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.

Soybean Aphid & Other Insects in Double-Crop Soybeans

I have received several reports and questions from Extension agents, consultants and company reps concerning near economic threshold populations of Soybean Aphid (SA). Fortunately, all of these fields so far are in R6 or later stages. However, in addition a number of these reports included the observation that there are many other fields that are still in the R3 to R5 stages. These earlier stage plants will remain at risk to SA until they reach the R6 growth stage. These are the fields in which you should spend your scouting time.

The SA economic threshold is 250 aphids per plant, on 80% of the plants, with an increasing population. This threshold holds through plant stage R5. For more mature plants a great many more aphids per plant would be required to provide a benefit for an insecticide application. The exact number is currently under investigation but it is likely at least 500 aphids per plant and may well be 1000 aphids per plant.

In addition there have been scattered questions concerning stinkbugs and bean leaf beetles. Both of these insects are still present and will be feeding directly on the pods. At least one report I have seen, contains stinkbug numbers much greater than the threshold and bean leaf beetle populations very near thresholds. Both of these insects bear close observation as beans progress to maturity.

Soybean Aphid: Numbers are on the rise in Central Kentucky… At least a little!

Over the previous week we have seen an increase in the number of locations reporting the presence of soybean aphid (SA), and in one case a substantial increase in the number of reported aphids per plant. Neither of these finds is unexpected, nor do they indicate an immediate problem but they do illustrate that pest numbers are increasing slowly.

This is typical for SA in Kentucky. Experience has shown me that when soybean aphid populations are detected they will most likely be found in the counties between I-65 and I-75. Also, this area generally has larger populations than found in the western production area. In addition the only SA populations that have approached threshold levels have occurred in these counties. Nevertheless, we do know that this pest is active state wide so no one should dismiss it out of hand.

Our history with this insect tells us that we are unlikely to need a treatment but insects are very adaptive, and local populations can vary from the norm. Keep an eye on them!

See Kentucky Pest News at: http://www.uky.edu/Ag/kpn/kpnhome.htm for the complete story.