THE BEACH PLUM 9 



fruits to shrivel and drop so that no > icld records could be obtained. This drought 

 turned what looked like a good beach plum year into one of almost total failure 

 for the whole beach plum area. 



In 1943 these three plots were again treated in the same fashion. A fourth 

 plot was treated with cottonseed meal. Enough was applied to give 20 pounds 

 per acre of nitrogen, equivalent to that in the 400 pounds per acre of 6-5-4. A 

 second experiment was started in a beach plum planting near East W'areham, 

 consisting of 5 rows of 10 bushes each set about 10 x 10 feet. Half the area was 

 fertilized on May 17 with cottonseed meal to give 20 pounds of nitrogen per 

 acre and half was left unfertilized. Since this area was covered with sod which 

 seemed to be getting all the benefit from the fertilizer, a second and slightly 

 heavier application was made to the fertilized half on June 10. 



Again in 1943 the beach plum crop was nearly a total failure with a good crop 

 in a few small isolated areas. Again the plots at Sandwich lost almost all of their 

 fruit. There was a very light set on each of the fertilizer plots and the leaves of 

 the bushes were a darker, richer green than those on the unfertilized plot. No 

 fruit set on the unfertilized plot. 



A total crop of 105 pounds of plums was harvested from the plots near East 

 Wareham. Observations made during the summer indicated little, if any, 

 difference in yield between the plots. 



Since 400 pounds of 5-6-4 per acre, containing onl>- 20 pounds of nitrogen, is a 

 pretty light application, it is suggested that in the future enough fertilizer be 

 applied to give 35 pounds of nitrogen per acre; for example, 500 pounds of a 

 7-7-7. A single application broadcast as growth starts seems best. 



Pollination 



It is a commonly expressed opinion among beach plum growers that the failure 

 of crops is due to unfavorable weather at blooming time. It is true that weather 

 at blossoming time has a marked effect on the set of an>- fruit. The effect may 

 be direct by influencing the growth of the flowers or indirect by influencing the 

 activity of pollinating insects and disease. A frost may destroy the blossoms. 

 Cold, wet weather may prevent the shedding of pollen or, even though pollina- 

 tion has taken place, may so retard the growth of pollen tubes down the style 

 that the ovule degenerates before fertilization takes place. On the other hand, 

 pollination may be poor because pollinating insects either do not fly at all or 

 are much less active during cold, rainy or windy weather. Also, rainy weather 

 increases certain fungus diseases, particularly the blossom blight form of brown 

 rot, which interfere with set. Nevertheless, such an obvious factor as the weather 

 should not be blamed for every crop failure without just cause. In the same area, 

 cultivated blueberries which bloom only a week or ten days later set good crops 

 year after year. Because of the equalizing effect of the ocean on climate, it is unlike- 

 ly that, in such a short time, the weather would change enough to repeatedly cause 

 the failure of beach plums and have little or no effect on cultivated blueberries. 



To study the relation of insects to crop success or failure, observations of the 

 insects working beach plums and collections of these insects for identification 

 were made at several places on the Cape during the blooming seasons of 1942, 

 1943, and 1944. Wild bees were found to be the most common pollinators, fol- 

 lowed by bumblebees, syrphid flies, and some miscellaneous insects including a 

 few honeybees. It was also observed that in some places there were very few 

 insects, probably not enough to insure good pollination; while at other places 

 on the same day plenty of insects were present. At one place, bumblebees were 

 working apple blossoms in preference to beach plums although the beach plums 

 were all around the apple tree and were in almost full bloom. 



