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Native budworm caterpillars are damaging cereal crops

  • Geraldton
  • Mullewa
  • Tardun
  • Mingenew
  • Kalannie
  • Merredin
  • Wongan Hills
A native budworm caterpillar and wheat plant with chewing damage
Native budworm caterpillar and chewing damage on wheat. Photo courtesy of: Christiaan Valentine (DPIRD).

David Stead (Anasazi Agronomy) reports finding a lupin crop at Kalannie which had 3-4 native budworm caterpillars per plant. The crop was at primary pod fill stage and the caterpillars were starting to get into the pods. David also has noticed budworm in cereal crops in the central agricultural region which are causing some concern for growers in regards to what level of damage they are likely to do.

A farmer near Merredin reports finding more than six budworm caterpillars in 10 sweeps in an early flowering field pea crop. The farmer is also finding 10 plus budworm grubs per 10 sweeps in a serradella paddock, while in nearby canola and lupin crops the grub numbers are much lower.

Ty Henning (TekAg) reports finding native budworm in lupin crops north of Kalannie, the budworm caterpillars are causing some feeding damage to the flowers and young lupin pods. Ty also reports finding budworm in some wheat crops near Wongan Hills.

These reports of native budworm grubs doing some damage to lupins pods at this growth stage is unusual as lupin pods will not normally be damaged by native budworm until they are close to maturity and begin to lose their green colouration and leaf fall commences.

Native budworm caterpillars
Native budworm caterpillars. Photo courtesy of: Mark Flannagan.

Grower Mark Flannagan reports finding 10 – 20 caterpillars per 10 sweeps in wheat crops east of Mullewa. Mark mentioned they were finding 3 to 4 budworm caterpillars per 10 sweeps in their later sown Sceptre wheat and 15 to 30 per 10 sweeps in the more mature Devi wheat. Mark was surprised to find such high numbers as there have been no traditional hosts such as radish or lupins in the area. Radish, canola and lupins are usually needed for the budworm to lay eggs on and build up in numbers.

Two agronomists in the Geraldton area have also reported similar scenarios.

Owen Mann (Nutrien Ag Solutions) has observed damage from budworm on the earlier maturing wheat varieties two to four weeks ago at Geraldton. The majority of damage has now transitioned to later sown or later maturing wheat varieties where the heads are just starting to emerge. This may suggest that late booting to early flowering may be a window of susceptibility.

Caterpillars damage cereal crops by chewing holes in leaves, including the flag leaf, chewing the heads, and sometimes cutting the base of the head or eating and damaging the developing seed.

Thresholds for budworm numbers on wheat haven’t been developed and growers are making judgement calls based on rough estimates of damage to decide if they should spray.

Estimates from agronomists suggest that between 10 to 20% of wheat crops have been sprayed for native budworm north of Mingenew.

Nearly all reports are from budworm damaging wheat. There has been little information coming in to suggest any significant damage on barley and oats.

Grower John Flannagan mentioned a wheat crop at Tardun had high numbers of caterpillars with more than 10 budworm caterpillars per 10 sweeps, while the adjacent lupin crop had only had 1 or 2 per 10 sweeps.

Unusual native budworm activity in cereals

The last three years has seen unusually high numbers of budworm caterpillars found in cereal crops, and although some cases may be the lesser budworm, which is known to damage cereals, many cases have been confirmed as native budworm.

On a number of occasions the presence of confirmed populations of native budworm in cereals has not led to significant crop damage and the budworm numbers have declined over a few weeks. While in other cases there have been reports of significant damage to cereal crops without a confirmed identification of the culprit involved.

In the absence of a cereal crop threshold regular crop monitoring over a period of time to determine whether the budworm population is in decline and an assessment of the overall damage to the cereal crop during the same period is the only way a control decision can be made.   

What should you do if you find native budworm caterpillars in cereal crops?

Agronomists or farmers who find native budworm caterpillars in cereal crops causing damage that requires spraying to control the populations are encouraged to forward a caterpillar sample for identification.  Please mail samples to one of the following DPIRD staff;

  • Alan Lord. 3 Baron-Hay Court, South Perth, WA 6151 on +61 (0)409 689 468.
  • Dusty Severtson. 75 York Rd, Northam WA 6401 +61 (0)427 196 656.
  • Svetlana Micic. 444 Albany Highway, Albany WA 6330 on +61 (0)427 772 051.

Native budworm moth trapping surveillance

  • Usual automated and manual trapping locations

Budworm moth numbers reported by volunteer farmers, agronomists and DPIRD staff have remained low for most of WA’s wheatbelt over the past week. The higher numbers reported this week include Geraldton (17 moths), Varley (10), Walkaway (6), Bindi Bindi (4) and Binnu (4).

A mapped view of the native budworm trap captures is available at cesar’s MothTrapVisWA page. For recent native budworm field reports refer to DPIRD’s PestFax map.

The economic spray threshold levels will vary with crop type, grain price and control cost; these can be calculated for each grower’s particular situation using a simple formula outlined in DPIRD’s Management and economic thresholds for Native Budworm page.

More information on native budworm can be found at DPIRD’s 2020 PestFax Issue 7 article Native budworm and other moths are active and PestFax Issue 10 article Native budworm update. Caterpillars are being found in cereals.

For more information contact Alan Lord, Technical Officer, South Perth +61 (0)8 9368 3758 or +61 (0)409 689 468.

 

Article authors: Alan Lord (DPIRD South Perth).

Article input: Christiaan Valentine (DPIRD Northam) and Dusty Severtson (DPIRD Northam).