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Latest FAW Report

Updated Feb 25, 2026

Fall armyworm update – late February

Fall armyworm (FAW), Spodoptera frugiperda, remains active across much of the country. Pressure is still highest in Northland. Several sites continue to report moderate to high infestations. A second large moth flight has now been recorded in the Far North. Smaller flights are also being detected in other regions, including traps at Foundation for Arable Research NCRS. These flights indicate continued breeding and movement between crops. Generations are overlapping. Larvae of mixed sizes are present in many paddocks. This pattern is typical for late February.

Crop stage and risk

The first maize crops are now being harvested. Many others are close to maturity. At this stage, most FAW larvae are feeding in or around the cob. Damage is less visible than earlier whorl feeding, but yield loss can still occur through kernel loss and contamination. Late-planted or replanted crops remain at greatest risk although many of these are progressing well. Green leaf area and fresh silks continue to attract egg laying. These paddocks should still be checked weekly.

Do not assume risk has passed because the crop looks nearly finished. Late-season infestations can still reduce grain fill and silage quality.

Post-harvest management – do not miss this step

After harvest, pupae may remain in the soil. These pupae can emerge as moths and move into nearby standing maize, sweetcorn, or other host crops.

Grazing harvest residue and simple cultivation or “pupa busting” can significantly reduce survival. Shallow tillage or soil disturbance breaks cells and exposes pupae to birds, drying, and predation. This is one of the few actions that lowers the next generation without chemical input. This step is often overlooked. But it may reduce local pressure.

FAW has been recorded feeding on more than 350 plant species, with a preference for C4 grasses. Volunteers, pasture edges, and grassy weeds can all support carryover populations. Clean-up after harvest matters.

Scouting remains essential

Traps confirm flights. They do not tell you whether to spray. Direct crop checks remain the only reliable decision tool. Walk the full paddock. Look at multiple sites. Open cobs and inspect for larvae and frass. Check both edges and centres. A short, regular inspection can prevent unnecessary cost. Poorly timed sprays on large larvae or protected stages rarely give good control.

Other pests to consider

Two additional caterpillar pests are also active and may be confused with FAW:

  • Helicoverpa armigera (corn earworm) is present in many regions. Larvae feed in silks and kernels with little early sign. Damage is often hidden until harvest.

  • Mythimna separata (cosmopolitan armyworm) remains a strong foliar feeder. Large populations can strip leaves quickly and reduce yield, especially in stressed crops.

Broad insecticide use can disrupt natural enemies and allow these pests to increase. Consider thresholds and timing carefully.

Seasonal pattern

Late February often marks a transition. Early crops dry down. Later crops stay green and attract moths. Populations concentrate in these green “islands”. This can make local damage appear sudden and severe. Focus effort where the crop is still actively growing. Mature or drying crops are lower priority.

Key actions for this week

  • Continue weekly scouting of all late maize and sweetcorn.

  • Check cobs as well as leaves.

  • Avoid spraying large or hidden larvae.

  • Cultivate or disturb soil soon after harvest to reduce pupae.

  • Share observations with neighbours and advisers.

Local information improves timing and outcomes. Your observations are important. Please report FAW activity and outcomes to ashley.mills@FAR.org.nz.

Regional Updates

Northland

Updated Feb 25, 2026
  • Crops are progressing well despite multiple larval stages present across the region. Far North trapping has seen a second large moth flight for February. Most maize crops will have passed the high-risk stage as they mature and become ready for harvest. Later-planted crops can become "green Islands" for adult FAW seeking to lay eggs.  These crops should still be scouted regularly.

Auckland and Waikato

Updated Feb 25, 2026
  • FAW is widespread in small populations, and small moth flights have been recorded.

Bay of Plenty

Updated Feb 25, 2026
  • FAW is present in some maize and sweetcorn paddocks. Walk your crops and identify larvae when they are small and easily identified by "window pane" type damage.

Gisborne

Updated Feb 25, 2026
  • FAW reports have been received of low-level infestations, some male moths have also been caught in pheromone traps. Walk your crops and consult your advisor if you have concerns.

Westland

Updated Feb 25, 2026
  • Populations are widespread across Westland, with some significant populations nearing the 20% threshold.  There are multiple stages of the lifecycle present, making intervention decisions challenging.  Beneficial species have been observed late this season, likely related to poor weather conditions. Cotesia ruficrus and an abundance of Meterorus spp. have now accounted for a decent proportion of FAW larvae, and plants are beginning to grow rapidly.

