preharvest fruit drop can occur independently of fruit ethylene production ( Sun et al., 2009 ). Losses resulting from preharvest fruit drop can be mitigated by applying either naphthaleneacetic acid (NAA; Fruitone L; AMVAC Chemical, Newport Beach, CA) or
efficacy. Various growth regulators have been shown to promote flower bud formation in apple. Harley et al. (1958) reported that flowering in apple was increased by NAA to a greater extent than could be accounted for by fruit removal alone, providing
retained on cuttings and any remaining leaves were removed. Retained leaves were bisected to reduce water loss. The basal 5 cm of cuttings were dipped for 10 s in 1030 ppm IBA (0.1%) and 660 ppm (0.066%) NAA dissolved in 9.8% isopropyl alcohol (Woods
Chemical fruit thinners were applied to limbs or whole trees of spur `Delicious' at various stages of fruit development as indicated by fruit diameter. Carbaryl, naphthalene acetic acid (NAA), and ethephon all reduced fruit set when applied at a fruit diameter of ā4 to 15 mm. Fruit thinning for NAA and carbaryl, alone or combined, generally was greater when applied at an average fruit diameter of 8 mm, rather than at 4 mm. Repeated applications of NAA or carbaryl were no more effective than single applications. NAA + carbaryl applied at 9 mm was more effective than NAA applied at 4 mm followed by carbaryl at 8 mm. Applied when fruit diameter averaged 17 to 22 mm, ethephon and ethephon + carbaryl were effective fruit thinners. When applied at full bloom to ā10 and 20 mm, the insecticides ethion and oxamyl, respectively, were effective fruit thinners.
Biennial bearing of apple trees can be overcome either by the use of a blossom chemical thinner or by early application of a postbloom thinner. Carbaryl (Sevin) is a post-bloom fruit-thinning chemical with an effective thinning period of 4 to 5 weeks after bloom. Sevin was compared in 1992 and 1993 with NAA as an early petal-fall spray. Sevin treatments reduced fruit set to one fruit per cluster with no adverse side effects on the foliage. NAA inconsistently reduced fruit set and the remaining fruit were in clusters, The NAA-treated foliage was adversely affected; having small curled leaves. NAA at 10 ppm under-thinned in 1992 and seriously over-thinned in 1993, whereas Sevin treatments were consistent for fruit thinning in both years. Sevin applied at petal-fall or at petal-fall + 7 days effectively reduced fruit set and reduced fruit competition.
Hydrogen cyanamide (Dormex, 50% a.i.) for blossom thinning `Early Spur Rome' and `Law Rome' apple (MalusĆdomestica Borkh.) and `Flavorcrest' peach (Prunus persica L.) was applied with air-blast sprayers on a commercial scale. Full-bloom applications of hydrogen cyanamide at 4 pts formulation per 200 gal/acre (1288 mgĀ·Lā1) and 5 pts formulation per 200 gal/acre (1610 mgĀ·Lā1) significantly reduced fruit set in apple and peach. In `Early Spur Rome', a postbloom application of carbaryl [Sevin XLR Plus, 4 lb a.i./gal (0.48 kgĀ·Lā1)] following a full-bloom spray of hydrogen cyanamide increased fruit thinning with a significant increase in fruit size compared to an application of hydrogen cyanamide alone. In `Law Rome', trees receiving a full-bloom application of hydrogen cyanamide followed by a postbloom application of 1-naphthyl-N-methylcarbamate (carbaryl) + naphthalene acetic acid (NAA) had significantly lower fruit set and larger fruit than those in the carbaryl + NAA treatment. Apples or peaches were not marked by hydrogen cyanamide.
