

The pine leafhopper genus Pinopona Viraktamath & Sohi was previously classified within the tribe Grypotini. In a recognized classification system, it has been categorized as the subtribe Grypotina of the tribe Koebeliini within Deltocephalinae, based on morphological characteristics such as a crown exhibiting few transverse fine striations along the anterior margin; short antennae measuring less than 1.5 times the head length but not extending to half or more of body length; ocelli positioned below the anterior margin of the crown and not visible from above, with a considerable distance from the eyes; and an anteclypeus that is narrow and tapered beyond the anterior margin of gena, alongside metatarsomere I presenting platellae on the plantar surface. Two new species, Pinopona gongshanensis and Pinopona daliensis spp. nov., are described herein from Yunnan Province and illustrated accordingly. This study also provides a checklist and key for all species within this genus. Full article

(This article belongs to the Special Issue Revival of a Prominent Taxonomy of Insects)

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16 pages, 1011 KiB

Open AccessArticle

Inheritance and Resistance Mechanisms of Field-Evolved Resistance to Pyrethroids in a Fall Armyworm (Spodoptera frugiperda J.E. Smith) (Lepidoptera: Noctuidae) Strain from Puerto Rico

by Omar Alejandro Posos-Parra, Barry R. Pittendrigh, John C. Wise, Christina DiFonzo, Eric Patterson and David Mota-Sanchez

Insects 2024, 15(12), 912; https://doi.org/10.3390/insects15120912 - 21 Nov 2024

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Abstract

This study examines resistance inheritance to the pyrethroid insecticides esfenvalerate and deltamethrin in a Puerto Rican strain of fall armyworm (FAW), Spodoptera frugiperda, a major global pest of corn. The resistant strain (PPR) showed significantly higher resistance compared to a susceptible strain (SUS), with a 62-fold X-linked and 15-fold autosomal-linked resistance ratio (RR₅₀) for esfenvalerate and deltamethrin, respectively. Resistance was incompletely dominant for both insecticides. Synergist bioassays revealed that detoxification enzymes play a key role in resistance, with PPR exhibiting increased toxicity across all tested synergists, especially with a 12-fold increase when all were combined. Deltamethrin assays confirmed the importance of these enzymes, with a 17-fold increase in PPR toxicity when combined with esterase inhibitors. These findings highlight the complexity of pyrethroid resistance, involving multiple non-target site mechanisms, and suggest that heterozygous individuals could survive in treated crops due to incomplete dominance. The results emphasize the need for diversified pest management strategies, including insecticide rotation, to effectively control FAW populations. Full article

(This article belongs to the Section Insect Physiology, Reproduction and Development)

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12 pages, 6338 KiB

Open AccessArticle

The Mechanism of Damage to the Midgut by Low Concentration of Bacillus thuringiensis in the Silkworm, Bombyx mori

by Hongbin Zou, Haoyi Gu, Jialu Cheng, Chao Tian, Qilong Shu, Peilin Peng and Bing Li

Insects 2024, 15(12), 911; https://doi.org/10.3390/insects15120911 - 21 Nov 2024

Viewed by 287

Abstract

Bacillus thuringiensis (Bt) has been extensively applied in agricultural pest management, posing a notable ecological risk to beneficial insects like Bombyx mori (silkworms). However, the toxicological mechanisms of Bt at low concentrations on silkworms remain largely unexplored. In this study, we determined the LC₅₀ (96 h) of Bt for fifth-instar silkworm larvae to be 0.08 × 10⁻³ mg/L. Exposure to a sub-lethal concentration of Bt (1/2 LC₅₀) led to significant reductions in body weight, pupal size, and the weights of both the whole cocoon and cocoon shell. Histopathological and ultrastructural examinations revealed that Bt exposure caused severe damage to the microvilli and epidermal cells of the midgut. Transcriptome sequencing of the midgut identified 290 differentially expressed genes (DEGs), with these genes predominantly involved in metabolic processes and apoptotic pathways. Notably, apoptosis-related genes such as Apaf-1 and Caspase-3 were upregulated by 5.08-fold and 1.27-fold, respectively. Further validation through TUNEL assays and Western blotting analysis confirmed a significant activation of apoptotic signaling. These findings suggested that low concentrations of Bt could trigger apoptotic pathways in the midgut of silkworm larvae, providing valuable insights into the toxicological evaluation of Bt at sub-lethal doses in insect species. Full article

(This article belongs to the Section Insect Physiology, Reproduction and Development)

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Insects, Volume 15, Issue 12 (December 2024) – 4 articles

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