Tough spraying season leaves crops at greater risk
Published 24/05/2011 | 05:00
This is surely the most difficult spraying season in memory. Strong winds followed by brief spraying opportunities followed by heavy showers. It is doubtful that there was any chemical sprayed under ideal conditions over the past three weeks. Results will therefore be variable and it is critical that crops are inspected regularly to monitor efficacy.
These inspections are very important on winter wheat after T2s. It is not safe to assume that crops are relatively safe for three weeks after spraying in a normal year and certainly not this year.
Winter crops look good, but there are some very poor spring crops following late sowing in loose, cloddy seedbeds. Manganese and magnesium deficiency symptoms are to be found on many spring crops.
The flag leaf is fully emerged on all apart from some very late sown winter wheat crops. Most crops have four to five leaves without disease symptoms but there are some crops with septoria evident on the third leaf.
Rust has been reported in crops in Louth and Meath. All crops should have their T2 applied by now, and if not, then at the next spraying opportunity. Fungicides cannot be expected to give any more than three weeks effective cover. Keep notes of all spray applications and the weather conditions under which they are applied.
These notes will be invaluable when deciding on the T3 spray which should be applied three weeks later. The T2 should consist of Chlorothalonil and a fungicide containing prothioconazole. Products containing epoxiconazole will be used on some crops. So far I have not seen mildew on any wheat crop but, if present, a morpholine should be added.
Most winter barley crops are flowering. Crops are generally disease free and appear to have good potential. Some thin crops have a lot of late tillers developing which may present a risk of late mildew.
Chlorothalonil should be included with all products. Bontima, Siltra, Cauldron and Venture Extra are combinations of triazole and SDHI chemistry. Fandango/Coyote, the barley packs or mixes of triazoles and strobilutrons provide very good options. Products such as Allegro Plus provide cheaper but effective alternatives. Amistar Opti with a triazole can also be very effective.