Insecticide resistance and alternative chemistries for mite control
- Researcher's Name:
- Dr Paul Umina
- Organisation:
- Department of Zoology, The University of Melbourne
- Email:
- pumina@unimelb.edu.au
- Phone:
- 03 8344 2203
- Fax:
- (03) 8344 2279
- Project Code:
- UM00043
- Contract Start:
- 30/6/2010
- Contract End:
- 29/6/2013
Summary
Invertebrate pests that attack emerging seedlings are a significant threat to the establishment of pasture and grain crops, with over $1.8 billion spent in Australia on pesticides annually. There are over 40 invertebrate species that damage crops at emergence in Southern Australia. Of particular concern are redlegged earth mites and blue oat mites, the newly emerging pests Bryobia mites and Balaustium mites, and the lucerne flea. Reliance on a narrow range of chemicals to control pests leads to problems in resurgence, secondary pests and the development of pesticide resistance. The need for alternatives to conventional chemicals has been recognised, with testing of several ‘softer’ control options currently being carried out, including seed coatings and new foliar sprays. In the past, viable ‘soft’ chemical alternatives have not been successful in a broad-acre setting due to high application costs making them unviable options for crops with narrow profit margins. With significant investment now occurring in R&D projects and renewed interest from chemical companies, particularly in light of emerging resistance issues, it has become worthwhile to pursue ‘soft’ chemicals.Chemicals are still the only effective mite control option in grains, despite an increasing knowledge on beneficial invertebrates and their impacts on pests. Unfortunately, chemicals are generally applied in an ad hoc fashion with little concern for the longer-term ecological and evolutionary implications. As predicted by our group some time ago, the long-term application of chemicals resulting in enormous selection pressures have now led to resistance in the redlegged earth mite to the synthetic pyrethroids in Western Australia. A high natural tolerance to currently registered pesticides, including omethoate, bifenthrin and alpha-cypermethrin, has also been identified by our work on the emerging mite pests Balaustium mites and Bryobia mites, and may be contributing to the emergence of these pests. A number of recommendations to grain producers will emerge from the project around three areas. First, we will provide data to indicate the potential for new and established chemistries against the full range of establishment pests. These data can then be used to assist chemical companies in moving towards registration. Second, we will develop a resistance management package for redlegged earth mites. This package should lead to specific recommendations about pesticide applications and include recommendations for ongoing genetic screening. Third, we will establish threshold data based on shade-house trials and preliminary field enclosures for canola for major pest species. The outcomes of this project will be achieved through collaboration between CESAR and CSIRO WA. The testing of unregistered ‘soft’ chemicals will be carried out using well-established protocols. Initially laboratory assays and microcosm experiments will be conducted, followed by field trials if appropriate chemicals are identified. This extends upon work already being performed by our group. We will expand upon work performed under GRDC project “developing and demonstrating the role of alternative chemistries and integrated management for crop establishment pests” (project UM00033), which is investigating the distribution and level of resistance in redlegged earth mites. We will continue to monitor field resistance across southern Australia, identify the mechanism(s) conferring resistance and accurately assess movement patterns of mites. This information will be used to model the spread and make predictions about the extent of resistance in future years. A provisional assessment of economic thresholds will be performed against pest mites and lucerne flea. This will be achieved using microcosm experiments and later followed up by field plots.We believe that a key strategy to successful establishment pest control is the correct identification of pests and pest pressures. Results from GRDC project UM00033 has emphasized that the effectiveness of 'soft' chemical options will depend on the mite pressures exerted in a paddock. Thus packages and recommendations need to focus on assessing species and current densities as well as future densities. It is likely that many soft chemical options will not be effective at high pest densities when applied at crop emergence. This is largely due to the mode of action of many soft chemicals (i.e. translaminar properties), which are most effective when applied to crop plants with considerable plant foliage. Moreover, it is already apparent that the effects of new chemistries are species specific, emphasizing that pest pressures need to be accurately identified. To fully take advantage of new chemistries, a combination of pest species, pressures and economic thresholds needs to be considered within an adequate monitoring framework.
Background
Pasture and grain crops in southern Australia are subject to attack by multiple invertebrate species threatening seedling establishment, with damage and control conservatively costing several hundred million dollars each year. Within southern Australia, there are several species of mites as well as the lucerne flea that are considered to be important pests of grain crops at establishment, and the damage caused by these pests in Australia seems to have increased in the past decade. Of particular concern are crop emergence pests, including redlegged earth mites, blue oat mites, Balaustium mites, Bryobia mites and the lucerne flea. Currently, broad-spectrum chemicals are the main method of control against these important pests and these are often applied in an ad hoc fashion. This is concerning as reliance on broad-spectrum chemicals can lead to problems in pest resurgence, secondary pests and the development of pesticide resistance as has previously been seen with synthetic pyrethroids and redlegged earth mites. Furthermore, laboratory tests have shown that these mite species and lucerne flea differ in their tolerance to pesticides, therefore application rates for one species may not be effective against another species. Given this, there is a need to improve current control options against these pest mites and lucerne flea to prevent the development of further resistance to existing and/or new pesticides. This will also lead to a reduction in the number of inappropriate chemical sprays applied to control these pests as well as chemical control failures involving these pests.
