3.3.1. Wireworm Predators

Numerous vertebrates are predators of elaterid larvae and adults, but birds seem to be the major group with more than 100 different bird species mentioned for Europe and North America [105–107]. Mammals, plus amphibian and reptilian predators, are probably of lower importance than birds [105,106]. However, general predation by vertebrates is unlikely to substantially lower wireworm numbers over a large area, even though attempts to use poultry for this purpose were made early on [106]. Predation of click beetles and wireworms by other arthropods, especially by large predatory beetles (Carabidae, Cicindelidae, Staphylinidae) or predatory flies (Asilidae, Therevidae), has occasionally been observed [106,108–110], but as unspecialized predators, they only remove occasional wireworms or beetles. *Agriotes* larvae are predominately, but not exclusively, herbivorous, while species of other genera are predominantly or fully carnivorous [110–112].

#### 3.3.2. Wireworm Parasitoids and Parasites

Generally, wireworms with infections or parasitoids are not commonly found in the field [104,113]. Studies listed by Subklew [106] found no parasitoid in *Horistonotus uhleri*, *Limonius californicus*, *Sinodactylus cinnamoneus*, and *Selatosomus aeripennis destructor* (formerly *Ctenicera aeripennis destructor*). Kleespies et al. [104] examined about 4000 *Agriotes* spp. larvae mainly from Germany. Of these wireworms, only 25 were infected by entomopathogenic fungi, 29 by nematodes, and 66 by bacteria.

Entomopathogenic bacteria (EPB) appear to be the least tested group of microorganisms against wireworms, although they have been known for considerable time. Langenbuch [114] mentioned an unknown bacteriosis in wireworms. Recently a new bacterium (*Rickettsiella agriotidis*) was found and described [104,115], but no information has been published about its potential associated mortality. Danismaszoglu et al. [116] found that some members of the bacterial flora of *Agriotes lineatus* and related bacteria caused mortality up to 100%. Mites, in most cases probably from the family Tyroglyphidae, commonly occur on field-collected wireworms (Figure 4A). Whether these mites have a parasitic or phoretic connection to the wireworms is unknown, but the latter appears more likely [105].
