Harvester ants (Messor galla Forel) defied various control strategies. Two field experiments were conducted to evaluate the effects of Spent Engine-Oil and other nature-based materials on their emergence in Maiduguri, Borno State of Nigeria. The treatments evaluated are spot application of spent engine-oil and some natural materials in experiment 1 and individual and equal mixture of Pure Neem Seed Kernel oil and Spent Engine-oil in experiment 2. Spot application of permethrin served as control. Experiment 1 results shows no significant difference (p > 0.05) between permethrin and spent engine-oil (which was the most effective treatment). While neem seed oil was significantly (p < 0.01) more effective than the untreated control, the result on the 28th day after application showed no significant difference (p > 0.05) in the population index of ants that emerged from nests treated with aqueous neem seed extract, salt/potash solution and extract of Eugenia aromatic fruit from those of the control. Experiment 2 result showed no significant difference (p < 0.05) between Permethrin, Spent Engine-oil, Neem Seed Kernel Oil and, equal mixture by volume of Pure Neem Seed Kernel Oil and Spent Engine-Oil in controlling the emergence of the ants. These were however, significantly different (p > 0.05) from the untreated control. While the result shows no significant difference between the treatments, it was observed that equal mixture of Spent Engine-oil and Neem Seed Kernel Oil was most effective, followed by Spent Engine-Oil, Permethrin and Neem Seed Kernel Oil, in that order.