The thorny issue of the American Bramble

The American Bramble (Rubus cuneifolius) is the thing of nightmares for most foresters. As an alien species that thrives in South African conditions, it has an uncanny knack of surviving most control methods thrown at it.

In the throws of bramble fighting season, TIPWG spoke to Alasdair Mackenzie from Midlands Spray Chem. Alasdair has spent 40 years in the agrochemical industry, working in both agriculture and forestry, which is why we asked him to share his bramble eradicating experiences and knowledge. So over to Alasdair…

A thorny invader, the American Bramble is now widespread, well established and hard to control but where there is a will, there is a way.

While there are many products on the market with a registration for its control, some are better and more cost effective than others. We have found Metsulfuron Methyl, a well-established product in both forestry and conservation, to be the product of choice. A Sulfonyl Urea, Metsulfuron Methyl is an easy to use, dry, flowable 600g active ingredient/kg, water soluble granule.

Its mode of action inhibits plant enzymes, with no effect on animal enzymes making it a relatively safe product when considering its potential human health implications. Absorption of the product is mainly through the leaves and canes, but root uptake can occur after rain. The product is also absorbed by the cambium layer of freshly cut stumps.

When considering the environmental implications of this form of control, the fact that Metsulfuron Methyl is selective (meaning it has little or no effect on established grasses), makes it an ideal product to use. It must be remembered that the product does have soil activity, but breaks down readily in warm, moist, acid soils (slower breakdown occurs in alkaline soils). Contamination is unlikely to occur due to the low application rates and degradation in the soil although there is a holding period for follow crops (i.e. gums) after application – so READ THE LABEL! Metsulfuron Methyl will not vaporise and drift unseen onto desirable plants, but physical spray drift should be avoided.

Control should be done in the latter half of the season, when all the prima canes are above ground, giving you the best leaf-to-root ratio. Application methods are numerous, ranging from knapsacks, mist blower, bakkie sakkies, motorised knapsack and tractor mounted boom sprayers. That being said, the mixing ratio will always remain the same at 25g/ 100L H20 with the recommended adjuvant. When spraying, ensure the foliage, green canes and peripheral runners are thoroughly wet to point of run off.

Be warned: physical signs of control are slow to show but be assured the bramble will stop growing soon after application. Visible signs will then appear after four to five weeks, site and weather depending.

The application rate for an average infestation will be 300–400 litres of mix per hectare, equating to 75–100g of product. Make sure you check the weather conditions, as rain within four hours of application will reduce the treatment’s efficacy.

When it comes to storage, only mix what you need and do not store the mixed product for more than 12 hours otherwise significant breakdown will occur.

One final point, if in doubt – READ THE LABEL – on second thoughts, read it anyway.

/ Pesticide interest piece