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Robert W. McMahon, Cecil R. Stewart and Richard J. Gladon

Chlorophyll a and b contents were determined in developing tomato fruit (Lycopersicon esculentum Mill. `Heinz 1350') at 5-day increments from 10 or 15 days past anthesis to fulIy ripe (55 to 60 days). When presented on a whole-fruit basis, chlorophyll a and b contents increased from 15 days past anthesis to 35 days and then decreased to zero at 55 days. Porphobilinogen (EC 4.2.1.24; PBG) deaminase activity was measured in extracts from the fruit, and changes in PBG deaminase activity correlated with changes in chlorophyll and protein contents with respect to fruit age. Partial characterization of tomato PBG deaminase enzyme showed similarities to PBG deaminase enzymes isolated from other sources.

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M.J. McMahon, J.W. Kelly, D.R. Decoteau, R.E. Young and R.K. Pollock

`Spears' (nonpinched and pinched) and `Yellow Mandalay' (pinched) chrysanthemums were grown in growth chambers equipped with panels filled with liquids that served as spectral filters. Light quality was altered by reducing blue light, increasing red: far-red (R: FR) light, or reducing R: FR. Control panels did not selectively alter light transmission. Photosynthetic photon flux was the same in all chambers. All plants grown under increased R: FR filters had reduced height, reduced internode length, and increased chlorophyll content compared to controls. Reduction in blue light decreased chlorophyll content of pinched plants compared to controls. Pinched plants grown under increased R: FR light and !ong days developed fewer nodes than controls due to the formation of abnormal capitula; the controls and plants from the other treatments developed more nodes before producing similarly abnormal capitula. Stem diameter and leaf area did not differ due to treatments.

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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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Dennis R. Decoteau, Heather A. Hatt, John W. Kelly, Margaret J. Mcmahon, Nihal Rajapakse, Roy E. Young and Robert K. Pollock