Tasman

Updated Feb 25, 2026
  • Populations of FAW have been observed in multiple maize paddocks.  Maize is now well advanced and should have outcompeted any FAW pressure, although grain crops and sweetcorn crops should still be scouted regularly.  Walk your crops and identify damage and larvae. Consult with your advisor if you have any concerns.

Taranaki and Manawatu-Whanganui

Updated Feb 25, 2026
  • A small number of suspected male FAW moths have been caught in pheramone traps in the region.  Scouting crops should be factored in as often as possible to identify any larvae in paddocks that may be at risk.

Canterbury

Updated Feb 25, 2026
  • There have been FAW observations in a small number of Canterbury maize crops.  These are likely moths that have been blown in recently from neighbouring regions that saw moth flights in late January or early February.  Maize crops are well advanced, and the small FAW populations reported should not pose a threat to crops.  Scouting is still important to track the pest, especially in any sweetcorn or later planted maize crops.

Hawke's Bay

Updated Feb 25, 2026
  • FAW reports have been received this month however, only small populations have been observed and do not appear to be a threat to advanced maize.  We urge sweetcorn growers to continue to stay vigilant.

Is it Fall armyworm?

There are three key characteristics used in combination that will help identify FAW.

  • First, a distinct ‘Y’ on the head leading into the dorsal line.
  • Second, four trapezoid patterned dots on the body segments.
  • Finally, four pronounced dots in a square pattern at the rear.   

Other pests may share a similar identification but not all three key markings together.

 

How to identify FAW

Photo courtesy Bioeconomy Science Institute (PFR) 

Fall armyworm lifecycle and damage

Should I be monitoring my crop?

Crop monitoring is vital for managing pests in maize and sweetcorn effectively. Regular monitoring starts as soon as crops are planted.  The most effective crop monitoring tool is crop scouting, which is defined as 'careful continuous observation', where a crop scout walks the whole crop to assess infestations and fresh damage. Crop scouting helps detect pest presence early, preventing significant damage during the vulnerable establishment stage of crops. It enables growers to assess pest populations, identify affected areas, and determine the most effective and timely control measures. Monitoring also supports integrated pest management (IPM) by providing insights into the activity of natural enemies, like Cotesia ruficrus. This ensures that interventions, such as selective insecticides, are used only when necessary, reducing costs and minimising environmental impact.  It is also a great opportunity to assess crop status, nutrient requirements, other pests present, and disease and virus pressure, like Northern leaf blight.

How do I monitor my crop?

1. Identify the crop stage and plan the scouting choose a pattern (zig-zag or "W" shape) to cover all parts of the field.

2. Walk the field properly follow the planned path, and stop at regular points across the field.

3. Inspect the plants check several plants at each site for FAW signs:

  • Damage on leaves
  • Frass (insect droppings)
  • Larvae feeding in the whorl or on leaves
  • Identify and record the presence of other pest species.
  • Observe and record any beneficial species, especially Cotesia ruficrus.

4. Count and record

  • Record the total number of plants checked.
  • Record the number of plants with FAW damage or larvae.
  • Record the size of FAW larvae.
  • Record sightings of other pests or beneficial insects.

5. Calculate the percentage use the formula:

  • (Number of damaged plants ÷ Total plants checked) × 100
  • Example: (24÷150) ×100=16%

6. Compare to the threshold use the threshold table to decide if action is needed

7. Repeat scout crops as often as possible, ideally once a week at a minimum, following a different path each time.

Note: Checking more sites within a crop gives a far better picture of Fall Armyworm infestation than checking more plants per site. The key is spatial coverage—aim for around 50 sites (more for large paddocks, fewer for small ones)— or enough until you are confident you understand the infestation’s spread and severity

 

When plants are small and it is easy to move through the crop, we recommend a "W" shape scouting pattern.

 

 

When plants reach the later whorl stage, it can become harder to move through the crop.  We recommend a zig-zag-shaped scouting pattern, allowing quicker and more effective coverage of the field.

Monitoring for adult FAW moths

Why does the size of the caterpillar matter?

Identifying the size of Fall armyworm (FAW) larvae is important for effective targeted chemical intervention because smaller larvae are more vulnerable to insecticides. Early detection of young larvae, typically less than 10 mm in length, allows for more effective control before they burrow into the whorl or cob. As larvae grow larger, they become harder to kill, cause more damage, and may require higher chemical inputs, which increases cost and environmental impact. Accurate assessment of larval size ensures the timely and efficient application of control measures.

 

Source: Corteva Agriscience

Economic Thresholds

Economic thresholds are very important in an Integrated Pest Management (IPM) strategy because they help make smart decisions about pest control. An economic threshold is the level of pest numbers or damage at which action must be taken to prevent the pest from causing too much damage and reducing the crop yield in a way that would cost more money than the cost of controlling the pest.

