Column Gilbert Heijens

Responding well to change is the key to success

Fusarium, viruses, advancing insects, drier and warmer summers - the list of challenges in greenhouse horticulture keeps growing. Yet that doesn't have to be bad news: growers who know how to respond well actually reap the benefits. Greenhouse horticulture is a wonderful, innovative sector. In recent years a great deal has changed, and challenges have followed one another in rapid succession.

Increasing disease pressure

Think of (root) fusarium in tomato in the past, where grafting increasingly provided the answer, but also corynebacterium and verticillium, which were a challenge. In pepper we see stem fusarium and "elephant's feet," and in recent years increasingly more problems with root fusarium. Viruses have also played tricks on us, such as cucumber mosaic virus, pepino mosaic virus (PepMV), TSWV and ToBRFV.

More pressure from insects

Insects are playing an increasingly large role. Alongside familiar species such as thrips, whitefly (Bemisia), aphids, tuta, russet mite and caterpillars, new species are rapidly advancing: Nesidiocoris, Nezara, the brown marmorated stink bug, new aphid species and new thrips species.

Innovation as the answer

Fortunately, greenhouse horticulture is innovative by nature. Where installing a cultivation gutter was once already a challenge to counteract a poor root profile, this has now become standard - just as full-LED lighting is increasingly becoming. Every grower is adapting their greenhouse ever more specifically to the challenges at hand, causing greenhouses to increasingly differ from one another. Think of insect screens, humidity control via misting, double screens, and disinfection of all outgoing water including rainwater.

Crop rotation and climate

We are also seeing temporary crop changes, such as high-wire cucumber cultivation instead of tomato. The most current challenge, however, is dealing with low humidity combined with higher temperatures. Daily average temperatures have been rising for years. Northern Europe still has the advantage of cooler nights than the south, and along the coast nighttime temperatures also remain cooler than inland.

Four responses to heat

Growers respond very differently to high temperatures. There are essentially four options: whitewashing, whitewashing combined with misting, screening, or doing nothing. The general conclusion is that doing nothing is the worst choice - it is precisely stressed crops that benefit from some help and gain the most from it. Screening and whitewashing naturally cost light, but during this period there is usually more than enough light available. In countries where high daily average temperatures in summer have long been the norm, misting and whitewashing are increasingly applied as standard - sometimes even in double layers. By pinching mainly on the windward side, moisture is kept inside and the cooling capacity of the crop results in a lower temperature than outside.

Summer screens and drones

The summer screen is also gaining ground. This screen can close completely under high solar radiation - sometimes with a small gap - and opens again easily as soon as it gets darker. Interest in whitewashing with a drone is also growing, in order to respond quickly to changing weather forecasts.

Conclusion

There is thus a wide variety of responses to today's challenges. Naturally, other themes also play a role, such as energy and labor. What is clear: whoever manages the challenges best is the winner in quality and production - and ultimately in profitability. As advisors, we are increasingly becoming a sparring partner, working together with the grower to find a suitable answer to all these challenges.