Management of ‘Marion’ blackberry to reduce thorn contamination of harvested fruit
In a thorn survey done in 1998 (Strik, unpublished), thorn content in machine-harvested fruit was high relative to hand-harvested fruit. “Thorn” contaminants ranged from large, woody thorns originating from floricanes, small thorns, likely originating from fruiting laterals, pedicels, sometimes with berries attached, and petioles. Although ‘Marion’ is deciduous, leaves often do not senesce in our mild winters or the leaflets abscise and the petiole is persistent. Thus, these old (last year’s) petioles can be dislodged and fall into the fruit during machine harvest. The processing industry considers thorns one of the most serious biological contaminants of ‘Marion’ (Oregon Raspberry and Blackberry Commission, personal communication).
The objectives of this study were to evaluate pre-harvest mechanical and chemical methods to minimize thorn contamination of machine-harvested ‘Marion’ fruit. Year one: In 1999/2000 we evaluated the following treatments in mature ‘Marion’ at a grower cooperator site: I. 0.6% Copper Chelate, applied Nov. 2, 1999; II. 0.6% Copper Chelate (Dec., 1999); III. Ethephon at 1086 ppm (Nov. 2, 1999); IV. 1.2% Copper Chelate (Jan. 26, 2000); V. one pass of a mechanical harvester with standard rotary heads followed by a harvester equipped with brushing heads (Feb. 4, 2000); VI. one pass of a harvester equipped with brushing heads (Feb. 4, 2000); VII. Treatment I + treatment VI; and VIII. an untreated control. Each plot was 100’ long and there were 5 replicates arranged in a block design.
The mechanical harvester used was a Littau (Littau Harvesters Inc., Stayton, Ore.) with two free-wheeling rotary picking heads equipped with fiberglass rods that moved in a horizontal motion. In treatments V, VI and VII we used a similar machine harvester modified with brushing heads instead of picking heads.
Treatments were machine harvested by the grower in July, 2000 using the same rotary picking machine we used for treatment V. The winter treatments had no significant effect on yield per plot, percent bud break or fruit/lateral the following season. In 2000, the rotary harvester followed by brushing removed 2.8 and 0.8 kg debris per plot in the alternate year (AY) and every year (EY) production systems, respectively. Brushing alone, removed 0.7 kg/plot in both the EY and AY systems.
View Project Final Report
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