Small increases of zinc fertilizer boost maize leaf nitrogen, increasing fall armyworm (Spodoptera frugiperda) performance in the greenhouse, but effect does not translate to the field
Nutrients, such as zinc, determine plants’ abilities to respond to insect attack; however, the effect of zinc on herbivores is poorly characterized. We hypothesized that because zinc deficiency would compromise plant physiology, herbivores would perform best at low concentrations of zinc, while at intermediate concentrations of zinc, plants would have sufficient nutrients to mount defense. We tested this hypothesis in a greenhouse experiment where we explored the interaction of maize (Zea mays L.) and two noctuid caterpillars, black cutworm (Agrotis ipsilon Hufnagel) and fall armyworm (Spodoptera frugiperda Smith), in which we evaluated the effects of a normal range of zinc in Pennsylvania soils (0 – 11.7 ppm). To determine if zinc affected maize pests in the field, we investigated the effect of zinc fertilization on early season damage by resident herbivores, performance of fall armyworm on excised leaf tissue, and yield. In the greenhouse, we found zinc increased uptake of other nutrients, particularly nitrogen, and fertilizing with just 2.5 ppm zinc maximized maize plant growth. Fall armyworm performance marginally increased logarithmically with zinc fertilization. In addition, while caterpillars were not directly affected by zinc concentrations in leaves, fall armyworm caterpillars responded to leaf nitrogen. Fertilizing with zinc, therefore, may make plants more susceptible to herbivores because it increases protein concentrations in leaf tissue. Fertilizing with zinc in the field, however, had a much smaller effect on zinc uptake and nitrogen concentrations. While nitrogen still affected fall armyworm performance, nitrogen was not directly related to zinc dose. Furthermore, zinc treatments did not affect maize yield. We conclude that a small amount of zinc maximizes maize growth and subsequent increases in fertility may cause plants to become more susceptible to herbivore damage.
|Small increases of zinc fertilizer boost maize leaf nitrogen, increasing fall armyworm (Spodoptera frugiperda) performance in the greenhouse, but effect does not translate to the field
|CC0 1.0 (Public Domain Dedication)
|August 14, 2020
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