Talking Agronomy with Luke Wheeler: Flea beetle and slugs are on the radar

AgronomyCrop protection


With the past weeks’ weather mainly dry and rather hot, harvest is almost complete with only winter and spring beans to cut. Crop yields have been somewhat average this year, with late frosts and little sunlight in May and June effecting oilseed rape yields and causing very low winter barley bushel weights.


Winter wheat didn’t fare too badly, but following the previous two years’ bumper yields, things were always going to seem slightly average. Spring barleys yielded well and due to its potent black-grass suppression and healthy gross margins more will be planted this coming year. Spring wheats look to be slightly down on last year – a difficult, wet spring is more than likely to blame, with root systems failing to fully really establish.


With August being unusually dry, the challenge of establishing OSR came from a slightly different angle this year. Early drillers, with sub-soiler drills, found ground was heaving up and seedbeds were left cloddy, making moisture retention difficult. Minimal soil disturbance in black-grass-prone areas is key when drilling OSR and therefore this unwanted soil disturbance, has not only caused problems for crop establishment but may also have adverse effects on later black-grass control.


Delaying drilling until later in August seemed to pay dividends, as light rain showers softened the ground, resulting in better seedbeds and crops racing out of the ground. Earlier drilled crops remain small and now face the battle against slugs and flea beetle.


Slugs and flea beetle are the next potential problems on the radar. Slug populations in some fields are very high, and in some cases have caused crop failure requiring re-drilling. The cause of these damaging populations is the mild winter and wet spring/early summer with no prolonged cold spell to bring populations under control and ideal conditions later on for reproduction.


From mid-August to the first week of September, flea beetle levels were generally low and showed no signs of causing a problem. However, the hot spell in the middle of the month caused flea beetle populations to explode leading to widespread damage. Smaller crops, drilled at higher seed rates, are most at risk and flea beetle sprays are now being applied with the hope resistance is not going to be too much of a problem. Staying vigilant and proactive is essential to protect the crop until it is robust enough to cope on its own as pest populations decline into winter.


Propaquizafop plans for volunteer cereal control and clethodim objectives where black-grass populations are of any significance are now being drafted. Clethodim must be applied after a crop has reached the two true leaf stage and a two-week, no-spray window both before and after the application can make flea beetle and fungicide application timing tricky. Smaller crops will offer the most difficulty, as clethodim timing may clash with the beginning of the phoma control season.


Stale seedbeds have started to green-up nicely, with the last couple of weeks’ of rain really getting black-grass going. Black-grass dormancy might be high this year, so delayed drilling and the creation of fine, consolidated seedbeds to allow pre-emergence sprays to work most efficaciously will be key.


Winter wheat crops will begin to be drilled in the next couple of weeks in areas where black-grass levels are low, and more spring cropping will be taking the place of some winter crops in areas of high black-grass infestation. Where winter crops are being grown and black-grass is a problem, I will be advising growers to delay drilling for as long as possible, but ensuring conditions allow seedbeds, establishment and pre-em herbicide applications all to be conducted in as close to perfect, uncompromised conditions as possible.


Arable Farming
Posted by Arable Farming
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