Rhopalosiphum rufiabdominale

Identification Initial detection can be difficult as root aphids preferred surroundings are in the soil or media. If sticky traps are employed, it may be the first indication of their presence. Ants have a mutualistic relationship with aphids and are attracted to the honeydew they produce; their presence is a strong indication that aphids are populating. Morphology Adults are 1.4-2.4 mm long with a soft rounded body; they are distinguished from Rhopalosiphum padi by their five antennal segments and more dense setae. Body hairs, known as setae, are generally short and dense while the hairs on the five segmented antennae are longer. The cauda, a tail-like extension, is shorter than the cornicles syn. siphuncles, which are also rather short and slightly swollen towards the tips. In their native range, rice root aphids have a heteroecious holocyclic life cycle. They alternate between the aerial plant parts of Prunus species through the fall and winter while colonizing other herbaceous hosts' roots for the remainder of the year. Mitotically derived eggs are also produced if necessary, to overwinter until environmental conditions improve. While they prefer below surface locations, winged adults can persist for weeks on aerial plant parts. Rice root aphids have a rasping-sucking mouthpart that facilitates the efficient removal of plant phloem. Both nymphs and adults feed on all development stages seedling, vegetative, or flowering, but survival can be limited to a few days without a host plant present. == Ecology ==

Distribution Rice root aphid is a Palearctic species that are distributed worldwide, in every terrestrial habitat, except for Antarctica. From Japan, it has migrated throughout Asia and Oceania and is now established in over fifty countries as an occasional or severe pest of many important growing regions. Within American borders, the pest is particularly advanced and has been identified in nearly half of the fifty-two states. In Europe, it was reported that rice root aphid will also colonize host plants belonging to Araceae, Asteraceae and Ranunculaceae. Research has shown that they can infest a large number of dicotyledonous plants, although their affinity lies predominantly within monocotyledon taxonomic groups. This preference is similar to the closely related R. maidis and R. padi and is especially true for plants that belong to the family Poaceae. The main plant hosts are categorized and listed below. • Agriculture crops including cereals, grains, and grasses: rice, barley, wheat, oats, millet, sorghum, cotton, sugarcane, and tobacco • Vegetable crops: aubergine, tomato, pepper, potato, corn, cauliflower, celery, and squash • Ornamental plants and fruit trees: '''Prunus spp. (17 known stone fruit and ornamental trees and shrubs), grasses', Dieffenbachia'' spp., and irises • Other: cannabis sativa, sedge, and forestry trees • Primary hosts are denoted in bold == Impact ==

While rice root aphid damage had been reasonably chronicled, the economic effects are far less documented. It may be due in part to the aphids subterranean habitat or unknown influence on overall plant fitness. In both Europe and Canada, root aphid has been cataloged as a persistent or occasional pest in hydroponically grown plants with the first infestation in Ontario greenhouse tomatoes and peppers occurring in 2005. The recent legalization of cannabis in eleven states in the United States and nationally in Canada has increased the dialogue and studies. Still, approval at a federal level is needed to elevate the research and funding to develop management strategies across stakeholders. Plant parts may also appear desiccated and distorted or display the formation of rosettes. This indirect injury can vector sugar cane yellow leaf virus and barley yellow dwarf virus. The pest was more recently identified, for the first time, as severely damaging an organic celery crop in California. While Hyadaphis foeniculi, honeysuckle aphid, was also detected and uncommon pest for celery, the combined infestation resulted in yield losses of up to 80% due to severe stunting. Periodic losses due to barley yellow dwarf virus have been described in North America and Europe, including Turkey, where barley cropping is commonplace. ==Management==

An integrated pest management system is the best approach to regulating rice root aphid. It is a relatively complicated pest to manage because it primarily resides below the soil line, limiting biological control options and rendering foliar insecticides ineffective. It makes early detection through systematic crop monitoring and visual observation essential. Additionally, preventative measures through cultural and physical controls in conjunction with carefully selected biological control organisms and judicious use of biopesticides offer the best defense. Physical and cultural control In late spring, winged adults are known to migrate to new hosts both in the field and greenhouses. After subsequent inoculations on other crops, the assertion was made that suppression could be achieved, leading to its routine use on the pest. Imported plant material can be treated with insecticidal soap or Beauveria bassiana before introduced to production facilities. Many of these pesticide formulations are now prohibited for use; this includes endosulfan, one of the few insecticides known to be effective against rice root aphids. Carbofuran, a chemical soil treatment, once touted as a useful tool, is now proven to be highly toxic with environmental and ecological implications that negatively affect multitrophic level interactions. With scant chemical products and further reassessments and de-registrations expected as research evolves, this control method remains an unviable option for rice root aphid. == References ==