February 12, 2008
As spring approaches, along with the subsequent "green-up" of Ohio'swheat crop, growers are looking to prevent the development and spread ofbarley yellow dwarf virus.The virus, which is transmitted by several aphid species in either thefall or early spring, was found in relatively high levels in some wheatfields across Ohio last year, with as much as 20 percent of the plantsshowing symptoms of the disease in some cases.Pierce Paul, an Ohio State University plant pathologist with the OhioAgricultural Research and Development Center, said that growers are temptedto use insecticides this spring to control aphid populations and prevent thedevelopment and spread of the disease. OSU Extension specialists, however,are recommending an Integrated Pest Management approach, and indicate thatspraying insecticides to control aphids may not be cost-effective."Any aphids present prior to spraying may have already transmitted thevirus, while other aphids may continue to arrive in the field after thespraying. When spraying insecticides to control aphids early, growers shouldknow that the residual effect of the insecticide may not last long enough toprotect against later aphid population buildup nor virus transmission," saidRon Hammond, an Ohio State University Extension entomologist. "Thoughinsecticides applied after infection will reduce the aphid population, itwill not prevent the disease from developing once the plants have beeninfected."Paul said that growers should be aware of the fact that barley yellowdwarf virus development and the success of insecticide treatments to managethe disease are affected by several factors including the efficiency ofaphid transmission of the virus, the source and strain of the virus beingtransmitted, the difference in aphid mobility and feeding habits, the ageand susceptibility of plants when infected, and weather conditions.Hammond added that spraying insecticides in the spring might not becost-effective since yield reduction due to barley yellow dwarf virus isgenerally greater when infections occur in the fall rather than in thespring.³Fields planted before the Hessian fly-free date are at greater risk forbarley yellow dwarf virus development in the spring,² said Paul, who alsoholds an OSU Extension appointment. "Barley yellow dwarf virus tends to bemost severe in fields planted before the Hessian fly-free date at a timewhen aphid populations are high and aphids are still actively feeding or inyears such as last year when warmer than usual fall and winter conditionsoccur."Recommended management tactics to prevent and control barley yellowdwarf virus include:* Planting varieties less susceptible to barley yellow dwarf virus.* Delaying planting until after the Hessian fly-free date to avoid fallinfections.* Implementing a balanced fertility program.* Controlling volunteer wheat, barley and oats. For aphids tosuccessfully transmit the virus, they normally need between 12 and 30 hoursfeeding to acquire the virus, and then four or more hours of feeding totransmit it. However, aphids are capable of acquiring the virus afterfeeding on infected plants for only 30 minutes and once they acquire thevirus, they can transmit it to healthy plants for the rest of their life.There are acceptable situations where spraying for aphids might bewarranted. They include:* Spraying when wheat is under drought stress with aphids present.* Growing a variety known to be susceptible to barley yellow dwarf viruswith aphids present.* Growing wheat for seed.* Intensively managing wheat for a 100-plus bushel per acre yieldpotential.* Planting wheat before the Hessian fly-free date.If using insecticides is warranted, log on tohttp://bugs.osu.edu/ag/545/sgiap.pdf for a list of labeled materials. Formore information on wheat management, log on to http://agcrops.osu.edu .