Cotton aphid is a fairly consistent and predictable pest of cotton in Georgia. Aphids will typically build to moderate to high numbers and eventually crash due to a naturally occurring fungus, Neozygites fresenii. This fungal epizootic typically occurs in late June or early July depending on location. Once the aphid fungus is detected in a field (gray fuzzy aphid cadavers) we would expect the aphid population to crash within a week.
Over the weekend we received several reports of fields crashing due to the fungus in the southernmost Georgia. Typically the fungus starts in the southernmost counties of southwest Georgia and moves north and east in time.
Aphids feed on plant juices and secrete large amounts of “honeydew”, a sugary liquid. The loss of moisture and nutrients by the plants has an adverse effect on growth and development. This stress factor can be reduced with the use of an aphid insecticide. However, research conducted in Georgia fails to consistently demonstrate a positive yield response to controlling aphids.
Invariably, some fields probably would benefit from controlling aphids during some years. Prior to treatment, be sure there is no indication of the naturally occurring fungus in the field or immediate vicinity. Also consider the levels of stress plants are under, vigorous and healthy plants are able to tolerate more aphid damage than stressed plants.
Stink Bug Update
Observations and correspondence with agents, scouts, and consultants suggest that stink bug numbers are higher than we have observed in recent years. Once plants begin setting bolls begin monitoring for internal damage.
AgFax Weed Solutions
Scout bolls approximately the diameter of a quarter. Bolls of this size are easy to squash between your thumb and forefinger and are the preferred size for stink bugs to feed. Bolls with callous growths (warts) and/or stained lint are considered damaged. Use the dynamic threshold based on week of bloom to make treatment decisions.
During the first week or ten days of bloom when bolls have not reached the size of a quarter, sample the largest bolls available. Stink bugs will feed on small bolls when 10-12 day old bolls (quarter sized) are not present. Feeding on small bolls will cause them to be shed by the plant.