Crop & Pest Report


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Cereal Aphids and BYDV Present in ND (07/11/19)

Southerly wind events have facilitated the movement of migratory cereal aphids into ND.

Southerly wind events have facilitated the ent.1 2movement of migratory cereal aphids into ND. In addition to causing feeding injury, cereal aphids are vectors for the viruses (Barley yellow dwarf virus and cereal yellow dwarf virus) responsible for barley yellow dwarf (BYD). Cereal aphids (mostly English grain aphids and bird cherry oat aphids) have been reported from small grains in southwest, north central and southeast ND (Sources: IPM Scouts for NDSU). Plants submitted last week to the NDSU Plant Diagnostic Laboratory from Cass County, ND were confirmed to have BYD. Cereal aphid populations in northern ND are lower and BYD has not been reported or confirmed. Minnesota and South Dakota also has reported increasing populations of cereal aphids.

Aphids damage plants by sucking sap and depriving the plant of nutrients. Generally, the greatest potential for yield loss is when the plant is between the boot and heading stage. After heading, the interval when aphid feeding can potentially rob small grains of yield decreases quickly.  Scout for aphids by examining the whole plant and underside of leaves. Thresholds for aphids on small grains are generally when 85% of plants are infested (have 1 or more aphids on them). Field scouting should be conducted from stem elongation until end of heading. If the risk of BYD is high (i.e.: wheat is at early vegetative stages with high levels of aphids and BYD symptoms are present), more aggressive pest management may be required.

Both the bird cherry oat aphid and English grain aphids are effective vectors of BYDV and CYDV, and when aphid populations are high, both viruses can spread quickly through small grain fields. The earlier a plant is infected, the greater the potential for yield loss. Although several fields are heading into the flowering growth stages, pay particular attention to late-planted small grain fields and scout for aphids and BYD symptoms. Insecticide applications targeted against aphids cannot cure infected plants but may prevent further spread of the disease. Most of the small grain varieties are susceptible to BYD. Please consult NDSU Extension E-1143, North Dakota Field Crop Insect Management Guide, for insecticide information.

Visible symptoms of BYD include leaf discoloration, stunting and disruption of normal plant development. Leaf discoloration includes shades of yellow, red (more common in oats), and purple (sometimes) often starting from the tip and progressing along the leaf margins towards the stem. If plants are infected with BYD in the 4- to 5-leaf stage, growth will be slowed, stunted, and maturity may be delayed. Later infected plants may not have obvious symptoms and are less likely to have significant yield loss. Infection sites within a field can appear as stunted yellow single plants or clusters of yellow plants among healthy plants. Because growth stages of small grains vary across the state (tillering to late flowering), producers/crop consultants should actively scout for cereal aphids and decide if an insecticide application is needed. The recent heavy thunderstorms across ND may wash cereal aphids off plants or drown them. Natural controls from parasitic fungal diseases should also help decrease aphid populations due to the high humidity.

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Janet J. Knodel                                                                                                  Andrew Friskop

Extension Entomologist                                                                                 Extension Plant Pathology, Cereal Crops

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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