2000-2001 Small Grains Performance Tests

The Georgia Agricultural Experiment Station
College of Agricultural and Environmental Sciences
The University of Georgia

Research Report Number 673
August 2001

Small Grains Updates: Insects

G. David Buntin, Department of Entomology, Griffin, Georgia

Cold weather in November and December limited wheat emergence and growth. Cold weather also limited infestations of the Hessian fly, Mayetiola destructor, throughout the 2000-2001 season. Infestations in the fall-planted variety test evaluations at Griffin and Plains were too low for separation of entries. The variety test was planted in late February at the Becham Research Farm near Griffin in an area where Hessian fly was present. Infestation results from this trial are presented in the next table. Varieties showing good levels of Hessian fly resistance were 'AGS 2000,' 'SS 516,' 'Pioneer 26R38,' 'Pioneer 26R61,' 'Roane' and 'Roberts.' 'NK Coker 9835' has been resistant in the past trials but rated as susceptible in this trial. 'Croplan SR218' was resistant in last year's trials but was not included in this trial. 'Pioneer 2684' and 'Fleming' had moderate or intermediate levels of resistance, but these varieties will not stand up to a heavy infestation. Although rated as resistant in past years, significant infestations occurred in 'Pioneer 2684' in 1999-2000, indicating that this variety has only a moderate level of resistance that is not effective under high levels of Hessian fly pressure. Both rye and oats are good Hessian fly resistant alternatives to wheat for forage production; rye is highly resistant and oats are immune to the insect.

Cold weather also limited aphid in the fall throughout the state. Aphids infested wheat in late winter in some areas, causing some transmission of barley yellow dwarf virus (BYDV) in those areas of the state. Although the level of expression of symptoms varies among varieties, no varieties are truly resistant or tolerant of BYDV infection. Systemic insecticide seed treatments and properly timed foliar applications of insecticides can greatly reduce aphid numbers and minimize BYDV incidence.

The cereal leaf beetle now is established throughout northern and most of southern Georgia. Populations continue to ncrease and caused noticeable damage this year in the Coastal Plain region. Larvae and adults are present in the spring during grain filling, where they remove the upper leaf surface and chew elongated holes in leaves. Populations in most areas still are below the treatment threshold of 0.5 larvae or adult per stalk. However, damage was very evident in the northwestern and central Piedmont region of the state, with some fields needing treatment with an insecticide. Cereal leaf beetle can be effectively controlled by a number of insecticides when applied to active larvae. Consult your local county extension agent for a list of recommended insecticides for this insect and for management practices for other insect pests of small grains.

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