|
Biocontrol News and Information
|
 |
December 2003, Volume 24 No. 4
IPM Systems
This section covers integrated pest management (IPM) including biological control, and techniques that are compatible with the use of biological control or minimize negative impact on natural enemies.
Harmonization Sounds Good for Biopesticide Business
The drive to improve farmer uptake of IPM technologies takes many forms, from participatory research at the field level to policy change. A meeting in Tanzania this July signalled the beginning of a process to overhaul legislation on biopesticide registration in eastern Africa. This initiative is intended to make it more straightforward and profitable for the small- to medium-sized producers, who are the mainstay of the biopesticide sector, to market their products throughout the region.
The selectivity of biopesticides makes them good for the environment because they have fewer non-target effects than conventional broad-spectrum pesticides, but makes them bad for business because the narrow target range means a restricted market niche. This paradox at least partly explains why, despite the growth of the environmental lobby and more stringent pesticide legislation in recent years, biopesticides still account for less than 1% of the global pesticide market (and a large proportion of that is accounted for by Bacillus thuringiensis, or Bt).
Conventional synthetic chemical pesticides typically have a broad host range: most insecticides usually kill many kinds of pest insects. Therefore, one product can be profitably produced for many uses. The development and registration costs for a pesticide are high, so the major agrochemical companies are compelled to target their research at agents with a broad spectrum of activity. However, broad-spectrum action means the products can kill beneficial insects.
In contrast, biopesticides have a narrow host range and are safer for use in IPM systems. However, the cost of developing and registering a biopesticide makes it a poor commercial proposition unless the market is particularly profitable. Bt is a case in point. It is effective against widespread lepidopteran pests of cash crops such as cotton, maize and vegetables - a market sufficiently large to make it a commercially attractive product. Even so, the global value of this market is estimated at some US$120 million (for all Bt products) - small in comparison to the average broad-spectrum insecticide (e.g. a new neo-nicotinoid). Yet, no other biopesticide has come close to reaching a market of this size, with the products in the sector usually worth less than $10 million.
The costs of developing and registering a biopesticide must be overcome by the small- to medium-sized enterprises that usually market them. Although the costs are less than for a conventional agrochemical, they are still disproportionately high compared to those for a major agrochemical company registering a new chemical pesticide. To add to the trials of the biopesticide manufacturer, the problem of inherently small markets is compounded because countries have different registration requirements. In spite of harmonization initiatives, different information is still required for markets covering several countries. Therefore biopesticides development is often not economically feasible, even when a product could potentially be used against a regional pest.
Recognizing both the potential for biopesticides in sustainable agriculture and the difficulties they face to become registered, the pesticide authorities of eastern Africa are seeking to harmonize biopesticide registration procedures in the region. They argue that by opening the potential market to the whole of the region, biopesticide development will become more profitable, making commercial development more cost-effective and attractive to manufacturers. This in turn would lower the purchase price and ultimately increase the uptake of the technology by farmers.
The Desert Locust Control Organization for Eastern Africa (DLCO-EA) hosted a workshop on 1-4 July 2003 in Arusha, Tanzania to begin the harmonization process. Members of the national registration authorities of five countries (Tanzania, Djibouti, Ethiopia, Kenya and Uganda) met to review a candidate biocontrol agent in a mock exercise designed to highlight the differences in how such a product would be treated according to the existing different national guidelines. The product chosen for this review by the 20 workshop participants was Green Muscle, a locust biopesticide based on the fungus Metarhizium anisopliae var. acridum that infects only locusts and grasshoppers.
The participants of the Arusha workshop on biopesticide harmonization committed themselves to revising guidelines by September. With some further revisions, a document will be presented for consideration by all member countries of the Southern and Eastern African Committee on Harmonization (SEARCH). SEARCH is a non-governmental organization comprising government regulators from countries spanning South Africa and Madagascar to Ethiopia. The group's ultimate goal is to develop guidelines that may be uniformly adopted throughout the region.
This workshop was funded by support from the African Emergency Locust and Grasshopper Assistance (AELGA) project of the US Agency for International Development (USAID). AELGA's biopesticide project is managed by Virginia Polytechnic Institute and State University in the USA, with partner institutions in Kenya, Ethiopia, Senegal and France.
Contact: Miriam Rich or Larry
Vaughan,
IPM CRSP, Office of International Research, Education, and Development,
1060 Litton Reaves Hall, Virginia Tech,
Blacksburg, VA 24061-0334, USA
Email: mrich@vt.edu/larryjv@vt.edu
Commercial Success from 15 Years Trichoderma Research
Several biological control products recently introduced to the market for control of crop diseases in New Zealand owe their success to a long running research programme that has involved both fundamental and applied research to optimize their efficacy. The products, produced and marketed by Agrimm Technologies Ltd of Christchurch, New Zealand, consist of selected Trichoderma spores formulated for targeted application to specific crops and cropping systems. This achievement was spearheaded by Alison Stewart, Professor of Plant Pathology at Lincoln University and Director of the newly established National Centre for Advanced Bio-Protection Technologies, whose research team has specialized in studying biocontrol mechanisms for control of soil-borne pathogens.
