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scottfsmith

Dormant spray timing

Scott F Smith
16 years ago

I am curious when people do dormant sprays. I used to do all my dormant sprays on some random day mid-winter which had good conditions, but clearly this is not optimal. The advantage of a dormant spray is there are no leaves and you can put down a huge amount of oil and copper or L/S which would not be tolerated by the leaves. But, putting it on in midwinter will not be as effective because the diseases and bugs are themselves dormant. So the best times to spray is as early as you can in the fall, plus as late as you can in the spring (i.e. as early and late that you can do a full strength spray: leaf fall and green tip or thereabouts). There is in fact a good reason for this pattern: when the bugs and diseases are either "waking up" or "going to sleep" they are much more susceptible to the chemicals. Waking/sleeping are complex biological processes which can be more easily disrupted. There is also concrete supporting evidence for this in the advertised control of shothole on peaches (spray full-strength copper at leaf fall), for fireblight on apples (spray full strength copper at green tip), and for control of aphids on apples (oil at silver tip).

Anyway, I have slowly been moving to "fall" and "spring" dormant sprays away from the "winter" model, and now I am thinking to get even more effective control I want to push this to the limit and spray as early as I can in the fall, and as very late as I can in the spring (leaving enough leeway so I don't miss the window and risk damaging the leaves). This year I waited longer than I ever have to do my spring dormant sprays, I just finished all except the still-sleeping grapes. Some apples were past green tip but most were at silver tip and I could have probably waited a touch longer on them. I am spraying Kocide 3000 plus dormant oil on everything - the oil helps the copper stick better so even on trees not getting aphids I like to add it. I used to also add a sticker (Nufilm 17) but stopped doing that.

Comments?

Scott

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