Breeding support

Travel summary

Insecticide resistance in the cotton bollworm Helicoverpa armigera has been one of the greatest limitations to successful pest control and economic cotton production in Australia. The introduction of transgenic cotton has reduced the dependence on insecticides for control of this pest, however sprayed conventional (non Bt) cotton is still a viable cropping option in its own right as well as acting as a refuge for transgenic cotton. It is imperative therefore that resistance is monitored and managed to ensure insecticides remain an effective option now and in the future.

This research project focussed on the incidence and cause of insecticide resistance by Helicoverpa armigera and to a lesser extent H. punctigera. The objectives included continuing the insecticide resistance monitoring program for Helicoverpa spp., investigating resistance development within a Helicovpera spp. population, assessing the impact of AWM/IPM on resistance management, and formulating and promoting improved resistance management guidelines. Key findings include:

• Detection of low frequency resistance to the newer IPM compatible chemistries used against H. armigera including indoxacarb (Steward®) and emamectin benzoate (Affirm®).

• Indication that resistance to spinosad (Tracer®)and chlorfenapyr (Intrepid®) which had been increasing in previous years has decreased to low frequencies.

• Resistance is still present at variable frequencies in field populations to those chemistries that H. armigera are known to have developed resistance to, including endosulfan, pyrethroids, methomyl and organophosphates (profenofos).

• Very low frequency detection of resistance to endosulfan, pyrethroids and abamectin (Agrimec®)by H. punctigera in some valleys.

• Information recorded on species complex across time and space within cotton growing regions which has implications for the monitoring project and also for resistance management.

This information was used in assessment of current strategies and formulation of new strategies for managing insecticide resistance by the TIMS committee. The results and general resistance management tactics and information were promoted to the industry both verbally and written.

Various external factors inhibited effective analysis of the effects of AWM and IPM practises on resistance management. These included drought effects, low H. armigera pressure and high H. punctigera pressure resulting in several farms in the Macintyre Trial in 2003/04 and 2004/05 exiting the trial to use harder chemistry on this pressure.

Attempts to study resistance development to indoxacarb and emamectin benzoate, key IPM compatible chemistries about which little is know in regard to resistance, were unsuccessful. Problems encountered however have implications for resistance management, with further research to be undertaken.

The aim of the project was to develop SIRATAC Plus by reimplementing SIRATAC to professional software engineering standards using current technology developed in knowledge engineering and data base management. The original SIRATAC code was written in FORTRAN over a period of 12 years and had become intractable, and having been patched and repatched many times, had reached the end of its useful product life.

Equipment purchase

The visits to research institutions proved extremely enlightening and valuable. Britain the parlous state of funding for domestic agricultural research was most evident, with University and Government research groups being closed down or severely cut back. Nevertheless , their appeared to be considerable support for overseas development projects in Africa and India, particularly for Heliothis work. The trip was most valuable in revealing the research techniques in use for studying insect flight and migration, and for work on sensory physiology and host plant selection. Some of these eg . tethered flight techniques may be usefully applied to research projects in Australia. Useful contacts were made with many researchers , particularly Dr. A.G. Gatehouse and Dr. M. Simmonds, and the trip emphasised the profusion of research groups involved in research on heliothis in Britain and Europe, where the insect is not itself a pest but for which considerable funds are available for research.

Equipment Grant

The GrassRoots Program allows cotton valley regions to investigate community grower projects.

Farm scale trials of Canopy Temperature Sensors (CTS ) across various irrigation lay out and systems over geographically different locations across the Macquarie Valley were carried out during the 2015/16 growing season . The idea was to combine CTS data with soil moisture probe data as well as weather stations and in field weather sensors. The project aimed to let growers use the technology and get support from commercial and industry specialists. A series of trials examined the effect of heat stress units on different irrigation systems ( drip, overhead, furrow ). Post season we looked at quantifying the relationship between canopy temperature and yield and the relationship between water use efficiency and canopy temperature.

Deep drainage below the root zone is still the least understood component of the water balance, especially in cracking clay soils. It represents a waste of a valuable resource and can leach nitrogen out of the root zone. It has the potential to cause watertables to rise, with the accompanying risk of salinity. Drainage can move contaminants, such as salt and agrochemicals, into the groundwater.

The lysimeter facility at the Australian Cotton Research Institute, near Narrabri NSW, was used to study drainage, its contaminants and its interaction with groundwater in a heavy clay soil under a furrow-irrigated cotton – wheat rotation from 2006 to 2011.

Drainage during the cotton seasons varied from 0 – 74 mm, under wheat it was negligible and under fallow it was 23 mm. Drainage occurred in two forms: matrix drainage and by-pass drainage. The former occurs when the water storage capacity of the soil is filled due to prolonged rainy periods with any extra water becoming drainage. Drainage rates are not high (<0.5 mm/day) but can continue for periods of a month.

By-pass drainage occurs after furrow irrigation when water flows rapidly down macropores and by-passes the matrix of the subsoil. Peak drainage rates are reached 25 hours after irrigation and can reach more than 3 mm/day. The rate then declines exponentially over a week to about 0.5 mm/day. The amount of by-pass drainage appears to be controlled by the soil water deficit in the upper metre of soil. Drainage increases as the 0 – 0.5 m layer becomes drier, possibly due to greater cracking. However, larger deficits in the 0.5 – 1.0 m layer decrease drainage and appear important in mitigating by-pass drainage.

The risk of by-pass drainage is greatest when irrigation is necessary early in the cotton season, when the crop is too small to create a subsoil deficit between irrigations, especially if the subsoil was already wet before sowing.

The risk of matrix drainage can be minimized by managing both the rotation and irrigation scheduling to ensure there is sufficient deficit to accommodate likely inputs of water and irrigation at any time of year. Nevertheless there will always be times of above average rainfall when the profile is filled to capacity and drainage occurs.

However, some drainage is necessary to leach salts from the irrigation water that accumulate in the root zone. The electrical conductivity (EC) of matrix drainage is greater than by-pass drainage, suggesting matrix drainage is more efficient at leaching salt.

In addition to salt, drainage leaches nitrogen from the topsoil. During the 2008/09 cotton season approximately 9.5 kg N/ha – equivalent to 6% of that applied as fertilizer – was lost in drainage.

Seasonal drainage from the root zone appears to recharge the watertable at 16 m depth within weeks, although this result is still tentative. There is continuous downwards leakage of salty water from the upper, watertable aquifer into the lower confined aquifer, from which water is extracted for a variety of uses. This leakage is exacerbated by pumping from the lower aquifer.

The lysimeter was also used to test less expensive methods of estimating drainage. A barrel lysimeter installed near the lysimeter facility overestimated drainage, whereas the chloride mass balance method underestimated drainage.