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Potential impacts of synergism between systemic seed treatments and sprayed fungicides in crops - PS2368

Although the toxicity of formulations is routinely tested in the regulatory risk assessment the use of sequential spray or tank mixes (with a few exceptions) is not assessed. Systemic seed treatments are being increasing used as a mode of application for insecticidal compounds as these result in lower numbers of spray application and control of pests at growing shoots. The use of systemic pesticides raises issues in interactions between compounds expressed in pollen, nectar and guttation fluid in the growing or flowering plant and spray applications of other pesticides such as fungicides. This is of particular concern for the highly toxic neonicotinoid insecticides which have been shown to act synergistically in the presence of triazole fungicides with increased toxicity of several hundred fold (thiacloprid + propiconazole) (Iwasa et al 2004). This suggests that even at the very low (ug/kg) levels of neonicotinoid insecticides detected in pollen and nectar toxic effects may occur with co-exposure to fungicides. However, as is the case with many studies, the realistic ratio of fungicide and insecticide were not investigated.
This study will use Pesticide Usage Survey data to identify active ingredients which may be applied before and during flowering to crops in which currently registered systemic insecticidal seed treatments have been applied. These periods are highest risk to non-target invertebrates as residues of systemic pesticides may be available through guttation fluid, pollen or nectar.
Using the identified fungicides laboratory studies will be undertaken using the contact and oral routes of exposure in adult honeybees to determine the impact of varying concentrations of the identified fungicides on the toxicity (LD50) of neonicotinoid seed treatments applied as a combination.
The data will be used to determine whether current risk assessment practices should be amended for seed treatments by taking into account other pesticides likely to be used on the crop.
1. Identify systemic insecticide treatments applied to crops and any available data on residues in pollen, nectar or the green parts of plants.
2. Identify fungicide spray applications applied to the crops identified in objective 1 and reported to result in synergism with insecticides.
3. Use the data identified assess the possible effects of varying concentrations of combinations of the fungicides and insecticides.
4. To assess the implications of the results for current risk assessment practices.
Project Documents
• EVID4 - Final project report : Potential impacts of synergism in honeybees between systemic seed treatments and sprayed fungicides in crops   (664k)
Time-Scale and Cost
From: 2010

To: 2012

Cost: £41,623
Contractor / Funded Organisations
The Food & Environment Research Agency
Fungicide use              
Insecticide use              
Pest and Weed Control              
Pesticide use              
Plants and Animals              
Fields of Study
Pesticide Safety