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  • Author or Editor: Donn T. Johnson x
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Single leaf gas exchange measurements were taken at a range of light intensities from 20 to 1500 μmol·m-2·s-1 PAR under greenhouse conditions on `Washington Spur'/EMLA seven potted apple trees subjected to either 1500 cumulative mite days (CMD) European Red mite (ERM) damage or no mite damage. 1500 CMD ERM damage significantly reduced assimilation (A) over all light intensities for leaves present during mite damage at 6 days after the mite population had reached the 1500 CMD level and the mites were killed. Mite damage did not significantly affect A of either leaves present during mite damage or leaves produced after the mites were killed on any other sampling date. However, a trend of reduced A of leaves present during mite infestation on the mite-damaged trees was apparent on all sampling dates after the mites were killed. Evapotranspiration (E) was not affected by mite damage. The mite damage by light intensity interaction did not have a significant effect on A or E on any sampling date.

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Since 1997, populations of Japanese beetle have settled into some of the major urban areas of Arkansas, especially Little Rock and Northwest Arkansas, due to transported turf and nursery material. Experimental trials at the University of Arkansas Agricultural Research and Extension Center, Fayetteville have sustained significant damage due to the increasing Japanese beetle population. Plantings of blackberries and blueberries were rated for feeding damage. Significant differences were observed among genotypes of both crops. Mean damage ratings varied from 0.6 to 4.0 for the blackberries and 1.2 to 3.5 for the blueberries. As evidenced by the mean damage ratings, some resistance or tolerance is present within these populations and may be exploited for improvement.

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The NE-183 project was established in 1993 and the first trial planted in 1995 with the objective of evaluating new apple cultivars for horticultural, pest and disease resistance, and qualitative characteristics. Arkansas (AR) is the southernmost location for the initial planting. The following cultivars are in AR trial: `Arlet', `Braeburn', `Cameo', `Creston', `Enterprise', `Fortune', `Fuji', `Gala Supreme', `Ginger Gold', `GoldCrisp', `Golden Delicious', `Golden Supreme', `Goldrush', `Honeycrisp', `NY75414-1', `Orin', `Pristine', `Sansa', `Shizuka', `Suncrisp', `Sunrise', and `Yataka'. Bloom of `Braeburn', `Yataka', `Orin', `Gold Supreme', `Fortune', and `Enterprise' were early and may be exposed to annual spring frosts. The following cultivars ripened in July or August and may be too early for southern markets: `Pristine', `Sunrise', `Sansa', `Ginger Gold', `Arlet', `Honeycrisp', `Golden Supreme', and `Orin'. The following cultivars were very precocious and had yields >7.5 kg/tree in the third growing season: `Fuji', `Enterprise', `Creston', `Golden Delicious', `Ginger Gold', `Suncrisp', and `Goldrush'.

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In 1995, greenhouse and orchard experiments of 11 apple cultivars were conducted in Fayetteville and Clarksville, Ark. Weekly cumulative mite days (CMD) were regressed against leaf bronzing (colorimeter value L) and compared among cultivars. European red mites, Panonychus ulmi and two-spotted spider mites, Tetranychus urticae, were found on leaves. `Liberty', `Royal Gala', and `Stark Spur Red Rome Beauty' had significantly more mites (>1940 CMD) than did `Arkansas Black' (1303), `Jonafree' (1150), and `Northern Spy' (973). A low CMD on `Northern Spy' caused leaves to bronze faster [y = 29.04 + 0.006(x); R 2 = 52, P = 0.0002] than did a high CMD on `Liberty' [y = 30.41 + 0.0027(x); R 2 = 70, P = 0.0001]. Field estimates were made of spider mites/leaf and bronzing from 20 June to 7 Aug. `Stark Spur Red Rome Beauty' and `Stark Spur Law Rome' had significantly more CMD than did `Northern Spy' and `Arkansas Black'. Apple cultivars differed in carrying capacity to mites (susceptibility) and how fast leaves bronze in response to mite feeding. Cultivar differences in hairiness of the lower leaf surface were not correlated to CMD.

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