Wet warm soils create conditions for midge
Warm soils and recent heavy rainfall across western and central England have already created the conditions for Wheat Orange Blossom Midge (OWBM) activity. The risk may be further exacerbated this year by drought stressed wheat plants coming into ear earlier than normal, with potential for an extended period at the susceptible growth stages.
ADAS has warned the greatest risk from OWBM occurs a week after heavy rainfall. Growers are advised to monitor for midge activity from GS 51-59, which could be protracted this season in some crops already triggered into early inflorescence.
Syngenta Area Manager, Jules Fairhead, reports soil temperatures have consistently exceeded the 13ºC required to initiate OWBM pupation. If the top 1cm of soil stays wet after recent rainfall, midge are likely emerge after each successive rain event. "Western counties are clearly more at risk after heavy rain, however the risk will be localised with the patchy nature of the showers," he warns. "Some eastern counties have still received little or no rain, with risk correspondingly lower."
Historical tracking of OWBM has seen pupation occurring from the second week of May, through to late June when conditions soil conditions and temperatures are right; that has resulted in midge emergence from the end of May. Whilst most crops are still at flagleaf emergence, Mr Fairhead highlights Syngenta has already had reports of ears emerging in some crops (5 May), especially on drought-stressed sandy soils.
"Growers should look to set pheromone traps early this year if conditions remain favourable for the midge activity," he advises. "With the current value of cereal crops any loss in yield and grain quality will prove costly. Hallmark Zeon provides a fast and cost effective control of adult midge and minimise the damage from subsequent larval feeding.
"The treatment window is incredibly short; egg laying by females peaks within three days of flight. You have to be ready for the first flight, and subsequent midge hatches during any crop’s susceptible growth stages, especially stages 53-57 as the ear emerges." Growers can make a total of up to four applications of Hallmark Zeon per crop, taking into account any previous treatments for aphids earlier in the season.
Samantha Brooke of Syngenta Seeds reports the majority of Group 1 and 2 wheat varieties have no resistance to Orange Wheat Blossom Midge, and that growers must prioritise their focus and attention on these premium crops to maintain quality and meet the milling specification. "However, there are a number of very good Group 3 and 4 wheat varieties, such as Denman and the new potential Group 3 SY Epson, that do have effective OWBM resistance.
"Using these varieties in the farm’s cropping mix is a practical Integrated Crop Solution, to help ease agronomy decisions during a busy part of the season," she added.
