Improving risk assessment of noctuid pests at North American ports and farms by differentiating egg morphology

Authors: Blanco, Carlos; ROSARIO-LEBRON, ARMANDO - Animal And Plant Health Inspection Service (APHIS); O'DONNELL, CHERYLE - Animal And Plant Health Inspection Service (APHIS); Portilla, Maribel; GULLBRONSON, CONNOR - Oak Ridge Institute For Science And Education (ORISE); Mowery, Joseph; SMITH-PARDO, ALLAN - Animal And Plant Health Inspection Service (APHIS); STOCKS, IAN - Animal And Plant Health Inspection Service (APHIS); NADEL, HANNAH - Animal And Plant Health Inspection Service (APHIS); TROZZO, LARA - Animal And Plant Health Inspection Service (APHIS); HASLEM, PATRICK - Animal And Plant Health Inspection Service (APHIS); YOUNG, JAMES - Animal And Plant Health Inspection Service (APHIS); DOWNES, SHARON - Commonwealth Scientific And Industrial Research Organisation (CSIRO); PARKER, TRACEY - Commonwealth Scientific And Industrial Research Organisation (CSIRO); WALSH, TOM - Commonwealth Scientific And Industrial Research Organisation (CSIRO); TAY, WEE TEK - Commonwealth Scientific And Industrial Research Organisation (CSIRO); OPPENHEIM, SARA - American Museum Of Natural History

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2019
Publication Date: 6/26/2019
Citation: Blanco, C.A., Rosario-Lebron, A., O'Donnell, C.A., Portilla, M., Gullbronson, C., Mowery, J.D., Smith-Pardo, A.H., Stocks, I., Nadel, H., Trozzo, L.R., Haslem, P.S., Young, J.D., Downes, S., Parker, T., Walsh, T., Tay, W., Oppenheim, S. 2019. Improving risk assessment of noctuid pests at North American ports and farms by differentiating egg morphology. Annals of the Entomological Society of America. saz029:1-8. https://doi.org/10.1093/aesa/saz029.
DOI: https://doi.org/10.1093/aesa/saz029

Interpretive Summary: Agriculturally damaging Heliothine moth eggs are commonly found on agricultural commodities and ornamental plants. One invasive moth that is damaging is the tobacco budworm (Chloridea virescens). Recently, however, increased numbers of interceptions of plants harboring the old world bollworm moth (Helicoverpa armigera) have occurred at various ports of entry into the United States due to the invasion of this pest in South America. The ability to distinguish the eggs of these moths is a critical component necessary for proper risk assessments by quarantine authorities, taxonomists, and crop consultants. We have developed a simple, rapid, inexpensive and accurate technique to identify the presence of multiple holes on the primary ribs on eggs of the tobacco budworm. These holes are not present in that specific region or are rare or smaller in size on eggs of other similar moths. These characteristic holes on the eggs of the tobacco budworm were easily visible at 40x magnification, while no such holes were found on the eggs of similar species when analyzed using optical, electron, and confocal microscopy. These characteristic holes and the microscopy technique described herein would eliminate the uncertainty of distinguishing tobacco budworm eggs from other species with very little equipment, at low cost, and with minimal personnel training. The distinguishing characteristic on the eggs of these moths along with the microscopy techniques provided will assist researchers, quarantine authorities, taxonomists, and crop consultants in federal and state governments and universities wanting to control the spread of devastating, invasive moths.

Technical Abstract: Heliothine eggs are commonly found on agricultural commodities and ornamental plants transported through domestic and international commerce. Tobacco budworm (Chloridea (Heliothis) virescens (F.)), C. subflexa (Guenee), and the corn earworm (Helicoverpa zea (Boddie)), are indigenous pests of the American continent. Recently, interceptions of the old world bollworm (Helicoverpa armigera (Hubner)) have increased at various ports of entry into the United States due to the invasion of this pest in South America, adding to the complexity and importance of decision-making at plant inspection stations. The ability to distinguish C. virescens eggs from C. subflexa and Helicoverpa species is a critical component for risk assessments by quarantine authorities, taxonomists, and crop consultants. We developed a simple, rapid (~60 minutes), inexpensive ($0.06 per sample), and accurate (100% reliability) technique to distinguish among these species based on the presence, number and/or size of aeropyle holes on the primary ribs of eggs, near the micropylar rosette. In this location aeropyles in 213 fresh and ethanol-preserved C. virescens eggs were easily visible at 40x magnification, once treated with Hoyer’s solution. One or two aeropyles were found in a few primary ribs of 36 C. subflexa samples, while no aeropyles were found in 411 H. zea or in 269 H. armigera eggs analyzed using optical, electron and confocal microscopy. Therefore, we conclude that multiple aeropyle holes are present for C. virescens but absent for H. zea or H. armigera, and are rare and/or smaller in C. subflexa. This technique would eliminate the uncertainty of distinguishing C. virescens eggs from those of the H. zea, H. armigera and C. subflexa which are all potentially encountered during surveillance at US borders of goods that are traded globally.