A cost-effective approach for combining nematicides, starter fertilizers, and plant growth regulators in order to create a sustainable management system for the southern root-knot nematode, Meloidogyne incognita, in corn
Type of DegreeMaster's Thesis
Entomology and Plant Pathology
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The southern root-knot nematode, Meloidogyne incognita, is one of the most problematic plant-parasitic nematodes in the southeastern United States. Significant yield reductions can occur for some of the most economically important crops in this area such as cotton, corn, and soybean. Literature suggests that a 30% reduction in yield can occur on corn due to this nematode. No resistant corn hybrids are available today, and cultural management techniques can be difficult to implement. We propose an integrated system combining nematicides with direct yield and growth promoting inputs such as pop-up and starter fertilizers and plant growth regulators in order to create a sustainable, profitable system. We evaluated this by first screening each individual product in a greenhouse setting to select the best input from each category. These inputs were integrated into field trials to assess their ability to reduce nematode population density, increase early growth, and thus increase yield. In greenhouse trials, Counter® 20G was the most effective nematicide reducing root-knot population density by 85%, which led to an 18% increase in plant biomass. Most in-furrow starter fertilizers (pop-ups) increased plant biomass at 45 days after planting (DAP) without increasing root-knot population density. The plant growth regulator, Ascend®, in-furrow application (IFS) was the only treatment that significantly increased plant biomass (23%) at 45 DAP. Field trials were planted over two growing seasons (2016-2017) at two different locations: a field with a very high root-knot population density, Plant Breeding Unit (PBU) in Tallassee, AL, and a field with a moderate population density, Brewton Agricultural Research Unit (BARU) in Brewton, AL. In the second season, a 5x5 (5 cm below; 5 cm beside the planting furrow) application of starter fertilizer was evaluated along with the previous pop-up fertilizers. For the 2016 growing season, the nematicide, growth regulator, and pop-up fertilizer combination significantly increased plant height and plant biomass at both locations; however, only at BARU did a significant increase in yield occur, proving that the integrated system has a greater effect on yield at a lower population density. At BARU, the net return on yield for the three input system was $113/ha, whereas at PBU the cost of application did not compensate for the gain in yield. Counter®20G + Ascend® IFS without pop-up fertilizers was the only combination to provide a positive return on yield at both locations ($2.61/ha at PBU and $54.98/ha at BARU). For the 2017 growing season multiple inputs increased early plant growth, but because of unforeseen environmental conditions, their effect on yield could not be accurately portrayed. All input combinations including the 5x5 starter fertilizer increased plant biomass by an average of 77% compared to the control at PBU, which was a 47% increase compared to pop-up fertilizers. Counter®20G + starter fertilizer provided the greatest increase (112%) at that location. Many input combinations increased biomass at BARU; however, pop-up fertilizer combinations averaged a 4% higher increase in biomass than the starter fertilizer compared to the control. Our system of combining a nematicide with pop-up or starter fertilizers and/or plant growth regulators shows promise in efficiently managing plant-parasitic nematodes in corn; however, the economic benefits were best under lower root-knot nematode population density.