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Apple growers of different regions need different chemical fruit-thinning responses for thinning trees of different tree ages, cultural conditions, rootstocks, climates, and amounts of fruit removal desired. In this research, a range of chemical thinning responses was achieved by combinations of thinning materials or addition of potentiating agents. Superior oil, certain organic phosphates, and a light-absorbing agent (ferbam, a fungicide) increased the thinning of carbaryl. In addition, combinations of 50 or 200 ml 6-BA/liter + carbaryl + oil defruited `Campbell Redchief Delicious'/M.111 trees, and 50 ml 6-BA/liter alone over-thinned in one year (however, oil or 6-BA has been shown previously to cause russet in `Golden Delicious'). Carbaryl 50 WP and the 4L carbaryl formulations were equally effective for thinning `Golden Delicious', `Stayman', and `Redspur Delicious', and did not affect fruit russet. Three days of cloudy weather is typical at least once in most seasons in the eastern United States during the fruit set period. Two days of artificial polypropylene shading (92%) (which was nearly equivalent to 3 days of cloudy weather) caused more thinning of `Golden Delicious' and `Stayman' than carbaryl or 10 mg NAA/liter + Tween. Shading reduced viable seed numbers about 50% for `Golden Delicious' in fruit remaining at harvest, but chemical thinning agents (NAA or carbaryl) did not affect viable seed number.
Abstract
Field efficacy of the Ramik-Brown formulation against pine voles was improved by increasing the concentration of diphacinone (DPN) from 0.005% to 0.216%. A 10-fold increase in diphacinone concentration in the Ramik-Brown formulation increased mortality of meadow voles (5% to 25%) in a laboratory cage trial without affecting bait consumption. The Ramik-Green formulation (fish-flavored) was equally effective for control of pine voles as the Ramik-Brown (apple-flavored). Chemical names used: 2-diphenylacetyl-1,3-indandione (diphacinone).
Abstract
Storage of brodifacoum (Volid) and chlorophacinone (Rozol) anticoagulant rodenticides with organic phosphate spray materials in a sealed container for more than 57 days slightly reduced Pine vole (Microtus pinetorum) mortality and bait acceptance of Volid, but did not affect Rozol efficacy. Storage of both materials with zinc phosphide bait did not affect acceptance or mortality of pine voles. Pine voles surviving a 3-day exposure to zinc phosphide surface-coated corn and oat bait (ZnP-grain) (2%, w/w) were much less susceptible to a subsequent 5-day exposure to ZnP-grain or ZP Rodent Bait-AG, 14 days after the first exposure. ZP Rodent Bait-AG caused greater mortality than ZnP-grain in both pre-exposed or voles not previously exposed to ZnP-grain bait. Chemical names used: 2-(P-chlorophenyl)phenyl-acetyl[-l,3]-indandione [Rozol; 0.005% chlorophacinone (CPN)]; and 3-[3-(4′bromo[1, 1′-biphenyl]-4-yl)-1,2,3,4-tetrahydro-l-napthalenyl]-4-hydroxy-2H-1-benzopyran-2-one [Volid; 0.001% brodifacoum (BFC)].
Abstract
Rodenticides applied in an apple orchard and containing zinc phosphide caused a shift in mixed pine (Microtus pinetorum) and meadow (M. pennyslvanicus) vole populations to more pine voles. The anticogulant, chlorophacinone (Rozol-pelleted formulation, CPN) caused a shift to more meadow voles. A lacquered wheat formulation of CPN was as effective as the Rozol-pelleted formulation when broadcast or hand-placed under shingles and appeared to weather better than Rozol. Cholecalciferol (Quintox-pelleted formulation) and one of the zinc phosphide (Ridall-pelleted formulation) formulations were not effective rodenticides. Chemicals used: 2-(p-chlorophenyl) phenylacetyl [-1,3-indanione [Rozol 0.005% chlorophacinone (CPN)]; 3-[3-(4’-bromo[1,1’-biphenyl]-4-y)-3-hydroxy-l-phenylpropyl]-4-hydroxy-2H-1-benzopyran-2-one [Maki 0.005% Bromodialone (BDL)]; cholecalciferol [Quintox 0.075% Vitamin D3 (vit D3)]; Zn3P2 pellet zinc phosphide [ZP Rodent Bait AG —2%, W-ZP Rodent Bait AG Zinc phosphide (ZnP)].
Abstract
Trunk looping of several apple cultivars on seedling roots reduced terminal shoot growth and trunk enlargement below the loop and increased root suckers. Growth was reduced most in the early years of tree growth. In the 5th, 6th, and 7th growing seasons, annual trunk enlargement was not affected, but growth suppression in the 2nd, 3rd, and 4th years reduced final trunk diameter measurements after seven seasons. Similarly, terminal shoot length was suppressed greatest in the early years and to a lesser extent in the 5th through the 7th growing seasons. Fruit number was unaffected by looping in the 5th growing season, but looping increased fruit number and fruit/cm2 trunk cross-sectional area in the 6th and 7th seasons in ‘Golden Delicious’, ‘Starkrimson Delicious’, and ‘Northwest Greening’, but not ‘Stayman’.
Abstract
Efficacy of several rodenticides was evaluated in laboratory and field tests. ZP Rodent Bait AG pellets gave greater mortality of pine (Microtus pinetorum) and meadow (Microtus pennsylvanicus) voles in field and laboratory trials than a similar-looking commercially available zinc phosphide (ZnP) pelleted formulation and a whole wheat and cracked corn formulation. Laboratory comparison of six new pelleted formulations (zinc phosphide, ZnP) revealed one that gave similar mortality as ZP Rodent Bait AG. Quintox (vitamin D3) gave average to excellent mortality of voles in laboratory trials, but very poor to fair control of voles in field trials.
