Two control strategies (with and without Macrolophus) in unlit tomato greenhouses are demonstrated in the pilot Tomato Growing without Sulphur. The cultivation started in week 4 and is now, in week 43, slowly coming to an end. Jeannette Vriend gives an update on behalf of Glastuinbouw Nederland.
One of the aims of the pilot was to assess the efficacy of Trichogramma parasitic wasps for controlling the golden twin-spot moth. The caterpillars cause damage to leaves, but also to bunches. Most caterpillar agents must be absorbed by eating the plants.
Trichogrammas are small parasitic wasps that fight the eggs of moths. They can do this in two ways. The first way is by host feeding, where the egg is pricked and sucked empty. The second way is by depositing a parasitic wasp egg in the moth egg. The egg of Trichogramma develops into a larva that empties the moth egg from the inside. As a result, there is no voracious damage to the plant. Eventually, a new Trichogramma parasitic wasp emerges from the parasitized moth egg.
The combination of Macrolophus and Trichogramma offers opportunities
To do full justice to the Trichogramma, we chose to work with one greenhouse without Macrolophus and one greenhouse with a combination Trichogramma and Macrolophus. The same mix product of two species of Trichogramma parasitic wasps was used in both greenhouses: the Tricholine TA+TB mix.
The Bioline dispensers were chosen, releasing Trichogramma into the crop over several weeks. By working with dispensers, the highest possible hatching rate can be achieved, which increases the reliability of deployment. The dispensers are a patented product of Bioline, originally developed for application in maize cultivation. The robust system provides additional protection in the greenhouse against predation by predatory bugs.
As many as five introductions of golden twin-spot moth
There were no spontaneous incursions of the golden twin-spot moth in the test greenhouse, partly because there is mesh in the windows. To properly test the biological pest control system, there have been up to five introductions of the golden twin-spot moth, from Vertify's culture. The Pats-C system installed in the greenhouse was able to properly monitor the activity during the days following the deployment.
It then scouted for caterpillars in the crop. At the last introduction in mid-September, the choice was made to work with a very high number of moths, over six times more than in the previous deployments. In all five introductions, the caterpillars failed to develop.
Also, no additional corrective measures were needed besides the standard deployment of biology. However, it should be noted that the predatory bug Macrolophus also managed to establish itself in the greenhouse, where it was not introduced. To reduce the impact of Macrolophus, before the last introduction of the golden twin-spot moth, the heads were removed from the plant and disposed of. This removed some of the predatory bugs from the greenhouse. From practice, we know that Macrolophus alone is often insufficient to fully control caterpillars. The combination of Macrolophus and Trichogramma offers opportunities and shows good results even under very high pest pressure.
Funding for this pilot
This project is being carried out by Vertify, location Demokwekerij Zwethlaan, as part of Greenhouse as Ecosystem. It is funded and coordinated by the innovation program The New Doing in Plant Health of Knowledge in your Greenhouse (KijK). It is half funded by the Tomato Crop Cooperative. And partly made possible by in-kind contributions from Biobest, Bioline, and Pats, who provided introductions to the biological control agents, monitoring hours, and reporting. The trial was followed and supervised by growers.
Source: Glastuinbouw Nederland