Alicia E. Timm

The corn leaf aphid is a major pest causes damage to a range of cultivated crops. Little is known about the population genetics of the species. In this experiment, we examined the population genetic structure of the Rhopalosiphum maidis based on nucleotide sequencing of the cytochrome oxidase I (COI) gene and microsatellite analysis. Thirteen microsatellite markers developed for related aphid species were tested for use with R. maidis. Nine loci were found to amplify in R. maidis. Of these, seven were polymorphic. Nucleotide sequencing showed low variation, with one haplotype dominating in the regions sampled and four other haplotypes, differing by only a single base, occurring at a low frequency. Microsatellites confirmed low levels of diversity, but also showed moderate levels of population structure over local geographic scales, although this structure was not a result of isolation by distance. Over broader geographic scales, cluster analysis showed that populations from all U.S. states and China were almost indistinguishable and population assignment revealed that only 30% of individuals sampled could be correctly assigned to the population from which they were collected. Populations collected from Sorghum bicolor and Sorghum halepense could not be discriminated, indicating that S. halepense may act as a reservoir for the aphid during times when sorghum is not cultivated. The close similarity between individuals from China and the U.S. suggests that the lack of variation in the species may be explained by the parthenogenetic mode of reproduction, where males are seldom found.

Codling moth Cydia pomonella is well established nearly everywhere apples are grown. Due to this almost global distribution, larvae are often intercepted at U.S. ports of entry where immature specimens cannot be identified accurately to species leading to unnecessary quarantine actions. To assist with identifying intercepted C. pomonella from port inspections, we developed a probe-based real-time PCR assay to amplify the internal transcribed spacer (ITS) region 2 of C. pomonella. The assay was tested for inclusivity using 110 C. pomonella specimens from six continents. Analytical specificity was examined by testing related species intercepted at U.S. ports of entry, as well as non-targets with the same geographic distribution and host species as C. pomonella. The assay developed here identified all C. pomonella individuals correctly and produced appropriately negative results for all non-target species. These results ensure that the assay provides a rapid and accurate tool for unambiguously identifying C. pomonella among material intercepted at U.S. ports of entry. Since C. pomonella is not actionable, the ability to identify all life stages of C. pomonella conclusively will save time, effort, and money while also directing identification efforts towards species of current quarantine concern.

Helicoverpa armigera is among the most problematic agricultural pests worldwide due to its polyphagy and ability to evolve pesticide resistance. Molecular detection methods for H. armigera have been developed to track its spread, as such methods allow for rapid and accurate differentiation from the native sibling species H. zea. Droplet digital PCR (ddPCR) is a preferred method for bulk screening due to its accuracy and tolerance to PCR inhibitors; however, real-time PCR is less expensive and more widely available in molecular labs. Improvements to DNA extraction yield, purity, and throughput are crucial for real-time PCR assay optimization. Bulk DNA extractions have recently been improved to where real-time PCR sensitivity can equal that of ddPCR, but these new methods require significant time and specialized equipment. In this study, we improve upon previously published bulk DNA extraction methods by reducing bench time and materials. Our results indicate that the addition of caffeine and RNase A improves DNA extraction, resulting in lower Cq values during real-time PCR while reducing the processing time and cost per specimen. Such improvements will enable the use of high throughput screening methods across multiple platforms to improve the probability of detection of H. armigera.

This academic journal is an open access, peer-reviewed, journal. It publishes articles on entomology in Africa.

This study was aimed to investigate the significant wheat yield losses in northern and central Iraq. The cause of these losses was examining the presence of wheat curl mite Aceria tosichella and three viruses vectored by this species – Wheat streak mosaic virus (WSMV), High Plains wheat mosaic virus (HPWMoV), and Triticum mosaic virus (TriMV). Mite specimens were collected from Erbil, Mosul, and Baghdad over three years (2020-2022) and identified using morphological characterization and DNA sequencing of the ITS region. Virus presence was determined using Double Antibody Sandwich-Enzyme-Linked Immunosorbent Assay (DAS-ELISA). Mites were identified conclusively as A. tosichella, providing the first record of this species in Iraq. All three viruses were found to be present, with WSMV having the largest presence as it was detected in 99.56%, then HPWMoV (79.5%) of mite colonies. This is the first record of HPWMoV anywhere in Eurasia besides Ukraine and its widespread presence in Iraq in all three sampled provinces. TriMV was detected only in Erbil. To date this virus has been recorded only in North America and its limited presence in Iraq. The confirmed presence of A. tosichella and three vectored-viruses in Iraq are all new records and critical information for reducing wheat yield losses in this country.

