Sean Pelham Boric Acid and Ant Repellency April 13th, 2005p.1Boric Acids Activity as a Possible Repellant to the Argentine AntSean PelhamAbstract With a greater emphasis being placed on organic farming as a means ofproduction, more focus needs to be on chemicals such as boric acid and their potential asorganic pesticides. This work aims to find the concentration at which boric acid may actas a repellant to Argentine Ants, ultimately determining how boric acid baits can be usedas a means of ant population control, rather than repellants. Two separate studies in Napaused different approaches to analyze ant repellency. The first involved a series of six baittubes each containing concentrations of boric acid from 0.0 to 1.0% in 25% sucrosesolution, placed under their own vines, to ensure activity from individual colonies, andtesting the general ant repellency of specific concentrations of boric acid. In the secondstudy, 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 acidconcentrations, gauging the ants’ preference for one concentration of boric acid. Theresults of first portion of the study show that generally, an increase in the concentration ofboric 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 concentrationsof 0.5 and higher.Sean Pelham Boric Acid and Ant Repellency April 13th, 2005p.2IntroductionAlthough organic farming has grown in popularity in the eyes of the public, fewpeople 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 thecontrol of ants, which take care of phloem feeding insect pests such as scales andmealybugs. The ants form mutually beneficial symbiotic relationships with such insects,harvesting the honeydew that these pests create as a waste product, all while protectingthe pests from natural predators and parasitoids (Siebert, 1992). These parasitoids wouldhave otherwise been helpful to agriculturists as they implant their eggs into their pesthost, with the developing larvae killing the host once it has reached maturity (Völkl,1994). With the ant population reduced however, farmers can successfully implementbiological 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 ofCalifornia, and has caused various problems in urban, agricultural, as well as naturalecosystems. It can easily establish itself within disturbed environments (such asagricultural 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 theArgentine ant tends and protects a persistent pest in vineyards, the mealybug (Vega andRust, 2001). As a phloem-feeding insect, the honeydew it exuded by the mealybug as abyproduct of its feeding has the tendency to cover the vine and allow an adequate foodsource and substrate upon which fungi may thrive, rendering a particular bunch uselessfor harvest (Kent Daane). This honeydew also attracts the Argentine Ant.For those organic vineyards that have such problems and resort to organic pesticidessuch as boric acid, farmers need to know whether or not boric acid itself is actuallyeffective in reducing Argentine ant populations, or is ultimately driving them away tofeed on the honeydew provided by certain pest insects. When boric acid is applied, it isgenerally done so mixed in with sugar water. If the ants can distinguish between the tasteof just sugar water and sugar water with boric acid, they may bypass bait stationsentirely, rendering the baits useless. In this case, the ants opt to continue harvestinghoneydew from the existing mealybugs or scales. Thus, an ideal situation would be forthe boric acid baits to have a high enough concentration as to cause mortality in antSean Pelham Boric Acid and Ant Repellency April 13th, 2005p.3populations, but not so much that they can distinguish differences in taste between aneffective concentration and just sugar water.The primary issue I plan to explore is to find the concentration at which boric acid insugar water does not repel ants. Based upon previous experience, the suggestedconcentration of 0.5% boric acid in 25% sucrose solution (Klotz, 2000) is one thatultimately repels ants, preventing boric acid baits from being truly effective. Ininvestigating this I conducted two tests. The first portion was a trial in general antrepellency, while the second tests for feeding preference within ants among differentconcentrations of boric acid.Work in this area has been conducted before (Klotz, 1998; Klotz et al, 2000), but theextent to which I wish to explore the issue is slightly larger. Previous studies weresomewhat limited in terms of their sample size, and with higher thresholds of boric acidconcentrations. For instance, the lowest concentration within Klotz’s study was 0.5%boric acid in 25% sucrose solution, and he ultimately determined that this concentrationwas adequate for attracting and killing Argentine ants. I believe that lower concentrationsmay prove to be even more effective at attracting ants, and that suggested concentrationsof 0.5 to 1.0% may be too high. In this study, a lower range of boric acid concentrationswere used, with more baits released into the field.MethodsThe study was conducted in south Napa California at Sutter Home Vineyards. Therewere 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 thesame 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 blockconsisted of six different concentrations of boric acid (0.0, 0.1, 0.2, 0.3, 0.5, and 1.0%) in25% sucrose solution in 50ml tubes. Because I am only concerned with measuring thedifference from the beginning to the end of when the ants feed, the actual amount
View Full Document
Unlocking...