Simulated corn earworm, Helicoverpa zea, injury in an indeterminate soybean cultivar at various growth stages under non-irrigated conditions in the southern United States

Authors: COELHO, MARIANE - University Of São Paulo; COOK, DONALD R. - Mississippi State University; CATCHOT, ANGUS L. - Mississippi State University; GORE, JEFF - Mississippi State University; LOURENÇÃO, ANDRÉ L. - University Of São Paulo; BALDIN, EDSON L. L. - University Of São Paulo

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2020
Publication Date: 9/23/2020
Citation: Coelho, M., Cook, D., Catchot, A., Gore, J., Lourenção, A., Baldin, E. 2020. Simulated corn earworm, Helicoverpa zea, injury in an indeterminate soybean cultivar at various growth stages under non-irrigated conditions in the southern United States. Agronomy. 10(10):1450. https://doi.org/10.3390/agronomy10101450.
DOI: https://doi.org/10.3390/agronomy10101450

Interpretive Summary: Soybean represents one of the world’s main crops when considering the oil and protein content. Several insect pests, which feed at different stages of development and cause damage to leaves, stems, roots, and pods, are associated with soybean. Corn earworm, also known as New World bollworm and corn earworm, is an important insect pest, being able to damage several crops of economic interest. The objective of this work was to evaluate the impact of flower and pod removal on the maturation and yield of the soybean plant, in order to simulate the damage of corn earworm in different reproductive stages of development under non-irrigated conditions that may limit yield potential. The results from this study demonstrated that under adequate to optimal growing conditions recommendations for managing fruit-feeding insects should be similar for the non-irrigated soybean. Soybeans planted before and at the end of the optimal planting, period responded similarly to fruit loss as soybeans planted at an optimum time in other studies. However, these results may not apply to extremely late-planted soybeans.

Technical Abstract: Soybean is considered one of the most valuable crops in the United States of America. Helicoverpa zea (Boddie) is among several insect pests which are associated with soybean, damaging leaves when infestations occur during the vegetative stages, and flowers and pods during the reproductive stages, which can directly impact yield. Artificial fruit removal is a method used to understand insect damage and to adjust action levels for control. The objective of this work was to evaluate the impact of five levels of fruit removal (0%, 25%, 50%, 75% and 100%) at four stages (R2, R3, R4 and R5) on maturity and yield of soybean. These methods were used to simulate H. zea damage under controlled conditions in non-irrigated environments, during 2016 and 2017. There was a significant interaction between fruit removal timing and fruit removal level for the percentage of non-senesced main stems and abscised leaves. For soybean yield, there was no significant interaction between fruit removal timing and fruit removal level. Plots that received fruit removal treatments at R5 had significantly lower soybean yields compared to plots that received damage at other growth stages and the nontreated control. Plots with 100% fruit removal had significantly lower yields compared to plots that received any of the other fruit removal treatments. These data demonstrate that indeterminate midmaturity group IV soybeans that are commonly grown in the midsouthern region of the United States may be able to compensate for even severe levels of fruit loss early during the reproductive portion of the growing season if favorable growing conditions occur.