Whiteflies in Cotton
Silverleaf whitefly (SLWF) infestations are being observed in cotton in parts of Georgia. Some fields in Cook County have reached threshold levels and have been treated; while whiteflies have been observed in other fields but not at threshold levels. Over the past several weeks we have had relatively frequent rainfall events. These environmental conditions have slowed growth of SLWF populations. However we should anticipate rapid population development during hot and dry conditions.
The image above shows immature SLWF (eggs) on the underside of the 5th leaf below the terminal.
SLWF Threshold: Treat when 50 percent of sampled leaves (sample 5th expanded leaf below the terminal) are infested with multiple immatures (≥5 per leaf). Insect Growth Regulators (Knack and Courier) are the backbone of SLWF management programs in cotton. Effects on SLWF populations are generally slow due to the life stages targeted by IGRs, however these products have long residual activity and perform very well when applied on a timely basis.
Disease Update – Bob Kemerait
- PEANUT: white mold (stem rot) and leaf spot diseases are developing. Growers should be aggressive with appropriate fungicide programs. Now is not the time to watch and wait. Rainfall will create favorable conditions for diseases of peanut, but timely rainfall will also help to move the fungicides from the leaves of the plant to the crown of the plant for better coverage. I would like to have 8-12 hours of drying time before a rain or irrigation event.
- COTTON: A lot of target spot is developing in the lower canopy of our cotton. Not all of the cotton, but certainly in some of our better cotton. Barely two weeks into bloom and I am already finding early stages of defoliation in some fields. Target spot starts quietly, but once it explodes, it cannot be stopped. Cotton scouts should be looking for it. Timely fungicide applications as early a the first week of bloom can be the difference in 200 lbs of lint. PRIAXOR has been our most effective material, but growers can also be successful with Headline, Quadris and Elatus. BACTERIAL BLIGHT is also developing quickly in some places, especially in more susceptible varieties in our County Variety Trials. There is little that can be done now to manage the disease, but we will have a better idea what to plant for next year.
- SOYBEANS: I am receiving an increasing number of reports of frogeye leaf spot on soybeans this year; weather conditions are perfect for it. Timing of fungicide applications are the same as for soybean rust- i.e., beginning between R1 bloom and R3 early pod set. The most effective treatments are likely to be a fungicide product that combines multiple modes of action.
Pecan Insect Update/Terminal Die Back
Here is a pecan insect update from UGA Entomologist, Dr. Will Hudson:
The yellow aphid spike many growers noticed in late June seems to have fallen off in most orchards, and the very hot weather now will really slow any further population increases. That takes some pressure off for now. I’ve had some calls and seen some leaf scorch in scattered orchards in middle GA, and some growers are worried it is mite damage. I don’t know what the cause IS, but I know it is NOT mites. Typical symptoms are the terminal leaflets turn gray-brown and wither, followed by the lower leaflets until the whole compound leaf drops. Mites cannot cause that type of symptom although there often are mites on the leaves. Spraying with a miticides will not help the situation.
If mite populations do approach damaging levels, Abamectin would be a good choice at this time. Be sure and consult the label for specific rates on Abamectin as there are several generic products out there with varying amounts of active ingredient. The heaviest pressure from mites is normally in mid to late August or following weevil sprays so save the more expensive and longer residual materials like Envidor and Portal for that time. Nexter could also be used where aphids are a problem as well.
I’ve also had some calls about webworms, especially in young orchards. Probably the cheapest effective treatment that will give long lasting control is Dimilin. The material is absorbed into the leaves and persists until the leaves fall, so one shot should hold for most of the rest of the season unless you get another flush of new growth. For small trees 4-8 oz will give good control of most caterpillar pests.
Follow up by Dr. Wells on the leaf scorching:
We have had calls from a number of orchards throughout the state over the last week with some leaf scorching symptoms that start from the tip of the compound leaflet and move backward. Eventually the entire compound leaf will turn brown and has a similar appearance to fire blight. This results form a fungal infection by a relatively minor pathogen called Neofusicoccum. Terminal die back is a common name for it. Once you see the symptoms it is too late to do anything about it. We see this pop up periodically under the right conditions, normally later in the season; however, never to a level of economic damage.
Insects in Hay/Pasture
Bermuda Stem Maggots are active in hay and pastures. I’ve got word of armyworms being treated in hay fields as well.
Tucker Price 507-8862