This Is AuburnElectronic Theses and Dissertations

An Evaluation of Plant Growth Regulator, Starter Fertilizer, and Nematicide Inputs to Promote Soybean Growth and Support Greater Yield in Meloidogyne incognita Infested Fields in Alabama




Dodge, Daniel

Type of Degree

Master's Thesis


Entomology and Plant Pathology


The Southern Root-knot nematode, Meloidogyne incognita, is a significant root parasite that poses a threat to sustainable production of many crops, including soybean. Management strategies for this nematode include: crop rotation, fumigation, and utilizing a resistant variety. An alternative management strategy implementing plant growth promoting inputs was proposed herein in order to provide a profitable and sustainable solution to diminished soybean yield due to root-knot nematode. The direct inputs of a nematicide, plant growth regulator, and starter fertilizer at planting will effectively reduce nematode population density and increase yield by supporting greater plant biomass in the vegetative stages of growth. This hypothesis was evaluated by: 1) greenhouse trials of starter fertilizer, plant growth regulator and nematicide inputs to determine their effect on soybean plant biomass and root-knot nematode population density; 2) inputs based on greenhouse performance were evaluated in field trials in two locations infested with M. incognita; 3) the effect and efficacy of nematicide treatment was further characterized on five soybean varieties planted in four root-knot nematode infested locations in Alabama. In greenhouse trials, starter fertilizer treatments increased plant fresh shoot weight in the first 45 days of soybean development and had no impact on M. incognita population density. Plant growth regulator treatments stimulated root and shoot growth, increasing total plant biomass within the first 45 days of soybean growth. The nematicide treatments significantly reduced nematode population density by as much as 93% at 30 days after planting. Combining nematicide seed treatment and starter fertilizer plus plant growth regulator treatments applied as in-furrow sprays did not significantly increase yield or reduce nematode population at either field location. However the combination of Avicta nematicide and the starter fertilizer treatment iii significantly reduced nematode population density at one location, and significantly increased yield by 20% over the control at the other site. In variety trials across four locations, the effect of the Avicta nematicide treatment varied by variety; a root-knot susceptible variety, Progeny 5333RY, responded significantly better to the nematicide than all other varieties tested. Avicta increased yield of Progeny 5333RY at two locations by 39% and 48%, respectively. The Avicta seed treatment did not significantly increase yield of a root-knot resistant variety (Mycogen 5N522R2) at any location, however the root-knot resistant variety produced the numerically highest yields at the location with the greatest nematode population density. Ultimately, the system of nematode management using inputs must be evaluated based on soybean variety, location, and nematode population density.