Response of Five Woody Landscape Plants to Primo and Pruning

Abstract

The use of Primo (trinexapac-ethyl) was investigated as an alternative to pruning of container-grown woody ornamental species. A foliar spray of 469, 938, or 1407 ppm (0.5, 1.0 or 1.5 oz/gal) was applied to pruned plants. A nontreated control (water) and an industry control [Atrimmec (dikegulac-sodium)] were also included for comparison. Monthly mechanical pruning or no pruning treatments were imposed during the production period. Monthly pruning alone reduced the height of euonymus, forsythia, Chinese privet, waxleaf privet, and azalea. Efficacy of plant growth regulator treatments differed among the five species. Primo was not effective in suppressing the height or trimming dry weight of forsythia, Chinese privet, or waxleaf privet and provided only a transient suppression of euonymus and azalea.

The impact of foliar dikegulac and Asahi SL sprays on the shoot production of highbush blueberry nursery plants

“…According to Cline [1996Cline [ , 1997, dikegulac can act as an anti-auxin, like 2,3,5-triiodobenzoic acid (TIBA), which blocks auxin translocation and reduces the apical dominance. Dikegulac most probably inhibits gibberellin biosynthesis by inhibiting the oxidation of ent-kaurene to ent-kaurenic acid [Thetford and Berry 2000]. Such a hypothesis is supported by the fact that its action is counteracted by GA 3 [Bocion and de Silva 1977].…”

“…In 2007, any legal use of dikegulac ended in EU member countries [Rademacher 2015]. However, it has been tested especially in micropropagation of woody plants [Thetford and Berry 2000, Pozo et al 2004, Sansberro et al 2006, Mendoza-de Gyves et al 2008, Sarropoulou et al 2014, Sun et al 2015, Antonopoulou at al. 2018.…”

Does dikegulac affect in vitro shoot proliferation and hyperhydricity incidence in olive explants?

“…Also, early studies on peas (Pisum sativum L.) have shown that the action of dikegulac is counteracted by GA 3 (Bocion, de Sil- va 1977). Moreover, the decrement in some woody species of shoot length was ascribed to the inhibition of gibberellin biosynthesis due to dikegulac addition by inhibiting oxidation of ent-kaurene to entkaurenic acid, which is a prerequisite for gibberellic acid biosynthesis (Thetford, Berry 2000). Hence, since dikegulac inhibits gibberellin biosynthesis, its inclusion in the nutrient medium at low doses could have similar results to chemical pinching, while at higher concentrations it inhibits shoot growth.…”