Orius predators and Diglyphus isaea: A matching pair for the control of leaf miners in Chrysanthemum

Abstract: Leaf miners (Diptera: Agromyzidae) are important polyphagous pests, that cause
damage to many horticultural crops. Parasitoids, such as Diglyphus isaea (Hymenoptera:
Eulophidae), are commercially available for leaf miner control, but additional pesticide
applications are often necessary. In many ornamental crops where leaf miners are problematic, Orius (Hemiptera: Anthocoridae) predators are frequently used, predominantly for the control of thrips. These omnivorous predators are known to feed on various arthropods, including aphids and whiteflies, however predation on leaf miners has not been previously evaluated.
This study evaluated the suppressive effects of Orius laevigatus and O. majusculus on
Liriomyza trifolii in cut Chrysanthemum, a crop frequently attacked by this pest. Their efficacy was compared to D. isaea in a greenhouse cage trial. Predators were released preventively and supported by Artemia cysts before infestation with leaf miner adults. Parasitoids were released a week later, when suitable leaf miner larvae were present.
Both Orius predators significantly reduced the number of mines, achieving suppression
comparable to D. isaea by the end of the cropping cycle. The least damage occurred in
treatments combining Orius and D. isaea, indicating limited negative interactions such as
intraguild predation between these natural enemies. Laboratory observations further revealed that Orius predators can feed on recently formed pupae before sclerotization, but predation of larvae within the mines was only rarely observed.
Our results suggest that a well-established population of Orius predators in the crop may
have an important role in suppressing leaf miners, complementary to that of specialist
parasitoids.