Masters Theses

Date of Award

8-1971

Degree Type

Thesis

Degree Name

Master of Science

Major

Agronomy

Major Professor

John H. Reynolds

Committee Members

Gary M. Lessman, Stelmon Bennett

Abstract

Three alfalfa weevil (Hypera postica Gyllenhal) experiments were conducted at the Plant Science Farm, Knoxville, Tennessee during 1970 and 1971. Treatments applied to the alfalfa (Medicago sativa L.) were different insecticides, varieties, and nitrogen fertilizers. The effects measured were dry matter production, protein-nitrogen, nitrate-nitrogen, and glucose concentration. Twelve combinations of two factors were incorporated into Experiment A. The alfalfa was sprayed either not at all, once, or twice with Alfatox at 1.15 1/ha. Four alfalfa varieties were included as split-plot treatments. Team, Weevlchek, Saranac, and Buffalo were the alfalfa varieties. Team produced the highest yield of the four varieties and Buffalo produced the lowest. Yields ranged from 7.09 to 8.73 metric tons/ha. Only one spraying of Alfatox was needed to control feeding under mild weevil infestation (1970) while two sprayings were needed under heavy infestation (1971). Protein-nitrogen concentrations ranged from 3.14 to 3.28 percent. Saranac had the highest concentration, but Weevlchek and Team were also significantly higher than Buffalo. Sprays did not affect protein-nitrogen concentration in 1970. Glucose and nitrate-nitrogen were not affected by spraying level or varieties. Larval feeding damage ranged from severe to slight. Damage was independent of varieties, but Spray 1 and Spray 2 were significantly better than Spray 0. Team had the lowest damage value and Buffalo the highest value. Experiment B was an evaluation of 8 chemical treatments and a check. Damage values ranged from 9 to 1.5. Twenty-five percent methyl parathion plus commercial 30 percent nitrogen solution gave the best protection followed closely by 25 percent methyl parathion. Commercial 30 percent nitrogen solution increased growth but had a damage value of 6.0. All other treatments offered no protection. Five nitrogen sources were used as main treatments in Experiment C. Subsidiary plots were solid and liquid application of the nitrogen sources. Nitrogen rate was 56 kg/ha. Forage dry matter yields ranged from 214 to 1533 kg/ha in the spring regrowth. Liquid forms were applied at the same rate except in 1.9 1 water. Check plots produced the highest yield, but solid applications produced almost twice the amount of forage that liquid plots produced. Liquid applications at this rate caused severe damage to the plants. Plots receiving urea produced the highest yield while ammonium nitrate plots produced the least. Nitrate-nitrogen concentrations ranged from .005 to .020. Solid sodium nitrate produced the highest concentration, and check plots pro-duced the lowest. Solid application of nitrogen sources increased nitrate-nitrogen concentrations in plants, but the concentration of nitrates was not enough to deter weevil feeding which was severe. Treatments receiving solid applications averaged .014 percent while check plots averaged .006 percent. Liquid applications caused severe chemical damage to leaves and stems. Glucose concentration ranged from 2.24 to 3.02 percent, but was not affected by nitrogen source or form of application.

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