Activities are underway to detect the presence of fall armyworm across key sites and information about damage thresholds for fall armyworm management have been sourced from Australia.
Response activities are under way to detect the presence of fall armyworm across key sites. Seed and Grain Readiness and Response along with partners Vegetables NZ, Process Vegetables NZ and Biosecurity NZ have begun with a series of activities to create awareness amongst growers, conduct trapping and monitoring and research the movement of this pest once detected.
The first workshop was successfully conducted in Gisborne on 28 September. It was attended by researchers, growers and industry representatives, with the aim of familiarising all stakeholders with the biology of fall armyworm, its threat to crops and the means to identify its presence. Further workshops are planned for October with dates soon to be confirmed at different locations.
It is key to control larvae at their earliest stages (1-3 out of 6) when they are more susceptible. Likewise, control is more effective in the early stages of crop development when fall armyworm larvae are feeding on extended leaves and have not entered the whorl; at this stage insecticide contact is easier to achieve.
The Davis Scale (see attached file) illustrates the damage that fall armyworm produces at different crop stages (photo credit Plant Health Australia fall armyworm continuity plan).
The Department of Primary Industries Western Australia says that recommended action thresholds for applying control measures for fall armyworm vary by growth stage:
- At seedling stage, if more than 5% of plants are cut.
- At early whorl stage (knee high), if more than 20% of plants are infested.
- At late whorl stage (shoulder high), if more than 40% of plants are damaged and live larvae are present.
- At tasselling/early silking stage, in sweet corn, if more than 5% of plants are infested and in maize, if more than 20% of plants are infested.
Control options
Due to the fact that fall armyworm is new to New Zealand, there are no insecticides on label to control it. However, work is already underway to get the necessary approvals. Meantime, it is possible to draw from overseas experience and list some of the options that are being currently used.
Below is a list of some of the chemicals that are on label for controlling other lepidoptera species in maize and sweetcorn in New Zealand. Check with your chemical reps and agronomists as to the agrochemicals already on label for other lepidoptera on maize and sweetcorn if there is detection of larvae that meet the thresholds for economic damage.
- Deltamethrin
- Cypermethrin
- Alpha-cypermethrin
- Chlorpyrifos