A STUDY OF SOME UNPRODUCTIVE CHERRY TREES IN CALIFORNIA > By C. F. KiNMAN Pomologist, Office of Horticultural Crops and Diseases, Bureau of Plant Industry, United States Department of Agriculture INTRODUCTION

Observations made in California over a period of years have disclosed an interesting problenn regarding unproductive cherry trees. An occasional tree, or portion of a tree, has been found that produces practically no fruit, yet branches of the same tree, or other trees of the same variety standing beside it, have been consistently prolific. The behavior of these unproductive trees suggests the presence of a virus disease such as mosaic, but the results of the studies thus far conducted indicate that from a commercial standpoint they may be treated as a result of bud variation. The Black Tartarian is the only variety of cherry widely grown in California in which the occurrence of this unproductive strain is frequent. In orchards of this variety it is common to find 1 tree in 10 made up entirely or largely of the unfruitful type of wood, and much higher percentages have been noted. Occasional trees of the Bing, Lambert, Black Eagle, and other varieties have been found with leaves much hke those of the unproductive Black Tartarian. Affected trees of these varieties have been found bearing considerable fruit, but it is misshapen and not marketable. The conditions under which the productive and unfruitful Black Tartarian trees are growing appear to be identical, and in some instances the two types of trees are so close together that their branches overlap. (Fig. 1.) Trees of the unproductive strain have been found in all the orchards in central California where a search for them has been made, and they have also been found in southern California and northern Oregon. Not all cherry-growing localities in these latter districts have been searched carefully for affected trees. The presence of 7 trees that were made up entirely or almost entirely of unproductive branches was recorded in one orchard in 1924, 17 in another orchard in 1925, and an additional 94 in a third orchard in 1926. In these orchards there are, respectively, 200, 190, and 980 trees of the Black Tartarian variety. A number of the trees that failed to fruit had been top grafted or removed from the first-mentioned orchard before these records were made. Many trees of the same type have been observed in other orchards. None of the affected trees or branches examined have improved and become productive, although the condition has become more noticeable on some trees with the growth of the affected branches.