This is the current New Zealand economic thresholds guide developed by Bioeconomy Science Institute (AgR)

What are other similar pests in maize?

What are beneficials?

Let the good guys do the work!

A wide range of beneficial predators and parasitoids contributes to the natural control of Fall Armyworm (FAW) in arable cropping systems, including maize and sweetcorn. These natural enemies can be categorised into resident and transient species. Resident species live within the crop environment year-round, playing a crucial role in controlling pests during crop establishment when the plants are most vulnerable. Transient species, on the other hand, move into the crop only when a pest population is present and serve as an important part of pest suppression.

Predators

Predators, such as spiders, are among the most effective natural enemies of FAW. Spiders can be abundant in maize and sweetcorn systems, preying on a variety of FAW life stages, including eggs and larvae. These predators are relatively easy to spot due to their larger size and active hunting behaviour. Their impact is immediate as they capture and consume their prey directly and may contribute to a significant reduction in FAW populations.

Parasitoids

Parasitoids, such as the wasp Cotesia ruficrus, are less visible but very important in controlling FAW. Cotesia ruficrus lays its eggs inside FAW larvae, and the developing wasp larvae consume the host from within, eventually killing it. This activity often goes unnoticed until the later larvae or pupal stage when the parasitoid creates a bunch of cocoons within or near the remains of the host. These parasitoids can also be monitored by examining host larvae for signs of parasitism or identifying cocoons in the crop.

Integration with Integrated Pest Management (IPM)

IPM strategies aim to maximise the populations of resident beneficial species, such as spiders, while encouraging the activity of transient species like Cotesia ruficrus. With the reduction or withdrawal of broad-spectrum insecticides, it may take time for resident populations to recover and establish, but transient species can readily colonise a crop when FAW is present. Encouraging biodiversity, maintaining habitats, and using selective insecticides can help optimise the roles of these natural enemies in FAW management.

Plant & Food Research has identified Cotesia ruficrus and spiders as key natural enemies of FAW in New Zealand maize and sweetcorn crops. However, many other predators and parasitoids also contribute to the natural suppression of FAW populations, forming a diverse and dynamic system of biological control. This natural management method is a critical component of sustainable FAW control and reduces reliance on chemical insecticides.

Natural predators of FAW

Fall armyworm resistance management

Insecticide options

Products Last Reviewed Jan 30, 2026
120 g/L Jemvelva® active (Spinetoram)
Sparta™

Mode of Action: Jemvelva® active is active on all larval life stages and enters the insect primarily through the digestive system (ingestion activity) and secondarily through the insect exoskeleton (contact activity).

IRAC Group: 5

Beneficial Impact: Anecdotal evidence suggests this active ingredient is suspected to be harmful to small parasitic wasps

Spray Information
Bacillus thuringiensis var. kurstaki
DiPel DF

Mode of Action: Microbial disruptors of insect midgut membranes

IRAC Group: 11

Beneficial Impact: Low Lepidopteran-specific microbial toxin that must be ingested.

Spray Information
Chlorpyriphos
Multiple generics

Mode of Action: Organophosphate. Has contact and vapour action and also acts as a stomach poison when ingested. Acts directly on the nervous system of susceptible pests.

IRAC Group: 1B

Beneficial Impact: High impact on all insects, very harmful to beneficials.

Spray Information
lambda-cyhalothrin
KARATE ZEON, CYHELLA, HALEX CS, LAVRON, TAEKWANDO 250 CS

Mode of Action: Synthetic pyrethroid. Primarily a contact and stomach poison with direct effects on the nervous system of susceptible insect pests.

IRAC Group: 3A

Beneficial Impact: Highly toxic to ALL beneficial insects

Spray Information
Tetraniliprole 480 g/L
Vayego Forte

Mode of Action: Group 28 compounds modulate insect ryanodine receptors (RyRs), which are calcium channels critical for muscle function. By binding to these receptors, they cause muscle paralysis and cessation of feeding, leading to insect death.

IRAC Group: 28

Beneficial Impact: Low impact on most beneficials, although effects on Cotesia ruficrus are currently unknown.

Spray Information
Chlorantraniliprole 200 g/L
Coragen®

Mode of Action: Group 28 compounds modulate insect ryanodine receptors (RyRs), which are calcium channels critical for muscle function. By binding to these receptors, they cause muscle paralysis and cessation of feeding, leading to insect death.

IRAC Group: 28

Beneficial Impact: Harmful to some beneficial insects – particularly some foliage-dwelling predators which may be used in Integrated Pest Management.

Spray Information