Impact of irrigation and micronutrient treatments on insect herbivore population dynamics in soybean

Authors: DEBNATH, RAHUL - University Of Arkansas; George, Justin; Bhandari, Ammar; KARIYAT, RUPESH - University Of Arkansas; Reddy, Gadi; Glover, James; Kharel, Tulsi; Reddy, Krishna

Submitted to: Frontiers in Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2025
Publication Date: 10/3/2025
Citation: Debnath, R., George, J., Bhandari, A.B., Kariyat, R., Reddy, G.V.P, Glover, J.P., Kharel, T.P., Reddy, K.N. 2025. Impact of irrigation and micronutrient treatments on insect herbivore population dynamics in soybean.. Frontiers in Agronomy. 7(1571675):1-13. https://doi.org/10.3389/fagro.2025.1571675.
DOI: https://doi.org/10.3389/fagro.2025.1571675

Interpretive Summary: Soybean (Glycine max (L.) Merr.) is the sixth most commonly grown agricultural crop worldwide. Effective irrigation and fertilizer regimes have been found to affect pest populations in different agroecosystems. However, their interactive effects on herbivore incidence are less understood. This study reports the abundance and diversity of insect pests encountered on soybeans throughout their vegetative and reproductive growth stages under varying irrigation and micronutrient treatments. The effects of irrigation and micronutrients on total insect pests and major hemipteran, lepidopteran, and stink bug species complexes were evaluated. We compared total insect pests and major pest population densities in irrigated and rainfed conditions. Afterward, we evaluated how insect pest frequency on soybean was affected by the foliar application of different micronutrients, such as ferrous (Fe), zinc (Zn), and Fe + Zn, compared to the control (no nutrient application), in a two-year field experiment during the 2023-2024 growing seasons. Results showed that insect pest populations were more abundant in control plots than treated plots with the combined micronutrients (Fe + Zn). However, compared to rainfed treatment, irrigated soybean attracted significantly more insect herbivores. Furthermore, micronutrients had no significant impact on reducing pest pressure when applied in conjunction with irrigation. These findings indicated that micronutrients and irrigation can have complex effects on plant-insect interactions and that the specific effects may depend on specific nutrients, crop species, and water availability.

Technical Abstract: Soybean production is substantially affected by insect pests, necessitating the implementation of appropriate management strategies. Effective irrigation and fertilizer regimes have been found to affect pest populations in agroecosystems. However, their interactive effects on herbivore incidence are less understood. This study reports the abundance and diversity of insect pests encountered on soybeans throughout their vegetative and reproductive growth stages under varying irrigation and micronutrient treatments. We evaluated the effects of irrigation and micronutrients on total insect pests, and major hemipteran, lepidopteran, and stink bug species complexes. First, we compared total insect pests and significant pest population densities in irrigated and rainfed conditions. Afterward, we evaluated how insect pest frequency on soybean was affected by the foliar application of different micronutrients, such as ferrous (Fe), zinc (Zn), and Fe + Zn, compared with the control (no nutrient application), in a two-year field experiment during the 2023-2024 growing seasons. Results showed that insect pest populations were more abundant in control plots than in plots treated with the combined micronutrients (Fe + Zn). However, compared to rainfed treatment, irrigated soybean attracted significantly more insect herbivores. Furthermore, micronutrients had no significant impact on reducing pest pressure when applied in conjunction with irrigation. These findings indicated that micronutrients and irrigation can have complex effects on plant-insect interactions, and the specific effects may depend on particular nutrients, crop species, and water availability. These findings also provide evidence that combining ferrous and zinc foliar applications in soybean fields can efficiently decrease insect pest populations independent of irrigation.