Trends in IPM and insecticide use in processing tomatoes in New Zealand

Abstract

The ongoing development of an integrated pest management (IPM) programme for processing tomatoes has contributed in several ways to changes in insecticide use. This paper documents insecticide use in processing tomatoes in New Zealand from 1986 to 2005 using a range of data sources, including typical use patterns, grower records, experimental comparisons and industry reports. Changes in use patterns were associated with the development of key IPM strategies that are reviewed in this paper. Helicoverpa armigera (Hübner) is the key pest of processing tomatoes in New Zealand. The establishment of effective larval parasitoids for this pest, together with pheromone trapping, plant scouting and action thresholds produced the initial incentive for growers to reduce insecticide applications. Risks from other pests in tomatoes, including aphids and thrips that transmit viruses, were identified and avoided by reducing virus sources. The minor but increasing risk of resistance by H. armigera to pyrethroid insecticides was quantified and provided additional impetus for reductions in early season applications of pyrethroids. Reductions of approximately 60% in overall insecticide use were associated with adoption of monitoring and increased parasitism. Typical use patterns and records showed that insecticide applications declined from approximately 8 pyrethroid applications per tomato crop in 1988 to 1 application per crop in 1994. The availability and choice of insecticide also changed over time, with trends to the use of more selective insecticides such as Bacillus thuringiensis and spinosad as they became available. The effectiveness of parasitoids allowed an increase in recommended action thresholds for insecticidal control, and the use of an adjustable threshold based on levels of parasitism was implemented by crop monitors and the processing industry. Annual records of insecticide use from 1995 to 2005 on about 60 crops that observed an adjustable threshold for H. armigera showed that by 2005 insecticide use was about one application per four crops. Overall, the decline in insecticide use over 20 years was in the order of 95%, and this was accompanied by a change to the predominant use of insecticides in classes with lower toxicity profiles. The relative importance of IPM components is discussed and the value of pesticide use data for evaluating the impact of IPM and directing research is emphasised.