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

19

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).

Number of eggs and % Hatch is from collections from all crops supplied for Bt and

Conventional Chemistry Resistance monitoring.

% H. armigera is from crops that attract both Helicoverpa species, cotton and pigeon pea,

to give an indication of species composition. Excluded are collections from maize and

sorghum.

% Parasitism is the percentage of eggs from all crops supplied to the Bt resistance

monitoring program that were parasitised by Trichogramma spp.

Fusarium oxysporum f.sp. vasinfectum (Fov) was first identified in Australia in 1993, and as

since become one of the most significant threats to the country's thriving cotton industry. The

interaction between a unique Australian biotype of Fov and cotton hosts with varying

susceptibilities to Fusarium wilt was studied. This research described the infection process an

associated host defence mechanisms of two commercial cotton varieties after inoculation with

Fov, and quantified their subsequent accumulation of antimicrobial terpenoids.

A rapid, reliable glasshouse bioassay that correlated with field resistance was developed for the

study of Fusarium wilt of cotton. Detailed observations of the infection process obtained through

light microscopy were used to formulate the disease cycle of Australian Fusarium wilt of cotton.

Using pathogen growth assays, varietal differences in root exudates and vascular tissues in the

cotton hosts were documented. Root diffusate from the most susceptible cotton variety to

Fusarium wilt, Siokra 1- 4, contained a lipophilic compound that promoted the germination of Fov

microconidia. On the other hand, a lipophilic compound present in diffusate from the least

susceptible variety, Sicot 189, inhibited the growth of Fov germ tubes.

A bioassay using inoculated whole plants showed that Fov colonisation of the vascular tissues of

Sicot 189 was restricted after 3 days. The basis for this inhibition was investigated further using

light and transmission electron microscopy. Infection induced the reorganisation of contact cells

in host vascular tissue, including an increase in cytoplasmic content and the partitioning of

vacuoles, which was concurrent with the accumulation of materials in adjacent vessel lumens, via

pits. Histochemical analysis indicated these globular materials secreted into the vessels were

terpenoids. These structural and terpenoid responses in Siokra 1-4 and SiCot 189 were similar,

however, they were more intense and rapid in the latter, less susceptible variety. The responses in

Sicot 189 also corresponded to the time period that pathogen inhibition was observed. Thus, a

correlation was demonstrated between the rapid and intense induction of both structural and

biochemical responses with decreased susceptibility to Fusarium wilt. Detailed HPLC analysis of

vascular tissues confirmed that terpenoids accumulated more rapidly and at higher concentrations

in the less susceptible cotton variety. These findings provided strong evidence for the involvement

of antimicrobial terpenoids in the determination of Fusarium wilt susceptibility of Australian

cotton varieties.

This work represents the most complete survey to date of the interaction of Australian biotypes of

Fov with cotton. These insights can contribute to future cotton breeding efforts and cultural

management of Fusarium wilt in the field. Thus, each part of this study has advanced

complementary facets of our understanding of Fov, and has provided a framework from which

future studies on phytoalexins and other putative cotton defences can be studied.

) used to support pesticide management decisions at the catchment-scale can deliver environmental protection while retaining farm production benefits. Presently, ERA’s in Australia are typically performed to evaluate farm-scale ecological impacts from pesticides. However, as pesticide exposure in rivers is usually a result of the activities of more than one farmer affected by spatially and temporally explicit factors such as climate, hydrology, geomorphology and land uses, a catchment-scale pesticide management approach seems a logical progression. The aim of this thesis was to investigate the potential effectiveness of applying ERA adapted to the catchment-scale as a pesticide management tool for agricultural catchments.

Initially, a catchment-based ERA of diuron, prometryn and endosulfan use in the Gwydir River catchment, NSW, Australia, was used to identify possible aquatic exposure sites. The classic phases of problem formulation, analysis and risk characterisation were established. The problem formulation phase identified hazard concerns and established assessment endpoints specific for areas that were considered to have high (95% of species protected 95% of the time) or lower (90% of species protected 95% of the time) ecological value. The analysis phase identified that the likely exposure sources of diuron, prometryn and endosulfan in the reaches of the Gwydir River catchment were agriculture, characterised using available ecotoxicology and regulatory exposure monitoring information using continuous probability distributions.

The characterisation of risk involved comparing distributions of exposure and ecotoxicity as species sensitivity distributions (SSDs) to estimate the probabilities that the endpoints were being exceeded (Solomon et al., 2000). With the exception of prometryn, significant risk from diuron (maximum risk = 8.95%) and endosulfan (maximum risk = 7.86%) exposure was found to occur in some reaches of the Gwydir River catchment. These areas, considered as “hot spots”, predominated where intensive agricultural production was most prevalent.

An uncertainty evaluation identified a number of information shortfalls in this ERA. These gaps included permanency of ecological effect resulting from pulse exposures, conservative risk estimation that was based on exposure data from a sampling regime targeted when chemical use and rainfall were more prevalent, and, for the purpose of supporting risk management, identification of specific areas in the catchment contributing chemical loads in areas of concern. These uncertainties led to the need for further research.

The consideration of organism recovery under a pulse exposure scenario likely to be observed in the Gwydir River catchment was investigated in a laboratory toxicity study. This study tested the potential for two duckweed species (Lemna minor and L. gibba) to recover from a seven day diuron pulse. The duckweed species were exposed to a range of diuron concentrations (0.3-200 μg L-1) for seven days, and placed in to clean growth media for a further seven days to simulate a recovery phase.

