The insecticides acephate, dichlorvos, and imidacloprid were assayed, using in vitro shoot cultures of apple (Malus×domestica Borkh.), to determine their phytotoxicity at several concentrations and their effectiveness for eradication of the Western Flower Thrip (Frankliniella occidentalis, Pergande) from infested apple shoot cultures. Commercial formulations of acephate (Orthene), dichlorvos (VaportapeII), and imidacloprid (Admire) and a technical grade of imidacloprid were used in the experiments. For acephate and imidacloprid, concentrations of 1 to 80 mg·L-1 a.i. in shoot culture medium were used, while for dichlorvos, a fumigant, particles of the formulated product containing concentrations of 0.7 to 6.4 mg a.i. were suspended in the head space of the 500-mL glass culture jar. Acephate, dichlorvos, and the technical grade of imidacloprid did not cause phytotoxicity and growth of shoot cultures was unaffected at all treatment concentrations tested after a 6-week treatment period. Imidacloprid (20 to 80 mg·L-1 of the commercial formulation) caused chlorosis at the end of the 6-week treatment period. None of the treatments tested resulted in the death of shoots. Thrips were eradicated by acephate or imidacloprid treatments of 5 mg·L-1 and by dichlorvos treatment of 0.7 mg per 500-mL culture jar. Shoot cultures grew normally after the treatment period. Chemical names used: O,S-dimethyl acetylphosphoramidothioate (acephate), 2,2- dichlorovinyl dimethyl phosphate(dichlorvos),1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine (imidacloprid).
Basdeo Bhagwat and W. David Lane
W. David Lane, M. Meheriuk, and R.A. MacDonald
Ian McIvor, Alexander Lang, W. David Lane, and Paula E. Jameson
The new apple (Malus ×domestica Borkh.) cultivar Sciros™, resulting from a cross of 'Gala' with 'Splendour', is marketed internationally from New Zealand. A characteristic of this cultivar is the presence of dense, dark green or black nodules in the fruit cortex, located in close proximity to the five sepal vascular bundles. Nodules are visible as green spots beginning about 40 days after bloom and they continue to develop, reaching a length of up to 8 mm at fruit maturity, although there is considerable variation in their size. Large vascular nodules often develop dark brown centers and reduce the visual quality of the fruit flesh. The frequencies of vascular nodules in 61 'Gala' × 'Splendour' hybrids from New Zealand and British Columbia, Canada, were examined. These ranged from a mean of 0 to 12.1, depending on the hybrid. Thirteen hybrids were in the high frequency class (2.76-12.1), 28 in the low frequency (0.04-1.86), and 20 were without nodules. The mean nodule frequency in Sciros™ was 12.1 nodules per fruit, the highest of all hybrids examined. Our survey of 44 other cultivars confirmed the occurrence of vascular nodules in 'Gala' and 'Splendour', with mean vascular nodule frequency of 1.9 and 0.5 nodules per fruit, respectively. Nodules were also found in 'Newtown Pippin' (frequency 0.8), and in a 'Newtown Pippin' × 'Granny Smith' hybrid (frequency 0.1).
Frank Kappel, W. David Lane, Richard A. MacDonald, and Hans Schmid
W. David Lane, Basdeo Bhagwat, Susan Wahlgren, and John D. Armstrong
A protocol for micrografting shoot tips harvested from in vitro shoot cultures directly to transplanted rootstock plants in the greenhouse was developed. Shoot tips of the apple (Malus domestica) cultivars Golden Delicious, Granny Smith and Fuji clone, Nagafu12, were harvested, stored in a water bath then prepared for grafting by cutting the stem immediately below the tip into a wedge shape leaving the tip approximately 3 mm (0.12 inch) long. The rootstock cultivar, Malling 9 (M.9) (M. domestica), was prepared by cutting into a young fast growing side branch to expose the cambium, creating a pocket into which the shoot tip was inserted. The cut section of the tip was oriented so as to contact the exposed rootstock cambium and was held in place by wrapping with a strip of pliable plastic film. Two weeks later the wrapping was loosened and the grafted branch cut back. Side branches of the rootstock were not removed until later in order to support rootstock growth. The scion shoots developed into nursery whips suitable for transplanting to a screen house or field after 2 months. The protocol proved to be a simple efficient way to rapidly grow nursery trees from tissue culture clones developed in genetic modification experiments and was used to propagate several hundred plants. Grafting success was often 100% but was reduced if quality of shoot tips was poor due to injury indicated by brown tip color. The protocol eliminates the steps of rooting, acclimatizing and growing shoots into plants to serve as a scion wood source.