PRUNING TEST COMPARISON OF TOMATO VARIETIES FLORIDA MH-1 AND WALTER

Pruning, restricted to the removal of 4-7 lateral branches up to, but not including the lateral shoot in the leaf axil below the first flower cluster resulted in earlier yield as well as an increased fruit size over a 5-week harvest period for both Tlorida MH-1' and 'Walter' to mato varieties. Pruning of both 'Florida MH-1' and 'Walter' resulted in the production of larger size grade which increased the value of the crop. The variety 'Walter' produced more marketable fruit as a result of pruning but no more than either pruned or unpruned 'Florida MH-1. ' Historically the tomato is thought to have orig inated in Peru although it was also cultivated by the Aztecs in Mexico. Evidence is that it had been Florida Agricultural Experiment Station Journal Series No. 4676. cultivated in South and Central America since around 400 B.C. It was introduced into Europe in the 16th century. The size and color of fruit appears to have been well established at the time of its introduction into Europe where it was cul tivated in Spain and Italy during the 17th cen tury. Strangely enough it was considered poisonous in England, Northern Europe and America until about 1800. The tomato was first quoted on the New Orleans market in 1812 followed by the Boston Market in 1835 (11). The Incas and Aztecs probably practiced prun ing plants since they had been growing tomatoes for some 900 years before the arrival of Pizarro and Cortez. One of the oldest illustrations of tomato, drawn in 1581 (11), shows plants with lateral branches removed. In Buist's garden guide for 1885 (2) the statement is made that "most cultivators allow their tomato vines to grow wild and support themselves; they perhaps have never given it a thought that by training and properly pruning them they will not only increase their productiveness, but the fruit will ripen better and be of much finer quality. " In 1918 Sherbakoff (10) 172 FLORIDA STATE HORTICULTURAL SOCIETY, 1972 reported that tomatoes in Florida were staked and pruned as a defense against ground rots and be cause pesticides were generally more effective with this type of culture. Experimental data comparisons of yield, qual ity, earliness and size between staked and unstaked tomatoes have been obtained by a number of in vestigators since the 1900's (4, 5, 6, 8, 9). Their data were based on indeterminate type plants and comparisons were made between staked plants pruned to 1, 2 and 3 stems and unstaked, unpruned plants, growing on the ground. Magruder (8) in 1924 reported that total yield was reduced in proportion to severity of pruning but that prun ing increased yield of early fruit, yield for the first 4 weeks of a 10 week season and also in creased the size of individual fruit. In 1923 the pink fruited determinate cultivar 'Cooper Special' was selected from a planting of indeterminate tomatoes growing in the Fort Lauderdale area. It was introduced as a variety in 1925 by C. D. Cooper. Although 'Cooper Special' (1) did not persist as a variety it became an important source of the gene which controls determinate vine growth and was used as a parent in the development of such varieties as 'Pritchard,' 'Victor' and 'Penred. ' Present day Florida mature-green tomato pro duction is wholly based on the recently released, highly disease resistant, determinate type tomato varieties 'Florida MH-1,' <Tropi-Red' and 'Walter. ' Plants of this type produce a flower cluster (often 2) on alternate internodes of the stem and at a given height apical growth stops, whereas the in determinate plant produces flower clusters (seldom 2) 3 and 4 internodes separated from each other and apical growth continues until the plant dies as a result of disease, insect attack, senescence or some other problem. Present day stake tomato culture in Florida is characterized by driving 48-inch wooden stakes between tomato plants when they are about 6-12 inches tall and then supporting them by the "string trellis" method first advocated by Kelbert (3). Usually growers do not prune determinate type plants and those who do, with the thought of achieving earlier maturity and an overall size increase, limit the removal of branches. Only 4-7 of the lowest lateral shoots are pruned because they realize that they are dealing with a plant of limited growth and fruit production potential. No guidelines have been established to indicate the best time and method of pruning. The nature of the tomato breeding program at AREC-Bradenton necessitates the growing of over 2500 tomato breeding lines annually, each different from the others. This mass of material is predominantly composed of determinate type plants. The evaluation of lines in replicated plots means that both determinate and indeterminate types are mixed in randomized design blocks. In such plantings errors in pruning are made from time to time and determinate types may be pruned to 2 and 3 stems. When this happens the results have always been a spectacular fruit size increase and a drastic reduction in number of fruit. How ever, where the error resulted in only the removal of the lower 5 or 6 laterals the result has been increased fruit size with only a small reduction in total number harvested. A pruning test was initiated in Bradenton in the 1972 Spring season to determine the effects of pruning on determinate type tomatoes. The re sults of this test are summarized herein. Materials and Methods The study was conducted in the field using a full bed mulch system with a flat topped bed 10 inches high and 28 inches wide. The field was prepared by applying an initial broadcast appli cation of 600 lb. /A. of superphosphate containing 5 lbs. of fritted trace elements. After bedding 1500 lbs. /A. of an 18-0-25-2 fertilizer was placed in narrow bands near each bed shoulder immediately prior to installing mulch, a 55 lb. craft paper covered with a 0.25 mil layer of polyethylene on both surfaces. Irrigation was supplied by a seep ditch system in which seven 54 inch beds were separated by a water ditch. The soil type was Leon fine sand with an approximate pH of 6.8. On March 1, 1972, 6 week old greenhouse grown plants of 'Florida MH-1' and 'Walter' va riety tomato were transplanted on 18 inch centers through 3-inch diameter holes cut in the mulch. Individual plots were 54 feet long and contained 36 plants. There were 2 varieties with 4 repli cations of two growing methods for the estab lishment of sixteen 36 plant plots. On March 20 prunes (4 to 6-inch lateral spi'outs) were removed from % of the plots by removing those shoots up to, but not including the one in the leaf axil immediately below the first flower cluster. Generally, this required removal of 4-7 prunes. On March 24 the pruned plots were chrecked to confirm that no prunes had been missed or had developed in the ensuing 3 day per iod. From pruning until time of harvest, plants were sprayed at regular intervals with approved BURGIS, CRILL: PRUNING TOMATOES 173 Table 1. Total marketable yield from pruned and unpruned 'Florida MH-1' and 'Walter' tomato plants expressed as number of SO lb packed boxes per acre at each harvest2. Table 2. Average size (lbs) of total market able fruit from pruned and unpruned plants of 'Florida MH-11 and 'Walter' tomatoes2. Harvest number Florida MH-1 Walter Pruned Unpruned Sum Pruned Unpruned Picking dates