Hedging our bets: choosing hedgerow plants to enhance beneficial insects to optimise crop pollination and pest management on Canterbury farms Davidson MM, Howlett BG June 2010 A report prepared for: MAF SFF, Grant No. L09-009 Melanie M Davidson Plant & Food Research, Location Brad G Howlett Plant & Food Research, Location SPTS No. 4104 PFR Client Report No. 37105 PFR Contract No. 24631 DISCLAIMER Unless agreed otherwise, The New Zealand Institute for Plant & Food Research Limited does not give any prediction, warranty or assurance in relation to the accuracy of or fitness for any particular use or application of, any information or scientific or other result contained in this report. Neither Plant & Food Research nor any of its employees shall be liable for any cost (including legal costs), claim, liability, loss, damage, injury or the like, which may be suffered or incurred as a direct or indirect result of the reliance by any person on any information contained in this report. This report has been prepared by The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research), which has its Head Office at 120 Mt Albert Rd, Mt Albert, Auckland. This report has been approved by: Melanie Davidson Scientist/Researcher, Vegetable, Arable & Southern Entomology Date: 23 June 2010 Louise Malone Science Group Leader, Applied Entomology Date: 23 June 2010 Contents Executive summary i 1 Introduction 3 2 Methods 4 3 Results 5 4 Conclusions and recommendations 9 5 Acknowledgements 10 6 References 10 7 Appendices 12 Executive summary Hedging our bets: choosing hedgerow plants to enhance beneficial insects to optimise crop pollination and pest management on Canterbury farms Davidson M, Howlett BG, June 2010, SPTS No. 4104 We undertook a desk-top study to examine the associations between plants, insect herbivores, their natural enemies and pollinators to evaluate the potential of using perennial plant assemblages on non-productive areas of a farm to maximise the establishment and abundance of beneficial insects. Pollination and pest suppression are key on-farm services provided by beneficial insects (pollinators, predators, and parasitoids). Yet the potential of beneficial insects to provide these essential services is often not realised because they are absent or low in numbers, generally due to historical management practices. Based on database (Plant Synz) and general internet searches, the present study revealed that many of the native plants examined are superior to existing hedgerow and shelterbelt species growing in Canterbury for their associations with pollinating insect species. • Only two pollinating species, Apis mellifera and Bombus terrestris , were found to be associated with Pinus radiata or Ulex europaeus , while none were found associated with Cupressus macrocarpa , the three most common shelterbelt or hedgerow species in Canterbury. • Seventeen of 45 pollinator species are associated with both exotic and native (including endemic) plant species. As for native plants acting as pest reservoirs, 41 insect pest species (out of 961 herbivorous species) were common to some of the native and exotic plant species included in this study. Eighteen were endemic (only found in New Zealand) or native, and 26 were exotic species. The vast majority of the 122 pest species identified in this study are not found in vegetable or arable crops. With regards to native plants becoming weeds, there was no information suggesting that the native plant species listed in Appendix 1 could become or had ever been described as weeds, unlike P. radiata and U. europaeus , which are well known weeds in New Zealand. From a beneficial insect perspective, evidence to date suggests improving resources for pollinators (e.g. food, habitats for establishing populations) may bring about the most obvious benefits at the farm scale. While there is also potential for natural enemies from surrounding non-crop vegetation to attack pests in a crop, how many and how far such insects will move into the crop, and how mortality factors (e.g. hyperparasitism, intraguild predation) will affect their ability to suppress pest populations is not known. This study provides a starting point for exploring plant–insect herbivore–beneficial insect associations and interactions. The associations outlined in the current research need to be verified in the field. Results suggest that the use of native plant species in non-productive areas has promise, but further research is required to confirm this. For example, it would be helpful to determine how far beneficial insects may move out of these native plant assemblages into the crop and whether the floral resources from the native plants provide optimal nutrition for Page i 4104 Hedging our bets: choosing hedgerow plants to enhance beneficial insects to optimise crop pollination and pest management on Canterbury farms. beneficial insects. Beyond the entomological questions, consideration should also be given to other factors that may promote or limit their use. These include: • the accessibility and cost-effectiveness of such native plant species relative to exotic species • the ability to quickly and easily establish the identified plants • how well they fit within the non-productive areas • how they may compete with or overshadow neighbouring crop plants • how they may affect livestock that may feed on them • what pathogens may be associated with the plants. For further information please contact: Melanie Davidson The New Zealand Institute for Plant & Food Research Ltd Plant & Food Research Lincoln Canterbury Agricultural and Science Centre Private Bag 4704 Christchurch 8140 NEW ZEALAND Tel: +64-3-325 6400 Fax: +64-3-325 2074 Email: Page ii 4104 Hedging our bets: choosing hedgerow plants to enhance beneficial insects to optimise crop pollination and pest management on Canterbury farms 1 Introduction We examined the associations between plants, insect herbivores, their natural enemies and pollinators to evaluate the potential for using perennial plant assemblages on non-productive areas of farms to maximise the establishment and abundance of beneficial insects. Pollination and pest suppression are key on-farm services provided by beneficial insects (pollinators, predators, and parasitoids). Yet the potential of beneficial insects to provide these essential services is often not realised because they are absent or low in numbers, generally due to historical management practices. Pest management strategies and honey bee pollination may be compatible with the use of “natural” beneficial insects, although greater scientific knowledge is needed to understand how this could be achieved. The aim of this project was to identify optimal host plant associations that could maximise and support stable populations of beneficial insect species. Beneficial insects have great potential to suppress insect pests and/or pollinate crops. For example, the predatory brown lacewing significantly reduced aphid levels in outdoor lettuces and was critical to the success of the integrated pest management programme (Walker et al. 2007). Increasing costs associated with honey bee management (up to $0.5 B to New Zealand’s agricultural industries over the next 15 years (MAF 2000, 2002)) may threaten the viability of some industries unless alternative pollinating species are encouraged. Recent research has demonstrated the benefit that many unmanaged bees and flies can provide to crop pollination in New Zealand (Rader et al. 2009). Introducing the right combination of indigenous vegetation into non-productive areas (e.g. hedgerows), could sustain larger populations of beneficial insect species while inhibiting pest populations (Altieri 1999). We determined the species composition of insect herbivores (pests and non-pests) associated with a range of crop plants, and existing hedgerow and shelterbelts composed of non-native species (predominantly Pinus radiata , Cupressus macrocarpa and Ulex europaeus ) in Canterbury. In the early 1990s hedges and shelterbelts on the Canterbury Plains were predominantly made up of these three exotic species and extended to a combined length of almost 300,000 km (Price 1993). We compared insect associations of these plant species with those of native plant species that could be used as alternative hedgerows, shelterbelts, or in other areas of non-productive land. We wanted to see if native plants would be less likely to act as a reservoir for crop pests than non-native species. We then examined the relationships of natural enemies and pollinators with native and/or exotic hosts (plant and/or insect species). The associations between plants and their herbivores was examined using current information to determine: 1) if the plants could support exotic insect pests, 2) whether the alternative prey/hosts of the native predators and parasitoids could become pests on nearby crops, and 3) whether the biology of the plants would limit/negate their ability to become weeds. Page 3 4104 Hedging our bets: choosing hedgerow plants to enhance beneficial insects to optimise crop pollination and pest management on Canterbury farms. 2 Methods We accessed all available published and unpublished information via the PlantSynz database and the internet in general and identified: 1) native plant species which would support beneficial insects, 2) common pest species and their host plants (both native and exotic), and 3) beneficial insect species. “Beneficial insects” were defined in this study as all known insect pollinators and natural