Description of work

The objectives of work during the first six months of the project were as follows:

To commence the development of models of the rate of heat accumulation in bark and wood chip compost heaps taking account of particle size, initial moisture content, aeration, urea addition and agitation.

1. To commence work on the determination of the heat conductivity coefficients (HCC) for different sizes and species of softwoods and further develop an existing computer model to predict the time required to reach critical core temperature in a plank of wood taking account of size, species, initial temperature and kiln type.

2. To develop appropriate equipment and techniques to test the response of pests and plant species to hot water dips.

3. To commence the work to determine the response of a range of plants to hot water dips.

4. To commence work on the determination of the response of a range of pests to hot water dips.

5. To develop, calibrate and test research equipment for conducting bioassays to test the response of pests and horticultural products to controlled atmospheres.

II. Description of work:
Sub-task 1.1: Experiments will investigate the effect of particle size, initial moisture content, artificial aeration through gas lines, added nitrogen content and agitation, on temperature, pH and moisture content, leading to the development of models of heat accumulation in compost heaps. Work will also determine minimum heap size needed for stable core temperatures. Initial work (spanning months 4-12) will measure the effect of the five variables on temperature, pH and moisture content with quantification of all three parameters from measurements at pre-set positions in heaps at different times during the composting process.

Sub-task 2.1: Wood planks of different sizes and species will be treated with a standard heat regime in controlled environment chambers. The rate of heat penetration into the samples will be measured and HCC’s determined. A mathematical solution for the HCC of timber will be developed to predict time required for planks of specified size to reach target core temperature

Task 3: A temperature indicating system based on heat sensitive paint will be investigated (months 9-18).

Sub-task 4.1: Water baths and monitoring equipment will be designed and calibrated against recognised standards to allow hot water dipping of plants and pests (months 1-3).

Sub-task 4.2: Three species of plants will be exposed in hot water dipping experiments to a range of temperatures and exposure periods and assessed for plant damage (months 3-12).

Sub-task 4.3: Selected species of invertebrate pests will be exposed to a range of temperatures and exposure periods to determine their thermal death parameters (months 3-12).

Sub-task 5.1: Gas tight chambers will be set up and fitted with suitable dosing and monitoring equipment for controlled atmosphere studies and calibrated against verifiable standards (months 1-6).

III. State of progress
Work leading to the development of models of the rate of heat accumulation in bark and wood chip compost heaps has been started. Literature searches on existing composting procedures have been undertaken and the design and specification of the required equipment has been completed, including items which had to be manufactured to a unique specification. Initial tests to determine optimal placement of measuring probes within compost heaps have been undertaken, and the output used in the early stages of specification of a model of rate of heat accumulation in compost heaps. The data has also been used in the design of experimental protocols for further composting experiments.

Work to determine HCC’s and to develop a new computer model to predict time required to reach critical core temperature in wood planks also commenced. Work to extend an existing model to incorporate a wider range of tree species and plank dimensions was undertaken. The model is also being designed to enable its use in the verification of a thermal indicator system which will be developed under a future component of this project.

Although not scheduled to commence until the second reporting period, work on task three has been started. Initial discussions with a commercial company have centered on the range of thermal indicating paints currently available providing the necessary basis for selection of the sub-set that will be utilised in experimental work. Thus work on task 3 is ahead of the planned schedule.

Hot water baths have been designed and manufactured and are currently in use at the laboratories of two partners. Rigorous tests of temperature stability under operational conditions have been completed with results meeting the required specifications for the work. Insect respirometry equipment has been obtained, calibrated and tested, but required to be free of moisture and plant material in order to measure the small changes in insect respiration rate resulting from temperature changes, making it unsuitable for investigation of life stages associated with plant material. it is therefore recommended that no further use is made of insect respirometry techniques in this study. Thus sub-task 4.1 has been achieved in full.

Using the hot water baths, extensive experiments investigating the damage caused to Dendranthema by hot water dips of different temperatures and duration have been undertaken. Plants plunged into cold water immediately after hot water treatment exhibited less damage than those left to cool gradually to ambient temperatures after treatment. Short treatments at temperatures below 44ºC caused little visible damage, but exposure to 43ºC for 20 minutes resulted in commercially unacceptable damage.

Investigations of the response of plant pests to hot water dips showed high mortalities of the eggs and pupae of Liriomyza huidobrensis and of the eggs of Thrips palmi at the critical 43-44ºC range. Work is ongoing to determine if temperature/exposure-time combinations can be established which result in complete control of pests but acceptable levels of plant damage.

Equipment has been developed at the laboratories of two partners to investigate the efficacy of controlled atmospheres or phosphine as a pest control method. Chambers large enough to take whole plants have been tested and calibrated, and found to meet the required specifications for this work. Thus sub-task 5.1 has been achieved in full.

IV. Achievements
Work in the first six months of the project has achieved all milestones stipulated in the Technical Annex for this period. All equipment for the early work has been sourced, tested and calibrated (completing the work on sub-tasks 4.1 and 5.1) and extensive work on hot water dip treatments has been undertaken.

