Wheat: Earlier Aphid Occurrences May Be a Consequence of the 2017’s Warm Winter

Raul Villanueva, Extension Entomologist, University of Kentucky 

Figure 1. Pictures of the bird cherry oat aphid and
 a winged English grain aphid found in wheat fields
 in February 2017. (Photo credits Yaziri Gonzales).

In Kentucky there is a complex of aphid species that feeds on wheat. The bird cherry oat, the English
grain (Fig.1), the greenbug, and the corn aphids are the most important species. Their role as vectors of plant viruses, particularly Barley Yellow Dwarf Virus (BYDV), branded them as the key pest on

wheat grain production. These aphid species overwinter as nymphs, and can be active when temperatures are above 45⁰ F. It is known that BYDV infections are more damaging when they occur in early growth stages of the wheat plant. Thus, aphids have more opportunities to infect young plants under this climatological circumstances.

Wheat Freeze Damage more Apparent, so are Viruses

Chad Lee, Extension Agronomist, University of Kentucky

Bleached head from freezing temperatures.
Source: Kenny Perry, Graves County ANR Extension Agent

The freeze damage on wheat became more apparent this week. The damage is spotty and tends to be more severe in the low areas of fields. Much of the wheat appears to have survived, but scouting to assess damage within fields is difficult. In order to understand the extent of damage within fields, almost the entire field needs to be walked. At the very least, the highest and lowest elevations need to be examined.

Bleached heads are a clear indication of freeze damage to heads. Girdling around the stem would be another indication of freeze. Heads that appear bent over may be a sign of damage to the stem directly beneath the head. As more days pass,  symptoms will become more visible (if damaged occurred). For more on wheat freeze damage, visit the Wheat Science Newsletter.

In central Kentucky, we are seeing a lot of Barley Yellow Dwarf Virus (BYDV) on wheat. In some cases, fields were sprayed with an insecticide. In at least one case, the field was sprayed twice. In other cases, people scouted fields, followed aphid thresholds and elected not to spray. In all cases, the warm winter most likely elevated aphid levels and climate and biology overwhelmed chemistry.