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Crop Crack 13.06.09
By Wendy Fearon
It is hard to believe so much has changed since the last crop crack. Ground is now cracking with the very dry conditions experienced over the last week. A large percentage of grass is now harvested with excellent quality and bulk compensating for the later cutting date.There is still some cereal crops yet to be sown with grass seed. Where a dense cereal crop has already emerged the newly sown grass seed is going to struggle for light and nutrients. Aphids are now flying into crops and should be monitored closely. Winter barley crops should now all have received the T2 fungicide.
Spring Cereals
The timing for some herbicides have passed and hormones must not be applied beyond GS31.Most sulfonylurea’s (Ally Max) can be used up to flag leaf emergence and should be tank mixed with STARANE XL to achieve effective chickweed and cleaver control. HUSSAR may still be applied for grass weed control onto later drilled crops before GS29.There is still quite a bit of crop silage with cereal and grass to be sprayed. Where Alistell is intended for use, it is very important to ensure the grass has 2-3 leaves and the clover has 1 tri- foliate leaf.
It is now time to be considering the wild oat problem in your crops. The performance of wild oat herbicides is adversely affected by other herbicides used on the crop. To avoid these antagonisms and possible damage to the crop, a minimum time interval must elapse between application of the BLW herbicide application and the wild oat herbicide application. The best option is to get the BLW treatment on as soon as possible to allow the maximum interval elapse for the wild oat treatment. Where the oat gets beyond the 1st node stage, AXIAL can be used, controlling the oat up to full flag leaf GS39. Axial requires the addition of Adigor.GRASP or AXIAL can also be used in spring wheat, but CHEETAH SUPER has a similar crop spray window and a wider wild oat window and does not require a wetter.
Spring cereal crops should now be treated with a fungicide as some varieties are showing a lot of disease, the most obvious being Quench. Weather can have a major influence on disease development. There has been a lot of talk recently of ramularia .Ramularia requires periods of wet weather during June and July, or periods when leaves remain wet for several days. Sunshine following wet humid spells of weather will result in greater risk of abiotic leaf spots. Bravo improves green leaf area retention and can also control ramularia and abiotic leaf spots therefore consideration should be given to the inclusion of chlorothalonil in the mix.
Current weather conditions will certainly slow down the spread of rhyncho but all crops should be treated with a fungicide as early protection is essential to manage this disease.
Winter Wheat
Winter wheat crops are all now between flag leaf and ear emergence. Mildew and septoria tritici are present in some crops with more visible mildew than septoria.The biggest disease at present especially on Robigus is yellow rust. Where rust has taken hold, fire brigade action will be required to contain the rust and ensure long term protection. Curatively CORBEL is still the best product choice and should be mixed with prothioconazole.Any crops not yet at ear emergence and requires growth regulator this should be done immediately.
Potatoes
Crops are now growing rapidly and consideration has turned to blight control where product choice and timing are extremely important. There has already been blight reported in Northern Ireland so don’t be fooled by present weather conditions.
Even in a year like 2008 when we experienced exceptionally high disease pressure, most growers managed to protect their crops well, and produced crops with very low levels of tuber blight. Foliar blight was widespread, yet good product choice used at tight intervals ensured that tubers coming out of store have been free of any tuber blight
There are three ways by which the blight fungicide can move through the plant..
Contact fungicides e.g. DITHANE, ELECTIS, RANMAN, SHIRLAN. These products protect only the outer surface of the leaf onto which they are deposited. They do not move into the leaf and therefore do not normally protect any new growth that emerges after application.
Translaminar fungicides e.g. BESEIGE, CURZATE M WG, INVADER, OPTION. These products move into the leaf onto which they are sprayed and then redistribute throughout the leaf tissue as it increases in size. They become rain-fast once they are in the leaf.
Systemic fungicides e.g. CONSENTO, FUBOL GOLD, INFINITO, MERLIN, TATTOO. These products move in through the leaf surface and upwards into the new growth that emerges between applications, protecting that new growth from infection also.
Grassland
Grassland herbicides use growth function to kill weeds, therefore peak growth periods particularly at this time of year should be used for herbicide application. There must be sufficient growth to allow herbicides to be effective and vegetive growth is the key time to apply, as the chemical then gets drawn down into the roots.
Herbicides are less successful once plants have progressed to the reproductive stage and have thrown a stem or began to seed. Once weeds are beyond the ideal growth stage for spraying they should be mown or topped and allowed to regrow again, and a herbicide applied to the fresh young growth.
To optimise efficacy of any herbicide, recommended water volumes should be observed, even when it means more time spent spraying. It is important to note ragwort plants in their second year are now coming close to flower and should be sprayed immediately as flowering ragwort is poorly controlled. The routine herbicide treatments for this weed are full rate MCPA or 2, 4-D, and they are most active on growing rosettes with reduced activity as the stem starts to extend. They are not clover safe. You can use a mixture of both these products as Nufarm Lupo which allows an increased dose herbicide compared with either alone, with a consequent activity benefit. Stock must be kept of until the weeds have rotted away, which can take up to six weeks.
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