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Magnesium deficiency is rare in California stone fruit orchards. Symptoms include a "V" shaped chlorotic area at the apical end of leaves. Irregular necrotic areas along the margin of leaves can also develop.
Boron deficiency of stone fruit is rare in the San Joaquin Valley (survey), even though B deficiency has been found in many vineyards in the area. Symptoms that have been observed include shoot dieback and the subsequent development of many side shoots.
We have tested dozens of chemicals that have potential for thinning peaches, plums and nectarines. Most are caustic materials that "burn" off flowers when applied at the time of bloom.
We have tried several approaches to mechanically thin peach, plum and nectarine flowers or fruit. These include trunk shakers to remove flowers or fruit and a drum shaker that has vibrating rods inserted into the canopy to remove developing fruit.
Generally, the earlier the thinning the better the improvement in fruit size and/or yield. Thus, we have demonstrated that blossom thinning can increase fruit value by as much as $2,000 per acre compared to fruitlet thinning (1997 KTFR Blossom Thinning Summary).
Peach trees are very sensitive to arsenic toxicity. The disorder has been found in several peach and nectarine orchards in the San Joaquin Valley. The toxicity is often caused by past use of arsenic based pesticides and herbicides, especially where grape vineyards were previously planted.
In 1999 we obtained 60 large (11' x 8' x 4' deep) plastic tanks and buried them in the ground at Kearney. We filled them with clean sand and planted a Zee Lady peach, Grand Pearl nectarine and Fortune plum in each.
Calcium deficiency has never been identified in California peach orchards. Most soils in the San Joaquin Valley are abundantly supplied with Ca and leaf samples generally show levels well above the deficiency threshold (1.0%).
