Armyworm Alert!!!

Dr Iona H. Basdew (Biosecurity Scientist)

15th March 2025

There are current reports of sporadic armyworm outbreaks in sugarcane on the North Coast, Umfolozi, Mkuze and Pongola regions. This alert aims to raise awareness and to help mitigate any signiﬁcant damage to the cane as a result of infestation by the pest.

There are two major types of armyworm in South Africa, namely Fall armyworm (FAW) (Spodoptera frugiperda) and African armyworm (Spodoptera exempta). Both species attack the younger foliage of the cane plant. Other plant species on which armyworm feed in South Africa include maize, sorghum, potato, soybean and groundnut.

Fall armyworm (FAW)

Fall armyworm feed day and night for approximately 10 to 14 days and generally remain hidden in foliage. Moths ﬂy at night only. Fall armyworm rarely display massing and aggregation activity, or marching activity.

Figure 1: Fall armyworm: Main identiﬁcation marks include the ‘inverted Y’ mark on the head and the ‘square’ black spots on the second last segment. Photo: SANBI.

Figure 1 (left): Fall armyworm: Main identiﬁcation marks include the ‘inverted Y’ mark on the head and the ‘square’ black spots on the second last segment. Photo: SANBI.

African armyworm

African armyworm feeds day and night and do not hide in the foliage like FAW. African armyworm also aggregate in long lines and literally march from area to area, unlike FAW. Increased bird activity in affected fields is the first sign of African armyworm infestation, where the birds feed on the exposed larvae.

Figure 2: African armyworm: Main identification features include dark green and black larval colouration with longitudinal white stripes down the length of the larvae.

Figure 2 (left): African armyworm: Main identification features include dark green and black larval colouration with longitudinal white stripes down the length of the larvae.

Management in cane

Spraying insecticides for the control of both species of armyworm can be effectively planned as they feed day and night. Table 1 shows a list of insecticides that are registered for the control of armyworm, but which are also registered for the control of Eldana saccharina on sugarcane.

Where growers do encounter severe infestation of armyworm in upcoming weeks, the application of insecticides in keeping with the start of the eldana spray programme (starting in March 2025) as recommended by SASRI will help manage any armyworm infestation.

TABLE 1: Registered agrochemicals to control armyworm in South Africa, also commonly used on cane for eldana management

Product name	Mode of Action
Coragen	Stomach and contact
Steward	Stomach and contact
Emma	Stomach translaminar
Ampligo	Stomach and contact
Malathion	Stomach and contact