Testing barley samples for potentional insect infestations with a conductance mill

Authors: Brabec, Daniel - Dan; Grothe, Sophia; ATHANASSIOU, CHRISTOS - University Of Thessaly

Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2023
Publication Date: 10/1/2023
Citation: Brabec, D.L., Grothe, S.M., Athanassiou, C. 2023. Testing barley samples for potentional insect infestations with a conductance mill. American Society of Agricultural and Biological Engineers. 39(5):535-541. https://doi.org/10.13031/aea.15663.
DOI: https://doi.org/10.13031/aea.15663

Interpretive Summary: Insect infestation in bulk grain is often difficult to detect because several species of stored product insect feed inside grain kernels. A conductance mill was previously developed as a means of detecting insect-infested kernels and its performance has been evaluated on a number of commodities and insect species. However, the efficiency of the instrument has not yet been tested with barley samples. Thus, the purpose of this study was to evaluate the efficacy of this mill in detecting lesser grain borer larvae and adults in barley. As in previous studies, detection of internally feeding larvae was dependent on size. Kernels infested with large sized larvae were detected in both wheat and barley at over an 80% detection rate. However, kernels infested with medium sized larvae were detected at rates of ~60% for wheat and ~40% for barley. In addition, the potential detection of adult insects outside of the kernels was evaluated and the conductance mill successfully detected ~65% of lesser grain borer adults in wheat while the adult detection rate was ~35% in barley. Although the mill is capable of detecting kernels infested with larvae and some adults outside of the kernels, the mill’s sensitivity is lower in barley than with the wheat samples, which could be due to several factors. For example, although barley is very similar in size to wheat, the barley’s hull remains attached during grain storage, which can impact the electronic conductance. Additionally, the barley samples took longer to mill and generated larger ground particles, which could also reduce sensitivity. Although the detection rate with barley is lower than with wheat, the conductance mill is less labor intensive compared to other pest detection methods and represents a useful tool that can be used to detect stored product insects in bulked wheat and barley samples.

Technical Abstract: A laboratory mill was developed by Pearson and Brabec (2007) which typically detects 50% to 80% of infested kernels and processes 1000g of wheat, brown rice, or popcorn in ~ 3 min. Barley is another cereal grain of similar size as wheat, but it normally is 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 for using the conductance mill to detect barley kernels infested by the stored-product insect Rhyzopertha dominica (F.), the lesser grain borer, 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 decreased to ~80% for large larvae and ~40% for medium larvae. Moreover, 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 the feeding of the material through the mill. Despite these pitfalls, Still, 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 1000g sample of barley could be processed in ~4 minutes.