Implications
Growers and advisers will be informed of relevant findings of research activities through industry related press, presentations at workshops, NIPI conferences and GRDC updates. Chemical control options and economic thresholds will be incorporated into AgNotes and other advisory material through NIPI or directly. A model will be developed to predict the spread of resistance in redlegged earth mites. We will also work with CropLife Australia to devise preliminary resistance management strategies for redlegged earth mites.
Objectives
A number of recommendations to grain producers will emerge from the project around three areas.
First, we will provide data to indicate the potential for new and established chemistries against the full range of establishment pests. This data can then be used to assist chemical companies in moving towards registration. In particular the project will focus on obtaining data for future registration of chemicals for control against Balaustium mites. This mite is an emerging pest that has a high natural tolerance to pestcides and currently has no chemicals registered for its control. Registration of a pesticide targeting Balaustium mites will reduce chemical control failures involving this mite.
Second, the project will develop a resistance management package for redlegged earth mites. This package should lead to specific recommendations about pesticide applications, limit the wide-spread development of resistance and include recommendations for ongoing genetic screening.
Third, the project will establish economic threshold data based on shade-house trials and preliminary field trials for canola and wheat for major pest species.To fully take advantage of new chemistries, a combination of pest species, pressures and economic thresholds needs to be considered within an adequate monitoring framework.
The research findings of this project will be delivered nationally through industry related press, presentations at workshops, grower groups, expos, the National Invertebrate Pest Initiative (NIPI) and GRDC updates. Findings will also be delivered nationally and internationally through publication in peer-reviewed scientific journals.
Outcomes
In this project we will map the continued spread of resistance, identify resistance mechanisms and assess mite movement patterns through genetic markers. This project will also investigate new control options for the spectrum of mite pests and lucerne flea, assess economic thresholds for several crop types and contribute to the registration of new chemicals for important crop establishment pests
Output 1 - Alternative chemistries will be investigated with the aim of assisting the registration of new products for broad-acre cropping. This will be performed using a combination of laboratory bioassays, microcosm experiments and if appropriate small field plots. Promising chemicals will be further investigated in a shade-house using microcosm experiments or in large field trials. This information will be released to chemical companies and industry to promote further development to registration of promising products. Encapsulated formulations will be considered against Balaustium mites as they appear most promising against this mite and they do offer improved efficacy, safer handling and a lower environmental impact than traditional formulations.
Output 2 - The distribution and level of resistance of redlegged earth mites in Western Australia will be investigated across two field seasons. The frequency and spread of resistance throughout southern Australia will be tracked by collecting mites from areas where known control failures have occurred and undertaking laboratory bioassays. This will be achieved by utilising and building upon an existing network of growers, advisers and state-department staff. The mechanism(s) conferring resistance in redlegged earth mites will be investigated using genetic, biochemical, and molecular assays. In order to make predictions about the likely spread of resistance in future years, movement patterns between populations of redlegged earth mites will be investigated using genetic markers.
Output 3 - Microcosm experiments and field trials will be used to assess economic thresholds. Microcosm experiments will be carried out in the shade-house targeting redlegged earth mites, lucerne flea and Balaustium mites on wheat and canola. Wheat and canola will be sown into replicate tubs and different densities of mites and lucerne flea will be introduced at different crop developmental stages. Recovery following spraying will be used to test whether badly damaged plants can recover. Large field trials on redlegged earth mites in canola will also be undertaken. Mite numbers will be manipulated by spraying plots at different rates with a pesticide and yield estimates will be taken in each plot to determine the impact different densities of mites had on the yield.
Related items
Entomologists with support from the Grains Research and Development Corporation (GRDC) are encouraging grain growers to explore integrated pest management (IPM) options and spray insect pests only when necessary this season and beyond. They say this will reduce economic and environmental costs and preserve insecticide efficacy into the future. To...
To avoid insecticide spray failures and prevent or delay the development of resistance, it is recommended that growers use a broad range of Integrated Pest Management (IPM) strategies.
Researchers are enlisting the help of growers and advisers to counter insecticide resistance in broadacre cropping pests.
Researchers are seeking input from farmers and advisers to assist with their ongoing investigations into insecticide resistance in broadacre agricultural pests.
Researchers are seeking input from farmers and advisers to assist with their ongoing investigations into insecticide resistance in broad-acre agricultural pests. Entomologists engaged in research projects funded by the Grains Research and Development Corporation (GRDC) are searching for locations where growers have experienced chemical control difficulties or failures when dealing...
Dr Paul Umina from cesar* and the University of Melbourne looks at the worrying rise of chemical resistance in redlegged earth mites in Western Australia
More detailed information is being generated to help the adoption 
of integrated pest management.
Growers and advisers are being asked to help researchers investigating insecticide resistance in broadacre agricultural pests across the southern grains region.
Insecticide resistance in several broad-acre agricultural pests across southern Australia is being investigated through a research project supported by the Grains Research and Development Corporation (GRDC). University of Melbourne researcher Dr Aston Arthur said the main focus of the project – for which assistance from grain growers and advisers is...
Take home messages • Growers are likely to face significant challenges in the future due to insecticide resistance in redlegged earth mites and other crop pests • More strategic and integrated approaches to insect pest management are needed • Insecticide sprays are effective at controlling crop pests, but do not...