Fall armyworm has been confirmed in North Canterbury sweetcorn this week.
Key Points:
- Fall armyworm (FAW) has been confirmed in North Canterbury sweet corn. Although the FAW larvae population is low and at an early stage of development, its presence, when combined with a large corn earworm population means crop losses could be significant.
- The total number of finds for the 2022-23 season remains at 133. Updates from MPI weekly have now ceased so any new confirmed finds will be reported periodically.
- A second large flight has been recorded, with 87 fall armyworm moths found in Northland traps this week.
- The insecticide Sparta™ is now on label for both aerial and ground applications for the control of fall armyworm on maize and sweetcorn crops. Consult with your advisor.
- Avoid the use of insecticides that are ineffective on fall armyworm and potentially harmful to beneficial insects.
- Many crops have been or are close to harvest around the country, which means their preferred food source is reduced. Therefore, it is important to stay vigilant and scout neighbouring paddocks, as fall armyworm could look to other crops for a food source in the absence of maize and sweetcorn. Volunteer maize should not be overlooked either.
- Some areas are still not safe to scout so please put safety first.
- There continue to be reports of fall armyworm larvae being parasitised by the parasitic wasp Cotesia sp. which will help contain the numbers.
- We have received questions on thresholds for economic damage. While we work on New Zealand specific information, international (Australian) guidelines suggest, that at whorl stage and above, economic damage will occur when at least 20% of plants have larvae present and/or signs of damage on 75% of plants. Scout crops (if safe) by using a “W” pattern; fall armyworm tends to feed along rows.
- We are still in a response. All finds must be reported to MPI here or call 0800 80 99 66
- There are no negative consequences to growers for reporting, as this pest will not be controlled by removing crops.
Photo: Fall armyworm (left) and corn earworm Helicoverpa armigera (right). A comparison shows similarities but also distinct differences. It should be noted that colours and shading can vary, even within the same crop.
Thresholds of economic damage:
For the latest identification guides click here and MPI Website here, or contact Ivan Lawrie ivan.lawrie@far.org.nz or Ash Mills ashley.mills@far.org.nz
For other useful tools and guides on detection and identification, consult the FAR website.