V. Future actions.
A slightly revised schedule for testing of composting variables has been developed to ensure efficient completion of this element of the work. It is anticipated that all other tasks for the second reporting period of this work will be undertaken as detailed in the Technical Annex.

Project objectives and benefits

The aim of the project is to develop a range of post-harvest plant quarantine treatments for timber and horticultural products to prevent the spread of non-indigenous pests and diseases into and around the European Union.

In view of the listing of methyl bromide as an ozone depletor under the Montreal Protocol and consequent international restrictions being placed on its use, the project will seek to develop treatment methodologies suitable for timber and horticultural produce that do not use methyl bromide. Such treatments must be proved capable of giving extremely high levels of kill (virtually 100%) consistently and reliably within defined parameters. This project will fulfil the EC’s obligations under proposed revisions to Council Regulation (EC) No 3093/94 and will help to ensure that treatments exist for new, unforeseen, problems where methyl bromide is not currently used and would be prohibited under these regulations.

The project will investigate the following techniques which previous work has shown have potential as quarantine disinfestation treatments.

  • Heat treatment of timber
  • Composting of bark and wood chips
  • Hot water dipping of ornamental plants and cuttings
  • Extreme controlled atmospheres treatments of ornamental plants and cuttings
  • Alternative fumigant treatments of ornamental plants and cuttings (phosphine and plant volatiles)

Combination treatments

Much of the work relies on physical treatments that are not subject to pesticide regulations. Of the chemical treatments involved, phosphine already has widespread registration and its use should cause no problems. No plant volatiles are as yet registered for use although there is intense interest in this area and the registration of some compounds is foreseen in the medium term. The use of carbon dioxide in extreme controlled atmospheres may require an extension of existing registration.

With the exception of the heat treatment of timber all of the techniques are novel in their application to the commodities concerned. It will therefore be necessary initially to establish the viability of the techniques for the effective quarantine treatment of selected commodities. The proposal also combines investigation of the temperature indicator system with refinement of the heat penetration equations for timber, providing an integrated system that will be applicable to both quarantine procedures and to kiln quality control for general use.

Techniques will be developed to produce effective quarantine treatments for a range of commodities against selected pests and to define the limits of their applicability. Where effective treatments are developed, these will be submitted to appropriate international bodies, such as the European and Mediterranean Plant Protection Organisation (EPPO), for adoption.

The work will concentrate on insect pests. However in all cases the possibility of control of pathogens will be considered and where the techniques are considered suitable (primarily heat treatment of timber and composting), the effect of treatments on relevant pathogens will also be investigated.

In line with EU environmental policy the project seeks to develop alternatives to the use of methyl bromide. The project will allow companies within the EU, and throughout the rest of the world, to reduce and possibly eliminate the use of this highly toxic and potentially environmentally damaging chemical. Even if it proves technically impossible to develop alternatives for existing treatments the requirement to demonstrate the lack of suitable alternatives necessary to allow the retention of methyl bromide for critical uses will have been demonstrated.

The development of effective quarantine treatment schedules will help to prevent the introduction and spread of damaging pests within the EU and support the export of EU resulting in less damage to crops and products and making it easier to ensure the maintenance of the quality of EU produce. Effective schedules will also assist in reducing the requirement for pest control in general. Because biological and other non-chemical control measures are rarely immediately available for new pests, this will be particularly useful in reducing the extent to which chemical control measures are used.

The development of non-methyl bromide quarantine treatments will allow growers and foresters to eliminate the use of an environmentally damaging chemical while still protecting the industry, and associated jobs, from losses that could be caused by the introduction of new, damaging, pests and diseases. It will also avoid the use of other pesticides that would be required to control them should they be introduced.

Horticulture is a growing industry, particularly in less developed areas of southern Europe where it often provides substantial employment. The introduction of damaging new pests and diseases may threaten the continued viability of certain of these and increase the cost of pest control in others. Less developed areas with a lower knowledge base may be less well equipped to deal with new pest introductions making them particularly vulnerable. Currently, the international trade in potted plants is almost non-existent, because of the difficulty of treating soil-born organisms. A reliable and efficient quarantine treatment would give a large impetus to the trade in rooted plant cuttings and orchids. Work currently being carried out by partner 1 on the treatment of miniature trees (Bonsai and Penjing) to control soil borne nematodes, suggests that the heat treatment of potted plants may be a viable option for the control of soil and root borne organisms. By protecting the industry from the potentially disastrous introduction of new pests the problems associated with their introduction can be reduced or eliminated and may allow the industry to expand into new areas. This in turn will result in a safeguarding of jobs in the horticultural area.

Forestry is an important source of income to the EU as a whole, and can be particularly important to the local economy in more remote rural areas. Again the introduction of new pests and diseases can threaten the success of this industry and put jobs at risk. Forests are also important environmentally, reducing flooding and providing habitats for other wildlife. The use of appropriate quarantine treatments can prevent the introduction of new pests and diseases that could cause severe damage to forests, both natural and managed.