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Ross E. Byers

AVG applied 2 to 6 weeks before the optimum harvest date for several cultivars dramatically reduced pre-harvest fruit drop. The loss of fruit firmness and starch loss after the optimum harvest date was reduced by AVG sprays. The development of watercore in `Starkrimson Delicious' and `York' and maturity cracking in `Rome' and `Golden Delicious' were delayed and/or prevented by AVG. Color development was slightly delayed for most red cultivars and `Golden Delicious'. Soluble solids concentration was generally unchanged. Airblast applications of 123 g·ha–1 AVG was no more effective than a standard rate of NAA (28 to 56 g·ha–1), but rates of 248 g·ha–1 AVG and above were more effective than NAA for most cultivars. When fruit were left on the tree for periods of 3 to 5 weeks after the optimum harvest date, NAA hastened the loss of fruit firmness and starch and NAA increased watercore of `Delicious' and maturity cracking of `Golden Delicious' and `Law Rome'. Soluble solids and red color were generally unaffected by NAA. Ethephon sprays hastened the rate of fruit drop. When NAA was tank mixed with ethephon, NAA delayed fruit drop caused by ethephon, but AVG did not. The use of superior oil or Regulaid surfactant did not affect NAA or AVG responses; however, the silicone surfactant Silwet L-77, in one experiment, promoted the effectiveness of AVG. Tank mixing NAA or AVG with pesticides (Guthion + Lannate + Captan) did not affect the responses of AVG or NAA on fruit drop.

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Steven McArtney, Dave Ferree, John Schmid, J.D. Obermiller and A. Green

A series of experiments were undertaken to compare the effects of individual and combined applications of GA4+7 and prohexadione-Ca (P-Ca) on scarf skin and fruit quality parameters on red strains of `Rome Beauty' and `Gala' apples. Three applications of GA4+7 at 10-day intervals beginning at petal fall (PF) significantly reduced scarf skin severity in all experiments. A single application of P-Ca at PF had no effect on scarf skin in one experiment but reduced scarf skin severity in two further experiments. Combining P-Ca with the first of three GA4+7 sprays as a tank mix reduced the severity of scarf skin more effectively than either material alone in two of three experiments at P < 0.05 and in all three experiments at P < 0.10. Combining P-Ca with the first application of GA4+7 as a tank mix generally reduced scarf skin as effectively as applying P-Ca and the first GA4+7 spray two days apart, although in one experiment, greater scarf skin control was achieved when P-Ca was applied 2 days after the first GA4+7 spray. A single application of P-Ca at PF consistently reduced, and three applications of GA4+7 consistently increased, mean fruit weight at harvest compared with the control. The economic benefits as a result of reducing scarf skin severity with P-Ca and GA4+7 sprays will need to be balanced against the negative effect of P-Ca on mean fruit weight. There is no antagonism between early season P-Ca and GA4+7 sprays for scarf skin control, and P-Ca may increase the efficacy of GA4+7 sprays for scarf skin control in apple.

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Mary Lamberts and Adrian Hunsberger

Many people, including growers and gardeners, fail to carefully read pesticide labels before each use because they assume they know what the label contains. The UF Miami-Dade County Extension pesticide trainer developed several hands-on exercises where participants had to find information on labels chosen for specific features. The first group was people taking the Core/General Standards training. Five pesticide labels were used. Participants were asked to find information from three different categories: 1) basic information used for record keeping and about the product;2) Personal Protective Equipment (PPE) and Precautionary Statements; and 3) additional product information such as irrigation and tank mix warnings. A second group, Private Applicators (growers and their employees), studied 6 labels (1 overlap with Core training). They were asked information that focused on Worker Protection Standard issues, resistance management, limits on number total amount applied, and pre-harvest intervals. For both types of licensed applicator training, participants were divided into groups of 5 to 6. On several occasions, growers and other licensed applicators said they thought labels should have greater uniformity regarding location of key information. Master Gardeners (MGs), the third group, were first given three general publications on labels and 1 on protecting the applicator. They then received labels of four homeowner products and were guided through finding information such as: labeled crops/sites, pests controlled, signal words, mixing instructions, preharvest intervals and replant information. MG knowledge was evaluated with a five-question quiz. All participants commented that they learned a lot about reading labels.

