Laboratory evaluation of an improved electronic grain probe insect counter.

An Electronic Grain Probe Insect Counter system, which incorporates modified passive grain probes, allows offsite monitoring and detection of insect pests in stored grain. An electronic count is generated whenever an insect falls through an infrared beam in the sensor head located at the bottom of the electronic grain probe. We report descriptions and laboratory evaluations of prototype electronic grain probes that were custom-made in-house (n=8) and by small-scale manufacturing (n=54). Laboratory tests, in which dead insects were dropped through a probe, were conducted to determine if electronic probes accurately count the numbers of insects that are captured. Accuracy of the manufactured electronic probes increased as the size of the test insect increased from 93.6% for the smallest insect tested (Cryptolestes ferrugineus, the rusty grain beetle) to 99.5% for the largest (Tribolium castaneum, the red flour beetle). Custom-made probes were significantly more accurate for C. ferrugineus (96.5% versus 93.6%) but there was no difference in accuracies for the larger insects. Comparisons among all probes found that probe accuracy was correlated with variation in the magnitude of the output signal from the infrared phototransistor. Thus, use of diode/phototransistor pairs with a more consistent beam or with improved beam focus may further improve probe accuracy. Good performance was obtained with the manufactured electronic probes. Tests with live insects under field conditions are needed to further evaluate the system performance.