During the pilot 'Growing Tomatoes without Sulfur', two organic pest control strategies (with and without Macrolophus) are demonstrated in unlit tomato cultivation. The cultivation started in week 4 and is being closely monitored for pests and introduced natural enemies. Jeannette Vriend provides an update on behalf of Glastuinbouw Nederland.
Since no sulfur is used in the cultivation, it became possible to preventively deploy the predatory mite Pronematus ubiquitus against powdery mildew and tomato russet mites. This very small predatory mite is not hindered by the glandular hairs of the tomato and can establish itself early, when pollen is applied. A decent density of this predatory mite is required to preventively control tomato russet mites. In both greenhouse compartments, the predatory mite was introduced twice (week 6 and week 8) and was first fed weekly three times with cattail pollen (500 g NutrimiteTM /ha) using a blower.
Good preventive establishment of the predatory mite has been achieved
Counts indicate that the predatory mite has taken well. The predatory mites often become easier to observe six weeks after introduction. The establishment is now good, with a density of around 0.4 predatory mites per leaf in week 12. A strong increase from the week before. For now, pollen is dropped onto the crop every other week, so that Pronematus can multiply and spread well. To allow the predatory mites to take well, a well-coordinated leaf picking protocol is applied: the balance of the crop is not disturbed, and at the same time, the predatory mites are given the chance to establish themselves well in the crop.
So far, no tomato russet mites have been found, which is quite logical because the pest often occurs later. Should no spontaneous russet mite infection occur in the pilot, the pest will be introduced later to demonstrate the effectiveness of Pronematus.
Other pest organisms already active in the greenhouse?
Thanks to a very preventive strategy against greenhouse whitefly with Encarsia formosa, the pest has not yet been observed. However, from mid-February, the first spots of spider mites were found, but through introductions of the predatory mite Phytoseiulus persimilis and the gall midge Feltiella acarisuga, the pest has been cleaned up.
Macrolophus build-up weeks
Macrolophus pymaeus was released in week 10, but only in one greenhouse compartment. An introduction of 2.5 individuals per m2 was carried out in the middle row. The predatory bug is fed together with Pronematus by blowing pollen together with 500 g/ha Artemia cysts. In the other greenhouse compartment, tomatoes are grown without Macrolophus, and the control of caterpillars must be achieved entirely by the parasitic wasps Trichogramma achaeae and Trichogramma brassicae. No Turkish moths or other caterpillars have been observed in any of the compartments yet.
Tomato growers are intensively involved in this pilot
To make this unlit tomato cultivation as successful as possible, an active guidance committee from the national tomato committee is also involved in the pilot. Weekly, a member of the BCO provides input to the cultivation process, in close cooperation with the other participating parties.
Funding for this pilot
The pilot is conducted within the framework of the pilot program 'Greenhouse as Ecosystem'. It is partially financed by the practical program 'Plant Health and the Knowledge in your Greenhouse' (KIJK), and partially by the Tomato Crop Cooperative. In addition, there is a significant in-kind contribution from the involved parties (Biobest, Bioline, and Pats). They are taking care of the introductions of the biological control agents, monitoring hours, and reporting. The demonstration is carried out at Vertify, location Demokwekerij Zwethlaan.