Disease control in summer crops and management strategies to minimise financial losses

Author: Jodie White, Sue Thompson, Mal Ryley and Sara Blake (Centre for Crop Health, University of Southern Queensland), Col Douglas (DAFQ, Hermitage Research Facility) | Date: 31 Jul 2015

Take home messages

  • Management of charcoal rot and fusarium stalk rot in sorghum relies on good agronomy, crop rotation, use of appropriate varieties and timely application of desiccants
  • Management of powdery mildew in mungbean and sunflower relies on timely fungicide application(s) and the best available resistance (mungbean)
  • Management of halo blight in mungbean relies on the use of seed with the lowest possible levels of infection, the use of clean harvesting equipment, weed management and crop rotation
  • Diaporthe species which cause stem canker and other diseases in sunflower and soybean have wide host ranges including weeds; infected living plants and dead residues of these hosts act as “Green” and “Brown” bridges that need to be managed

Background

Surveys and field observations have revealed that stubble borne pathogens such as Phomopsis/Diaporthe (sunflower, soybean, weeds), charcoal rot (soybean, sorghum, sunflower, weeds), Fusarium species (sorghum, mungbeans, weeds), Sclerotinia-spp and Sclerotium-induced base rots (sunflower, soybeans, mungbeans, weeds) are increasing in incidence. Strategic tillage may have a future role to play in managing stubble borne pathogens. More research under Australian conditions is required.

The current GRDC funded project DAQ00186 focusses on the dominant diseases of sorghum, sunflower, mungbeans and soybeans in the northern region – these include the sorghum stalk rot pathogens, sunflower and soybean stem and pod pathogens, mungbean halo blight, neocosmospora on peanuts and the powdery mildews on sunflower and mungbean.

Ongoing changes in the disease spectrum of the northern region also indicate an increased incidence of the two Sclerotinia species across both cooler and warmer areas of the northern region plus sclerotium base rot (Sclerotium rolfsii) a warm weather pathogen favoured by conditions in Central Queensland, the eastern Downs and NNSW. These survey results reflect the concerning emergence of more stubble borne pathogens.

Charcoal rot and fusarium stalk rot in sorghum

Charcoal Rot

Charcoal rot in sorghum is caused by the soil borne fungus Macrophomina phaseolina and is a major stalk rotting disease in sorghum which can lead to plant lodging. The causal agent, M. phaseolina can infect via the roots of sorghum plants at almost any stage of plant growth, but develops more rapidly in plants closer to maturity. Extensive colonisation of stem tissue generally occurs post flowering when plants are placed under a stress, such as unfavourable environmental conditions, particularly hot, dry conditions. This can be further exacerbated by the application of defoliants which also act as a stressor, further promoting growth and invasion of the stem. 

The pathogen is easily identifiable when stems are split longitudinally. The characteristic appearance of black microsclerota (resting bodies) in the vascular tissue and inside the rind of the stalk results in a “peppered” look in conjunction with shredded internal vascular tissue which is grey/charcoal in colour. The fungus is widely distributed throughout Australia infecting the root and stems of over 400 plant species (all major summer field crops and many summer and winter weeds). The microsclerotes can survive in the soil and on stubble for 4+ years. It is uncertain what soil conditions are necessary to reduce the survival of microsclerotes in Australia but overseas studies indicate wet soil can significantly impede their survival.

Fusarium Stalk Rot

Fusarium stalk rot is predominantly caused by the pathogens Fusarium thapsinum and F. andiyazi. Fusarium is prevalent in all sorghum growing regions, with some geographical preference occurring depending on the species.  The weather conditions conducive to infection and development of this disease are not well understood, however evidence suggests that infection can occur early in the crops development where it can remain latent and relatively asymptomatic during much of the vegetative stage.  As with charcoal rot, extensive colonisation of stems occur when stress is initiated post flowering (induced by moisture stress or other factors such as application of desiccant), leading to possible lodging.  

Diagnostic symptoms are easily identifiable when stems are split length-wise; visual symptoms include red – brown discolouration within the pith tissue of the stem, often initially concentrating at the base of the stem. F. thapsinum and F. andiyazi can survive in stubble for up to 3 years and possibly on alternative weed hosts. The host range for these pathogens is significantly more limited than M. phaseolina, however, given the saprophytic nature of the pathogen, survival on stubble of alternative crop and weed hosts is possible and is currently being researched.

