Red harvester ants cover crop seed preferences in south Texas

Harvester ants, known to selectively forage seeds, impact plant community composition as well as newly sowed seeds in agricultural fields. Little to no studies have been conducted to investigate ant cover crop preferences or biological seed predation. This study aims to determine ant preferences for commonly used cover crop seeds and predation deterrence by biological pesticides in South Texas. To determine this, we conducted a cafeteria study of 10 cover crop seeds using 37 ant colonies with no prior exposure to the selected seeds. A Petri dish containing the seeds was placed within a wire cage 2m from the entrance of each colony along a foraging trail. The ants foraged for 24 hours, with the seed counts conducted every 1, 2, 4, and 24 hours. Post initial study, the most preferred seeds were used in a follow-up cafeteria study to evaluate the effect of the seed inoculation on preference. During the preliminary trials, ants had noticeable preferences for some seeds over others. Of the seed pool, wheatgrass and oats were the first to be removed entirely, with vetch seeds often remaining after the trial. Seed inoculation trials yielded no significant difference between preference of inoculated and non-inoculated seeds. Vinegar trials have just begun, but interesting observations during the experiment have been made to align with our alternative hypothesis. Using results from our study, we can make management recommendations to growers to limit risks by using biological alternatives and less favorable cover crops to reduce harvester ant cover crop seed predation.