Ecotoxicology; Pesticides and Beneficial Organisms
Conference held by the Welsh Pest Management Forum, Cardiff 14th-16th October, 1996
By Alison Scott-Brown
Over the last 20 years members of the International Organisation for Biological Control (I.O.B.C.) have developed a standard procedure to test the side effects of new and commonly used pesticides on natural enemies and biological control agents. Use of these standard methods allow the exchange of results from one country to another and saves costs of repeated testing. The overall objective of rating the harmful effects of pesticides is to limit the availability and use of broad spectrum compounds worldwide and provide regulating authorities with information on selective, less harmful alternatives that can be incorporated into I.P.M. systems.
The aim of the conference was to evaluate the current procedure used to test the toxicity of pesticides on non-target organisms. The standard sequential tests are described below:
TIER I Laboratory tests(worse-case scenario)
Methods Glass plate bioassays. Beneficial arthropods are exposed to fresh pesticide residues.
Aims To establish per cent mortality of*, and sub-lethal side effects on, beneficial test insects.
TIER II Extended Lab testing. Semi-field tests
Methods Leaf tests or caged plants in a semi-controlled environment
Aims Observations on fecundity, growth and development of beneficial larvae/nymphs.
TIER III Field tests
Methods Uniform treatment plots or large scale field trials using testects of pesticides on beneficial organisms were published in an E.P.P.O. Bulletin (1985) and two I.O.B.C./W.P.R.S. Bulletins (1988, 1992).]
Seminars and debates were lead by delegates from international academic institutes, organisations, industry and pesticide regulators from European countries. The lively discussions which punctuated the conference programme highlighted the key concerns of each tier stage of the sequential tests:
1. Choice of four instead of two test beneficial types (one parasitoid, one foliage predator, one soil based predator and one predatious mite) for each active test compound.
2. Choice of beneficial species as an indicator of susceptibility to test compound. To represent a group for parasitoids or predators the indicator species must be generally susceptible to pesticides and be a valuable biological control agent.
3. A combination of life stages of beneficial arthropod must be tested, as susceptibility and vulnerability to pesticides may vary at each stage (e.g. Trichogramma sp. indirect contact . pupa developing in host egg and direct contact . adult).
4. A statutory level of <30% mortality of beneficial test organism is unacceptable for all indicator species.
5. Resistance to test compounds in laboratory cultures of beneficial insects.
Tier II and III
6. Acute toxicity and persistence of side effects should be measured by sampling the test
populations at periods of time after application of pesticide.
7. Accumulation effects should be assessed by monitored population of indicator species
after numerous pstudies are ignored by following the standard tests described above. A small change in the behaviour of predator/parasitoid (such as delayed egg laying) may effect resulting population in the field.
12. Absence of a separate procedure for the registration of biochemical pesticides in E.U. countries. Non toxic compounds such as pheromones are subject to standard pesticide testing rendering them unavailable for I.P.M. for lengthy periods of time.
Several projects undertaken within Biological Interactions, Jodrell Laboratory, focus on behavioural studies of predators and parasitoids used to control major insect pests (thrips, mealy bug, aphid and whitefly) found within the glasshouses of R.B.G., Kew. Detailed examination of the effects of individual plant species on the foraging success of introduced beneficials may highlight some of the problems encountered with the use of available biological control agents in the display houses. Laboratory and semi-field tests are being carried out with potential botanical insecticides to observe their effects on the behaviour, development and reproduction of insect beneficials. All studies aim to further the decrease in use of harmful pesticides in I.P.M. programmes at Kew, whilst identifying alternative .beneficial friendly. compounds.
I am very grateful to the Kew Guild for providing funds to enable me to attend this extremely interesting and worthwhile conference.