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Abstract
Butanedioic acid mono-(2,2-dimethylhydroxide) (daminozide) at concentrations ranging from 2000-8000 ppm applied when primocanes were 45 cm tall (12–16 nodes) greatly increased the early yield of ‘Heritage’ raspberries (Rubus idaeus L.). The addition of (2-chlorethyl)phosphoric acid (ethephon) at 300 ppm tended to further increase the effectiveness of the daminozide treatments. None of the treatments significantly affected the total primocane height. Microscopic examination of the axillary buds of untreated primocanes revealed that first signs of floral development occurred soon after the growth regulators were applied.
Abstract
Primocanes were sprayed after they reached about 18 cm in height with 4, 6-dinitro-o-sec-butylphenol (dinoseb) plus superior spray oil to kill the tops down to ground level. Additional treatments involved spraying after the second flush of growth reached 18 cm in height. Primocane suppression by this means increased yields by up to 70% over unsprayed plots. Plots of vigorous ‘Williamette’ raspberries (Rubus idaeus L.) were re-sprayed each year for 4 years and maintained the yield increase. A less vigorous ‘Sumner’ planting subjected to similar treatments did not develop adequate cane height and number after 2 or 3 sprays and yields the following year were greatly reduced. Berry size was sometimes increased. Most of the increased yields were due to greater numbers of berries. Primocane suppression had no effect on the number of berries on the upper laterals but greatly increased the numbers on laterals that developed from the middle and lower portions of the canes. The amount of carbohydrates per bud in dormant canes was reduced by dinoseb sprays applied the previous growing season.
At two-week intervals from 17 June to 15 July, three groups of `Meeker' red raspberry plants were infested with two-spotted spider mites (Tetranychus urticae) in a greenhouse. While populations on individual plants were allowed to develop freely, control plants were kept free of mites with a chemical miticide. Gas exchange measurements were made on 27 July prior to visible mite damage, and on 7 October after injury was apparent. The relationships between mite populations and leaf gas exchange and chlorophyll characteristics were described using a logarithmic function.
Physiological responses to mite feeding were observed prior to visible leaf injury. On both dates, CO2 assimilation rates decreased (p ≤ 0.001) with increasing mite numbers per leaflet. On 27 June, a significant relationship (R2 = 0.61***) was found between mite number and mesophyll conductance (gm). On 7 October, significant relationships (p ≤ 0.001) were also observed with gm, stomatal conductance (gs), and transpiration (E). Total chlorophyll content of leaves decreased with increasing mite populations, but chlorophyll a/b ratio and dry weight per leaf unit area were unchanged.