The use of plant growth regulators to manipulate European pear crop load
Commercial pear production requires a large, regular crop load of fruit of the right size to be economical. In commercial production, it is often found that European pear cultivars (Pyrus communis L.) differ in their ability to set fruit. Some cultivars naturally set too few fruit while others set too many fruit. This results in situations that either need input to increase set, while in others set needs to be reduced. In order to improve set one needs to know the reason(s) for flower or fruit drop, i.e., inadequate pollination and fertilisation, shoot growth competition or weak set potential of flowers. Various management practices can be used to improve fruit set, e.g., pruning and the use of plant growth regulators (PGRs). PGRs can be used to reduce shoot growth competition, improve flower bud quality or directly enhance fruit set. The PGRs used include those that inhibit gibberellin biosynthesis e.g., prohexadione-calcium or gibberellins that can be used to directly stimulate fruit set. Quite often fruit set is enhanced to such an extent that thinning is needed to reduce excess fruit load. Reducing the crop load by using PGRs as chemical thinning agents is widely applied in commercial pear production. The chemicals used include the following: 6-benzyladenine (6-BA), naphtylacetamide (NAD), naphthalene acetic acid (NAA), S-abscisic acid (S-ABA), metamitron, Ethephon and abscisic acid (ABA). The concentration and timing of applications vary with the chemical used and the pear cultivar it is applied to. The chemicals can also be combined in a programme to increase efficacy. In this paper the most recent research on the use of PGRs in fruit set enhancement and fruit thinning will be discussed.
Theron, K.I. (2021). The use of plant growth regulators to manipulate European pear crop load. Acta Hortic. 1303, 259-270
Pyrus communis L., fruit set, chemical thinning, plant growth regulators, fruit quality, fruit size