Date of Graduation
Master of Science in Entomology (MS)
Gus Lorenz III
Second Committee Member
Third Committee Member
Fourth Committee Member
Fall Armyworm, Spodoptera frugiperda, Mechanical Defoliation, Rice
The fall armyworm, Spodoptera frugiperda (J.E. Smith), (FAW) is a serious pests of many crops, and can be observed feeding throughout the entire growing season on rice, Oryza sativa, (L.). A new defoliation based threshold would help rice growers and consultants make more economically sound decisions for FAW. Work from this thesis focuses on determining the amount of damage caused by FAW feeding at different growth stages and effective insecticide seed treatments for controlling this pest.
Field plots were mechanically defoliated to determine grain yield loss across multiple growth stages and defoliation percentages. Results indicated that defoliation in late vegetative and early reproductive growth stages cause appreciable levels of yield loss. Yield loss was associated with large levels of growth recovery, which correlated with yield loss especially in late vegetative and early reproductive growth stages. Defoliating only the flag leaf was found to cause no significant yield loss, even when 100% removed.
Greenhouse studies were conducted to evaluate damage from FAW larval feeding and manual defoliation in a controlled environment. When rice was 100% mechanically defoliated at the 2- to 3- leaf and 2nd- to 3rd tiller growth stages, a yield reduction was observed compared to the untreated control. Larval infestations reached appreciable levels of defoliation only at the 2- to 3- leaf growth stage, where yield loss was observed to be similar to mechanical defoliation.
Choice bioassays were conducted to determine feeding preference from FAW once panicle emergence. Choice bioassays exhibited an increased percent of blank kernels and decrease in yield when FAW only had rice panicles to feed on. Yield reductions were not observed when FAW had the option to feed on the panicle or the flag leaf, but did have a significant amount of blanked kernels. When only the flag leaf was available to feed on, no differences were observed.
Greenhouse studies were conducted to determine effective insecticide seed treatments for control of FAW. Two insecticide seed treatments (cyantraniliprole and chlorantraniliprole) have the potential to effectively control the FAW. Cyantraniliprole controlled FAW for 49 days after planting, while chlorantraniliprole was still active for FAW at 73 days after planting. Neonicotinoid seed treatments thiamethoxam and clothianidin were not found to be effective for controlling FAW larvae.
These studies provide needed background on the potential impact and control of FAW, and should serve to provide a framework for more effective and economic control of FAW in Arkansas rice.
McCullars, L. D. (2019). The Impact of Fall Armyworm, Spodoptera frugiperda (J.E. Smith), Feeding and Mechanical Defoliation on Growth and Yield of Rice, Oryza sativa (L.). Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/3262