Gibbalaria Brown and Aarvik, new genus, is described to accommodate the following species: G. divergana Brown and Aarvik, new species (TL: South Africa); G. occidentana Brown and Aarvik, new species (TL: South Africa); G. chiloanei Brown and Aarvik, new species (TL: South Africa); G. scabellana Zeller, 1852, new combination (TL: South Africa); G. mabalingwae Razowski, 2008, status revised, new combination (TL: South Africa); G. longiphallus Brown and Aarvik, new species (TL: South Africa); G. bagamoyo (Razowski & Wojtusiak, 2014), new combination (TL: Tanzania); and G. analcis (Razowski, 2015), new combination (TL: Republic of Cameroon). Gibbalaria sistrata (Meyrick, 1911), new combination (TL: South Africa), is synonymized with G. scabellana, new synonymy. Although the male genitalia of Gibbalaria form two moderately divergent groups, the two groups share extremely similar female genitalia, which feature a broad, somewhat cylindrical antrum, followed immediately anterad by a conspicuously elbowed region of the ductus bursae forming a weak diverticulum on the left side, and a signum in the form of a patch of small arrowhead-shaped sclerites, usually with a shallow pocket. Male genitalia morphology shows many similarities with the Neopotamia group (Olethreutini), Afroploce Aarvik in particular. The monophyly of Gibbalaria is supported by the raised, curled, opalescent scales on the forewing in both sexes, which occurs in a few other genera scattered through the subfamily (e.g., Thylacandra Diakonoff in Grapholitini; Astronauta Diakonoff and Cosmopoda Diakonoff in Olethreutini); the angled diverticulum in the ductus bursae in the female genitalia; the subrectangular flange from the lower margin of the valva immediately basal to the cucullus; and the setose, protruding ridge immediate above the basal cavity, which appears to be homologous with the subbasal process of the valva in many members of the Neopotamia group of genera. In addition, Diakonoffiana graziani Razowski, 2015 (TL: Republic of Cameroon) is transferred to Cosmopoda Diakonoff, resulting in C. graziani (Razowski), new combination.

Helicoverpa armigera (Hübner) is one of the most important agricultural pests in the world. This historically Old World species was first reported in Brazil in 2013 and has since spread throughout much of South America and into the Caribbean. Throughout North America, H. armigera surveys are ongoing to detect any incursions. Each trap is capable of capturing hundreds of native Helicoverpa zea (Boddie). The two species cannot be separated without genitalic dissection or molecular methods. A ddPCR assay is currently used to screen large trap samples, but this equipment is relatively uncommon and expensive. Here, we optimized a newly designed assay for accurate and repeatable detection of H. armigera in bulk samples across both ddPCR and less costly, and more common, real-time PCR methods. Improvements over previously designed assays were sought through multiple means. Our results suggest bulk real-time PCR assays can be improved through changes in DNA extraction and purification, so that real-time PCR can be substituted for ddPCR in screening projects. While ddPCR remains a more sensitive method for detection of H. armigera in bulk samples, the improvements in assay design, DNA extraction, and purification presented here also enhance assay performance over previous protocols.

The tomato leafminer, Tuta absoluta (Meyrick), is a highly destructive pest of tomatoes, causing damage to leaves, stalks, buds, and fruits. Native to South America, T. absoluta is now found throughout Europe, South Asia, Africa, parts of Central America, and the Caribbean. Adults are small, with a wingspan of approximately one cm and lack distinctive markings, making morphological identification difficult. Larvae are also difficult to identify and resemble those of many other gelechiids. Due to the extensive time spent and expertise required for morphological identification, and the imminent threat to the North American tomato crop, we have developed a rapid molecular test for discriminating individual specimens of T. absoluta using a probe-based real-time polymerase chain reaction (PCR) assay. The assay is able to quickly distinguish T. absoluta from similar-sized moth specimens that are attracted to T. absoluta pheromone lures in the United States and is also able to identify larvae of T. absoluta. Decreased identification time for this critical pest will lead to more rapid identification at ports of entry and allow for more efficient trap screening for domestic monitoring programs.

Heliothine larvae, especially early instars, are difficult to identify, and determinations sometimes rely on indirect information such as origin and host data. The introduction of Helicoverpa armigera (Hübner) into the New World has undermined the reliability of host and origin data to identify intercepted Helicoverpa larvae, and suspect Heliothinae/Helicoverpa larvae intercepted at U.S. ports of entry are now screened for H. armigera and Helicoverpa zea (Boddie) using molecular methods. Here, we analyze heliothine larvae intercepted during 2014-2106 to identify nontargets and evaluate morphological characters traditionally used to separate taxa. In total, nine species were identified, with Chloridea virescens (Fabricius) making up the bulk of interception records. The majority of heliothine suspects originate from Mexico and Peru on pigeon pea, chickpea, tomatillo, pea, and corn. Helicoverpa armigera is commonly intercepted from Peru on pea. Chloridea virescens is recorded from every country where interceptions were identified for this study except Guatemala and is found on multiple hosts. Identification issues and specific host/origin associations are discussed in detail.