Summary

This project will include the first ever study on armyworms in rice in south-east Australia. It has been assumed that all armyworm in rice belong to one species (Leucania convecta), however this assumption has never been tested. Estimates of economic thresholds for armyworm have been based largely on guesswork and grower/agronomist experience, and the majority of chemical treatments have been used in rice on the strength of a general registration for ‘cereals’. Work on maize suggests that the parasitism rates for armyworm are very high, but this may not hold true for rice and needs to be investigated. Further, it has been believed that armyworm moths invade the crop after migration from breeding areas in western ranglelands, and caterpillars developing in rice do not lead to subsequent generations within that crop due to a combination of parasitism-induced larval mortality and inadequate pupation sites in flooded crops (armyworm usually pupate in the soil). All aspects of these assumptions will be tested in this project. Larvae will be collected from crops under different water management regimes and densities will be assessed within and across fields to determine if current sampling plans are appropriate and whether water management affects population levels. Collected larvae will be reared to adulthood and identified morphologically, with additional larvae and those that die due to parasitism being confirmed (or otherwise) as L.convecta using DNA barcoding. This aspect of the project will be conducted by Dr David Gopurenko, NSW DPI, Wagga Wagga. Armyworm colonies will be established in the laboratory and glasshouse experiments will be conducted to determine if adult moths are preferentially attracted to water-stressed plants. Field cages will be used to assess the effects of known larval densities on crop yield, and laboratory bioassays will be used to assess the efficacy of newer generation pesticides

Program

Rice

Research Organisation

(DPIE) The Crown in right of the State of NSW acting through the DPI within the Department of Planning, Industry and Environment

Objective Summary

1. To confirm that only one armyworm species (Leucania convecta) is present in southeast Australian rice crops;
2. To quantify armyworm densities within and across rice crops to validate sampling plans and determine whether crops grown using delayed permanent water or mid-season drainage are more vulnerable to armyworm attack, and the basis for that vulnerability;
3. To determine the level of parasitism in armyworm populations in rice and how that may affect implementation of spray thresholds;
4. To develop science-based thresholds for armyworm control, incorporating larval density, larval development stage, and crop stage;
5. To identify newer generation pesticides for further development for armyworm control;
6. To evaluate duck exclusion netting for use at bloodworm trial sites and develop fipronil and potentially other compounds for direct spray application against bloodworms;
7. (Alternate objective: subject to APVMA permit availability, conduct commercial trials of niclosamide against rice snails);
8. Determine the susceptibility of commercial rice varieties to stem rot;
9. Test for differences between stem rot isolates from different locations in southern NSW;
10. Undertake trials to investigate whether saline water increases the infectivity of stem rot.