Riparian land is usually the most fertile and productive part of the landscape: providing benefits to both agriculture and the natural environment.

Weather and climate news 13 July 2015

Controlling unwanted cotton in the farming system is an essential part of good integrated pest and disease management.

In August 2014, St George cotton growers took part in their first 'Spring Clean' event, turning the difficult business of disease management into a fun, social day; uniting the community behind the common goal of destroying disease harbouring volunteer cotton plants.

Deep drainage varies considerably depending on soil properties and irrigation management, and is not necessarily ‘very small’ - 50-100 mm/yr is typical, though 0 to 900 mm/yr has been observed. Soils used for irrigated cotton have much more diverse properties and management requirements than the simple description ‘clay soil’ suggests. Some drainage, or leaching fraction, is needed to avoid salt build up in the soil profile, but only where more saline water is used. This may be particularly relevant for CPLM and drip systems where the leaching fraction may not be provided by rainfall. The consequences of deep drainage are distinctly different where underlying groundwater can be used for pumping (fresh water, high flow rate) and where it cannot (saline water or low flow rate). Near saturated conditions can be found 2 to 6 metres under irrigated fields, conditions which do not exist under native vegetation.

The UQ35c twelve-month project continued on from the UQ32c research covering the Helicoverpa armigera microsatellite survey of field collections over twelve of the major cotton growing regions during the 2003-2004 season. This microsatellite survey provides information on population structure and movement of H. armigera at both the local and regional levels. Over the preceding three years of study, more and more collaborating groups have provided collections to the microsatellite research, and as such the work is reaching a national scale.

This studies primary object was to continue collecting data on the migration and recruitment of H. armigera and then to extend this research to include a description of (i.e. tracking) the movement of resistant and susceptible H. armigera across these regions. A secondary aim for the new project was to incorporate ecological data to provide a more comprehensive understanding of H. armigera movement. These combined outputs are intended to provide better and more specific information on the control for H. armigera into area wide management strategies for the cotton and grains industries.

This study followed on from a series of

focus groups run throughout the cotton

industry in 1997 to increase the

understanding of issues impacting on the

adoption of Integrated Pest Management

(IPM) technologies and strategies in the

industry. They explored the social,

economic and technological aspects of

IPM.

The 2001 study revisited industry

attitudes and use of IPM in the cotton

industry. It sought to identify any

changes in understanding and attitudes

since 1997 through the eyes of

participants, identify new issues affecting

IPM use and management, and provide

further guidance for research and

extension strategies into the future. It also

sought feedback on Area Wide

Management (AWM), which was a

relatively new initiative in IPM strategies.

Key changes to industry attitudes and

practices towards IPM are summarised in

Table 5 (p13-24), is detailed in the Final Report, together with key

activities that have been undertaken and

recommendations for the future.

In Australia, the cotton bollworm, Helicoverpa armigera, has a long history of resistance to

conventional insecticides, Transgenic cotton (expressing Bt toxin Cry1Ac) has been grown

for H. armigera control since 1996.

This project demonstrated that the strain of H. armigera, which came from from the survivors

of Dr Ho Dang’s resistance monitoring programme, are resistant to Cry1Ac toxin (275 fold).

Some 70% of resistant H. armigera were able to survive on Cry1Ac transgenic cotton

(Ingard), a small but significant proportion (5%) also survived on Bollgard II cotton. The

resistance is inherited as a non sex-linked semi-domminant trait. Resistance was associated

with elevated esterase iso-enzyme levels, which were inherited with resistance. Studies of

esterase binding to Cry 1Ac by conventional enzymatic techniques and ground-breaking

surface plasmon resonance real-time bimolecular analysis techniques showed that resistant

strain esterase could bind to Cry1Ac pro-toxin and activated toxin. Studies with live, first

instar larvae, showed that Cry1Ac resistant larvae, fed on Cy1Ac cotton or Cry1Ac treated

artificial diet, had lower esterase activity than non-Cry1Ac fed larvae, thus giving direct

mechanism for the selection of this esterase based resistance mechanism on transgenic cotton.

Cross-resistance studies in the Cry 1Ac resistant strain, showed that Cry 1Ac resistance was

linked to spinosad resistance. Spinosad resistance in H. armigera is also due to esterase

sequestration and thus both Cry 1Ac and spinosad have a common resistance mechanism in

H. armigera. Both Cry 1Ac and spinosad esterase mediated resistances were suppressed by

the insecticide synergist piperonyl butoxide.

Confirmation of Cry1Ac resistance in a strain of H. armigera derived from survivors of a

field Cry1Ac resistance monitoring programme in Australia and findings of an esterase

mediated resistance mechanism that can sequester Cry1Ac, are important to the future of Bt

crops. Of further concern, is the semi-domminant status of the resistance mechanism, which

will make H. armigera resistance management on Bollgard II cotton more difficult. Survival

on transgenic cotton, further emphasises the field significance of resistance to Cry1Ac.

Cry1Ac resistance will place additional selection pressure on the Cry2Ab toxin component of

Bollgard II cotton. Given that H. armigera is a cosmopolitan pest of cotton and other crops,

the finding of an esterase-mediated resistance mechanism may pose a considerable threat to

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the future efficacy of Bt transgenic crops, world-wide. The ability, however, of PBO to

“cross over” from synergising conventional insecticides to synergism of transgenic cotton

against resistant pests represents a considerable breakthrough in the battle to effectively

manage transgenic crops and to retain their efficacy against resistant insects

In July 2000, an Integrating Our Approaches workshop involving trigators from the Emerald

Irrigation Area (EIA) and Dawson Valley, private sector consultants, Industry Development

officers, and staff from NR&M, DPI and Sunwater explored how property planning

requirements could be rationalised. The workshop brought together the different groups

involved in such activities with cotton, and the fruit and vegetable sector - the development of best management practices, water use efficiency, water and vegetation reform, crop production, and property level land and water management plans. It was the first time all these different groups had got together to talk about how to make the property planning process simpler, be it voluntary or regulatory. The workshop explored issues such as duplication and rationalisation of effort, information access and management, grower experiences, cost and incentives, property versus landscape scale.

Field cropping systems in southern NSW have traditionally been associated with the production of grain crops. However since the 1998-1999 growing season there has been a rapid expansion in the area of cotton grown from approximately 1000 ha to a peak of 16000 ha in the 2001–2002 growing season. Due to the drought conditions experienced in the 2002–2003 season plantings of cotton declined due to water shortages. However, it is expected that dependant on the availability of water, the area of cotton production within the region will continue to rapidly increase in at least the short to medium term. The southern cotton growing region in eastern Australia faces production and environmental issues that differ from more northern areas. The main driver behind the differences is the short growing season experienced in the region. This means that production systems that have high inputs and have little tolerance to insect or pathogen damage. Furthermore production may be based on systems using ultra narrow row (UNR) and 15 inch row spacings and the strategic use of plant growth regulants in an effort to minimise the period from planting to harvest, (i.e. maximise earliness).