Preliminary laboratory and glasshouse inoculations of alternative crop “non-hosts” (both live plants and dead stubble), have shown that possible infection of other crops such as mungbean, maize and wheat may occur.  However, this initial work is under artificial inoculation conditions and may not reflect infield activity.  Ongoing field work is being conducted to confirm the possibility of natural infection of alternative crop non-hosts in an endophytic or saprophytic capacity.

Yield losses

Determination of yield loss associated with either fusarium stalk rot or charcoal rot in Australia has not formally occurred. Quantification of yield loss through in-field assessments is difficult and varies depending on a number of factors including:

  • weather
  • time of infection
  • cultivar susceptibility
  • degree of lodging

Field surveys have demonstrated that the simultaneous invasion of both stalk rotting pathogens (Fusarium and M. phaseolina) occurs regularly making losses difficult to apportion to individual pathogens. Recent field trials artificially inoculated with M. phaseolina resulted in dual infection of both Fusarium and M. phaseolina due to the wounding nature of the artificial inoculation process. 

Charcoal rot. Overseas yield losses have been estimated at more than 50%. Despite the lack of any formal quantification in Australia, significant yield losses have been associated with lodging over the last two seasons, where prevailing hot dry conditions have resulted in widespread high incidence of M. phaseolina and subsequent lodging.

Incidence and lodging were highest in Central Queensland where up to 30-40% total yield losses were associated with lodging, and patches of up to 90% in-field lodging was evident. Realised losses associated with lodging varied and was dependent on ability of individual growers to retrieve lodged heads with harvesting equipment available.

Fusarium species. In Australia, yield loss in the absence of lodging has not been found, but does not preclude the possibility that it occurs.  Although fusarium stalk rot can and has caused significant lodging, as was seen in 2009 season, more recent seasons have seen moderate incidence levels with low and sporadic associated lodging (less than 5%).  Regions that appear to be more prone to Fusarium infection include SEQLD and NNSW.

Management

Management strategies for fusarium stalk rot and charcoal rot are closely related and have subsequently been dealt with in the following section simultaneously. There are no effective foliar fungicides for either disease.  Management strategies that need to be taken into consideration include the following:

  • Soil moisture – planting into adequate soil moisture and ensure row spacing and plant populations are suitable for the field and seasonal situation, to minimise possible post flowering moisture stress.
  • Adequate nutrition – application of adequate fertilisers should be exercised to maintain plant health and vigour reducing nutrient related stress. More specifically, excessive Nitrogen and low levels of Potassium should be avoided.
  • Crop rotations – rotating out of susceptible crop hosts can be effective in reducing the build-up of Fusarium and/or M. phaseolina which may have occurred in mono-cropping systems.  Currently, the host range of F. thapsinum and F. andiyazi is thought to be limited, providing a number of options for rotations.  However, alterations and additions to the list are possible as maize is thought to host F.thapsinum at low levels and more recently a survey overseas has found infection of F. thapsinium on soybean seed. In Australia, surveys and research into possible hosts, including the role of stubble from alternative non-hosts is still ongoing. Rotating out of susceptible crop hosts is more difficult with M. phaseolina due to its extensive host list.  Overseas research suggests that the build-up of microsclerotes is less in some hosts than in others; in some U.S. trials the number of microsclerotes in the soil after several crops of sorghum was less than the numbers after maize or soybeans. This type of rotational farming systems work has not yet been conducted in Australia.
  • Use of lodging resistant, drought tolerant, non-senescent varieties.  In the absence of information regarding the genetics for resistance for M. phaseolina and Fusarium, which are not well understood, the use of cultivars which include some or all of the combined characteristics (drought tolerance, staygreen, standability) may reduce the development of disease, particularly charcoal rot.  While evidence has previously shown that staygreen lines have a better tolerance to M. phaseolina invasion than senescent lines, there is no conclusive evidence yet to suggest that this holds true for Fusarium species.  Preliminary results from field trials where cultivars were colonised with both M. phaseolina and Fusarium, demonstrate that assessment of disease levels based on internal lesion lengths correlated well with assessments for lodging.  However, the absence of lodging does not preclude high incidence levels of either disease, which means caution should be taken to avoid build-up of disease unknowingly, particularly in monoculture systems. 
  • Application and timing of desiccant and harvest.  Timing of application of a desiccant must be assessed with a number of factors in mind.  Early application of a desiccant can increase stress and lodging potential (if applied when <95% seed are at black layer) as much as a desiccant applied too late, particularly if lodging is already occurring and disease incidence is high. Timely harvest once application of the desiccant has been applied is essential.  Preliminary results demonstrate some varietal differences in reaction to application of a desiccant which needs further investigation to determine its role, if any in affecting structural integrity of the stem. 

