- 6 



A perfectly shaped strawberry fruit requires pollination, fer- 

 tilization and subsequent seed development of each pistil in the 

 blossom. When conditions are less than optimum for these processes, 

 deformed berries can occur, the degree of deformity being related 

 to the number of achenes that do not form. 



Present day strawberry varieties are self-fruitful and do not 

 require cross-pollination but there must be transfer of pollen from 

 the anthers to the stigmas of the pistils. Insects, primarily hon- 

 ey bees and solitary bees, are necessary for this transfer since 

 wind, rain, or gravity will not provide adequate pollination. 



In a pollination study in which we caged plots of 'Catskill' 

 strawberries to exclude bees, very few fruits developed and those 

 that did were severely deformed. Blossoms in the uncovered plots 

 pollinated by bees and those that were hand pollinated inside the 

 covers, developed into normal berries. Berries in screened plots 

 that allowed rain penetration and air movement were no better than 

 those in the plots covered with polyethylene cages. This study 

 showed that adequate bee activity is necessary in commercial plant- 

 ings for high yields of well-formed berries. Thus, improper tim- 

 ing of insecticides may result in catfaced berries due to the kill- 

 ing of pollinating insects. 



Frost injury may also deform fruit. The pistils are the most 

 frost susceptible part of the blossom. When all the pistils are 

 killed by frost, the fruit will not form. A light frost may kill 

 some of the pistils which results in a percentage of deformed ber- 

 ries. 



Insect damage, especiall)^ that of the tarnished plant bug, is 

 probably the most common cause of deformed berries. The tarnished 

 plant bug feeds on blossoms and developing berries causing the ber- 

 ries to be misshapen and if not controlled, heavy losses may occur. 

 In a field study of tarnished plant bug injury at the University 

 of Vermont in 1975, unsprayed plots produced 10 to 60% less fruit 

 than those sprayed with an insecticide just before bloom. The 

 yield reduction was due to less fruit because of blossom injury by 

 the tarnished plant bugs and the presence of small deformed ber- 

 ries. Differences among varieties occurred, with 'Midway' being 

 injured less severely than the other varieties in the trial (Table 1). 



Table 1. Average weight (gms) of strawberries harvested from sprayed 

 and unsprayed plots, University of Vermont, 1975. 



Variety 



Sprayed 



Size reduction 



28 

 30 

 3 

 27 

 32 



(gms) 



