The adipokinetic hormones of stored product pest insects: can this help to combat these insects?

There are numerous ways to control stored product pest insects, including chemical control in the form of fumigation or spraying insecticides. Such chemicals are, however, untargeted and may kill beneficial insects, as well as accumulating in the environment and harming other organisms. An alternative approach that alleviates non-specificity, environmental toxicity and possible chemical resistance, is to disrupt the physiology of the pest insects with a mimetic based on a peptide hormone that occurs naturally in the pest insect. We investigated and report here on the complement of adipokinetic hormones produced in the corpora cardiaca glands in the head of pest insects (11 Coleoptera, 2 Lepidoptera and 1 Diptera species) to identify a viable lead for potential development as a “green insecticide” to control stored products pest beetles. The adipokinetic hormone regulates energy metabolism in insects, functions via a specific protein receptor on the nutrient reservoir (the fat body) and is a well-studied hormone family. The peptide hormones were detected and sequenced via liquid chromatography-high resolution mass spectrometry. The studied beetle species all have an octapeptide AKH ending in a common C-terminal PNW amide. These are not beetle-specific AKHs and are found in bugs, cockroaches and termites. Thus, a PNW amide lead compound may also affect these other pest groups but not beneficial beetles (e.g. scarabs), as they have unique AKH structures. The AKHs from the moths and horse fly of the current study confirms the order-specificity previously recorded. • All primary AKH sequences of stored product pest beetles are octapeptides. • The grain moth Sitotroga cerealla produces a novel decapeptide AKH. • A peptide mimetic for pest beetles inspired by their AKHs is a real possibility.