Our Carbon Positive project is comparing conventional intensive process crop production with production applying regenerative farming principles. One of the aspects we are focusing on is the “softening” of the pest and disease control programme. In the regenerative treatment, we are particularly looking at a range of biocontrol agents. In effect, these are also playing roles in the other treatment areas as well, especially things that can fly!
Biological Control Agents (BCA)
In mid-December, we released biological control agents (BCA’s) into the trial area, as an alternative way of managing pest insect species. The main target is the regenerative treatment, however the nature of the species we have released, and our trial layout means it is hard to isolate to just one treatment. The three species we released are Tamarixia, Tasman Lacewing and Pirate Bugs. All BCA have been provided by Heinz-Watties, through Bioforce Ltd.
We have applied a single insecticide to all treatments so far. We applied Benevia (cyantraniliprole), which is effective for both sucking and chewing insects in potato and tomato crops. It is most effective as a preventative measure for pest control. The main target of this spray is Tomato Potato Psyllid (TPP), but it also controls onion thrips and aphids (FMC, 2023). We have found green peach aphids in the tomatoes, as well as a few thrips and whitefly, however the incidence of these insects seems to have reduced to virtually nil after the Benevia application. Formal monitoring of leaves for pest insects and disease started the week before Christmas.
Caution is being taken not to apply insecticides that will kill the parasitic wasps, and other beneficial insects. We have been using yellow sticky traps to monitor for TPP but by 20 December we have not found psyllids in our crop.
Tamarixia triozae – Parasitic Wasp
Heinz-Watties has used Tamarixia triozae to control TPP in their tomato crops. We released Tamarixia into our four regenerative treatments before Christmas, 8 weeks after planting. The insects are delivered in small plastic vials, to be distributed into target areas.
Tamarixia (T. triozae) is a small parasitic wasp that parasitises TPP. TPP was first found in New Zealand in 2006 and has since spread throughout the country. The small flying insects impact solanaceous crops (e.g., tomatoes, potatoes, capsicum, and eggplants), and vectors a disease called Candidatus Liberibacter solanacerum (CLso) or Zebra Chip virus (Bioforce Ltd, 2023b). In tomatoes the virus causes leaf curling and yellowing, and softening of fruit, causing the fruit to be unfit for processing (Anderson & Davidson, 2020). Adult female T. triozae will lay an egg on the underside of the host insects (4th– 5th instar TPP nymphs), actively seeking out and targeting TPP (opposed to generalist predators that target most prey). The larvae become an adult inside the nymph and will completely ‘excavate’ the body of the TPP and will pupate inside the shell of the host. It will then chew a hole in the shell and emerge, ready to hunt more TPP (Anderson & Davidson, 2020).
Micromus tasmaniae – Predatory insect (Tasman Lacewing)
We released Tasman lacewings into the Regenerative treatment in week 8 (before Christmas). Tasman lacewings are a generalised predator and predate pest insects such as aphids, whitefly, and psyllids (all of which are found in tomato crops). Lacewings are known to be a successful predatory insect in capsicum, citrus and cucumber crops (Bioforce Ltd, 2023c).
The insects are delivered as eggs attached to a small piece of hessian cloth. They are predatory at both the larvae and adult stages and will start to predate aphids soon after hatching. As they are released at an egg stage, moving into a larvae stage, they should be released into an area where prey is present, so they have an immediate food source (Bioforce Ltd, 2023c). Pest insect populations do appear to have been supressed from the initial Benevia application, so we do question if they will have enough to eat to start with. We hadn’t identified any particular ‘hot spots’ so we evenly distributed through the Regen treatments (8 small pieces of cloth per plot).
There are many different types of aphids in New Zealand, the most significant cause of damage is through the transmission of plant virus diseases, in tomatoes these viruses include alfalfa mosaic virus, cucumber mosaic virus (Cameron & Bourdot, 2005) and tomato yellow top virus (Bioforce Ltd, 2023a).
Orius vicinus – Predatory Insect (Pirate Bug)
Orius is a small predatory insect, and will predate a range of prey including aphids, thrips, whiteflies, and psyllids. The insect is an aggressive feeder in the lab but use of Pirate Bugs in the field is still experimental. Similar to aphids, thrips seem to mostly be under control in the trial area after the initial Benevia application.
Thrips are one of the main target species of Orius. Both adults and juveniles will attack thrips at all life stages. While thrips themselves will not generally cause economic damage to a crop, they can spread Tomato spotted wilt virus (TSWV) (Cameron & Bourdot, 2005).
The insects were delivered in a bottle of buckwheat husk media and sprinkled onto tomato leaves. It was advised to spread the insects out in the four corners of the trial area, which is what we have done (not necessarily specific to Regen treatment).
References
Anderson, S., & Davidson, M. (2020). Improved control of tomato potato psyllid with the parasitoid Tamarixia triozae: Final report SFF 404861 [A report prepared by both the Vegetable Research & Innovation Board and Plant & Food Research]. Vegetable Research & Innovation Board and Plant & Food Research
https://www.vri.org.nz/research/new-research-document-page-47/
Bioforce Ltd. (2023a, December 15). Aphid Control.
https://www.bioforce.co.nz/pests/Aphids.html
Bioforce Ltd. (2023b, December 15). Tamarixia for Psyllid Control. https://www.bioforce.co.nz/products/tamarixia.html
Bioforce Ltd. (2023c, December 15). Tasman Lacewing for Aphid Control. https://www.bioforce.co.nz/products/Tasman-Lacewing.html
Cameron, P. J., & Bourdot, G. W. (2005). In D. A. J. Teulon (Ed.), Plant protection in organic arable and vegetable crops: A grower’s resource (pp. 225–238). Crop & Food Research.
FMC. (2023, December 15). Benevia®—Superior protection against Potato pests. FMC. https://www.fmccrop.nz/Products/Insecticides/Benevia/Benevia-Strong-Control-of-Potato-Pests