Fire ants mediate competition between scale insects and fruit flies

Abstract Competition, as an interspecific interaction, significantly influences both species evolution and ecosystem stability; furthermore, its outcome can be shaped by interspecific dynamics and chemical communication. We studied the orchard populations of mealybugs, Planococcus lilacinus , and fruit flies, Bactrocera dorsalis , assessing both their damage rates and interactions with fire ants, Solenopsis invicta . We analysed their competitive dynamics across various rearing conditions and identified the chemical cues from honeydew and ant semiochemicals that mediate this competition. The abundance of S. invicta significantly influenced the damage rates of the pests we studied. An increase in the abundance of S. invicta reduced the damage caused by B. dorsalis but increased that caused by P. lilacinus . Competition in varied rearing environments revealed that B. dorsalis had a superior ability to exploit food resources in the absence of S. invicta . However, the presence of S. invicta reversed this competitive outcome. Further results showed that P. lilacinus honeydew attracted S. invicta , which in turn deterred B. dorsalis from laying eggs. This suggests a strategy by P. lilacinus to repel B. dorsalis and protect its population. Key honeydew attractants, such as ethyl lactate and cis‐linalooloxide, and repellents, including d‐limonene and dodecanoic acid from S. invicta , were identified. Our findings highlight the competition between B. dorsalis and P. lilacinus and emphasize the role of S. invicta in mediating these interactions through chemical communication. This contributes to our understanding of how these two pests coexist and has significant implications for developing new pest management strategies.