Effect of a Plant Growth Regulator Prohexadione-Calcium on Insect Pests of Apple and Pear

Abstract

The effect of prohexadione-calcium, a plant growth regulator that inhibits gibberellin metabolism, on Cacopsylla pyricoloa (Foerster) in pear trees, and Choristoneura rosaceana (Harris) and Aphis spireacola Patch, in apple trees was studied. C. pyricoloa and A. spireacola populations were significantly reduced in prohexadione-calcium-treated pear and apple, respectively. Insecticide control of both pests with imidacloprid was synergized in treatments with prohexadione-calcium. In apples treated with prohexadione-calcium, there was a significant reduction in the number of C. rosaceana shelters per tree and amount of fruit injury at harvest attributable to the C. rosaceana. There was an additive effect when tebufenozide was used to control C. rosaceana in trees treated with prohexadione-calcium. Prohexadione-calcium significantly reduced vegetative growth in both pears and apples. Synergistic and additive treatment effects of prohexadione-calcium and pesticides used in this study may be due to better penetration and coverage of pesticides due to reduced foliar growth or to changes in the nutritional quality of the host plants.

Effect of host plant makeup through nitrogen fertilization and growth regulators on the pear psylla population

“…Several studies have demonstrated that the use of growth regulators reduced pear psylla populations and their damage (Lombard et al, 1982;Paulson et al, 2005). We found that oviposition rate, nymph survival and development rates, were lower in trees that had been treated with growth regulators.…”

“…So far, it is not fully understood why these plant growth regulators inhibit psylla (Paulson et al, 2005). Our hypothesis was that growth regulators decrease the psylla population by reducing the nitrogen content of the growing shoots.…”

“…In contrast, application of plant growth regulators such as daminozide or prohexadione-calcium suppressed C. pyricola populations and decreased damage on 'Bartlett' pear (Westigard et al, 1980;Lombard et al, 1982;Paulson et al, 2005) In Israel the main commercial pear variety is 'Spadona', for which growers apply a wide range of nitrogen fertilization-from 50 to 200 kg/hectare.…”

Effect of the width of the herbicide strip on mite dynamics in apple orchards

“…Unfortunately, herbicide strips may also create problems, including soil erosion, reduced organic matter and leaching of nitrates into ground water (Sanchez et al 2003) plus increased incidence of plant diseases, insects and two-spotted spider mites, Tetranychus urticae Koch (Juvara-Bals et al 1990;Hardman et al 2005). Part of the reason for pest and disease problems is that the removal of competing ground cover vegetation promotes excessive growth of shoots which are prone to attack by pests and diseases (Brown and Glen 1999;Paulson et al 2005). Also leaf N is increased and levels of P and K are reduced (Johnson and Johnson 1980), changes which favour faster development and higher fecundity of T. urticae (Wermelinger et al 1991) and the European red mite Panonychus ulmi (Koch) ( Van de Vrie and Boersma 1970).…”

Influence of synthetic plant growth substances on the survivorship and developmental parameters of Spilarctia obliqua Walker (Lepidoptera: Arctiidae)

“…However, several studies have demonstrated nontarget eVects of diVerent plant growth substances on insects (Posnova 1974;Schutte 1978;Kristiansen et al 1992;CoVelt et al 1993;Nazir Ahmad et al 2003). When combined with insecticides, plant growth substances cause additive or synergistic eVects on insects (Pasqualini et al 1997;Iob 2000;Paulson et al 2005). In some cases, they increase the resistance of the plants to insects (Zummo et al 1984;Attah and Emden 1993;Ahmad et al 2003).…”