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R.E. Byers and K.S. Yoder

In 1995, BAS-125W applied at 125 to 500 mg/liter 23 days after full bloom (AFB) to `Starkrimson Delicious'/MM 106 and MM111 reduced average shoot weight and length of the longest shoots in the top and scaffold limbs by 50% at the highest rate. The number of nodes on the lower 40 cm of each shoot was increased by 1.8 times by the growth retardant. The number of pruning cuts, pruning time, and pruning weight per tree was reduce by 30%, 20%, and 29%. Fruit diameter, color, soluble solids, starch, fruit weight, and fruit number per tree were not altered by BAS-125 W. Growth suppression appeared to be greater on trees with heavier crop loads. In 1996, BAS-125W applied at 250 mg/liter 8 days after full bloom was more effective than when applied 19 days AFB to `Starkrimson Delicious'/MM 106 and MM111. Multiple applications of two, three, and four sprays to the same trees at 3-week intervals further reduced shoot growth with each application. Four applications reduced shoot weight by 72%, shoot length by 60%, and basal shoot diameter by 25%, and the number of pruning cuts, pruning time, and pruning weight per tree was reduce by 75%, 55%, and 80%, respectively. Thinning activity of NAA, Sevin, or Accel was not affected by tank mixed sprays with BAS-125W when applied to Gala/M.27 trees 20 days AFB. Tank mixing BAS-125W with combinations of Vydate + Accel or Carbaryl + Accel + Oil did not alter fruit thinning of Fuji/M.27 (at 10 mm fruit diameter). In one experiment, BAS-125 may have potentiated thinning by ethephon and NAA 10 days AFB in another experiment. BAS-125 W sprays at petal fall + 1 and 2 weeks later significantly suppressed % infection by fireblight, Erwinia amylovora, in inoculated shoots. In addition, BAS-125W reduced canker length in the first-year growth in shoots inoculated 2 weeks after treatment.

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Frank J. Peryea and Jennifer M. Lageschulte

Farmers often mix fertilizers, pesticides and other agricultural chemicals together in a spray tank to allow applications of multiple products in a single spray. Because polyborate-based B fertilizers may increase solution pH, adding B to tank-mixed sprays may impair the stability and efficacy of alkalinity-sensitive pesticides and growth regulators if an acidifier is not included. We conducted a laboratory experiment to determine the influence of 10 commercial B fertilizer sources in factorial combination with B concentrations ranging from 0 to 4 lb/100 gal (4.8 g·L-1) on solution pH values of distilled water and two natural waters. Two boric acid-based compounds produced acidic reactions relative to background water pH at all tested B concentrations. Their pH responses were influenced by initial water composition. Seven B products produced moderately to strongly alkaline reactions at all but the highest B concentration, regardless of the form of B (polyborate vs. boric acid) initially present in the formulated products. One polyborate product formulated with an acidifier showed intermediate pH behavior. The dependence of solution pH on B rate of the polyborate-containing products was identical in all three waters. The maximum pH values generated by all products occurred in the B concentration range <0.1 to 0.25 lb/100 gal (0.12 to 0.3 g·L-1). Solution pH values declined with increasing B concentration above this range. The pH responses qualitatively conformed to known aqueous chemical behavior of B and the product additives. The complexity of the interaction between initial water chemistry, B concentration, and B fertilizer product reinforces the need to measure the pH of B-amended spray water before adding pH-sensitive compounds.

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Warren C. Stiles

Potassium nitrate, potassium sulfate and potassium acetate were applied as foliar sprays at recommended rates for each material to Empire and McIntosh apple trees in a potassium deficient orchard. Five sprays of each material were applied at approximately one-week intervals beginning in mid-August All sprays were applied by means of a small air-blast sprayer calibrated to deliver 800 1 ha-1 of a 1.744X tank mix, i.e. equivalent to dilute sprays of 1400 1 ha-1. Total amounts of K applied per ha were 8.6 kg with K-acetate and 28 kg ha-1 with K-nitrate and K-sulfate. Leaf samples were collected from each plot at normal harvest date for each variety and washed prior to drying and analysis. Regression analysis indicated a significant (P=0.05) positive relationship, r = +0.4740, between total amount of K applied and leaf K regardless of the source. Significant positive relationships were found between average fruit weight and percent leaf potassium with both varieties.

