Adults
Related invasive species
- Harmonia axyridis
Related Farm Practice
- Production
- Processing
- Vineyards
- Pests
H. axyridis, a species of Asian origin, has been used as a biological control agent against aphids worldwide. The first releases were made in North America in 1916, but it was not until 1988 that the first individuals were found in the wild. Since then, it has rapidly invaded most of North America and Europe, and it is now spreading in other regions such as South America and South Africa. In most invaded regions, numbers have increased exponentially and H. axyridis has quickly become the most abundant ladybird in a wide range of habitats. The invasion of H. axyridis causes concern for the populations of native ladybirds and other aphidophagous insects, which it may displace through intraguild predation and competition for resources. It is also regarded as a grape [ Vitis vinifera ] and wine pest, and as a human nuisance because it aggregates in buildings when seeking overwintering sites in the autumn.
H. axyridis has recently been designated pest status of fruit production and processing (Koch, 2003). As insect prey become scarce in the autumn, adult H. axyridis begin to aggregate and feed on fruits such as apples (Malus domestica), pears (Pyrus communis) and grapes (Vitis vinifera). This is problematic to orchard crops and vineyards in particular. Not only do H. axyridis cause blemishing to the fruit, but they are hard to remove from clusters of grapes and so get crushed during harvest and crop processing. The toxic alkaloids contained within H. axyridis taint the vintage (Ejbich, 2003).
The potential threat that H. axyridis poses to wildlife is more worrying than its impacts on crops. H. axyridis is a polyphagous predator and as such has been used widely as a biological control agent of pest aphids and scale insects. However, a wide range of literature sources (Hironori and Katsuhiro, 1997;Cottrell and Yeargan, 1998;Phoofolo and Obrycki, 1998;Dixon, 2000;Lynch et al., 2001;Koch et al., 2003;Pell et al., 2008;Ware and Majerus, 2008;Ware et al., 2008) document that H. axyridis consume non-pest insects including: immature stages of many species of coccinellids (Adalia bipunctata, Adalia decempunctata, Calvia quatuordecimguttata, Coleomigilla maculata, Coccinella quinquepunctata, Coccinella septempunctata, Coccinella septempunctata brucki, Cyclomeda sanguinea, Eocaria muiri, Harmonia quadripunctata, Hippodamia variegata, Propylea japonica and Propylea quatuordecimpunctata);one nymphalid (Danaus plexippus) and one Chrysopidae (Chrysoperla carnea). It is widely accepted that this list is far from exhaustive because of the highly polyphagous nature of H. axyridis. H. axyridis is a voracious predator and as such has the capacity to directly outcompete other aphid and coccid predators, in addition to acting as an intra-guild predator, thus posing a serious risk to native biodiversity.
H. axyridis can also directly impact on humans through its aggregation behaviour. In the late autumn, H. axyridis migrate to overwintering sites and form spectacular aggregations. Buildings are a preferred overwintering location of H. axyridis in urban localities and the swarms of H. axyridis in homes may cause a human nuisance. Furthermore H. axyridis has been reported to bite humans and some people have developed an allergic rhinoconjunctivitis (Yarbrough et al., 1999;Magnan et al., 2002).