Are poor weather and harvest delays costing you more than you realise?
Are poor weather and harvest delays costing you more than you realise in terms of oilseed rape yield? Dominic Kilburn gets an update on varietal resistance to pod shatter. Yield losses in oilseed rape can be markedly reduced in varieties that carry a genetic resistance to pod shatter, a trait that is widely being recognised with increasing importance by growers in this country. In addition to saving yield, reducing the level of pod shatter in a crop close to, or at, harvest time results in less volunteer weeds in the following crop and evidence suggests it may also have a positive effect on reducing slug activity. Monsanto has been introducing a pod shatter resistance trait into its hybrid varieties since the late 1990s and is currently the only breeder with commercial material carrying it. Called the Ogura hybrid production system, the genetics were brought across from a radish species and all the companys commercially available oilseed rape hybrid varieties, including Excalibur, DK Extrovert and DK Expower, carry the trait. According to the companys seed breeding arm Dekalb, European trials over the past five years have demonstrated clear yield losses from pod shatter susceptible varieties ranging from 0.32t/ha yield loss in the Nordics (20112013) up to 3.15t/ha in Hungary in 2013 compared with varieties carrying its pod shatter resistance trait. Also in 2013, losses in UK trials were found to be as much as 1.47t/ha in susceptible varieties. At an oilseed rape value of 300/t, these translate into financial losses ranging from 36440/ha, points out Dekalb.
Speaking at the companys Cambridgeshire base, Dekalbs Dr Andrew Smooker (left) highlighted that a recent industry survey of 200 growers on their key OSR crop trait requirements, showed that vigorous establishment and then rapid autumn development were closely followed by pod shatter in preferential order; 56 per cent rated pod shatter as very important and 39 per cent rated it as fairly important. Establishment and early vigour are key traits that growers like to see in their crops, as well as pest and disease resistance, and while pod shatter is a less obvious problem, its becoming more important, said Andrew. Wind, hailstorms, rapid changes in temperature and humidity, a delayed harvest, combine losses and drought are all contributory factors, he added. He explained that seed losses from pod shatter are hard to quantify in most commercial situations but they proved particularly noticeable for UK growers in 2013 when poor establishment, intense pigeon pressure and a cold March contributed to a range of pod maturity within individual plants and across fields. Losses were exacerbated by clashes with cereals harvesting which resulted, in many cases, in OSR combining delays. And pod shatter is not just about yield loss, stressed Andrew, who pointed out that field-scale variety strip trials work by Openfield in the UK have left volunteer populations of up to 700/m2 three weeks after harvest. As well as putting extra pressure on weed control in the following wheat crop, this provides a substantial green bridge for early slug activity. So if we are looking more seriously at cultural control methods of slugs, ie doing everything we can to minimise populations, then growing crops with pod shatter resistance is one of the options, he added. Were not saying dont use podstick on crops, but it is difficult to know when to apply it and, as a result, its a timing headache. However, genetic resistance to pod shatter is a yield-protecting trait and an extra insurance. By all means growers can use podstick as a belt and braces approach, but resistance provides increased flexibility, concluded Andrew. For the 20132014 season, Dekalb has contracted a network of seven delayed harvest trials, three of which are run by NIAB TAG, to produce more evidence of the effects of pod shatter resistance for evaluation. The company is also in open discussion with HGCA regarding the pod shatter resistance trait.