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Novel approaches to invertebrate control in horticultural crops - enhancing the efficacy of physical barriers - HH3107TX

The revocation of many insecticides for use on UK vegetable crops (with the threat of even further withdrawals of use in the near future) will cause problems for the control of many serious pests of horticultural crops. This could lead to increasing imports of vegetables from overseas, where pesticide applications to crops are often higher than on UK crops. This conflicts with the demand from consumers, processors, supermarkets and Government for high quality, locally produced, sustainable food production with minimal agrochemical inputs.
The horticultural industry has to implement practical alternatives to synthetic insecticides in order to be able to compete with the threat of overseas imports, and to maintain a viable, sustainable field vegetable industry within the UK, and prevent an irreversible decline which will have a significant social and economic impact on rural communities.

The objective of the research outlined in this proposal is to evaluate several innovative approaches for the management of invertebrate insect pests of vegetable crops, that are based on enhancing the efficacy of physical barriers.

. Mulches have been utilised for many years in vegetable crops, particularly in the suppression of weeds. An innovative ‘flowable’ mulch derived from the biomechanical pulping of hemp (hemp hydromulch) will be used as a basis for applying to swede, calabrese and carrot crops for the management of invertebrate pests. Initial trials carried out at SAC on behalf of Biofibres Ltd., using various formulations and colours of the hemp hydromulch have demonstrated significant reductions in pest damage, as well as the typical mulch effects of reducing weed populations. Use of hemp hydromulch formulations of different colours and incorporating known invertebrate repellents and oviposition deterrents will be evaluated for their effectiveness in the control of invertebrate pests such as cabbage root fly, aphids, caterpillars and carrot fly.

. The use of processed-kaolin particle films as a sprayable treatment on top fruit has led to significant reductions in pest damage, as well as enhancing fruit quality and yield. The biodegradable kaolin particle films impede insect movement, blocking feeding and oviposition, and alter the visual and chemical cues of treated plants that insects use in host-location and acceptance. The lack of any detrimental effects on field beans indicates that its use on other vegetable crops may be as beneficial as its use on fruit. Incorporating insect repellents or oviposition deterrents into the formulation may enhance its efficacy against some pests. Various formulations of the kaolin films will be assessed for their effectiveness in preventing pest infestation of brassicas and carrots.

. The application of sprayable nonwoven fibre barriers applied to the base of plants has been shown to be effective in the management of serious vegetable root pests such as cabbage root fly. Cabbage root fly oviposition is interrupted by the physical barrier-effect of the nonwoven fibres at the base of the plant. The efficacy of this method for preventing damage to brassicas by cabbage root fly, and to carrots by carrot fly will be determined using formulations of the fibres with or without chemical repellents and oviposition deterrents.

These objectives will be achieved through a combination of laboratory, glasshouse and field trials in Scotland and in England. Additionally, the effects of these innovative, enhanced physical barriers on crop yield, crop quality, plant physiology, non-target invertebrates, weeds, crop diseases and soil nutrients will also be assessed.
Detailed investigation into the mechanisms by which these barriers reduce invertebrate pests populations on crops will be undertaken, so that the principles underlying their effectiveness in the crops in this study can be extrapolated to other vegetable crops and other cropping systems.

Development of innovative, effective, and practical approaches to the management of invertebrate pests on UK vegetable crops, where pesticide inputs are restricted, will lead to the development of sustainable pest management systems for many field vegetable crops.

The benefits of this approach are that there will be a reduction in pesticide inputs, but no loss in the quality and yield of produce, which will pacify many of the concerns expressed by consumers and supermarkets regarding intensive vegetable production, and will help stem the flow of imported vegetables into the UK.

These objectives are consistent with DEFRA’s aim to promote a sustainable UK horticultural industry, by reducing pesticide inputs and minimising the environmental impacts often associated with vegetable production in this country.
The overall objective is to develop and several innovative approaches based on physical barriers for the management of major insect pests of brassica and carrot crops.
The specific objectives to achieve this are:

1. In glasshouse and laboratory studies, screen various formulations and colours of hemp hydromulch, kaolin particle films and nonwoven fibres (with and without repellents), for their activity against pests of brassicas and initial assessments of phytotoxicity.

2. Develop pest management programmes in swedes, calabrese and carrots using hemp hydromulch, kaolin particle films and non woven fibre formulations identified from Objective 1 to assess protection from pest damage and promotion of crop yield and quality under field conditions.

3. Assess the impact of hemp hydromulch, kaolin particle films and nonwoven fibres on weeds, crop diseases, and non-target invertebrate biodiversity under field conditions.

4. Identify the mechanisms by which hemp hydromulch, kaolin particle films and nonwoven fibres control crop pests and influence the growth of the crop.

5. Promote and encourage the use of, and further research into, integrated pest management programmes that adopt the use of novel physical barriers for the control of pests of horticultural crops.

The outcomes of Objective 1 are to provide formulations of materials to be used in further objectives. Whilst it is not envisaged that all formulations of hemp hydromulch, kaolin particle films and nonwoven fibres will be suitable, several formulations may be rejected due to phytotoxicity and lack of efficacy, limiting the range of materials for use in field trials. However, as some of the materials have already been proven to be effective in limited glasshouse and field trials (15, 18, 19, 20, 56, 57, 58, 59), there should not be a shortage of materials for use in field trials.

As with most field trials, the appearance of pests on crops can be affected by the season and the underlying weather conditions. To this end, several trial sites will be used throughout Scotland and England to overcome any problems due to low pest incidence. If necessary, pests can be introduced into gauze field cages sited over trial plots to simulate pest pressure, however the choice of trial sites will reflect past problems with pests such as cabbage root fly and carrot fly, and augmentation of pests should not be necessary.
The detailed study of the mechanisms underlying the effectiveness of the various treatments will be concentrated on pests of brassicas. Previous experience in attempting to rear and work with carrot fly in the laboratory suggests that a lot of time and effort could be spent with little gain. Consequently studies on carrot fly will be confined to field observations, with the bulk of the laboratory and glasshouse research concentrating on cabbage root fly, which has host-choice behaviour similar to carrot fly, aphids and caterpillar pests of brassicas. Laboratory and glasshouse studies will be carried out on willow-carrot aphid.
Project Documents
• Final Report : Novel approaches to invertebrate control in horticultural crops - enhancing the efficacy of physical barriers   (504k)
Time-Scale and Cost
From: 2003

To: 2006

Cost: £338,887
Contractor / Funded Organisations
University - Wye College, Imperial College London, University - Scottish Agricultural College
Organic Farming              
Pest Control              
Sustainable Farming and Food              
Sustainable Production              
Fields of Study