1/22/2024 0 Comments Spraying potatoes for blightOverall the adjuvant Bond performed better than Indostick in terms of mancozeb retention on both potato and onion leaves. Mancozeb with Bond in potato resulted in less late blight incidence than with spraying mancozeb without adjuvants. However, also with Bond after rain simulation high amounts of mancozeb were washed off. With rain simulation in both onion and potato more mancozeb residue was present when using the adjuvant Bond than when spraying mancozeb without an adjuvant. Therefore, it is not recommended to spray when rain is expected within the same day as spraying. The impact of rain simulation was much bigger than the impact of adjuvant on mancozeb residue and late blight incidence. In onion the spreader characteristics of the adjuvants resulted in higher mancozeb residue concentrations than without adjuvant. Under dry conditions the effect of adjuvant on mancozeb residue in potato was limited. In potato lower mancozeb residue levels were measured at high spray volumes. Subsequently, disease symptoms were observed and visually rated as percentage of infected leaves. Five days after spraying the potato plants were inoculated with Phytophthora infestans and onions with Peronospora destructor. After five days, plant leaves were analysed on mancozeb residue. After spraying, rain was simulated (0.5, 3 or 6 hours after spraying and a control without rain) to test the sticker properties. In both crops these three treatments were applied with high and low spray volumes. ![]() In both crops mancozeb was sprayed with and without the adjuvants Bond and Indostick. Blight is often recognised by a white furry ring on the underside of leaves that outlines the brown splodge (see top picture).As part of the vegIMPACT project a laboratory test in the Netherlands was done with potato (Solanum tuberosum) var. Unless you have a really hot compost system, you will need to move the foliage away from your site, disposing of it safely. If you notice blight on the leaves, cut the stems at ground level leaving the tubers in the ground for at least ten days before moving them. Ensure beds are as weed free as possible. This will ensure there’s an airflow between growing plants. When placing the seed potatoes into the soil, use the maximum spacing suggested.This will help to protect the potato tubers in the ground should blight attack. Keep earthing up potatoes as they grow (bringing the soil up around the stems).However, in 2011 warnings were issued mid-May so that can’t always be guaranteed. Planting early crops of potatoes (new potatoes) will help as the idea is that they will have matured before blight warnings are issued.Setanta (maincrop) and Orla (early) are Irish varieties that have shown good resistance too. Sarpo Miras (an early maincrop), Sarpa Axona (maincrop) and Blue Danube (early maincrop) all show excellent blight resistance. The method that has been the most effective in my experience is to plant resistant varieties.It can attack leaves, stems and tubers and can also cause Tomato Blight as tomatoes and potatoes are in the same (Solanacea) family. What can organic growers do to prevent blight affecting crops?īlight is a parasitic fungus (Phytophthora infestans) that usually attacks in the summer months in humid conditions and is carried on the wind. However, on enquiry at the local pharmacy I was told that they were no longer allowed to sell Bluestone and that it was illegal to make up my own solution, so that scuppered that idea. ![]() ![]() Here we are, almost at the end of August and three months after first being alerted, still hearing potato blight warnings in Ireland. Not surprising really given the damp warm conditions Ireland has been under for many weeks, but if you’re growing potatoes or tomatoes it’s imperative you keep vigilant.īlight is tricky to control organically and there’s a lot of confusion about what home growers are ‘allowed’ to use or not.Ī couple of years ago I was informed that I could use copper sulphate, which was available as Bluestone in most chemists and that I could make up my own Burgundy mixture (a mix of copper sulphate, washing soda & water).
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