The diseases at the centre of this investigation were two economically important fungal pathogens of vegetable crops. Sclerotium cepivorum is the causal agent of onion white rot which results in losses of 30-70% p.a. of New Zealand's largest export earning vegetable crop, whilst Sclerotinia species cause soft rots in a wide range of fruit and vegetable species. Neither pathogen is well controlled by existing chemical sprays owing to difficulties in targeting soil-borne pathogens and, in S. cepivorum 's case, the chemicals are no longer effective due to accelerated microbial degradation in soil. The pathogens' problematic nature is compounded by the fact that both may persist in cropping soils for many years owing to the presence of hard, over-wintering structures called sclerotia.
Research on biocontrol of onion white rot was begun by Professor Stewart in 1985, when large numbers of soil microorganisms were screened for antagonistic activity towards the pathogen. Promising microbes were then incorporated into S. cepivorum -infested soil in large boxes for glasshouse-based trials, in which a Trichoderma atroviride strain was found that gave between 40-75% disease control compared to untreated boxes.
The research group then entered into a joint partnership arrangement with Agrimm Technologies Ltd to facilitate commercialization of this strain. Agrimm, run by directors Dr John Hunt and Mr David Gale, was already formulating Trichoderma spp. as soil bio-inoculants, and brought to the partnership a wealth of technical experience. This expertise enabled the researchers to test a wide range of delivery strategies to best target the pathogen in field trials.
Fundamental studies complemented these applied studies by enabling the researchers to optimize the biocontrol activity. To determine the best time for application, a genetic fingerprint of the biocontrol agent was developed and used to track its survival and spread in field sites. Other studies indicated that the biocontrol agent antagonized the pathogen via several means: antibiotic production, competition for nutrients, and plant growth promotion.
The research on onion white rot control had provided plenty of insights into the issues involved in developing biocontrols for sclerotial pathogens. This experience was then used in developing a biocontrol agent for control of Sclerotinia minor lettuce drop. Using similar glasshouse and field based screens, a T. hamatum strain was identified that directly affects the pathogen by occupying the root zone space and competing for nutrients. Field evaluations over the last 5 years have shown that by applying the biocontrol agent around seedling roots and stem bases, protection that equalled or bettered that of chemical fungicides was obtained. This work, conducted on both Lincoln University and growers' properties, culminated in successful commercial scale trials during 2000-2002.
Currently, several bio-inoculant products are utilizing proprietary strains of Trichoderma from the above research as the active ingredient. TrichopelTMAli 52 is a granule that is applied to the furrow during seed sowing, and uses T. atroviride's growth promotion properties to help establish vigorous roots in onion seedlings. The sustained release formulation enables the beneficial fungus to colonize the soil around developing seedlings, and to grow with the roots throughout the life of the onion. Use of Trichopel Ali 52 typically increases harvest yields of field onions by 8-12% and spring onions by 34%.
The lettuce product was formulated with the transplant lettuce nursery industry in mind. A combination of two formulations ensures the establishment of dominant beneficial fungal populations in the root zone of the lettuce, thus producing a strong seedling for field planting. TrichodryTM6S flake is incorporated into the seedling mix prior to cell tray filling, and a top-up of TrichoflowTM6S WP is applied to each lettuce seedling 'plug' several days prior to planting out. Treatment of seedlings in this way typically increases harvests giving pack-outs of 85-90% due to improved seedling establishment and stress tolerance.
The commercial products are currently marketed in New Zealand and are likely to soon be available in other countries through arrangements with local distributors. Whilst they have no withholding period and are certified as suitable for organic farming by AgriQuality in New Zealand, the products are also compatible with most fungicides applied after plant establishment. Research in this area is continuing, with Agrimm hoping to extend the market into Australia through an active research programme in collaboration with the Department of Primary Industries at Knoxfield, Victoria, in which the products are being tested under Australian cropping conditions.
All parties involved in this programme believe that the success of the commercial implementation of these Trichoderma-based products has been due to good science backed up by a sound commercial outlook. With this success under their belts, Prof. Stewart, Dr Hunt and Mr Gale are keen to expand their collaboration to combat other crop diseases.
Contacts: Alison Stewart,
Bio-Protection,
PO Box 84, Lincoln University,
Canterbury, New Zealand.
Email: stewarta@lincoln.ac.nz
Web: http://bioprotection.lincoln.ac.nz
John Hunt, Agrimm Technologies
Ltd,
PO Box 13-245, Christchurch,
New Zealand.
Email: j.hunt@agrimm.co.nz
Web: www.tricho.com
Strawberry IPM Paradox
In Queensland, Australia, two-spotted mite (Tertranychus urticae) is the major pest of strawberries and can greatly reduce both yield and quality in this high-value crop. So it might come as something of a surprise to learn that most strawberry growers in southeast coastal Queensland are deliberately releasing the pest in their crops.
