A leading independent consultant specialising in alliums says that every single crop of onions, leeks, garlic and shallots would receive pendimethalin. “No other herbicide is as universally used in allium crops,” says Andy Richardson of Managing Director of the Allium and Brassica Centre.Advising on over 10,000 acres of alliums and brassicas, Andy puts pendimethalin as the mainstay of the residual herbicide programme. “Why? Because it offers broad weed spectrum and largely residual activity. Weeds such as knotgrass, fat-hen and small nettle are hard to control with any other chemistry. Newer herbicides tend to have a much narrower weed spectrum and are not as long-lasting. Pendimethalin has been universally used by allium growers for many years and they are familiar in how to use it.”“The formulation change for Stomp (pendimethalin) however has been very important in terms of ease of use and safety. Stomp Aqua is, in my view, significantly safer to crops than the old EC formulation and it stains machinery much less. In alliums, because the crop is not at all competitive, pendimethalin is used both pre and post emergence. Crops grown from seed are drilled around the first week of March which coincides with emergence of polygonum weeds. Crops from seed also take a long time to produce roots to any depth. Low dose pendimethalin with a top up application works well and is standard practise.”Andy also uses Wing-P, a co-form of pendimethalin and dimethenamid-p, and sees it as a potentially popular herbicide for brassica growers.
“Pendimethalin, as an active straight or in coform, is also important for brassica growers. As an active it is a relatively new to brassica growers though and they are learning how to use it pre-planting.”Wing-P has many EAMU’s including transplanted cabbage, leeks, bulb onions, garlic, shallots, salad onions and chives. “Last year transplanted broccoli, transplanted Brussels sprouts, transplanted cauliflower, outdoor ornamentals and a range of herbs were added to the list of EAMU’s for this herbicide,” reports Rob Storer, Speciality Crop Manager for BASF.Andy Richardson also uses the coformulation of metazachlor and dimethenamid-p (Springbok). “It offers annual meadow-grass and groundsel control as well as improved control of polygonums.” Springbok has been developed in field vegetables and last year outdoor broccoli, Brussels sprouts, cabbage, Chinese cabbage and cauliflower were added to its list of Extensions of Authorisation for Minor Uses (EAMU’s).“Using Springbok in brassicas is a way of helping to reduce the metazachlor loading restriction of 1000 gms per hectare over a three-year period and adds another viable option for growers,” says Rob Storer.Andy Richardson is concerned that brassica growers don’t have much choice when it comes to herbicides. “There is Butisan (metazachlor) post-emergence but you have to be careful with the loading limits over 3 years. There is Kerb (propyzamide) but it has too narrow a weed spectrum and with summer plantings of brassicas, there is generally low soil moisture. Gamit (clomazone) controls cleavers but can cause phytotoxicity to the crop and can only be used once a year, difficult with double cropping. In any case any herbicide in brassicas needs to control knotgrass, fat-hen and small nettle. It is so important that we keep hold of those herbicides that we have now. If anyone of them is taken away, growing these important vegetables economically would become nigh impossible.”The Allium and Brassica Centre in Kirton, Lincolnshire was founded in 1982 to independently advise growers and packers on all aspects of bulb onion and brassica production and storage. The Centre now has a major emphasis on confidential Research and Development as well as an established role in specialist consultancy. It also has state of the art Controlled Atmosphere storage for up to 3,100 tonnes of produce and glasshouses or tunnels for in house plant breeding and a purpose built seed store.