Testing Barley Samples for Potential Insect Infestations with a Conductance Mill

Abstract

Highlights The conductance mill successfully detected seeds infested with large larvae, over 80% in barley and wheat. Barley seeds, infested with medium larvae, were detected at a lower rate than wheat; ~40% for barley vs. ~65% for wheat. The feed-rate of barley samples was slower than the wheat and the resulting ground barley material contained higher fractions of large particles, over #20 mesh sieve. Abstract. A laboratory mill was developed by Pearson and Brabec (2007) which typically detects 50% to 80% of infested kernels of wheat, brown rice, or popcorn. Barley is another cereal grain of similar size as wheat. Barley is normally sold with its hull attached to the seed, which makes detection of insect infestations more difficult. The objective of this study was to determine the potential of using the conductance mill to detect barley kernels infested by the lesser grain borer, Rhyzopertha dominica (F.), in comparison to detection in wheat. As in previous studies, these experiments found that the conductance mill could detect infested kernels of wheat containing large and medium larvae at a rate of ~90% and ~65%, respectively. For barley, the detection of infested kernels was over ~80% for large larvae and ~40% for medium larvae. Also, we showed that adults that were freely moving throughout the grain mass could also be detected. Approximately ~65% of the adults were detected in wheat while that percentage was reduced to ~35% in barley. The hull on the barley seems to function as an insulator during the conductance measurement and thus reduces detections. Also, the hull seems to affect the feed rate of material through the mill. The feed-rate for wheat was 500 g in 50 s, while the feed-rate for barley was 500 g in ~80 s. Despite these pitfalls, the conductance mill could still be considered as a useful tool with inspecting barley sample, because there was significant detection of insects in the samples and 1000 g sample of barley could be processed in ~4 min. Keywords: Barley, Detection, Rhyzopertha dominica, Sampling, Wheat, X-ray.