A comparable amount placed in the calyx end of the receptable surface 

 resulted In "typey" fruit at harvest whereas treatments applied to 

 the pedicel (flower stem) we re intermediate. A 10-fold increase in 

 volume of Promalin applied to the spur leaves caused no fruit elon- 

 gation. Thus, 2 years of research indicates that it is essential for 

 the Promalin droplet to come in direct contact with the flower part 

 that eventually will become the fruit. Application to any other 

 part of the flower or spur has either no effect or a reduced effect. 

 Thorough uniform spray coverage is absolutely essential for a con- 

 sistent Promalin response. 



Field Observations Following Promal i n Application 



Within 2-3 days following a Promalin application calyx swell- 

 ing and closing is apparent, first on the king blossom and then on 

 lateral blossoms. Promalin merely accelerates that which normally 

 occurs on pollinated flowers. Ten to 12 days after application, 

 Promalin appears to increase fruit set. About 15 days after bloom, 

 yellowing of the pedicels occurs on many of the developing fruit in 

 the cluster. By 3 weeks after bloom most of the less vigorous fruit 

 have dropped and within 4 weeks fruit set has been determined and 

 subsequent drop is minimal. 



Thinning Due to Promalin Application 



It has been our impression, as a result of observations made 

 the past 2 years, that thinning due to Promalin may be more apparent 

 than real. We believe that Promalin causes earlier removal of many 

 fruit that would normally drop later. It would certainly appear 

 that Promalin was increasing thinning if you assessed fruit set 2-3 

 weeks after bloom. However in most situations it appears that Pro- 

 malin has advanced the 'June-drop' by about 2-3 weeks, thus giving 

 only the impression of thinning. While Promalin can indeed cause 

 thinning, caution should be exercised in concluding that this has 

 happened on your trees. 



Chemical Thinning Following Promalin Application 



Since Promalin applied by itself is capable of thinning, it is 

 important to know if excessive thinning is likely to occur if Pro- 

 malin treatment is followed by an application of Sevin* (Sevin is 

 the only chemical thinner recommended for use on Delicious in Massa- 

 chusetts). This is particularly important to know since it is well 

 established that the thinning responses may be increased when 2 dif- 

 ferent thinning agents are applied. We attempted to answer this 

 question in 1979. 



In 1 experiment, Promalin at 25 ppm-plus-Glyodin was applied 

 as a dilute spray at full bloom (Table 2). (This is about a 3-fold 

 over-application since the label recommendation is for 125-150 

 gal/acre). Half the trees sprayed with Promalin-plus-Glyodin also 

 received Sevin about 20 days after bloom. Other trees received Sevin 

 alone. The Promalin-plus-Glyodin spray increased the L/D ratios of 

 the fruit but also caused thinning (Table 2). 



*Trade Name 



