|
Crop Crack 18.06.11
By Wendy Fearon
The unsettled cooler weather over the last couple of weeks has offered very little spray opportunity. It has been a very trying spell for silage contractors and farmers as suitable silage days were few and far between. Those who did manage to get the grass in were then faced with the delay in putting out slurry with the heavy rain. Spring barley crops are almost all at awns visible or beyond and many have yet to receive a fungicide.
Rhnchosporium is present on all varieties especially the more lush crops and mildew is also present on Doyen. Crops are certainly much shorter this year as germination was triggered and then held back during the dry period. The main response timing for a fungicide onto spring barley is GS49 and this is when the T2 fungicide should be applied. Ramularia (also known as leaf spot) is now a common disease in spring barley with the newer barley varieties showing more sensitivity to this late developing disease. It shows itself late on in the season (usually after booting), symptoms are very similar to manganese deficiency showing as brown necrotic speckling on the upper leaves. Chlorothalonil (BRAVO) is very effective when used preventatively, helping to maintain green leaf area when used along with a triazole/strob mixture.
The new SDHI chemistry also gives excellent control of Ramularia and where these are used therefore, the chlorothalonil need not be added. SILTRA which contains prothiconazloe and Bixafen the new SDHI is an excellent product choice or alternatively MOBIUS with BRAVO, both will protect against most barley diseases including Ramularia.
After the prolonged period of wet windy weather, a common issue now is the late application of the T2 fungicide treatment onto winter wheat. In such cases there may be a temptation to let this T2 treatment take the crop right through to harvest. Yet maintaining a clean flag leaf and head accounts for almost 75% of the yield. If this T2 becomes the final spray, recent summers tell us this will run out of activity long before we get into our wet August weather. With ripening still about 8 weeks away and harvest some weeks beyond that, a robust and long-lasting T3 head spray is essential to keep the head clean, maximise grain-fill and so yield and quality.
Current grain prices suggest a very healthy return to this treatment. Wet weather promotes all late ear diseases. Late developing Septoria Nodorum (glume blotch), as well as Tritici, a range of late season ear moulds and Fusarium are all favoured by damp and humid weather, especially at the later grain filling stages when the glumes prevent the grain from drying out properly between periods of rain. Fusarium (pink mould on the ear) is a disease that produces mycotoxins that are very damaging to feed intake and rumen function. There are now maximum limits acceptable by the compounders and severe penalties or rejection if these are exceeded.
The cornerstone for the T3 head spray fungicide is a strong triazole that as well as being effective on Septoria is also effective on Fusarium. Prothioconazole & epoxiconazole remain the most effective products to give ongoing Septoria protection. Tebuconazole particularly, and metconazole are a very strong triazoles for Fusarium in particular and an important contributor at this time. PROSARO and BRUTUS are the two highest rated triazole products at this timing in last years’ Teagasc trial results.
The addition of a strobilurin is also essential to maximise the persistence of the triazole and strengthen activity on Yellow Rust which is important this year as I have observed yellow rust in several varieties across the province. Good grain fill is totally dependent on retaining green leaf area for as long as possible, and the addition of the strobilurin extends the retention of green leaf tissue.
Yellow Rust
|
