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Predatory beetle controls mealy bug well in rose

After the final crop rotation, rose grower Henk van Os from Os Roses Holland disinfected an entire department of the greenhouse to eliminate the mealy bug. Despite this rigorous method, the mealy bug returned within four month. "When you have mealy bug, you will keep mealy bug" says adviser Kees Kouwenhoven of Royal Brinkman. "The major problem is the eggs. They are well protected and are everywhere; not only in the crop, but also in the ground." This problem occurs in all crops.

Eight years ago, Henk van Os recognized the first sign of problems, which increased over the last few years. "There are crop protection products that work, but we try to build up a good working biological system. Then, it is always a bit harder", he says.

Os Roses Holland grows 4.5 ha Talea in three departments. The age of the plant differs in each department. The oldest crop is seven years. The leaves of the roses are very tight which complicates the removal of the mealy bug when using the proper crop protection products.

Mealy bug is still an increasing problem for growers. Henk van Os was able to control the mealy bug population by using the predatory beetle Cryptolaemus, thanks to the persuasiveness of Kees Kouwenhoven. “It will succeed if you adjust the chemical approach at the same time.”  

Adjust the chemical approach to the beetle
"The predatory beetle Cryptolaemus montrouzier is a well-known natural enemy of the mealy bug" explains Kouwenhoven. "I was convinced that it would work, if the circumstances improved. This means that you need to change the chemical approach to the beetle." "It took a while for me to be convinced", says van Os with a smile. "in 2013 we released some beetles on a couple of mealy bug populations. It went very well. Over time you saw the second generation larvae from more than ten meters away. "

Rapid Spread
The year after, in 2014, they released beetles on a 2000m2 area. They spread over the entire 1ha department. "They spread more rapid than expected. The beetle is like a lady bug, with good search behaviour. He flies towards the mealy bug population", says the adviser. This season there was no need to release any new beetles in that department. It multiplies well. At the moment, van Os releases the beetles into the entire greenhouse. "I am very satisfied" he says. "The mealy bug is not gone yet, but the level is acceptable now. In the past we spent 1.50 Euro per meter on the control of mealy bug.

Kees Kouwenhoven adds: "Royal Brinkman is the only one with practical experiences. It is very important how the integrated system of the beetle is adjusted. Currently there are more success stories from different companies who have mastered the system.