Zinc and boron are the most frequently lacking elements in the trees of Greece. I’ll stick to them. The foliar diagnostic shows with relative certainty if we have a zinc deficiency. If you see symptoms, we are burned out, you have done a very poor job in recent years. Many already know that zinc deficiency is treated by spraying the wood in mid-winter with zinc sulfate. Most trees can handle up to 25 pounds of zinc sulfate per ton of spray. This application does not need to be done every year. It can be done every three years if we don’t have a serious shortage. Be careful with zinc sulfate application. It must be sprayed at least 2 weeks away from other sprays (copper and oil) and from pruning. So sometime in the middle of winter, when you won’t be doing any other tree work, apply it, if the foliar analysis has shown a lack or a relatively low content. The good producers in Macedonia add about 10 kg of zinc sulfate to the sprayer ton every year for maintenance.
Boron is one of the main trace elements and is missing from almost all tree crops in Greece. It is very essential for proper flowering and fruit set and ‘hidden starvation’ (lack of symptoms) is associated with many problems in horticultural crops. Our leaf diagnosis shows any deficiency. This is treated with borax in the soil in winter, which is not easily washed off and its boron is not easily available to the plant. Here the borax should be applied sparingly in the irrigation area of each tree because it easily becomes toxic if concentrated. The borax that will be applied in one winter should not exceed 20 kg per acre, more than that may become toxic to the roots. Also usually one application is enough for 3 years. In many horticultural crops, it has often been found that early autumn foliar applied boron (along with nitrogen, which we mentioned earlier) helps significantly with good boron nutrition and successful flowering and fruiting the following spring. 200-300g of boron (not borax, but water-soluble forms of boron) to the spray ton along with 2% urea in September is suggested here.