Plenum currently only has approval under the Specific Off-Label Approval (SOLA) arrangements (Approval No. 1478b of 2003) and growers must be in possession of a copy of the SOLA certificate before they use the product. A SOLA approval means that product use is at the growers own risk with regard to efficacy and crop safety. While Syngenta, under the terms of a SOLA approval can not recommend or actively promote the use of Plenum on brassicas, they have provided the following information based on current trials data to help growers achieve the best results from the product. Syngenta are continuing with the development of pymetrozine in brassicas and hope to have enough data to obtain a label approval from PSD in the future.
Users should be aware of the following regarding the use of the product:
Plenum provides good control of M.persicae but, compared with a pyrethroid or carbamate based product, Plenum is relatively slow in providing this control. The contact effect of pymetrozine is limited and good activity depends upon getting the product into the leaf of the crop and then aphids sucking up sap which contains pymetrozine. Because the aphids starve / dehydrate to death, in cool conditions they can survive for a number of days (3-5 usually) following feeding. If they are not feeding then the level of control will be significantly reduced.
Because of the need to get pymetrozine into the leaf structure it is very important to treat the crop before M. persicae has done a lot of feeding damage. When leaves are damaged they will not take up pymetrozine nearly as well as when they are healthy, and pest control efficacy will be reduced. Syngenta trials indicate that pymetrozine will not knock down large established aphid populations for this reason. While pymetrozine has systemic activity it is particularly important in a waxy crop, like brassicas to achieve good crop coverage because the product is less able to get into the leaf structure. It is therefore important to maximise the contact effects of pymetrozine and to optimise the chances of getting the active into the leaves.
Coverage in brassicas
Achieving good coverage in brassicas is very difficult. Whilst Syngenta do not have a lot of data relating specifically to pymetrozine application it is likely that a medium fine spray will produce the best results, as this can drift into the crop canopy. Very high water volumes will almost certainly create droplets that are too coarse to drift into the foliage.
Trials on brassicas
Trials have shown that Plenum when applied alone to brassicas (rate recommended on the SOLA certificate 0.4 kg product per hectare) is intrinsically more active against M. persicae than mealy cabbage aphid (Brevicoryne brassicae). Activity against both species has been shown to increase where an adjuvant is included and a number of adjuvant products have been trialled but at present no approval exists for their use.
Use as a tank-mix
Where mixed populations of different aphid species are a problem, a tank mix of Aphox and Plenum should be considered as a means of optimising activity against both species
Aphid susceptability to pymetrozine
There is no indication of any change in the susceptibility of aphids to pymetrozine and Plenum continues to provide a viable alternative in the current difficult conditions.
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