Powdery mildew of mungbean

In Australia, powdery mildew of mungbean is caused by the fungus Podosphaera fusca which is found wherever the crop is grown. Powdery mildew most commonly appears around flowering time and is first evident as small circular powdery spots on the lower leaves, rapidly covering the entire leaf and spreading to younger leaves up the plant. Small powdery spots can also be found on stems and leaf petioles. The powdery growth consists of minute fungal threads on the leaf surface from which simple fruiting structures bearing spores develop. When mature, these spores become airborne and can spread in the wind for many kilometres. The powdery mildew pathogen survives in Australia on plants of volunteer mungbean and other legume hosts, including phasey bean; it does not survive in soil, stubble or seed.

Yield losses

Fungicide trials conducted at different localities in southern Queensland since 2000 have demonstrated that losses in mungbean yield due to powdery mildew can range from 2.7% to 46% (most commonly 10-15%), depending on the variety, plant growth stage at time of appearance of powdery mildew and the rate of development of the disease. These latter two factors are highly dependent on weather conditions, particularly air temperature and humidity, rainfall and leaf wetness. The available evidence suggests that disease development is favoured by mild temperatures (daily mean temperature of 22-26°C) and high humidity in the canopy, particularly after rainfall or irrigation. Overseas research has shown that yield losses in mungbean due to powdery mildew result from a reduction in seed size and pod number.

Management

The only viable options for management of powdery mildew are resistance and foliar fungicides. The black mungbean variety Regur has the highest level of resistance (moderately resistant – moderately susceptible), while cv. Berken and cv. Celera have the lowest (susceptible). All other varieties are considered to be moderately susceptible, although cv. Crystal and cv. Jade AU have slightly better resistance than the rest. It may be some time before varieties are released with powdery mildew resistance significantly better than either Crystal or Jade AU.

Although several formulations of sulphur are either registered or under permit for management of the mungbean powdery mildew pathogen, the systemic fungicide tebuconazole currently under APVMA permit (Permit PER13979 in NSW and Qld only) and sold as Folicur 430SC® or Hornet 500SC® is superior to sulphur. Trials conducted over many seasons indicate that good control will be achieved if the first fungicide spray is applied at the first sign powdery mildew on the lower leaves and another spray is applied 2 weeks later. Good control has also been achieved when the first spray is applied just prior to flowering even if powdery mildew is not present.

In a trial conducted in 2015 at Warwick, we tested 5 Folicur treatments on cv Jade AU. Folicur is permitted for use on mungbeans under APVMA permit number PER13979 expires 30th June 2017. A spray applied at the first sign of disease with or without a second spray 14 days later (FS, FS+1), a spray applied when powdery mildew was 1/3 – ½ the way up the plant with or without a second spray 14 days later (1/3C; 1/3C+1), and a spray applied before flowering (6 weeks after emergence), followed by two more sprays, 14 days apart (Be). The results are summarised in Table 1 and show that yield from Be (3 sprays) treatment was significantly greater than the unsprayed control (P≤0.05).  Yields from all other spray treatments were not significantly different from the unsprayed control.

Table 1. Yield data and predicted profits of fungicide sprays from the 2015 Warwick trial

Treatment

(no. sprays)

Yield (t/ha)
and % increase 1

$ value increase
at $1200/t

$ Application costs 2

$ Profit

Trial yield

1.5t/ha

Yield 3

Be (3 s)

2.31c4 (9.5%)

240

60

180

96

FS+1 (2 s)

2.25bc (6.6%)

168

40

128

69

1/3C+1 (2 s)

2.18abc (3.3%)

84

40

44

14

1/3C (1s)

2.13ab (0.9%)

24

20

4

-5

FS (1s)

2.04a (-3.3%)

-84

20

-104

-74

Unsprayed

2.11ab

1 % increase over unsprayed treatment
2 Application costs are a total of $20/ha/application for Folicur 430SC at 145mL product/ha + ground rig application
3 Calculations based on a yield of 1.5t/ha for the Be (3 s) treatment
4 Yield means with the same lowercase letters are not significantly different at P≤0.05.

