|NJOROGE, A - International Centre Of Insect Physiology And Ecology|
|AFFOGNON, H - International Crops Research Institute For The Semi-Arid Tropics (ICRISAT)|
|MUTUNGI, C - International Centre Of Insect Physiology And Ecology|
|ROHDE, B - University Of Florida|
|RICHTER, U - University Of Kassel|
|HENSEL, O - University Of Kassel|
Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2016
Publication Date: 6/16/2016
Citation: Njoroge, A.W., Affognon, H., Mutungi, C., Rohde, B., Richter, U., Hensel, O., Mankin, R.W. 2016. Frequency and time pattern differences in acoustic signals produced by Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) and Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae) in stored maize. Journal of Stored Products Research. 69:31-40.
Interpretive Summary: Larger grain borers and maize weevils are important economic pests of stored maize in sub-Saharan Africa. Scientists at the USDA, Agriculture Research Service, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, Florida, in collaboration with the International Centre of Insect Physiology and Ecology, Nairobi, Kenya, the University of Kassel, Witzenhausen, Germany, and the University of Florida, Gainesville, Florida, investigated sounds produced by larval and adult larger grain borers and maize weevils in stored maize. It was found that adult maize weevils produce sounds with different temporal patterns than the adult borers or the larvae of either species. The use of acoustic sensors can be helpful in identifying infestations of internally feeding borer and maize weevil larvae in maize, and in some cases it is possible to acoustically distinguish between the borers and the weevils. The use of this acoustic technology and knowledge can help reduce the economic damage caused by maize pests for farmers and agribusiness in sub-Saharan Africa.
Technical Abstract: The acoustic signals emitted by the last stage larval instars and adults of Prostephanus truncatus and Sitophilus zeamais in stored maize were investigated. Analyses were performed to identify brief, 1-10-ms broadband sound impulses of five different frequency patterns produced by larvae and adults, trains of sound impulses, and trains (termed bursts) which had characteristic temporal patterns produced frequently by insects but only rarely by background noise sources. The frequency patterns were designated Broadband, HighF, High-midF, Low-midF and LowF to indicate differences in their peak energies and broadness of frequency range. Mean counts of impulses per burst and rates of bursts and impulses in bursts were calculated and compared among the two species and stages. The counts of broadband and Low-midF impulses per burst and the rates of broadband and Low-midF impulses in bursts were significantly different for adult than for 4th instar S. zeamais and either stage of P. truncatus. These findings can be useful in developing a single maize based acoustic sensor for the detection of cryptic insects including P. truncatus and S. zeamais in bulk storage warehouses. In addition, the findings provide new insights into movement and feeding behaviors of these important pests.