Lime Sulphur Wash

[AndyJ]

Hi folks!

I’ve spent the morning removing all the leaves from two of my beech trees a good 2 1/2 hours of careful snipping! Both trees suffered quite badly last year from whitefly - so much so that it did affect the growth of the new shoots. I’ve noticed on both trees, what appears to be whitefly hibernating (not sure if that’s possible) - although I guess it could be the remnants from last years infestation. I really don’t want to have another year with these blighters!! Can I still spray with lime sulphur to try and kill any alive whitefly and / or their eggs? What is the best ratio for mixing lime sulphur to use as a wash?

Also, my red cowered hawthorn suffered from what looked like peach leaf curl last two years. Can I use lime sulphur to treat this too?

Many thanks,

Andy

 

[bwaynef]

It is my understanding dormant oil is used to treat overwintering insects and LS is primarily used to treat disease. The problem is that there needs to be 4-6 weeks between their application to prevent a phytotoxicity that develops between the two.

That said, I just looked up online the label for the LS brand I use:

FRUIT TREES, ROSES AND DECIDUOUS HEDGE PLANTS, SHADE TREES AND SHRUBS (DORMANT AND DECIDUOUS ONLY): San Jose Scale, Oyster Shell Scale, Brown Apricot Scale, Black Scale, Overwintering Insect Eggs, Many Overwintering Fungus Spores, Or Plant Disease. Apply 4 fl . oz. plus 1 1/4 fl . oz. dormant spray oil per gallon of water. Apply one dose as Winter buds swell before opening. Keep agitated during spraying.

But the dormant oil label says:

NOTE: DO NOT APPLY ALL SEASONS(R) HORTICULTURAL OIL AND DORMANT SPRAY OIL WITH SULFUR SPRAYS OR WHERE SULFUR IS ON THE FOLIAGE. TO DO SO MAY CAUSE FOLIAGE INJURY, LEAF DROP.

In digging for the two quotes above, I did come across some information leading me to believe that some folks do mix the two, but it comes at some risk. (In keeping with completeness, I came across a lot of information detailing LS as an insecticide as well, and specifically whitefly.)


Anyway, it looks like you're dealing with two separate issues on two separate trees, so that's an easy problem to solve if you're concerned about mixing the two.

 

[TomB]

Hi Andy,

You can spray Lime Sulphur now at a 20:1 dilution. It's fine as long as the leaves aren't open yet. Then treat with a systemic insecticide in a few weeks.

Your hawthorn leaf problem may well be gall mites. Removal of affected leaves, unless it's a very heavy infestation, is my usual approach. Using LS on the hawthorn as well is fine though.

 

[AndyJ]

Great stuff. Thanks Tom.

I might look into some oil if the LS doesn’t work Bwaynef