Sucrose as a Feeding Deterrent for Fruit-Eating Birds

Economic losses due to bird damage to small fruits such as blueberries, grapes, and cherries can be very high and are expected to increase in the future. The primary sugars in these fruits are glucose and fructose. Sucrose is present in very low concentrations only. Our research has unveiled a physiological trait common to many fruit-eating species in the phylogenetically related families Muscicapidae, Mirnidae, and Sturnidae. These birds are unable to digest sucrose because they lack the intestinal enzyme sucrase which hydrolyzes sucrose into glucose and fructose prior to absorption. In cage tests these birds prefer glucose and fructose to sucrose solutions and reject concentrated sucrose solutions and artificial gel fruits made with sucrose. Is it reasonable and feasible to attempt development of highsucrose cultivars with the goal of deterring birds in fruit crops? Variation in the proportion of sucrose in mature fruits is present among strawberry, cherry, and blueberry cultivars. Consequently, genetic resources are available to develop high-sucrose cultivars through traditional breeding practices or bioengineering. We suggest that major fm i t-depredating species, such as American robins and European starlings, will avoid eating high-sucrose fruits in an agricultural setting provided that (1) sucrose concentration in these fruits is sufficiently high, (2) there is alternate food available, and (3) high-sucrose fruits are planted in relatively large stands. Despite the obvious need for more data, we believe that increasing the sucrose content of small-berried fruits is a promising direction in integrated pest management research that can result in substantial reductions in bird damage.