Population monitoring and morphometrics of Helicoverpa armigera (Hübner), Helicoverpa zea (Boddie), and their hybrids (Lepidoptera: Noctuidae) in Puerto Rico

Abstract

Helicoverpa armigera and H. zea are serious pests in many crops; H. armigera was detected in 2014 in Puerto Rico. In the period February 2016 to January 2017, 112 traps with a lure for H. armigera were installed in Guanica, Santa Isabel, Guayama, Isabela, Lajas, Juana Diaz, Añasco, Aguadilla, Sabana Grande, Mayagüez, San Juan, Gurabo, Villalba, and Jayuya. The two lepidopterans were identified with morphology. Insects identified as H. armigera with morphology were corroborated with molecular tools. Comparisons of Helicoverpa populations between localities and among crops in each locality were done with non-parametric tests. Data of moth capture by a bell pepper farm in Santa Isabel was used to analyze relationship with weather variables. A total of 5,122 Helicoverpa specimens were captured, four were identified as H. armigera, and the remaining were H. zea. In San Juan, Gurabo, Villalba, and Jayuya any Helicoverpa was captured. The highest H. zea populations were in the period February to May. Santa Isabel had the highest H. zea populations. In the comparisons among crops, only okra in Guanica had higher H. zea populations over sunflower. In Santa Isabel, populations of H. zea had a significantly negative relationship with maximum temperature, and precipitation depending on the period analyzed. F1 hybrids between H. armigera and H. zea were obtained at the Center for Excellence in Quarantine and Invasive Species. For morphological comparison, the following variables were analyzed: number of lobes, number of cornuti, length of valves, length of aedeagus, and depth in the posterior excavation in the eighth sternite. The species H. armigera is characterized by the presence of one lobe while F1 hybrids and H. zea showed three lobes. Statistical analysis with the other quantitative variables showed that H. zea had the biggest structures or more cornuti, followed by the hybrids, and finally H. armigera with the smallest size of structures and a minor number of cornuti. The principal components analysis of quantitative variables showed that F1 hybrids were closer to H. zea. Currently, we can infer that using only morphology is very difficult to identify one Helicoverpa as a hybrid or distinguish a true hybrid from a parental species.