Parasitism of Adult Pentatomidae by Tachinidae in Soybean in the North Central Region of the United States

First Description of the Nuclear and Mitochondrial Genomes and Associated Host Preference of Trichopoda pennipes, a Parasitoid of Nezara viridula

Trichopoda pennipes is a tachinid parasitoid of several significant heteropteran agricultural pests, including the southern green stink bug, Nezara viridula, and leaf-footed bug, Leptoglossus phyllopus. To be used successfully as a biological control agent, the fly must selectively parasitize the target host species. Differences in the host preference of T. pennipes were assessed by assembling the nuclear and mitochondrial genomes of 38 flies reared from field-collected N. viridula and L. phyllopus. High-quality de novo draft genomes of T. pennipes were assembled using long-read sequencing. The assembly totaled 672 MB distributed among 561 contigs, having an N50 of 11.9 MB and a GC of 31.7%, with the longest contig at 28 MB. The genome was assessed for completeness using BUSCO in the Insecta dataset, resulting in a score of 99.4%, and 97.4% of the genes were single copy-loci. The mitochondrial genomes of the 38 T. pennipes flies were sequenced and compared to identify possible host-determined sibling species. The assembled circular genomes ranged from 15,345 bp to 16,390 bp and encode 22 tRNAs, two rRNAs, and 13 protein-coding genes (PCGs). There were no differences in the architecture of these genomes. Phylogenetic analyses using sequence information from 13 PCGs and the two rRNAs individually or as a combined dataset resolved the parasitoids into two distinct lineages: T. pennipes that parasitized both N. viridula and L. phyllopus, and others that parasitized only L. phyllopus.

Comparative morphology of antennal ultrastructure in Tachinidae parasitoid flies (Diptera): The phylogenetic importance of antennal sensilla

Tachinidae are one of the most diverse clades of Diptera. All tachinids are parasitoids of insects and other arthropods, and thus are considered an important source of biological pest control. Antennae are the most important olfactory organs of Tachinidae playing key roles in their lives, especially in locating hosts, and details of antennal ultrastructure could provide useful features for phylogenetic studies and understanding their adaptive evolution. Despite the ecological and evolutionary importance of antennae, the current knowledge of antennal ultrastructure is scarce for Tachinidae. Our study examined antennal sensilla of thirteen species belonging to thirteen genera within eleven tribes of all the four subfamilies (Phasiinae, Dexiinae, Tachininae, and Exoristinae): Beskia aelops Walker, Trichodura sp., Voria ruralis (Fallén), Zelia sp., Cylindromyia carinata Townsend, Phasia xenos Townsend, Neomintho sp., Genea australis (Townsend), Copecrypta sp., Hystricia sp., Belvosia sp., Leschenaultia sp., and Winthemia pinguis (Fabricius). Types, length and distribution of antennal sensilla were investigated via scanning electron microscopy (SEM). Our comparative analysis summarized 29 variable characters and we evaluated their phylogenetic signal for subfamilial, tribal and generic/specific levels, showing that antennal ultrastructure could be a reliable source of characters for phylogenetic analysis. Our findings demonstrate the remarkable diversity of the antennal ultrastructure of Tachinidae.

Natural Enemies and Biological Control of Stink Bugs (Hemiptera: Heteroptera) in North America

Stink bugs comprise a significant and costly pest complex for numerous crops in the US, including row crops, vegetables, and tree fruits and nuts. Most management relies on the use of broad-spectrum and disruptive insecticides with high human and environmental risks associated with them. Growing concerns about pesticide resistance in stink bugs are forcing pest managers to explore safer and more sustainable options. Here, we review the diverse suite of natural enemies of stink bugs in the US, noting that the egg and the late nymphal and adult stages of stink bugs are the most commonly attacked by parasitoids, whereas eggs and young nymphs are the stages most commonly attacked by predators. The effectiveness of stink bugs' natural enemies varies widely with stink bug species and habitats, influencing the biological control of stink bugs across crops. Historically, biological control of stink bugs has focused on introduction of exotic natural enemies against exotic stink bugs. Conservation and augmentation methods of biological control have received less attention in the US, although there may be good opportunities to utilize these approaches. We identify some considerations for the current and future use of biological control for stink bugs, including the potential for area-wide management approaches.

Halyomorpha halys (Hemiptera: Pentatomidae) on Kiwifruit in Northern Italy: Phenology, Infestation, and Natural Enemies Assessment

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an Asian invasive plant-feeding insect and an emerging kiwifruit pest. Knowledge about the BMSB dynamics and damage to kiwifruit outside the bug native range is scarce. This 2-yr study was aimed at describing phenology and infestation dynamics of BMSB in green-fleshed and yellow-fleshed kiwifruits. Natural enemies were investigated as well. Field surveys were performed weekly in two sites in Northern Italy by pheromone-baited traps and visual samplings, from early Spring to mid-Autumn. All BMSB life stages were collected and kept under observation to assess occurrence of parasitoids. A sample of fruit was dissected weekly to detect BMSB feeding injuries. In 2018-2019, BMSB was found throughout the growing season with two generations per year with a large overlapping of all life stages. Pheromone-baited traps and visual samplings gave consistent results and can be both considered effective sampling methods on kiwifruit. Fruit injuries were significantly related to kiwifruit development stage, weekly captures of BMSBs by traps, and cultivar. Several BMSB egg masses were found on kiwifruit leaves. Anastatus bifasciatus Geoffroy (Hymenoptera: Eupelmidae), a native egg parasitoid with Palearctic distribution, emerged from 20.14% of eggs in 2018, but the percent parasitism dropped to 0.47% in 2019. In both years, other natural enemies were found exerting negligible pressure on BMSB populations. The determination of reliable economic thresholds for BMSB on kiwifruit is urgently needed to develop a robust and sustainable integrated pest management (IPM) strategy, and this study provides data towards that direction.

Challenges for Adoption of Integrated Pest Management (IPM): the Soybean Example

Soybean is considered one of today's most important crops. Planted on millions of hectares worldwide, the management of soybean pests usually requires large amounts of chemicals. However, a key component to meet the increasing demand for food due to the rapidly growing global population is protecting crops from pests while maintaining environmental quality through ecologically and economically sound integrated pest management (IPM) practices. Not only can IPM result in more profitable agriculture due to the reduction of pest control costs but also assures equitable, secure, sufficient, and stable flows of both food and ecosystem services. Despite those ecological and economic benefits, the vast areas of cultivated soybean as well as the convenience of spraying insecticides are encouraging the adoption of prophylactic pest control as a relatively inexpensive safeguard compared to IPM practices. Thus, in this forum, we discuss the reasons for soybean IPM not reaching its potential. We give examples of how we can revive this once successful pest management program with a focus on experiences in Brazil and the USA. We analyze IPM case studies to illustrate the need for growers to have easy and fast access to IPM information on its medium- and long-term benefits. Overall, this forum highlights the importance of IPM for agricultural sustainability including ecological and financial benefits.