Biological innovations: a new tool for biological control of powdery mildew

Abstract: Ladybird beetles (family Coccinellidae) are generally viewed as aphidophagous
predators, but their diet is much more diverse and often includes hemipterans, beetles, fungi,
and plant materials. Recent studies have advanced understanding of their mycophagy, which is classified as either obligate or facultative. Facultative species feed on a wide range of diets,
including fungi as supplementary food, such as members of the Tytthaspidini tribe and
aphidophagous Coccinellini. In contrast, obligate species rely exclusively on fungi to complete
their life cycle, such as members of the Halyzia tribe. Species belong to Halyzia and
Tytthaspidini possess some structural specialization indicating adaptation to mycophagy. Both feeding strategies hold potential for the biological control of pathogenic fungi, particularly the causal agents of powdery mildew (Erysiphales), an important disease in many greenhouse and open field crops. Therefore, my project will study native Dutch mycophagous ladybird beetles for powdery mildew (PM) control in strawberry greenhouses, focusing on four species: Halyzia sedecimguttata (H16), Vibidia duodecimguttata (V12), Tytthaspis sedecimpunctata (T16), and Psyllobora vigintiduopunctata (P22). Insect collections were conducted from April to September 2024, when PM was the most prevalent in open field. The ladybird beetles were found actively feeding on PM on various host plant species, indicating them as one of the important PM consumers. This holds a promise for application inside greenhouses. My key objectives will include: (1) identifying essential dietary components and breeding behaviors, (2) evaluating how environmental factors, such as light and temperature, influence their development and activity, (3) assessing their capacity to consume and control PM in laboratory and greenhouse conditions, and (4) developing an early-season biocontrol strategy, incorporating a standing army and open-rearing system. By addressing knowledge gaps in the biology and biocontrol potential of these beetles, we hope to provide growers with biological tools for PM management strategies.