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Crop Crack26.06.10
By Wendy Fearon
The warm settled weather experienced over recent weeks has allowed the best hay made for a long time. It is unusual for Northern Ireland to have very little spray opportunity because of hot dry conditions. Some crops are really under drought stress and it is important not to apply pesticides in high temperatures. Weed control in spring cereals has been difficult as there were very little weeds emerged at the time when the herbicide was applied and chickweed is now appearing as the head is emerging. Where this is the case the only product choice to control these weeds will be a pre harvest treatment of glyphosate.
Spring Barley
All weed control is now complete on spring cereal crops. Disease levels are the lowest seen for some time.
Ramularia (also known as leaf spot) is widespread 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 appearing as brown necrotic speckling on the upper leaves. Symptoms appear where crops are subjected to stress from alternating periods of wet weather & sunshine, or man-made as a result of scorching. Chlorothalonil (BRAVO or JULIET) is very effective when used preventatively, helping to maintain green leaf area when used along with a triazole/strob mixture.
T3 Wheat
With ripening still approx 6 weeks away, the T3 treatment has to persist for all of this duration to prevent infection from a range of diseases such as SeptoriaNodorum (glume blotch), as well as Tritici, late season ear moulds and Fusarium. The cornerstone for the head spray fungicide is a strong triazole, giving strong curative activity to control any disease already on the plant as well as good persistence to prevent re-infection right up to ripening. Prothioconazole & epoxiconazole remain the most effective products to give ongoing Septoria protection as well as controlling fusariums and microdochiums on the ear. Prothioconazole (PROSARO) is the highest rated triazole for this range of diseases. The addition of a strobilurin is also essential to extend the persistence of the triazole and improve activity on Yellow Rust. 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. Talius should also be applied where there is the risk of mildew.
Aphids in cereals
The continued warm weather has encouraged high populations in all crops. As the grains begin to fill they feed at its base, drawing off the sugars that should be filling the grain if left unchecked.
Growers need to continue checking crops for aphid’s right up to milky ripe stage (GS73), and spray if present in numbers. A new pest becoming more prevalent in all cereals crops over the last couple of years and re-appearing in the last few weeks is the cereal leaf beetle grub. This small grub (10mm) looks the most like a small slug and leaves a slime trail after it on the leaf. The grubs eat out one side of the leaf, leaving the outer layer of cells from the other side of the leaf intact. Whilst they can cause a fair bit of damage to the upper leaves, there is no effective control, and they only graze for 2-3 weeks before pupating into beetles.
Grassland
Grassland herbicides use growth function to kill weeds, therefore peak growth periods 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.
Grain Store Hygiene
Ensuring stores are clean and pest free is essential to prevent any problems after all the hard work of growing and harvesting the crop. Now is the time to make grain stores ready for the coming harvest. Pest problems in stored grain arise from within the store itself, so a good clean-out is essential to minimise the carry-over of grain beetles, weevils and mites. The store should be empty and thoroughly cleaned before any treatment is carried out, removing all traces of grain and dust that might harbor insects or mites. Apply using an applicator to spray all surfaces including underside of roof and floor, concentrating especially on areas where dust can collect – cracks, light fittings, around equipment etc. RELDAN can be applied up to one month before filling the store and has no with holding period when applied to the fabric of the store.
Horticulture
Carrot willow aphid is now flying into crops and they carry several virus diseases that affect both carrots and parsnips. They may cause leaf distortion and stunting if they infest plants at the seedling stage. Crops should be checked for aphids and an aphicide used if present. DOVETAIL or APHOX are extremely effective. The dry conditions will certainly have an impact on the efficacy of Garlic sprayed for cabbage root fly in turnips, therefore treatment is best applied early in the morning with the dew or after rainfall. It is critical to inspect orchards at this time for red spider mite as conditions are highly favourable.Where 5 or more per leaf are found MASAI may be applied.
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