Given the assumptions for the trial yields, selling price and application costs, the $ profits for the best two treatments ranged from $128/ha to $180/ha. For a target yield of 1.5t/ha with the same selling price and application costs, the profits range from $69/ha to $96/ha. For a target yield of 1.5t/ha, a selling price of $800/t and the same application costs the figures are $32-$44/ha. Profits would be even greater in years where fungicide applications resulted in higher % yield increases and if a fungicide spray was combined with an insecticide spray.

The results of this trial confirm that the timing of the first application is critical in controlling powdery mildew of mungbean – it should be applied either before or when powdery mildew is first seen, with one or two follow-up sprays (depending on disease progress).

Halo blight of mungbean

Although the cause of halo blight, the bacterium Pseudomonas savastanoi pv. phaseolicola (Psp), was recorded on mungbean many decades ago in Australia, it is only over the past 8 or so years that it has become a problem. The first symptom of halo blight is often a general yellowing on young developing leaves, followed by the appearance of small roughly circular spots a few days later. On older leaves the spots are dark, often shiny and water-soaked particularly on the lower leaf surfaces, and are surrounded by a yellow halo which disappears as the leaves age. Circular shiny spots may also develop on green pods and seeds which develop in these pods usually become infected internally. Seeds may also become externally infected during harvesting when they come into contact with infected leaf segments.

Under moist conditions bacterial cells ooze from these spots and are spread on the plant and between plants by water droplets from rainfall or overhead irrigation. Outbreaks of halo blight are favoured by wet weather and moderate temperatures. If these conditions occur early in the crop and symptoms of halo blight appear, the symptoms often become less obvious if the weather remains hot and dry for the remainder of the crop’s growth.

Yield losses

Determining the actual and potential losses in yield are difficult because there is no effective bactericide which can be applied to either the seed or the foliage of mungbean plants.  The National Mungbean Improvement program has identified sources with major genes for resistance (one large seeded and two small seeded lines) and incorporated these into their breeding program to develop more resilient varieties, the first of which, Celera II-AU was released in 2014. In-field assessments of nearly 140 breeding lines were conducted in 2013/2014 across a number of sites (Biloela 2013, Emerald and Warra 2014, Hermitage and Liverpool plains 2013, Hermitage 2014 and plant disease nurseries at Hermitage and Kingsthorpe. Halo blight pressure was high in 2013, 2014 in Southern QLD and NSW (Hermitage and Liverpool plains sites) and there was a strong pattern of lines with the highest yields having yield linked to disease resistance/pedigree under these conditions. Low/no disease pressure was observed in CQ sites where the majority of experimental genotypes yielded equivalent to Crystal. Some halo blight resistant pedigrees suffered a yield penalty at the Emerald site in the absence of disease pressure.

Plans are underway to collect data on potential yield losses by comparing the yields in plots which have been inoculated with the halo blight pathogen for various times with the yield of uninoculated plots.

Management

There are no effective chemicals for the control of the halo blight pathogen on infected plants or seeds, and all current green-seeded commercial varieties are either susceptible or moderately susceptible (the varieties Crystal  and Jade AU have the best levels of resistance). The black gram variety cv. Regur is rated as moderately resistant – moderately susceptible. Although improved sources of resistance have been identified, the recent identification of new strains of Psp which can overcome this resistance means that the breeding effort in the National Mungbean Improvement program will need more resources.

Current management for halo blight relies on minimising the impact of the pathogen using a variety of strategies –

  • Save planting seed harvested from a crop which did not display symptoms of halo blight during the season; AMA approved seed is sourced from crops which have been inspected for symptoms during the growing season
  • If you plan to save some of your seed for planting, ensure that harvesting equipment brought onto your property is thoroughly clean of mungbean residues preferably with an antibacterial compound, as bacterial cells of Psp can be transferred from infested residues onto the surface of seed during harvest
  • Harvest crops which did not display any symptoms of halo blight before crops which were infected with halo blight if you plan to save some of your seed for planting
  • Other crops and weeds (including bellvine, cowvine, morning glory and native glycines) are known to host the halo blight pathogen so management of these plants in and near mungbean crops is warranted
  • Although the importance of survival of the halo blight pathogen in infested crop and weed residues is unknown in Australia, mungbean crops should not be grown in succession in the same paddock to avoid any potential risk from this and other pathogens.

