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R.W. McMahon, R.K. Lindquist, M.L. Casey, A.C. Witt, and S.H. Kinnamon

A demonstration study was conducted to compare the effectiveness of biological and chemical control treatments on the greenhouse whitefly (GHWF) (Trialeurodes vaporariorum, Westwood) using poinsettia (Euphorbia pulcherrima Wild.) stock plants. Two identical greenhouse compartments, each containing 84 stock plants, were used. In the biological control compartment, three biweekly releases of Encarsia formosa (EF) were made, while in the chemical control compartment eight weekly applications of resmethrin or acephate aerosol treatments were made. Results showed that overall greenhouse whitefly populations in the chemical control compartment were slightly lower than in the biological control compartment. Cuttings taken from stock plants in the biological control compartment at the end of the experiment were commercially acceptable with regard to the presence of GHWF adults. Chemical names used: O,S-dimethyl acetylphosphoramidothioate (acephate), [5-(phenylmethyl)-3-furanyl] methyl 2,2-dimethyl-3-(2-methyl-1-propenyl)cyclopropane-carboxylate (resmethrin).

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R.W. McMahon, R.K. Lindquist, B.D. Baith, T.L. Makin, and M.L. Casey

A 2-year demonstration study was conducted to compare the effectiveness of two sources of Encarsia formosa (EF) on the biological control of the sweetpotato whitefly (SPWF) (Bemisia tabaci Gennadius) on poinsettias (Euphorbia pulcherrima Wild.). Commercially produced EF were raised on the greenhouse whitefly (GHWF) (Trialuerodes vaporariorum Westwood), while the locally produced EF were raised on the SPWF. Results showed that SPWF populations were reduced considerably both years, and maximum nymph parasitism ranged from 60% to >80%. No large differences were observed in the ability of EF to control SPWF populations whether raised on SPWF or GHWF nymphs. This study suggests that there is potential for controlling SPWF populations on poinsettia by EF in conjunction with an integrated pest management (IPM) program.

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Stephen A. Carver and Harry K. Tayama

The influence of poinsettia (Euphorbia pulcherrima Wild. ex Klotzsch) stock plant shoot maturity on subsequent splitting of cuttings taken from the shoots was evaluated. Terminal cuttings (7.5 cm) taken from `Lilo' poinsettia stock plant axillary shoots that had 4, 8, or 12 nodes were rooted, planted, then observed for initial signs of splitting (conversion of the vegetative terminal buds into floral buds). The percentages of cuttings that split were 22, 77, and 100 for those taken from shoots with 4, 8, and 12 nodes, respectively. By implication, cuttings should be taken just as stock plant axillaries reach a size adequate for propagation to help reduce the incidence of splitting.

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Mogens Nicolaisen

Phytoplasma PoiBI is responsible for free branching in poinsettia (Euphorbia pulcherrima Wild. ex. Klotzsch). In this study, PoiBI was transmitted by dodder from poinsettia to crown-of-thorns (E. milii Des Moulins) in one out of ≈100 attempts, whereas grafting transmission was unsuccessful. PoiBI was shown to be viable in E. milii, as it was detected in the recipient plant and in its cuttings over 1.5 years by polymerase chain reaction. It was shown that PoiBI induces free branching in E. milii as well as in poinsettia. Smaller leaves, reduced growth rates, and delayed flowering were other effects of PoiBI infection.

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Jing-Tian Ling, Roger Sauve, and Nick Gawel

Randomly amplified polymorphic DNA (RAPD) techniques were used to compare the DNA from leaf tissues of nine commercial poinsettia (Euphorbia pulcherrima Wild ex Klotzsch) cultivars. Amplification occurred in 57 out of 60 (95%) tested primers. Nine primers that revealed polymorphisms among cultivars were selected for further evaluation. Forty-eight RAPD bands were scored from these primers, and 33 (69%) were polymorphic. All tested cultivars could be discriminated with seven bands generated from primers OPB7 and OPC13. Results of a UPGMA cluster analysis and principal components analysis placed the nine cultivars into two groups: one group consisted of `Jingle Bells', `Supjibi', and `V-17 Angelika', the other of `V-14 Glory', `Red Sails', `Jolly Red', and `Freedom'. `Lilo Red' and `Pink Peppermint' belonged to the latter group, but were relatively distant from other cultivars in that group. These results indicate that RAPDs are efficient for identification of poinsettia cultivars and for determination of the genetic relationships among cultivars.

