Acetic Acid Fumigation of Fruit Storage Bins to Control Diapausing Codling Moth Larvae

Abstract

Fumigation with glacial acetic acid (AA) vapor successfully kills post-harvest pathogens on tree fruits and berries and reduces their spoilage in storage. In this study, we investigated whether a similar approach could be implemented to eradicate diapausing larvae of the codling moth, Cydia pomonella (L.), from fruit harvest bins they commonly infest. In 24-h tests conducted in 0.023-m3 fumigation chambers using two concentrations of vaporized AA [117,360 and 174,823 cumulative parts per million-hours (ppm-h)], mortality of diapausing larvae was 81% and 100%, respectively. A similar 24-h exposure to a 61,940 cumulative ppm-h treatment of AA caused no mortality. A 24-h fumigation of diapausing codling moth larvae placed in scaled-down plastic fruit bins treated with 55 mL of AA evaporated into a 1-m3 chamber caused 100% mortality. The same fumigation treatment of artificially infested, scaled-down wooden fruit bins caused no significant mortality of test larvae. Atmospheric concentrations of AA vapor in 1-m3 fumigation chambers containing wooden bins could not be maintained at levels necessary to cause insect death, even after multiple injections of AA. We hypothesize that either the wood or the moisture contained therein absorbs or in some other way interacts with the AA vapor. The use of AA as a fumigant targeting codling moth larvae in wooden bins is not practical or economical at this time. Fumigation of plastic fruit bins with AA would provide an economical and environmentally friendly method of killing diapausing codling moth larvae. The successful disinfestations of plastic fruit bins of codling moth would prevent these bins from being an external source of infestation, thereby decreasing overall codling moth infestation in orchards, which in turn benefits current density-dependent management practices used for the area-wide control of codling moth. chemical name: Glacial Acetic Acid (AA).