Powdery mildew of sunflower

In Australia, sunflower powdery mildew is caused by the fungus Golovinomyces cichoracearum, whose hosts are confined to the plant family Asteraceae, that is, the daisy family including noogoora burr, etc. The pathogen survives year round on living plants of volunteer sunflowers, wild sunflower and other hosts. It does not survive in soil, infested stubble or on seed.

 The first sign of infection is the appearance on the lower leaves of small, white, round powdery colonies which rapidly expand to cover the entire leaf. Under cool, humid conditions powdery mildew spreads rapidly up the plant onto younger leaves, with colonies also developing on stems, leaf petioles and the green bracts on sunflower heads if infection is severe. Spores produced on the fungal growth give the powdery white appearance on the tops of the leaves and are spread from plant to plant in the wind, often for many kilometres.

As there is little known resistance in Australian sunflower varieties to the pathogen, practical management of sunflower powdery mildew relies predominantly on the strategic use of the fungicide propiconazole as Tilt 250EC Systemic Fungicide® (or other registered products) under the APVMA permit PER14777 which expires on 30 June 2016.  Generally, infection risk is highest during cool and humid conditions early and late in the season.

Field trials conducted between 2010 and 2012 assessed the effectiveness of various combinations of fungicide rate (250 or 500mL of Tilt/ha), number of sprays (one or two) and time of first spray (at first sign of powdery mildew or at 5% ray floret emergence). This latter time is defined as when an average 5% of the ray florets (the 1st yellow petals) on a sunflower head are present.  In the trials, powdery mildew infection was approximately ½ way up most plants in the unsprayed treatment at the 5% ray floret stage. The results of the trials show that a single spray of 500mL Tilt product/ha applied at 5% ray floret emergence can effectively control powdery mildew under moderate and late-appearing powdery mildew infections.

Based on three years of trial results, it is recommended that one application of Tilt 250EC (or other registered products) at 250-500 mL product/ha applied from budding up until no later than 5% ray floret emergence (RFE) (5 heads in 100 showing the first signs of yellow ray florets) will adequately protect the crop until physiological maturity.

Choose the rate of Tilt 250EC or other registered product after considering future weather conditions and the level of inoculum already present in the region. For instance, a late crop with a ‘skirt’ of powdery mildew in the bottom third at budding or at 5% RFE and finishing in cool conditions would benefit by the application of a 500mL product/ha rate as it is more likely that powdery mildew levels will increase in these conditions. An early crop finishing over the hotter conditions around December is less likely to suffer from late powdery mildew infection although cooler humid nights will increase risk.

Important Note: The current permit states that NO fungicide applications are permitted after 5% ray floret emergence; check the information on www.apvma.gov.au for the conditions of use of this fungicide on sunflower. Further residue studies are underway to enable later applications of fungicide, if necessary.

Yield losses.

Although yield differences between treatments in these trials were not statistically significant (due to only moderate infection levels and harvester issues), differences in seed weights indicated that all treatments showed a trend of increasing yields compared to the unsprayed treatment. Field observations also indicate that heavy powdery mildew infection in the top third of the canopy from flowering onwards as the seeds fill can cause pinched seed and subsequent yield loss.

Phomopsis/Diaporthe diseases of summer crops and weeds

The fungal Phomopsis/Diaporthe species survive on stubble and cause stem canker on sunflower and soybean, pod and stem blight in soybeans and other crops in Australia, and a range of other diseases on a wide variety of plants. In sunflower, serious outbreaks of stem canker can cause lodging, while in soybean pod and stem blight causes premature senescence, pod death and yield losses from reduction in the number and quality of seeds.

Outbreaks of Diaporthe diseases are favoured by warm, wet weather, when spores produced in fruiting bodies in infected stubble or on alternative hosts are spread to the host plants.

A serious outbreak of stem canker on the Liverpool Plains in 2010 was the catalyst for investigations to quantify the diversity of Diaporthe species on summer crops in the northern region, to gain an understanding of the host range of these species and to study different modes of survival in northern farming systems. To date 13 Diaporthe species including many new species have been isolated from sunflower stem cankers, eight species from live soybean plants and three species from mungbeans. Diaporthe helianthi, a highly damaging species on sunflower in the United States, Argentina and Europe has not been found in Australia.