Biocontrol of the pest mite using the predatory mite Phytoseiulus persimilis is an established component of an IPM management system in strawberries. The predators are traditionally supplied on bean or soyabean leaves, with instructions to release them in the field by placing them among the foliage of infested plants. However, under a release system developed by Horticultural Crop Monitoring (HCM) consultant Paul Jones, the predatory mites are released at marked sites through the crop, together with relatively high numbers of the two-spotted mite prey. The prey population grows and provides a concentrated breeding site for the predatory mite, which can thus increase in numbers and disperse through the crop before natural pest mite populations reach damaging levels. Although initially rather cool to the concept of releasing the pest, once the logic was explained the growers were prepared to try, and they were rewarded with substantially reduced mite damage. Miticide resistance is a serious issue, so a biological control that works and reduces the need for spraying is very welcome. The `simultaneous releasing' technique has now been successfully used for the last 7-8 years and has significantly reduced miticide use. Rarely, HCM may recommend two miticides per season, but in the majority of cases no miticides are used. In contrast, without the predatory mites some growers will use up to 12 miticide sprays per season.
There is a double paradox in this story, however. Jones comments that good IPM practice in the strawberry sector is compromised in southeast Queensland if the crop is to be exported to Victoria. In this case, there is a requirement to apply dimethoate (in the first week of September). The requirement is targeted at eliminating Queensland fruit fly (Batrocera tryoni) from imports to the more southerly state, but the practice disrupts IPM and can cause mite outbreaks. Although fruit fly baits have been shown to be successful in trials, they are not yet permitted as an alternative to the dimethoate sprays.
The conflict between maintaining effective IPM in strawberries in Queensland and preventing the fruit fly's possible incursion further south is a tricky issue to resolve. The fruit fly, a tropical and subtropical species with a wide host range, is Australia's most costly horticultural pest. A number of countries refuse to import Australian horticultural produce because of the fear of importing the fruit fly along with the produce, while in others, market access for Australian citrus and stone fruit depends on areas maintaining `area freedom' from the fly. An outbreak of fruit flies in such areas prohibits exports of fruit until they are certified free of this pest again.
A Fruit Fly Exclusion Zone (FFEZ) was created in southeastern Australia, spanning the three states of New South Wales, Victoria, and South Australia. Because this zone is considered to have area freedom from fruit fly, produce grown there has a greater market value nationally, and can also be exported to countries with stringent quarantine regulations designed to prevent introduction of the fruit fly. Although it can live and breed in the FFEZ area, the fruit fly does not normally occur there and is (expensively) eradicated when found. It is not known whether or not a permanent population could be established if eradication were abandoned, so preventing incursions is seen as the best strategy for this otherwise costly pest. Unfortunately, this has a knock-on effect on IPM for other pests, and other farmers, outside the zone.
Sources: Australasian
Biological Control News, August 2003. Horticultural crop monitoring
develops new release technique for persimilis in strawberries.
www.goodbugs.org.au/news.htm
The ABC (Australasian Biological Control) website is the virtual home of
the Association of Beneficial Arthropod Producers, Australia.
www.goodbugs.org.au/default.htm
Fruit fly: www.ento.csiro.au/research/pestmgmt/IPMModellingNetwork/QFF.htm
Contact: Paul Jones,
Horticultural Crop Monitoring,
Queensland, Australia.
Email: pjones@hotkey.net.au
Fax: +61 412 714 905
Hot Pepper Source for Strawberry Protection
Colletotrichum and Phomopsis fungi are economically important pathogens, inflicting significant damage to small fruit crops such as strawberries in the USA. A naturally occurring compound found in cayenne peppers may soon add heat to the battle to control them.
US Department of Agriculture - Agricultural Research Service (USDA-ARS) scientists have been awarded a patent for a novel fungicide, CAY-1, which was isolated from cayenne peppers by Anthony De Lucca (ARS Southern Regional Research Center, New Orleans, Louisiana). De Lucca isolated the saponin 5 years ago while screening for natural compounds to protect crops from fungi. Found widely in plants, saponins have detergent properties that allow them to penetrate fungal cells.
Since then, De Lucca has teamed up with David Wedge (ARS Natural Products Utilization Research Unit, Oxford, Mississippi) and Barbara Smith (ARS Small Fruit Research Station, Polarville, Mississippi) to test its efficacy against fungi attacking strawberry. A year of successful laboratory and plant-based trials has allowed the testing to progress to the greenhouse stage, which may pave the way for commercialization. CAY-1 has been shown to be effective at low application levels against both Colletotrichum and Phomopsis. In addition, the compound has a range of other potential applications, including as a mosquito larvicide or molluscicide, and for mildews in domestic situations. This has led to a welter of interest from commercial companies; a number of them have been supplied with the cayenne extract by ARS and are investigating its potential.
Source:
USDA-ARS news release, 29 August 2003
www.ars.usda.gov/is/pr/2003