Potential impact of fall armyworm on sugarcane
Broadacre crops at particular risk of fall armyworm are the grass species of maize, sorghum, rice and sugarcane.
Overseas, sugarcane is not typically impacted by fall armyworm, although it is reported to feed on it. It is possible that under high fall armyworm pressure, sugarcane can be defoliated to some extent, but at this point it is unknown to what extent this may happen in Australia.
There are a number of other species of armyworm and loopers that defoliate sugarcane in Australia, but they rarely require chemical control. It is likely that the management recommendations for these species will be applicable to the fall armyworm. The potential for crop loss is greatest when defoliation occurs repeatedly through early-mid summer.
Overseas, fall armyworm has rapidly developed pesticide resistance where subjected to repeated and prolonged use of insecticides.
What to look for
Egg masses and small larvae will be difficult to find in sugarcane. With other armyworm species, larval activity is often overlooked until defoliation is severe and leaves are stripped. Larvae may be more visible at night when they are actively feeding.
How to manage an outbreak
Infestations of armyworm typically do not warrant spraying in sugarcane.
If an infestation is not detected until severe defoliation is evident, it is unlikely that spraying will be of benefit as the damage has already been done. If a crop has been defoliated previously, regular monitoring for larvae and leaf damage through summer is advised to prevent further loss.
Armyworm may move into cane from weeds and grass in and around the cane fields.
Key to the control of any pest is an integrated pest management approach. Early or frequent spraying of armyworms will disrupt the activity of these biocontrol agents. With industry, we are working to identify strategies and tactics for the medium to long-term response.
Some insecticides used for the control of Helicoverpa armigera, other armyworms and caterpillar pests may provide some level of control of fall armyworm. Biocontrol agents released for Helicoverpa are also expected to have an impact on fall armyworm.
It is essential with any pesticide use for fall armyworm control that the implications for chemical resistance development in other pests that may be exposed and the potential impact on natural enemies are considered.
The Australian Pesticides and Veterinary Medicines Authority (APVMA) is currently assessing, as a priority, applications for permits for the use of chemicals against fall armyworm. Check for the latest chemical permits applying to fall armyworm by using the APVMAs permit portal—search for 'fall armyworm' and tick the 'pest/purpose' button.
You should already have strong on-farm biosecurity measures to protect your crops from pests and diseases and should implement good farm hygiene for weed control to remove hosts that could build populations.
Read the sugarcane fall armyworm fact sheet.