We looked at some bronze sorghum yesterday that is approaching milk stage. The heads have not expanded yet. This sorghum is definitely holding out for a rain which will help advance it a little more. We did get rain across much of the county yesterday. Sugarcane aphids are now in the heads, and we can still see yield loss until hard dough stage. There are lots of lady bugs present, but beneficial cannot handle these populations of the aphids.
SCA can hurt us when we harvest. You will notice the honeydew on the leaves. SCA are up to the top leaves in this field. Lots of honeydew present and you can smell it too.
Treatment
Here is information from UGA Extension Grain Entomologist Dr. David Buntin on pre-harvest intervals, rates, and efficacies:
- Sivanto Prime (Bayer Crop Protection). Sivanto prime has a full section 3 label and a supplemental 2ee label for lower rates on sorghum and other grain crops. The rates are 4 – 7 fl. oz per acre. Sivanto was very effective in my trials at rates of 4 to 7 fl. oz. per acre with Control usually lasting 21 days or more. At the 4 oz rate it can be applied up to 7 times during the season but has a 21 day PHI.
- Transform WG (Dow AgroSciences). Transform WG federal label was vacated last winter and a new federal label has not been approved yet. But Transform WG has an approved Section 18 emergency exception for use on sorghum in Georgia in 2016 through April 8, 2017. The big label change for 2016 is Transform cannot be used during bloom to protect pollinators. The label allows for 2 applications per season and not more than 3 oz per acre per crop and has a 14 day PHI. In my insecticide trails last season, rates of 1.0 and 1.5 oz per acre were effective. Use the 1.5 oz rate if aphid populations are increasing rapidly.
- Chlopyrifos (Lorsban Advanced, Nufos, other). Lorsban is labeled at 1 to 2 pints per acre. The 2 pint rate has a 60 day harvest interval. The 1 pint has a 30 day harvest interval, but is usually not effective. The 2 pint rate was 60-90% control for up to 2 weeks. At the 2 pint rate it cannot be used after the boot stage due the 60 day PHI. DO NOT USE CHLORPYRIFOS ON SWEET SORGHUM.
- Dimethoate ( Dimethoate, Cygon). Not recommended. In my trials dimethoate is variable in control and control if it occurs is only for a week or so.
Sooty mold grows on the top of the leaf on honeydew excreted from aphids
Aphids present in the heads
“White spots” are cast skins from SCA. Blue colored aphids were parasitized by Aphelinus wasp.
Lady bug pupae
Thomas County Ag 