The Q&A Archives: Rotting Plums

Question: Some years (the preceding several) the fruit on my 'Shiro' plum and several other unknown varieties rots on the trees. Could this be 'brown rot'? I've heard of using a sulpher spray - is this the same as lime-sulpher? How and when do I use it, and how soon after an oil spray is it safe to use? I've even read it's o.k to combine the two!

Answer: It may be brown rot, which is a common problem with stone fruits. There are plum varieties resistant to brown rot ('Au Rosa' and 'Crimson'). The first sign of brown rot is brown speckling of the blossom and blossom stem, and may eventually turn the whole thing brown. Fruit also display brown specks that enlarge to ring-shaped spots, and then take over the fruit entirely. If this doesn's describe the problem with your plums, your extension agent (ph# 257-7967) can help you to identify the problem, and recommend a solution.<br><br>Either elemental sulfur or lime-sulfur (garden lime mixed with elemental sulfur) can be used to control the problem. Lime added to sulfur helps the sulfur penetrate deeper into the plant surface to nab those tiny, pesky fungal spores. Spray twice at bloom (when petals start to turn pink and when petals fall), and right before harvest. Oil and lime sulfur are safe for use as a dormant spray only - the combination of sulfur and oil is toxic to growing plant tissues. As always, follow label directions to a "T" for best effect and safety. Hope this does the trick!

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