More than 25 new species of Diaporthe have been identified from various crops and weeds to date from this study, of which 11 have been described as new species and a similar number are yet to be formally described. Identifying the various species is of importance as the first step to looking at host range and virulence. Pathogenicity testing of many of these species is underway and a range of crop and weed hosts for many of these Diaporthe species have been identified.

Damaging outbreaks in the future will be influenced by weather conditions and the amount of inoculum surviving in crop and weed stubble as well as on live plants.

Some key findings from this research are (i) D. gulyae is highly virulent on sunflower, chickpea, soybean and mungbean, and has been isolated from naturally-infected, field grown plants of soybean, sunflower and mungbean, (ii) D. kongii is highly virulent on chickpea, sunflower and mungbean, and has been isolated from naturally infected plants of chickpea, sunflower and mungbean, and (iii) D. masirevicii is highly virulent on chickpea, soybean, sunflower, lupin, and mungbean in glasshouse trials, and has been isolated from field grown plants of all except lupin. Both D. gulyae and D. masirevicii have been isolated from symptomless, field grown plants of maize suggesting that these species may form an endophytic association with maize plants, which is highly significant from the context of aiding survival on ‘non-host’ crops in the rotation.

The role of weeds in aiding survival. The wide host range of many of these Diaporthe species also extends to live and dead plants and residues of common weeds in the northern region. For example D. gulyae, the most virulent of all species discovered during this study, has been isolated from lesions on live plants of the crops sunflower, soybean, and mungbean and the weeds bathurst burr, noogoora burr, saffron thistle and sesbania, and from dead plants of bathurst burr, bishop’s weed, cobbler’s peg, noogoora burr, thornapple and turnipweed. Another new species, Diaporthe masirevicii, which has moderate virulence on soybean and sunflower, has also been isolated from living plants of the weeds bitou bush, sesbania and turnip weed.

These findings are highly significant and have important implications for northern farming systems. Firstly, Diaporthe species have been shown to be capable of being (i) pathogens of a range of crop and weed species causing stem lesions (in mungbean, sunflower, soybean and weeds), lodging and yield loss in sunflower when conditions are conducive, and early senescence, pod infection and yield loss in soybean, lesions and early senescence in mungbeans in wet or irrigated conditions (2015 trial) (ii) saprophytes by invading dead plant residues of many crops and weeds, and (iii) potential endophytes which invade plants of certain hosts, eg., D. gulyae in maize without displaying symptoms.

Green’ and ‘brown’ bridges. Consequently, depending on the Diaporthe species, living volunteer plants of crop hosts and living plants of weeds in paddocks and adjacent areas can act as the “green bridge” between highly susceptible crops, while colonised dead plants and stubble of crop and weed hosts can act as the “brown bridge” between major crops. Almost 30 months after the severe Diaporthe lodging event in sunflower crops on the Liverpool Plains in 2010, D. gulyae was isolated from crop stubble lying on the soil surface after zero till farming practices and two cereal crops planted into the sunflower stubble.

Results of a 2015 stubble Diaporthe spp. trial in the Lockyer Valley are in the process of being collated – sunflower, soybean and mungbean planted into an irrigated site with treatments of infected stubble on the surface, stubble incorporated and a fallow. The aim of the trial is to investigate the effect of infected stubble on crop infection, early senescence and potential yield loss.

Acknowledgements

The research undertaken as part of this project is made possible by the significant contributions of growers through both trial cooperation and the support of the GRDC, the authors would like to thank them for their continued support.

The support of the private seed companies in providing seed, trial sites, planting, trial upkeep and background advice on genetics and maturity types has been invaluable – without this input much of this work could not have been done.

Molecular identification by DAFQ Ecosciences colleagues and other interstate and international scientists has also been essential to the findings of this research.

The authors also thank staff of Hermitage Research Station (Warwick), J Bjelke-Petersen Research Facility (Kingaroy) and staff of the Regional Agronomy Initiative (Toowoomba, Emerald) for their assistance with various field trials.

Contact details

Dr Jodie White
Centre for Crop Health, University of Southern Queensland
West St, Toowoomba Q 4350
Ph: 0457 546 633
Email: jo.white@usq.edu.au

Sue Thompson
Research Fellow
USQ
West St
Toowoomba. Qld. 4350
Ph: 0477 718 593
Email: sue.thompson@usq.edu.au

Reviewed by

Professor Malcolm Ryley, University of Southern Queensland

GRDC Project code: DAQ00186