Exposure toxicity and recovery were evaluated through plant and frond counts, and wet and dry weights. The inhibition of growth was used as the toxicity metric by comparing growth response with control (0 μg L-1) populations. Significant growth inhibition of L. minor (EC50 = 34.9 and 52.8 μg L-1 for dry weight and frond count, respectively) and L. gibba (EC50 = 50.3 and 47.6 μg L-1 dry weight and frond count, respectively) was observed at the end of the seven day exposure. By the end of the seven day recovery phase, growth inhibition compared to the controls were shown to decline for a range of treatment exposure concentrations to the point that inhibition was not significantly different from the control for both L. minor (50 and 100 μg L-1, for dry weightand frond count, respectively) and L. gibba (200 and 50 μg L-1, for dry weight and frond count, respectively). With reference to the literature, growth inhibition was determined to be in response to photosynthesis inhibition (Haynes et al., 2000; Fai et al., 2007). Population recovery for treatment concentrations greater that observed in the Gwydir River catchment suggested was a clear reversal of this effect. It was concluded that both L. minor and L. gibba could sufficiently recover from a prolonged exposure event, suggesting the possibility of keystone aquatic plants and algae resilience to diuron exposure occurring in the Gwydir River catchment.

To clarify the risk characterisation uncertainty of diuron in the Gwydir River catchment, a spatial exposure modelling framework was required. A modelling procedure with the capacity to provide a daily time series exposure concentration pointing to catchment areas contributing to chemical load was selected. This framework involved combining two models, a chemical fate model (Pesticide Root Zone Model, PRZM) and a chemical routing model (Riverine Water Quality model, RIVWQ). The inputs to these models were obtained and processed from readily accessible databases and/or literature. Required inputs included soil, land use and weather station information; characteristic agronomic practices for different land uses and their respective label application rates. In accordance with the chemical labels all maximum application rates were used for the respective land uses of cotton, wheat, chickpea, canola and pasture in the simulations. To account for the full range of in season applications two scenarios were required to be run. Specifically, pre- (i.e. chemical incorporated in the top 4 cm of soil) and post-emergence (chemical applied directly to the surface) were simulated for cotton.

The simulation results showed that under the post-emergence application regime the highest chemical loading for streams was predicted. This was the result of chemical being more readily available at the surface to be entrained in runoff. It was found that the post-emergence application scenario reflected more closely the peak concentration magnitude and timing observed in the monitoring data. However, when compared with monitoring data, the model framework was unable to predict peak exposure concentrations on precisely the same dates. This indicated a degree of error in the model predictions, an outcome likely to be the result of uncertainties in the model inputs, especially with respect to pesticide applications, timing and crop rotation scenarios. However, the modelling framework did perform in a way that was consistent with chemical fate and fugacity principles. Subsequently, from these different scenarios, the sub-catchments contributing chemical loads were able to be identified, potential pulse durations were characterised as were their probabilities of re-occurrence, with the longest pulse exceeding the toxicity threshold lasting 6-9 days. It was concluded that this approach to estimating exposure at the sub-catchment level could be a useful tool for catchment management, devising and directing risk management strategies associated with monitoring. However, this will require further calibration and validation for effective use as a risk management tool.

The outputs of this thesis are suggested to provide justification for further development of catchment-based ERA strategies in Australia. These would include site specific chemical loading,employ probabilistic risk characterisation and account for ecosystem biodiversity value and resilience. This strategy would take ERA in Australia from the top-down approach now taken by national regulators to a bottom-up alternative, inclusive of catchment managers

operating at the local level interacting directly with stakeholders. Pesticide exposure concerns identified through an ERA should then be addressed through the implementation of a management strategy. This strategy would utilise outputs from spatial modelling supported by monitoring, as a basis for directing management to areas of a catchment where it is most needed. The thesis concludes that managing pesticide exposure in agricultural catchments with more informed ERA can provide a sounder basis for pesticide use in crop production coexisting with ecosystem protection.

Globally, natural wetlands are under threat from water resource development

reflecting the need to support a growing population. In the Border Rivers Catchment

in Queensland, Australia, a large irrigation industry coupled with a highly variable

flow regime has necessitated the building of large on-farm water storages and often

associated destruction or isolation of their natural counterparts. With the decline in

abundance of natural wetlands, the presence of these storages on the floodplain has

raised the question of their suitability as alternative aquatic habitat. This project

aimed to investigate the diversity of storages and the structure and function of the

aquatic assemblages they support compared with nearby natural wetlands. These

results were then used to recommend best management practice for optimising both

diversity and ecosystem function in storages.

Initially the physical variety of water storages in the Border Rivers Catchment was

described and their morphology and hydrology compared to that of natural wetlands.

Storages and natural wetlands formed two distinct groups based on morphology.

Storages tended to be large, deep structures with a more regular shape, while natural

wetlands were irregular and shallow with large perimeters. Although there was a

degree of variability amongst storage sites, most fell into one group and were

considered to be a ‘typical’ storage in this region.

Storages primarily function as water supplies and their associated management makes

them mostly unsuitable as ‘replacement’ wetlands. However, given the large numbers

of storages across the catchment, if managed effectively, they may provide an

additional source of aquatic habitat and help maintain regional biodiversity. To

maximise the biodiversity of storages it will be essential to reduce the morphological

homogeneity of storages across the landscape and increase habitat diversity within

storages. In the future, improved design of new storages and alterations to existing

storages and their management could help overcome this problem of low diversity of

habitat.

As a group, storages in the Border Rivers Catchment are still fundamentally different

to natural waterbodies, with storages being a mostly homogeneous group. If we are to

sustain the aquatic biodiversity in the Border Rivers Catchment and other similar

irrigation regions it will be necessary to preserve the spatial and temporal variation in

habitat evident in natural wetlands.