Sean Pelham Boric Acid and Ant Repellency April 13th 2005 Boric Acids Activity as a Possible Repellant to the Argentine Ant Sean Pelham Abstract With a greater emphasis being placed on organic farming as a means of production more focus needs to be on chemicals such as boric acid and their potential as organic pesticides This work aims to find the concentration at which boric acid may act as a repellant to Argentine Ants ultimately determining how boric acid baits can be used as a means of ant population control rather than repellants Two separate studies in Napa used different approaches to analyze ant repellency The first involved a series of six bait tubes each containing concentrations of boric acid from 0 0 to 1 0 in 25 sucrose solution placed under their own vines to ensure activity from individual colonies and testing the general ant repellency of specific concentrations of boric acid In the second study all six individual concentrations were tied together and wrapped around the vine Each belt had one colony that could choose from the six different boric acid concentrations gauging the ants preference for one concentration of boric acid The results of first portion of the study show that generally an increase in the concentration of boric acid leads to fewer ant visits for the bait stations with high boric acid concentration which means that ants could ultimately be avoiding toxic baits entirely at concentrations of 0 5 and higher p 1 Sean Pelham Boric Acid and Ant Repellency April 13th 2005 Introduction Although organic farming has grown in popularity in the eyes of the public few people realize that it recognizes the use of certain chemicals as organic pesticides Amongst these pesticides boric acid has been shown to be particularly effective in the control of ants which take care of phloem feeding insect pests such as scales and mealybugs The ants form mutually beneficial symbiotic relationships with such insects harvesting the honeydew that these pests create as a waste product all while protecting the pests from natural predators and parasitoids Siebert 1992 These parasitoids would have otherwise been helpful to agriculturists as they implant their eggs into their pest host with the developing larvae killing the host once it has reached maturity V lkl 1994 With the ant population reduced however farmers can successfully implement biological control measures to keep pest populations below a certain economic threshold The Argentine ant is an invasive species of ant that is found all over the state of California and has caused various problems in urban agricultural as well as natural ecosystems It can easily establish itself within disturbed environments such as agricultural fields and can quickly adapt to new ones in a relatively short period of time For Napa California the control of these insects is particularly important as the Argentine ant tends and protects a persistent pest in vineyards the mealybug Vega and Rust 2001 As a phloem feeding insect the honeydew it exuded by the mealybug as a byproduct of its feeding has the tendency to cover the vine and allow an adequate food source and substrate upon which fungi may thrive rendering a particular bunch useless for harvest Kent Daane This honeydew also attracts the Argentine Ant For those organic vineyards that have such problems and resort to organic pesticides such as boric acid farmers need to know whether or not boric acid itself is actually effective in reducing Argentine ant populations or is ultimately driving them away to feed on the honeydew provided by certain pest insects When boric acid is applied it is generally done so mixed in with sugar water If the ants can distinguish between the taste of just sugar water and sugar water with boric acid they may bypass bait stations entirely rendering the baits useless In this case the ants opt to continue harvesting honeydew from the existing mealybugs or scales Thus an ideal situation would be for the boric acid baits to have a high enough concentration as to cause mortality in ant p 2 Sean Pelham Boric Acid and Ant Repellency April 13th 2005 populations but not so much that they can distinguish differences in taste between an effective concentration and just sugar water The primary issue I plan to explore is to find the concentration at which boric acid in sugar water does not repel ants Based upon previous experience the suggested concentration of 0 5 boric acid in 25 sucrose solution Klotz 2000 is one that ultimately repels ants preventing boric acid baits from being truly effective In investigating this I conducted two tests The first portion was a trial in general ant repellency while the second tests for feeding preference within ants among different concentrations of boric acid Work in this area has been conducted before Klotz 1998 Klotz et al 2000 but the extent to which I wish to explore the issue is slightly larger Previous studies were somewhat limited in terms of their sample size and with higher thresholds of boric acid concentrations For instance the lowest concentration within Klotz s study was 0 5 boric acid in 25 sucrose solution and he ultimately determined that this concentration was adequate for attracting and killing Argentine ants I believe that lower concentrations may prove to be even more effective at attracting ants and that suggested concentrations of 0 5 to 1 0 may be too high In this study a lower range of boric acid concentrations were used with more baits released into the field Methods The study was conducted in south Napa California at Sutter Home Vineyards There were two major portions to the study The first involved a general ant repellency test while the second involved a basic ant preference test Both essentially investigated the same question at what concentration does boric acid act as a repellent to Argentine Ants But each portion of the experiment differed in how they generate their respective results The general repellency test was split up into 30 experimental blocks Each block consisted of six different concentrations of boric acid 0 0 0 1 0 2 0 3 0 5 and 1 0 in 25 sucrose solution in 50ml tubes Because I am only concerned with measuring the difference from the beginning to the end of when the ants feed the actual amount of liquid within each tube can vary Each tube was placed 5 vines from one another five vines equals roughly twenty feet while each experimental block was spaced twenty p 3 Sean Pelham Boric Acid and Ant
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