chlorotic peartrees could be given a third treatment after a 2- or 3-week 
interval. 
Peaches and Sweet Cherries. Encouraging results are being obtained 
in Washington State with soil-applied chelated zinc as possible replace- 
ment for zinc sulfate sprays for zinc-deficient peach and sweet cherry 
trees. In this cooperative research of the Washington Agricultural Experi- 
ment Station and the ARS, peach and sweet cherry trees have taken up 
through their roots worth-while amounts of either zinc-EDTA or zinc- 
HEEDTA. The best time for these soil treatments has proved to be in 
spring. Zinc chelates applied in sprays have been less successful--in 
fact, not so beneficial as zinc sulfate sprays. 
In further cooperative experiments with Washington State at the Tree 
Fruit Experiment Station at Wenatchee, a chelated zinc treatment has 
been developed which overcomes arsenic toxicity of peach trees in soils 
where apples or pears have previously grown. Until recent years, arseni- 
cal insecticides sprayed on apple and pear trees caused so much arsenic 
to be deposited in the soil that young peach or other stone fruit trees 
planted later in these soils developed serious leaf damage and in some 
instances lost all of their leaves. Zinc sulfate has heretofore been the 
best treatment known, although its protective value is low in calcareous 
soils. Some growers have resorted to bringing virgin soil to old apple 
and pear lands to assure a favorable start for stone fruits. 
A spray containing 2 pounds of zinc-EDTA in 100 gallons of water is 
the most effective and economical treatment yet found for overcoming this 
arsenic toxicity in peach trees. The spray has been most effective when 
applied in 3 treatments at 3-week intervals, starting in mid-June. 
Apples. Adding a zinc chelate spray to other treatments for zinc- 
deficient apple trees may enable Pacific Northwest growers to correct 
stubborn conditions of zinc deficiency. In this area, where zinc deficiency 
of apple trees is common, many growers can correct it by spraying trees 
with a zinc sulfate solution in the autumn after harvest, or a Similar spray 
in the spring just before trees start growth. When a Single spray is in- 
effective, spraying at both seasons corrects the condition in most cases, 
but not in all. 
In limited trials, considered only preliminary, ARS scientists at 
Wenatchee, Wash., have obtained complete correction of serious zinc de- 
ficiency in apple trees byfirst sprayingtrees with zinc-EDTA in the grow- 
ing season and following with zinc sulfate spray at the customary times, 
in autumn and the succeeding spring. 
In other experiments at Wenatchee, soil applications of chelated zinc 
have been tried as possible replacements for zinc sulfate sprays in treat- 
ing zinc-deficient apple trees, but without success. The soil-applied che- 
lating treatments that failed to improve the apple trees were the same 
treatments that did benefit peach and sweet cherry. 
ZO 
