ARS | Publication request: INTRODUCED LADY BEETLES (COLEOPTERA; COCCINELLIDAE): BENEFICIAL AGENTS OR ALIEN INVADERS? INTRODUCED LADY BEETLES

Submitted to: Brazilian National Congress of Entomology
Publication Type: Other
Publication Acceptance Date: June 16, 2002
Publication Date: N/A

Technical Abstract: Lady beetles (Coleoptera; Coccinellidae) are valued for their role in the suppression of many plant pests. They are common predators in natural ecosystems, as well as cultivated gardens, orchards, rangelands and agricultural fields. These beneficial insects can be utilized in a number of ways: Indigenous lady beetle species can be manipulated to maximize their control potential through the use of food sprays, artificial shelters and covercrops. In addition, some locally occurring species (e.g. Coleomegilla and Stethorus spp.), can be mass-reared and released to provide early season or more complete control of field and greenhouse pests. Unfortunately, not all pest problems are amenable to such domestic solutions. Many of the more severe plant pests are exotic in origin and lack effective control agents among the native lady beetle fauna. In the United States, the advent of classical biological control is marked by the successful release and establishment of an Australian lady beetle, Rodolia cardinalis (Mulsant), against an introduced pest of citrus, the cottony cushion scale. In the more than 100 years since that outstanding success story, about 180 exotic lady beetle species have been introduced into North America, but only about 10% have resulted in successful establishment, and some of the established species have not demonstrably contributed to target pest suppression. In general, scale-feeding lady beetles have proven more effective as classical biocontrol agents than the aphid-feeders have. The establishment, either from biocontrol introductions or accidentally from commerce, of several Old World coccinellids that are generalist aphidophages has led to a cry for more stringent importation regulations, and focused attention on the plight of native lady beetles whose densities have declined as those of adventive coccinellids have increased. Surveys of the Canadian lady beetle fauna indicate that over 60% of the lady beetles sighted during a recent five-year study belong to two exotic aphidophagous species. Less complete data on pre-establishment conditions exist for the United States, with the exception of a few well-monitored crops, but the rarity and even disappearance of particular native species within the last decade suggests a similar effect. Field and laboratory studies point to inter-guild predation as a contributing factor in the displacement of these natives. Other concerns include effects to non-target prey organisms which may themselves be beneficial, and in the case of one anthropophilic species, Harmonia axyridis (Pallas), the creation of a new household nuisance.