Crop Health Updates - September 2019
The weather continues to hamper cereal harvests, with a great deal done over the previous weekend before the rains came again mid-week. Cereal yields are reported from below average to very good, although grain is needing to be dried to try and get moisture contents down. Some wheat crops are causing concern as they have gone down and slugs are feeding on the grain. The slow harvest is delaying sowing of winter cereals and some oilseed rape is still in the bag.
Potato blight outbreaks are occurring almost on a daily basis, with 80 in Scottish crops at the time of writing. The appearance of aggressive and fluazinam insensitive strains in Scotland does not bode well for blight management for future potato cropping.
The warm wet end to the summer has further fuelled the risk of tuber blight and it is more important than ever to maintain effective fungicide protection until the haulm is completely dead. SRUC trials over many years, together with practical experience, have repeatedly shown that tuber infection can occur even when foliar blight severity is low. The risk of tuber infection is enhanced in wet soils.
Additionally, there is an increasing concern within the potato industry about how much land in Scotland is now infested with potato cysts nematodes. Read more here.
Oilseed rape crops have generally emerged well in moist warm soils, despite some being slightly later drilled than is the norm, and the acreage seems broadly similar to previous years. In recent years the number of pest challenges to the crop has increased and the key pests to consider in winter oilseed rape this autumn are flea beetle, cabbage stem flea beetle, peach-potato aphid (and turnip yellows virus – TuYV). Later in the autumn rape winter stem weevil is an additional pest to check for. Slugs are a perennial problem. Read more here.
With a wetter than usual harvest this season, the risk of pests problems flaring up in stored grain in higher than usual, particularly if stores and associated machinery have not a good clean beforehand. With many cereals being harvested at higher moisture contents than preferred, driers will be active this season, and grain needs to be 14% moisture content or less to prevent pests from breeding. Read more here.
Wheat bulb flies will be laying eggs through to late September. Growers are strongly advised to consider an assessment of egg numbers from early-September in fields planned for wheat, particularly in light of the unavailability of chlorpyrifos as an egg hatch treatment which only leaves a seed treatment as a control option. Note that this season is the last chance to use fludioxonil + tefluthrin seed treatment, which can no longer be used after 31st August 2020. Read more here.
For crops not treated pre-emergence, there are a number of metazachlor-based herbicides that can be applied once the crop has two expanded cotyledons. Generally speaking, formulated mixes are a better option post-emergence than straight metazachlor as they give root or shoot uptake rather than only the root uptake with straight metazachlor. Read more here.
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