Sugarcane Aphid in Kentucky Sorghum

The sugarcane aphid (SCA) was spotted in Kentucky last week in Fayette and Monroe Counties on sweet sorghum. This invasive pest can cause up to 100% crop loss if left untreated on grain, forage, and sweet sorghum. SCA cannot survive Kentucky winters and migrates from southern Texas every summer. While low numbers of this aphid were found last week, their presence in southern and central Kentucky indicates that SCA is likely present in many Kentucky counties already. SCA can be identified by the black antennae, feet, and cornicles (tailpipes). Scouting for SCA in sorghum should begin immediately.

Management

Growers should begin scouting their sorghum weekly by searching the undersides of 40 leaves between knee and chest height in a field. If SCA is found, scouting should be increased to twice a week as SCA can reproduce rapidly. If over 25% of those leaves have 40 or more aphids, management action is recommended. Preventive insecticide sprays are not recommended before this, as infestations do not always reach damaging levels. For example, the leaf in Figure 1 contains 160 SCA, which makes this plant infested. However, only one of the 40 checked leaves had aphids, so no action was needed.

Figure 1. Sugarcane aphid colony of 160 (Photo: Nathan Mercer, UK)

The only labeled insecticide for SCA management for sweet sorghum growers is insecticidal soap. As application rates vary among insecticidal soaps, please read the label for specific rates.

A section 18 emergency exemption was granted by the EPA for use of Sivanto Prime on sweet sorghum for management of SCA for 2019. A section 18 emergency exemption was also granted for use of Transform WG on grain and forage sorghum for SCA for 2019. In order to use Sivanto Prime in sweet sorghum or Transform WG on grain or forage sorghum you must: (1) have a copy of the section 18 label in your possession (Sivanto prime: Figure 2, Transform WG Figure 3), (2) be a certified applicator (private or commercial) and (3) report the acreage and volume sprayed to the Kentucky Department of Agriculture (e-mail: ag.web@ky.gov). This reporting is to aid Kentucky in obtaining the emergency exemption from the EPA in the future.

Figure 2: Sivanto Prime Section 18 emergency exemption

Figure 3: Transform WG section 18 emergency exemption

Sivanto Prime is already labeled for SCA management on grain and forage sorghum in Kentucky, with no emergency exemption needed. Sivanto Prime may be applied to grain, forage, and sweet sorghum at 4 to 10.5 fluid ounces per acre. No more than 28 fluid ounces may be applied per year and there must be a minimum of 7 days between applications with no more than four applications per year. There must be a minimum of 21 days between application and harvest.  Please see the Transform section 18 for specific rates on grain and forage sorghum (Figure 3).

 

Nathan Mercer, Laboratory Technician  and Ric Bessin, Extension Entomologist

 

 

Posted in Grains