In five experiments with `Redchief Delicious' and one with `Braeburn', oxamyl (Vydate 2L) was used alone or combined with other chemicals to thin apples. The thinning response to oxamyl depended on dose. In most cases, oxamyl at 600 mgĀ·Lā1 and carbaryl at 900 mgĀ·Lā1 thinned trees similarly, but the combination of oxamyl plus carbaryl was no more effective than either chemical alone. The combination of oxamyl plus NAA (2.5 to 5 mLĀ·Lā1) was slightly more effective than either material alone. The thinning response to oxamyl and carbaryl was related to the concentration of superior oil added to the spray solution; for both chemicals, adding oil at 5 mgĀ·Lā1 or Tween 20 at 1.25 mLĀ·Lā1 gave equivalent thinning. Apples on trees sprayed with oxamyl plus oil had a dull finish. Adding Tween 20 at 1.25 mLĀ·Lā1 improved the thinning activity of carbaryl (Sevin XLR-Plus) more than oxamyl. Similar thinning occurred whether oxamyl was applied when fruit diameter averaged 4 or 10 mm. On `Braeburn' oxamyl, carbaryl, Accel, and NAA were mild thinners, but all combinations of oxamyl or carbaryl plus Accel or NAA overthinned the trees without improving fruit size. In general, oxamyl at 600 mgĀ·Lā1 (2 pints of vydate 2L/100 gal.) and carbaryl thin apple trees similarly, and the efficacy of both chemicals is improved by adding a surfactant.
A juneberry (Amelanchier alnifolia) cultivar trial was conducted to evaluate fruit yield, quality, and other characteristics for juneberry cultivars and a native biotype. One-year old micropropagated material was transplanted and established in North Dakota in 2004. The native biotype is available as a conservation plant from Towner State Nursery (Towner, ND) and was included as a readily available juneberry for producers. Fruit diameter, soluble solids content, yield (total and marketable), and plant size measurements were taken during the 2010 and 2011 season. āMartinā, the native biotype, āParkhillā, āPembinaā, āRegentā, and āThiessenā produced the highest total yield in 2010, whereas āParkhillā had the highest total yield in 2011, followed by āThiessenā and then āMartinā. Cultivars Martin, Parkhill, and Thiessen produced the highest marketable yield over the 2-year study. āMartinā and āThiessenā fruit were larger and heavier than the rest of the cultivars. The largest plants were āMartinā, āParkhillā, āRegentā, and āThiessenā. Soluble solids concentrations were similar among all cultivars. Cultivars Martin or Thiessen should be recommended to commercial producers wanting a high yielding cultivar with uniform fruit ripening, whereas Parkhill should be recommended to producers with a you-pick operation wanting a high yielding cultivar with an extended fruit ripening period.
In five experiments, singlenode cuttings of `Red Cascade' miniature rose (Rosa) were treated with a basal quick-dip (prior to insertion into the rooting substrate) or sprayed to the drip point with a single foliar application (after insertion) of Dip `N Grow [indole-3-butyric acid (IBA) + 1-naphthaleneacetic acid (NAA)], the potassium salt of indole-3-butyric acid (K-IBA), or the potassium salt of 1-naphthaleneacetic acid (K-NAA); a single foliar spray application of Dip `N Grow with and without Kinetic surfactant; or multiple foliar spray applications of Dip `N Grow. Spray treatments were compared with their respective basal quick-dip controls {4920.4 Ī¼m [1000 mgĀ·L-1 (ppm)] IBA + 2685.2 Ī¼m (500 mgĀ·L-1) NAA, 4144.2 Ī¼m (1000 mgĀ·L-1) K-IBA, or 4458.3 Ī¼m (1000 mgĀ·L-1) K-NAA}. Cuttings sprayed with 0 to 246.0 Ī¼m (50 mgĀ·L-1) IBA + 134.3 Ī¼m (25 mgĀ·L-1) NAA, 0 to 207.2 Ī¼m (50 mgĀ·L-1) K-IBA, or 0 to 222.9 Ī¼m (50 mgĀ·L-1) K-NAA resulted in rooting percentages, total root length, percent rooted cuttings with shoots, and shoot length similar to or less than control cuttings. Exceptions were cuttings sprayed with 0 to 2.23 Ī¼m
(0.5 mgĀ·L-1) K-NAA, which exhibited shoot length greater than the control cuttings. Addition of 1.0 mLĀ·L-1 (1000 ppm) Kinetic organosilicone surfactant to spray treatments resulted in greater total root length and shoot length. Repeated sprays (daily up to seven consecutive days) had no or negative effects on root and shoot development.
acid (IBA) and 1-naphthaleneacetic acid (NAA) treatments, and our auxin rates were selected based on these results ( Carvalho Pires et al., 2010 ; Chaves et al., 2004 ; Gurung et al., 2015 ; SabiĆ£o, 2013 ). Based on these results, we hypothesized