519 The Negative Impact of Sevin XLR Plus Thinner Use on Apple Fruit Quality under Certain Environmental Conditions
Year: 1999
Type: article
Abstract: The use of Sevin XLR Plus in chemical thinning applications at or shortly after petal fall in 1998 resulted in serious negative fruit quality effect, especially on `Red Delicious'. This negative fruit quality impact was worse in certain Henderson Co., N.C., orchards. Fruit diameter was reduced by 9%, fruit weight was reduced by 22%, misshapen fruit increased by 30%, eliminator fruit (<2.25″) increased by 102%, severely stunted fruit (<2.0″) increased by 317%. Surface russetting increased by 160% and seed numbers per fruit dropped by 27%. These are “never before seen” fruit quality problems for North Caronlina, which appear to be related to the unusual environmental conditions between full bloom and fruit thinning. Comparing the 30-year weather records, Apr. 1998 was the wettest April on record with twice the average rainfall. There were only two rain free days between bloom and petal fall, and only 9 of the 30 days following bloom were rain-free. Daily lows were at or above while daily highs were below the 30-year average, resulting in an extremely small daily temperature fluctuation. The departure from normal for average daily temperature was highly negative from partial petal fall until 2 weeks post petal fall. Daily relative humidity values for daily minimum, average and maximum were consistently and substantially above 30-year average values. It appears that these environmental extremes with Sevin XLR Plus use has an impact on fruit quality. In one `Golden Delicious' orchard where Sevin formulations could be compared side by side, fruit russetting jumped from 5.3% with 50 WP to 36.2% with the XLR Plus formulation.
Source: HortScience
Author: C.R. Unrath
Language: English
Subfield: Plant Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: gold
Estimated APC paid: $3,000
OpenAlex ID: W2584101316