Flea beetle move
Cabbage Stem Flea Beetle are increasingly active into the west and north of the UK, so growers who may not have had an issue before should be vigilant, according to Syngenta insect pest specialist, Dr Max Newbert.
“With warmer autumns we could see adult damage into November, as the adults appear to remain mobile at around 3°C, with egg laying occurring even down to 3.2°C.
"However, it takes females around two weeks of feed to mature their eggs, allowing a window of control to reduce larvae burden in the crop,” advised Max (below).
Sowing OSR earlier aims to create bigger plants better able to cope with adult feeding damage, reported Max. But larger numbers of pests will build up over a longer autumn egg laying period.
“Drilling the last week of August seems to be the best balance between adult damage and larvae numbers,” he added.
Initial work by ADAS and AHDB suggests that leaving significant areas of volunteer OSR in the ground until September can attract CSFB away from freshly drilled OSR in nearby fields, resulting in lower damage in the crop. Subsequent control of the volunteers will stop the life cycle and limit further movement of the adult CSFB, to reduce pressure on farm.
This harvest Berkshire iOSR grower, Joe Dilibero, left his winter barley stubble longer than normal during combining, using a trick that other Syngenta iOSR group growers believe could help reduce Flea beetle movement and damage to emerging OSR seedlings. After the long and extremely hot period, Joe is hoping Flea beetle pressure may be reduced, especially with one 130 ha block going into an area with no recent OSR history.
Joe believes that, for both winter barley and oilseed rape, hybrid crop vigour gives plants greater capability and reliability to cope with increasingly difficult challenges from pests, diseases and weather extremes.
Damping off losses
Slugs and Flea beetle typically get the blame for OSR seedling losses at establishment. But sometimes seedlings fail to emerge or wither and die with no sign of pest activity. The culprit could in fact be the soil-borne pathogen Rhizoctonia, resulting in damping off and death of the seedlings.
The Nottingham University-based ICAROS project, supported by Syngenta, industry partners and government science funding, is seeking to identify and evaluate the issues, as well as provide potential solutions for growers.
Assessing losses in the field is difficult, reported lead researcher, Dr Rumiana Ray (above). “If infection is not too severe, they may see wire stem symptoms on the seedling stem or roots and brown lesions on the hypocotyl. But if the pathogen is there in numbers, the plant is just likely to be lost.
“High risk factors include frequency of OSR crop in the rotation, where shorter rotations with OSR select for AG2-1, which is the main Rhizoctonia solani pathogen causing damping off losses,” she advised.
“R. solani AG2-1 prefers lighter soils and dry to moderately moist soils.”
Trials have shown some differences in susceptibility between varieties, but only relatively small in current commercial genotypes. Growers could increase seed rates to compensate, but since the effects are so variable with environmental factors, it may result in crops that are too thick.
"Seed treatments currently under evaluation offer a more reliable solution," she suggested.