Bemisia tabaci, a Poinsettia grower’s number one worry
B. tabaci has become the primary pest in Poinsettia production in Western Europe. A worldwide pest and virus vector, this whitefly originated in sub-tropical crops but has since spread to protected crops in temperate areas − including most of Europe.
In addition to virus transmission, B. tabaci causes direct damage by its feeding activity as well as indirect damage through sooty moulds developing on honeydew excreted on the host plant. In Poinsettia crops the presence of sooty mould generally leads to plant rejection, impacting on commercial margins.
“B. tabaci populations in the South-West of France are becoming increasingly resistant to authorized conventional chemical controls creating a major issue for growers in this region,” explains Biobest’s Product Manager Rosy Pauwels. “Standard biocontrol strategies rely on regular releases of Amblyseius swirskii to help keep whitefly populations below the damage threshold of a maximum 30 larvae or adults/plant – but that in itself is not always sufficiently effective. We therefore suggested the use of our Nutrimite product, a highly nutritional food supplement based on specially selected pollen. This can strongly enhance and accelerate the population development of predatory mites such as swirskii.”
Ecophyto’s 2014 trial set-up
In a bid to improve the biocontrol strategy, the Ecophyto trial compared two strategies. In Plot 1 A. swirskii was introduced at 100/m² together with Nutrimite pollen bi-weekly at 500g/ha plus Eretmocerus eremicus and Encarsia formosa.
In Plot 2 A. swirskii was again introduced at 100/m² but this time in combination with the bio-insecticide Mycotal at 1kg/ha and E. eremicus and E. formosa.
The Ecophyto trial involved five varieties of Poinsettia – Bella Italia Red, Bravo Bright Red, Premium Polar, Premium Lipstick Pink and Premium Ice Crystal.
Regular applications of Nutrimite in Plot 1 had a spectacular effect on swirskii development and on overall B. tabaci control. With a whitefly population beneath the damage threshold, Plot 1 had the highest % of Class 1 Poinsettias commanding the best price. These plants had no visible sooty mould.
In contrast, in Plot 2 the pest was not kept beneath the damage threshold and resulted in 9% unmarketable plants due to visible signs of sooty mould.
Incorporating Nutrimite in the control strategy can boost turnover by reducing the number of unmarketable plants. Moreover, the superior result in plot 1 was achieved at less than half the cost: plant protection cost for Plot 1 was 1,08€/m² compared to 2,32€/m² for Plot 2.
In terms of labour cost, Nutrimite applications can be made three times more quickly than swirskii applications – this adds further to the bottom line. All in all the Nutrimite strategy helped increase operational margin by a substantial 33%.
The 2015 set-up
The 2015 trials confirmed the important effect of Nutrimite on swirskii development. Following four applications of Nutrimite and only two introductions of swirskii at 100/m², the predatory mites were found on 70% of the plants. However, in spite of the high swirskii population in the crop, the Bemisia tabaci population did exceed the damage threshold at certain times. To achieve good biological control of Bemisia careful monitoring throughout the season remains crucial.
Rosy Pauwels comments: “When pest population levels are higher, the predatory mites have enough pest to feed on and Nutrimite as an alternative food source is no longer required. Ecophyto is continuing the work during 2016 to further optimize the strategy.”
A worldwide success story
“Also in North-America Poinsettia growers are satisfied with the integration of Nutrimite in their biological control strategy”, says Rosy Pauwels. Schmidt Brothers Inc (Ohio, US) is pleased with the results of the new program set up in 2015 together with Biobest distributor Plant Products. Through continuous communication, regular scouting and timely visits the program was a success. The integration of Nutrimite boosted the population of beneficials helping to lower the cost of both labour and overall insect control.
For more information
Biobest Belgium NV
Ilse Velden 18
2260 Westerlo - Belgium
T +32 14 25 79 80
F +32 14 25 79 82