Crop protection for mandevilla

Keeping the white fly population under control has been a challenge for many years for Theo van Neerven of Neervenplant in Helenaveen, The Netherlands. Having tested various strategies, a combination of biological predators and a space treatment with BotaniGard proved to be the solution.

"To do something that others don’t do". That was the driving force for the grower and his wife Lida to start the cultivation of patio plants and conservatory plants in 1997. Until then, the entrepreneur had been cultivating tomatoes and eggplants. Nowadays the grower, whose company amounts to 1.2 hectares, specializes in cultivating mandevillas. In addition, the assortment consists of Cyperus papyrus, Jathropha integerimma and Plumbago auriculata. "We have been experimenting for years with the use of biological predators," says Theo van Neerven. "After all, the number of available crop protection products continues to decline. An additional problem is that the leaves of the mandevilla have a wax layer, which fully or nearly fully prevents crop protection products from penetrating the crop."

Also the use of biological predators did not immediately go smoothly. "We soon found out why: the mandevilla plant turned out to be poisonous, which made it difficult to keep the population of wasps, predatory mites and mirid bugs at the required level."

In consultation with Bart Joosten of supplier Mertens, Van Neerven has in recent years succeeded in developing a strategy for controlling the white fly - the biggest problem in the cultivation of mandevilla. "We placed banker plants between the crop, which gave the development of the Macrolophus pygmaeus mirid bugs a boost," says Joosten. "We also additionally fed the predatory mites with pollen. In addition, we experimented with various types of predatory mites. Amblyseius swirskii and Amblydromalus limonicus proved to be the most effective."

If Van Neerven comes across a white fly or if the pest pressure becomes too high, then he'll use BotaniGard. This occurs mostly in the autumn. "Our cultivation starts in the summer," he says. "As soon as humidity exceeds eighty percent, we will use BotaniGard fluid if necessary. We want to enter winter with the greenhouse as clean as possible."

The grower performs a space treatment using LVM (low volume misting). Performing a regular spray is not an option. "Spraying does not reach the lower leaves of the plant, while most larvae often are there. Online, I found that positive effects were achieved with LVM at a high humidity. That proves to be the case. We then continue to repeat the treatment for six weeks. That's important, as the flies lay new eggs."

Advisor Lianne van Wijk from Certis indicates that a space treatment can be a good application technique to get the spores on the flies. "For optimal application of BotaniGard, it is important that the spores come on the insect immediately during application."

According to Van Wijk, the general advice is to use the product at temperatures above 15°C, but the optimum is at a higher temperature. "A temperature of 15°C is not always reached," Joosten acknowledges. "But with a high humidity you're already one step ahead. After all, the water drops are the carriers of the spores."

With the outlined strategy, Van Neerven can keep the white fly population well under control. But he stresses that BotaniGard alone would not be sufficient. "That product mainly reduces the pest pressure, but it is not a solo product. This product supports the biological predators. In short: it's the combination that guarantees success."