Fall armyworm research, development and extension for horticulture

Grains and horticulture agronomists and consultants from the Bowen-Burdekin region attended a fall armyworm field day at the DAF Bowen Research Facility on 28 September. DAF entomologists Dr Melina Miles, Dr Siva Subramaniam, Dr John Stanley and Vasanthaverni Sivasubramaniam talked with the group about three FAW trials underway at the facility. The trials are:

• testing the yield and growth-rate response of sweet corn to FAW defoliation in the vegetative stages
• testing the effect of insecticides and adjuvants on FAW
• demonstrating non-chemical and soft options for FAW management in sweet corn to reduce reliance on insecticides.

Key points discussed during the visit

The FAW defoliation trial:

• The defoliation threshold trial is designed to understand if, 1) FAW damage equals sweet corn yield loss, 2) FAW damage impacts maturity timing and uniformity and, 3) FAW density is a useful predictor of damage and crop loss.
• The results so far are presented in the graphs of FAW density and treatment biomass (Figure 1 & 2).
• Harvest of FAW-damaged plots will reveal the impact on yield and delayed maturity.
• Field walk attendees offered suggestions on how to assess the impact on sweet corn yield and quality.
• A fresh market harvest will be done around 23 October.

The insecticide and adjuvant trial:

• This sweet corn trial was established to evaluate the performance of registered insecticides with and without adjuvants (in a paired comparison).
• The adjuvants were selected based on the results of previous work.
• In the trial, three insecticides (Vayego®, Success Neo®, Proclaim Opti®) were tank mixed with three different adjuvants.
• The treatment efficacy was assessed against FAW larval mortality, crop damage, and residual toxicity in the silk.
• The insecticide combined with adjuvant had a lower level of FAW larvae in tassels and silks (15 to 20% less) than the insecticide-only plots and prolonged residual toxicity of insecticides in the silk for up to 7 days.
• Detailed results will be presented after the completion of the trials. For further information please get in touch with either Dr Siva Subramaniam or Dr John Stanley.

The sweet corn demonstration site:

• The sweet corn demonstration site aims to treat FAW based on destructive sampling and egg and larval density assessment. The longevity of insecticide residual efficacy determined in earlier field trials will be used to assess when re-infestation is likely and backed up with in-field assessment of larval survival and density.
• The egg parasitoid Trichogramma pretiosum is being released weekly from crop emergence at a rate of 150,000 per ha. Two rows of buckwheat to every 8 rows of sweet corn were established prior to planting sweet corn to provide a refuge for natural enemies and nectar for the parasitoid. Nectar is known to increase parasitoid longevity and egg lay.
• Parasitism levels will be documented throughout the trial in weekly collections of FAW eggs.
• The buckwheat will be sampled to determine whether T. pretiousum (or pests) are persisting.

Working together to design the demonstration site:

• The industry participants were interested in learning more about the contribution of predators to FAW mortality. As a result, the minute pirate bug (Orius sp) will be added to the demonstration and released weekly across the plots at a rate of 5000 per ha.
• The participants were also keen to have more information on the efficacy of multiple polyhedrovirus (SfMNPV): Fawligen, SpodovirPlus. The trial has now been divided up to provide replicated plots with and without SfMNPV at a rate of two applications per week.

The meeting was hosted by the Queensland Department of Agriculture and Fisheries (DAF), and facilitated by Ramesh Puri (extension officer, DAF).