Experimental study of acoustic equipment for real-time insect detection in grain bins –Assessment of their potential for infestation risk predictionduring long term storage periods

Abstract: An insect detection probe was recently developed to detect and identify the sounds ofdifferent stages and species of primary grain pest insects whilst operating directly from thesurface of grain bulk. A laboratory acoustic device with the same technology as the probe wasalso developed for hidden insect detection in grain samples. A campaign for the testing of theperformances of the acoustic probe and the laboratory acoustic device in field conditions wasundertaken by the ONIGC in the cereal production area of western France after the 2007 harvest.The data on insect presence / absence from the acoustic probe were compared in parallel with theobservation of insect presence / absence in grain samples taken at the acoustic probing location.This comparative study was carried out on 60 grain storage sites. The parallel grain samples weresieved after transport at the official laboratory (ONIGC, La Rochelle) prior to a check for hiddeninfestation by the “laboratory acoustic device”. Afterwards, samples were incubated at roomtemperature (23-25°C) before a second sieving 35 days later for recovery of emerged adults.From the data delivered by the acoustic probe compared to the insects recovered from theincubated grain samples, it was established that this equipment enables to predict the presence oflive hidden insects with a confidence factor greater than 90%, as it is capable of detecting theactivity of all insect stages, either adults or hidden stages, and a range of acoustic detectioncovering a 30kg grain mass. The confirmation of hidden infestation performed with the “labdevice” before sample incubation showed that convergence of diagnosis for presence / absencewas observed in 79% of samples. This study confirmed the detection of a hidden infestation at adensity level far lower than the threshold of conventional detection of adults by sieving alone. Itenables to predict the risk of adult detection during a further storage period. Additionally, theearly detection of insect presence in a grain bulk is valuable information for the grain storekeeperwhich enables optimisation of insect control strategy or grain lot sale before the insect presencebecome detectable with the reference method.