A shrinking number of pest control products and more stringent requirements are making crop protection across all crops that bit more complicated. Potted hydrangeas are no exception, and here too, biology is becoming increasingly significant. Dutch plant nursery P. van Geest is extremely satisfied with the work of the beneficials. ‘It’s never been so easy to keep our potted hydrangeas looking so good.’
The Netherlands-based plant nursery grows tomatoes and peppers and produces potted hydrangeas, mostly for retailers including IKEA and Albert Heijn. Potted hydrangea cultivation is complex. Once the cutting material has arrived from Portugal, there is a propagation period. Then, when the shoots and buds have developed sufficiently, the topped plants have to spend at least 1000 hours in a cold store. After that, there is the finishing process before delivery to customers.
‘IKEA and Albert Heijn are super-strict customers,’ explains cultivation manager Pieter van der Lugt. ‘Our strength lies in our ability to produce some 2.5 million units every year, which means that we can send out large numbers of plants every week if necessary, all of excellent and uniform quality. It works out very well, but we have to do a lot of work to get there.’
A strong army in the crop
With their key customers placing extremely stringent requirements on crop protection, the company needs to resort to biological control methods to fight pests wherever possible. The most troublesome pests in Van Geest’s potted hydrangeas are thrips, aphids, and spider mites. Thrips are tackled once at the start of cultivation using a combination of Mainspring and an attractant; aphids are treated several times with Teppeki, and spider mites are dealt with using a range of enemies, including Spidex, Spical, and Swirski-Mite. At the same time, the feed mite Carpoglypus is also scattered over the plants to give Swirski-Mite in particular, which can also control thrips, whitefly, and tarsonemid mites, a helping hand. This supplementary feed is usually given after one and two weeks using the Airobug from Koppert.
‘This way we have a number of strong armies in our crops at the start of the finishing process,’ explains Pieter. Entonem and Hypoaspis miles product are also used at the start.
An astonishing result
The approach is virtually the same in the propagation phase, except that no Entonem is used. Pieter continues, ‘The topped plants go into the cold stores virtually spotless. Crop protection this year was a piece of cake. It’s just a snapshot of course, and next season might be much more difficult, but we’ve been able to keep our crop looking great with very few beneficials and minimal work. We’ve been really astonished by the result.’
For Pieter, the greatest threat is not in the shrinking number of pest control products or more stringent rules, but in the lack of uniformity in legislation. ‘Customers are increasingly limiting the number of products that they will allow, but those products vary between customers or certificates. For growers, workability would increase if the rules were more uniform. We’re hopeful that the government will take a leading role in this; a valuation based on environmental impact would to me be a better place to start.’
Consultant Wim van der Meer agrees. ‘More uniformity would be nice as growers are always having to contend with new issues.’ He mentions Thrips setosus, or Japanese thrips, which began to settle in hydrangeas a few years ago without being noticed. ‘They were a problem that needed to be solved. It’s easy to see why Koppert invested so heavily in R&D for protection against thrips. The predatory insect Thripor-L has been successful at controlling Western flower thrips and other species of thrips. It’s possible that Thripor-L, perhaps with supplementary feeding, might be able to control the Japanese thrips as well.’