Stored product pests are one of the biggest heavy-hitter pest groups when it comes to economic loss caused by pests. In post-harvest losses alone, stored product pests are estimated to damage up to 9% of the grain produced in developed counties, and up to 20% of the grain produced in developing countries.* Despite the huge amount of economic loss they cause in the world, we understand very little about the flight behavior of these pests, which could provide more context for appropriate treatment. 

Enter, Ephestia kuehniella, or more commonly known as the Mediterranean Flour moth. Previous studies had focused on the flight initiation, or what prompts stored product pests to begin flying, but there was little data on the flight capacity and actual behavior of the pests once they were in flight. This is important data to know, as it provides context on how far Mediterranean Flour Moths and other stored product pests may be willing to fly for food and mating pheromones.  

To test this, the researchers essentially built a scientific version of tying a fly to a string. Except, the fly was a moth, and the string was an extremely sensitive flight mill with sensors that measured how many times the flight mill rotated. Moths in the flight mills were additionally exposed to three treatments: unbaited control, a sex pheromone cue, known as (Z,E)-9,12-tetradecadienyl acetate (ZETA), and a food cue, made of a mixture of various wheat and brewer’s yeast.  They left the moths for 24 hours and then analyzed the data.

 

 

The total distance flown by these moths in the flight mills over 24 hours ranged between 24.7 to 34.3 kilometers, or 15.3 to 21.3 miles. This is an astonishing distance to potentially fly for such a tiny moth, and highlights how easily a Mediterranean Flour moth could travel from one building to another.  

While the treatments had no effect on the distance flown, they did have an effect on the distance per flight bout. Moths exposed to pheromones were traveled a further distance on average in their flight bouts compared to those exposed to the control and food. In fact, moths exposed to a food stimulus had the shortest flight bouts.  

Similarly, the number of flight bouts was also impacted by the treatment, where the moths exposed to pheromones were 1.6 times more likely to initiate a flight bout compared to food cues. This is thought to be because the exposure to ZETA may initiate a more localized searching behavior, which would mean that it would encourage a higher number of flights at a longer distance to find that special someone.  

The researchers also found that flight velocity was lower in moths that were exposed to food or pheromones. This could illustrate the same point of the localized searching behavior, as moths who feel that they are close to a source may feel the need to slow down in order to search.  

In addition to the flight mill tests, the researchers additionally tested for flight initiation by placing moths in a cage, and then pumping in either the food cues, the pheromone cues, or a control. Interestingly, moths that were exposed to food cues were the most likely to initiate flight in the cage assay when compared to the other treatments. Therefore, this study also calls attention to the importance of studying all aspects of a behavior, as clearly food still can be a driving factor for moth flight initiation.  

These results emphasize the power of pheromones, and that pheromone-based and behaviorally targeted management strategies may be the best option when it comes to management of Mediterranean flour moths. However, it also emphasizes that these flight behaviors are not black and white, as clearly some moths are more driven by food than finding a mate. Overall, this study lays important groundwork and provides more behavioral context on how to improve pheromone traps for not only Mediterranean Flour Moths, but potentially stored product pests in general.  

Article by: Laura Rosenwald, BCE

References

*Phillips TW, Throne JE. Biorational approaches to managing stored-product insects. Annu Rev Entomol. 2010;55:375-97. doi: 10.1146/annurev.ento.54.110807.090451. PMID: 19737083. 

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