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Claudio C. Pasian, Daniel K. Struve, and Richard K. Lindquist

The effectiveness of two application methods of the insecticide imidacloprid in controlling 1) melon aphids (Aphis gossypii Glover) on `Nob Hill' chrysanthemum (Dendranthema ×grandiflora Ramat) plants and 2) silverleaf whitefly (Bemisia argentifolii Bellows & Perring) on `Freedom Red' poinsettia (Euphorbia pulcherrima Wild.) were compared. Plants were grown in containers with their interior covered by a mixture of flat latex paint plus several concentrations of imidacloprid (0, 10, 21, 42, and 88 mg·L−1), or treated with a granular application of the insecticide (1% a.i.) according to label recommendations. All imidacloprid treatments effectively reduced aphid survival for at least 8 weeks. The two most effective treatments were the granular application (10 mg a.i.) and the 88-mg·L−1 treatment (0.26 mg a.i). All imidacloprid treatments effectively reduced whitefly nymph survival. The 42- and 88-mg·L−1 treatment and the granular application (1% a.i.) were equally effective in reducing nymph numbers in lower poinsettia leaves. None of the plants given treatments with paint exhibited any phytotoxicity symptoms. These results suggest the possibility of a new application method for systemic chemicals with the potential of reducing the release of chemicals to the environment. Paint and imidacloprid mixes are not described in any product label and cannot be legally used by growers. Chemical name used: 1-[(6-chloro-3-pyrimidil)-N-nitro-2-imidazolidinimine (imidacloprid)

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Claudio C. Pasian, Daniel K. Struve, and Richard Lindquist

The effectiveness of two methods of application of the insecticide imidacloprid in controlling 1) aphids (Brachycaudus helichrysi) on Chrysanthemum plants, Dendranthema ×grandiflora (Ramat) (cv. Nob Hill) and 2) whitefly (Bemisia argentifolii) on poinsettia, Euphorbia pulcherrima (Wild.) (cv. Freedom Red) were compared. Plants were grown in containers with their interior covered by a mixture of flat latex paint and several concentrations of imidacloprid (0, 10, 21, 42, and 88 mg·L–1), or treated with a granular application of the insecticide (1% a.i.) according to label recommendations. All imidacloprid treatments were effective in reducing aphid survival after 8 weeks. The two most effective treatments were: granular (1% a.i.) and 88 mg·L–1 with an average of 0.2 aphid per plant as opposed to 50.4 aphids per plant for the control. The 42-mg·L–1 treatment had an aphid survival rate 1.6 aphids per plant. All imidacloprid treatments were effective in reducing white fly larvae. The 42 and 88 mg·L–1 and the granular (1% a.i.) were equally effective in reducing larvae numbers in lower poinsettia leaves: 0.5, 1.9, 0.9 larvae/2.5 cm leaf disk, respectively, while the control treatment had 62.9. None of the plants given treatments with paint showed any sign of phytotoxicity. These results suggest the possibility of a new application method for systemic chemicals with the potential of reducing or eliminating Worker Protection Standard (WPS) Restricted Entry Intervals (REI) and reducing the release of chemicals to the environment. Chemical name used: 1-[(6-Chloro-3-pyrimidil)]-N-nitro-2-imidazolidinimine.

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He Lisi, Su Jiale, Liu Xiaoqing, Li Chang, and Chen Shangping

, J. Xu, X.Y. Yu, J. Cao, C. Liang, G. 2010 Cloning and expression of cell wall acid invertase gene fragment from poinsettia ( Euphorbia pulcherrima wild.) Afr. J. Biotechnol. 9 443 448 Tian, H.M. Kong, Q.G. Feng, Y.Q. Yu, X.Y. 2009 Cloning and

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Peter Alem, Paul A. Thomas, and Marc W. van Iersel

Niu, G. Heins, R. Carlson, W. 2002 Using paclobutrazol to control height of poinsettia ‘Freedom’ HortTechnology 12 232 236 Nowak, J.S. Strojny, Z. 2001 Effect of different soil water potential on summer grown poinsettia ( Euphorbia pulcherrima Wild

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Christopher J. Currey and Roberto G. Lopez

no significant differences in survey gas exchange or light response curves across light sources within species in our study. Similarly, survey measurements of P n , and g S of Euphorbia pulcherrima Wild. ex Klotsch ‘Novia’ did not vary across