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Don C. Elfving and Dwayne B. Visser

A new bioregulator, cyclanilide (CYC, Bayer Environmental Science, Research Triangle Park, NC 27709), was compared with a proprietary formulation of 6-benzyladenine and gibberellins A4 and A7 [Promalin (PR), Valent BioSciences, Walnut Creek, Calif.] for branching effects on sweet cherry trees. CYC stimulated the formation of lateral shoots on current-season's shoot growth under both orchard and nursery conditions. In the nursery CYC was as effective or better for feathering compared to PR in all cherry cultivars tested. There were no synergistic effects of CYC/PR tank mixes on feather development. Crotch angles of induced feathers were not different from the angles of feathers that formed spontaneously. The growth of CYC-induced feathers was sufficient to produce acceptable quality feathered trees. Trunk caliper of nursery trees was either not affected or reduced to a very minimal degree. CYC is effective for lateral branch induction in sweet cherry, especially in the nursery. Chemical names used: 1-(2,4-dichlorophenylaminocarbonyl)-cyclopropane carboxylic acid (cyclanilide); N-(phenylmethyl)-1H-purine-6-amine + gibberellins A4 and A7 (Promalin); polyoxyethylenepolypropoxypropanol, dihydroxypropane, 2-butoxyethanol (Regulaid).

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L. Gene Albrigo and Jude W. Grosser

In Florida, pesticides, nutritional and growth regulators are often sprayed in tank mixes to reduce sprayer use. Many individual spray components are phytotoxic and result in spray burns in combination or if applied with adjuvants. The toxicity level of standard spray materials is not known and new product testing for phytotoxicity is not routine. Three tests were developed to allow testing of cellular and whole fruit susceptibility to spray chemicals. Cell suspension cultures initiated from `nucellar derived' embryonic callus of `Hamlin' sweet orange were grown in log phase for 2 weeks with various levels of test chemicals. Fresh weight increase was measured. Peel disks of orange or grapefruit were grown for 4 weeks on solid media. Color changes and callus growth were used to evaluate phytotoxicity. Dilute sprays and droplet applications to on-tree-fruit were used to evaluate individual and combinations of chemicals with and without spray adjuvants. The 3 tests combined effectively demonstrated levels of phytotoxicity and are useful for testing new citrus production chemicals.

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Michael J. Roll, Steven E. Newman and Ronald J. Harkrader

A formulation of quaternary benzophenathridine alkaloids (QBA) was combined with piperalin as a tank mix. The QBA was applied at 150 mg/L and piperalin, at the labeled rate, was applied as a spray application to greenhouse roses infected with Sphaerotheca pannosa var. rosae (powdery mildew). Copper sulfate pentahydrate and fenarimol were also applied to mildew-infected plants within the same greenhouse at their respective label rates for comparison. Initial infection for the QBA/piperalin combination spray was 45% of the leaflet surface area, 3 days after application the infection was reduced to 10%, 6 days after application infection was reduced to 5%, and 14 days after application the infection remained at 5%. Initial infection for a QBA application without piperalin was 25% of the leaflet surface area. Three days after application, the infection was reduced to 15%; 6 days after application the infection remained at 15%; and 14 days after application, the infection was reduced to 10%. The data reveals that the QBA/piperalin combination gives a short-term as well as a long-term fungicidal and fungistatic activity.

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Sunghee Guak, Norman E. Looney and Leslie H. Fuchigami

We propose that return flowering of `Fuji' apple can be improved if sufficient flower clusters are removed during or shortly after bloom. In this study conducted at Corvallis, Ore., we evaluated two synthetic auxins, MCPB-ethyl and the Na salt of NAA, each at 0, 4, 8 and 16 ppm, as blossom cluster thinners. Each auxin treatment was applied alone or with 100 ppm ethephon as a tank mix. Six-year-old `Fuji'/M.26 trees were sprayed at full bloom of the king flowers (≈85% of whole-tree full bloom). A follow-up treatment of Sevin XLR (800 ppm carbaryl) was made at 11-mm fruit diameter to determine if carbaryl's known effectiveness as a fruitlet thinner was influenced by the bloom-time auxin or auxin + ethephon treatments. MCPB-ethyl proved ineffective as a bloom-time thinner, whereas the NAA effect on cluster removal was linear with concentration, 16 ppm NAA completely defruiting 33% of initial flower clusters. On control trees fewer than 12% of flowering clusters failed to set fruit. Ethephon alone defruited 25% of the clusters and NAA+ethephon defruited 51% of clusters. It is notable that the NAA and ethephon + NAA treatments did not reduce fruit set on the remaining clusters, resulting in considerable need for hand-thinning. Carbaryl effectively reduced total crop load by increasing the number of defruited clusters and reducing the incidence of doubles and triples. There was evidence to suggest that its effectiveness was compromised by the bloom-time NAA and/or ethephon sprays.