Oklahoma State University Stillwater, OK
Oklahoma Alfalfa Oklahoma Cooperative Extension Service Oklahoma Agricultural Experiment Station

Beneficial Insects - Pollinators
It is fortunate for alfalfa growers that many of the insects found in this crop are natural enemies that attack the plant-feeding insect species. Although natural enemies do not typically maintain populations of some insect pests such as the alfalfa weevil below economic threshold levels, others such as aphids and foliage-feeding caterpillars are effectively controlled in most years. The need for insecticide applications would be increased greatly were it not for the presence of these natural enemies. A second group of beneficial insects that are of critical importance in alfalfa seed production is the pollinators. Without pollination by several species of bees, seed production in alfalfa is not profitable. Pollinators The most effective pollinators of alfalfa in Oklahoma are bumble bees and leafcutter bees. While both of these bees occur naturally, their population levels are typically not high enough to provide all of the pollinators needed for a highly productive seed crop. There is no process available for rearing bumble bees for use as pollinators. Although leafcutter bees are reared as pollinators in some areas of the western U.S., they are not used extensively in Oklahoma. The most common species used to supplement naturally occurring pollinators for alfalfa seed production in Oklahoma is the honey bee. With exception of those who place honey bees in fields, most alfalfa seed producers in Oklahoma rely on native bee populations for pollination. Over the years, there have been adequate numbers of bees of various species to sustain profitable seed production. However, wild populations of honey bees, in particular, have been reduced greatly by diseases and tiny parasitic mites. The need to supplement native bee populations by moving colonies of bees into seed production fields is greater than in the past. Also, the need to restrict the use of pesticides in seed fields once plants start blooming is critical. Follow recommendations related to sampling fields for potential pest problems before the onset of bloom. If applications are required after alfalfa plants start blooming, take care to minimize mortality of pollinators (spray in late evening and remove bee colonies from fields).
Richard Berberet, Alfalfa Entomologist  Department of Entomology and Plant Pathology  Oklahoma State University

 

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