Poinsettias and other floral crops when treated with the growth retardant uniconazole, Sumagic™, are more compact in growth habit. They have also been shown to have reduced stem strength. Calcium applied as a drench has been demonstrated to increase plant height and plant dry weight of poinsettias. Unicomazole reduced plant height without affecting dry weight. Bract color was more intense when calcium was applied as a weekly spray. Poinsettia plants had greater levels of foliar calcium when applied as a drench. Poinsettia plants sprayed and drenched with calcium and treated with uniconazole had greater levels of foliar calcium, however, this was not significantly greater than the control plants treated with uniconazole alone. The lowest level of foliar calcium was observed in uniconazole treated plants where calcium was applied as a spray. Uniconazole applications weakened the stein structure of poinsettias as with other floral crop species.
D.K. Harris, A.D. Owings and S.E. Newman
D.K. Harris, A.D. Owings and S.E. Newman
Uniconazole has been demonstrated to not only reduce plant height, but suppress the development of xylem and phloem in stem tissue. Supplemental calcium nutrition in poinsettias has been demonstrated to reduce marginal bract necrosis, reduce leaf puckering and increase stem strength. Studies were conducted to determine the influence of uniconazole on Gutbier V-14 Glory poinsettias grown with supplemental calcium applied either as a foliar spray or a media drench.
Supplemental calcium applications improved the growth habit of uniconazole treated poinsettia plants. Bract coloration was intensified by foliar applications of calcium and uniconazole.
Leonardo Lombardini*, D. Michael Glenn and Marvin K. Harris
Trials were established in Summer 2002 and 2003 to test the consequences of the application of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural predators (insects and arachnids) on pecan (Carya illinoinensis, cv. `Pawnee') trees. Film application started immediately after bud break and was repeated every 7-10 days for seven (2002) or nine (2003) times during the season. On both years, treated trees frequently showed lower leaf temperature (up to 4 °C) than untreated trees. Leaf net assimilation rate, stomatal conductance and stem water potential were not affected by film application. Nut size and quality did not differ between the two treatments. In 2003, shellout (percentage of nut consisting of kernel) was in fact 54.2% and 55.5% for treated and control trees, respectively. Moreover, the two treatments yielded similar percentage of kernel crop grading as fancy, choice, standard and damaged. Similar were also the percentages of kernels that showed damage caused by stink bugs. Only on one date the number of adult yellow pecan aphids (Monelliopsis pecanis) counted on film-treated leaves was lower than in control leaves. In general, the density of common natural predators (lady beetles, green lacewings, spiders) of pecan pests did not differ between the two treatments; however, the number of green lacewing eggs was frequently lower on film-treated leaves. In film-treated trees the number of nutlets damaged by pecan nut casebearer (Acrobasis nuxvorella) was significantly higher than that observed on trees treated with conventional insecticide (24.2% infested nutlets vs. 9.3%, respectively) and did not differ from trees that did not receive either product (29.9%).
Leonardo Lombardini, Marvin K. Harris and D. Michael Glenn
Trials were conducted during summer months of 2002 and 2003 to evaluate the effects of a kaolin-based particle film (Surround WP, Engelhard Corp.) on gas exchange, nut quality, casebearer density and population of natural enemies (insects and arachnids) on pecan (Carya illinoinensis `Pawnee') trees. Film application was repeated for seven (2002) or nine (2003) times during the growing season. In both years, treated trees showed lower leaf temperature (up to 4 °C) than untreated trees. During the warmest hours of the day, kaolin-treated leaves were generally 0 to 2 °C cooler than air temperatures, compared to 4 to 6 °C for control leaves. Leaf net assimilation rate, stomatal conductance and stem water potential were not affected by film application. Nut size and quality did not differ between the two treatments. Shellout (percentage of nut consisting of kernel) was not affected by treatment and averaged about 55%. Crop grade distribution (fancy, choice, standard, and damaged) was also similar among treatments in both years. In both years, numbers of green lacewing eggs was less on kaolin-treated compared to control leaves. The density of common natural enemies (lady beetles, green lacewings, spiders) of pecan pests did not differ between treatments. The average number of developing nuts damaged by pecan nut casebearer (Acrobasis nuxvorella Neunzig) was significantly higher in kaolin-sprayed trees (24.2%) compared to control trees sprayed with conventional insecticides (9.3%). The results suggest that kaolin-based particle film may not be a viable alternative to conventional methods of controlling pecan pests. Also, under adequate irrigation conditions, carbon assimilation, water relations and productivity may not benefit from kaolin particle film application.
J.R. Evans, J.A. Balles, B.A. Brinkman, V.E. Harris, J.D. Helm, K.B. Kirksey, T.E. McKemie, G.G. Thomas and W. Rademacher
Prohexadione-Ca (BAS 12511W or Apogee™ Plant Growth Regulator) acts within a plant by blocking the biosynthesis of growth-active gibberellin. The result is decreased cell and shoot elongation; thus, vegetative growth in apple trees can be reduced. Air blast applications of prohexadione calcium were made in the Spring 1998 in commercial orchards. Application rate was 125 ppm a.i. applied twice beginning at 5 to 12 cm of new shoot growth. Reduction of shoot growth averaged 45% across locations. As a result of reduced vegetative growth, dormant pruning was reduced. In total, significant benefits to the grower included reduced pruning costs in addition to other positive effects such as improved light penetration and enhanced resistance to some pathogens. Research will continue with the effect of prohexadione-Ca on pruning in multiple year studies.