Combinations of aminoethoxyvinylglycine (AVG, ReTain) and NAA gave better control of fruit drop of `Golden Delicious' than either alone. When the full rate of ReTain (50 g/A) was compared to a reduced rate of ReTain (86 g/ha) plus NAA, equivalent control of fruit drop of `Golden Delicious' resulted. ReTain delayed softening and starch depletion of `Golden Delicious' fruit. NAA in some cases promoted earlier fruit maturity; but when used in combination with ReTain, maturity was similar to ReTain-treated fruit. Fruit with the highest firmness and starch came out of cold storage in the best condition. Neither 1-methylcyclopropene (MCP, EthylBloc) or NAA inhibited fruit drop of `Golden Delicious' fruit when applied at harvest; but previous ReTain and NAA data indicate that late applications are frequently much less effective than if applied 4 weeks before harvest. Ethephon spray treatments caused more rapid and extensive fruit drop than the control. Trees gassed or sprayed with EthylBloc before ethephon sprays also dropped rapidly. `Golden Delicious' fruit on the tree were dramatically maintained firmer by the EthylBloc gas, and to a lesser extent by EthylBloc sprays by 19.1 N and 10.2 N firmness, respectively, tested on 28 Oct. Starch was maintained by the EthylBloc gas, but not by the sprays. These data indicated that EthylBloc applied as a gas or spray did have a physiological affect but did not control fruit drop. Fruit diameter, soluble solids and color did not appear to be affected. Further study of earlier applications of EthylBloc or combinations with fruit drop control agents may be needed to get fruit drop control. NAA plus Silwet L-77 inhibited fruit drop of `Law Rome', but none of the EthylBloc sprays inhibited fruit drop when applied at harvest. Previous data with ReTain and NAA indicated that late applications are frequently much less effective than if applied 4 weeks before harvest. EthylBloc sprays applied 21 Oct. dramatically maintained fruit firmness tested on 3 Nov. Starch was not maintained by the EthylBloc gas, but starch had almost disappeared by the application time on 21 Oct. Fruit diameter, soluble solids, and color did not appear to be affected. Further study of earlier applications of EthylBloc may be needed to demonstrate fruit drop control. Shading trees with 92% polypropylene shade material for 3 or 7 days caused more rapid fruit abscission at 7 days than 3 days and both were greater than the control.
`Fuji'/MM.111, `Pink Lady'/M.7A, and `Summerfield'/M.7A apple trees were planted in several types of individual root restrictive bags in the field in 1995. Bags were made of Knit and Woven fabrics, Galvanize hardware cloth (6.4 cm) with various holes sizes and of different bag volumes. The bags confined the development of large roots to within the bag. Roots that penetrated the bag resulted in root branching and large root inhibition. As the roots enlarged, roots penetrating the bags were restricted in diameter by the fabric hole size. Roots enlarged to some degree on both sides of the fabric holes but were not killed by girdling within the first few years. Root restriction bags decreased trunk caliper, shoot growth, pruning weights, number of cuts per tree, increased flowering, fruit numbers, and weight per tree. Fruit firmness, soluble solids and color was increased and starch was lower than the nonbagged controls. In cage and tank trials pine and/or meadow voles easily penetrated all of the fabric and polypropylene bags within 24 h, except for the galvanized hardware cloth (6.4 cm). Susceptibility of each material to vole damage was tested by placement of an apple inside a small bag of each. Root restriction bags seemed to be a viable alternative to dwarfing rootstocks for control of tree size, early flowering, and early fruiting.
Prohexadione calcium applied as a series of three applications starting soon after petal fall to `Fuji'/M.9 apple trees reduced the number of pruning cuts, pruning time, pruning weight per tree, current season's shoot length, individual shoot weights, and increased number of nodes on the lower 40 cm of shoots. Fruit diameter, soluble solids, starch, or individual fruit weights were not affected by Apogee sprays. Fruit color and firmness were slightly increased in only one experiment. Growth suppression appeared to be greater on trees cropping more heavily. When trees were more heavily thinned, less shoot growth control was achieved. Apogee applied at 250 mg/L in three applications caused a significant increase in fruit set when compared to the control. Alone Vydate, Carbaryl+Oil, or Carbary+Accel+Oil caused fruit thinning, but neither ethephon nor shading 3 days caused significant thinning. Apogee did not influence results of chemical thinners when applied between the first and second Apogee applications. The 10% and the 27.5% Apogee formulations gave similar shoot growth inhibition when applied with Regulaid or Oil+Silwet L-77. When using hard water (well water), the 27.5% Apogee formulation was not as effective as the 10% formulation. The 10% Apogee formulation has more NH4SO4 than the 27.5% formulation w/w; NH4SO4 is used to prevent inactivation of Apogee by calcium and other cations when hard water is used for spraying. The addition of CaCl (frequently used to reduce bitter pit and corkspot disorders) to the 27.5% Apogee formulation caused poorer growth control than with hard water alone. When Apogee was used at 125 mg/L, the addition of NH4SO4 restored the effectiveness of the hard water+CaCl mixture. Alone the additives NH4SO4, Ca Cl, Regulaid, and/or Oil plus L-77, had no effect on tree growth. Apogee plus L-77+Oil provided additional growth suppression when compared to Apogee+Regulaid. In 1998, three applications of Apogee (63 mg/L) or ethephon (135 mg/L) did not affected shoot growth of `Fuji'/M.9 trees at these low rates. Combinations of Apogee and ethephon gave good control of tree growth. Flowering and fruit set were not promoted by any of these applications.
Effectiveness of pollination/fertilization inhibitors for flower thinning depends highly on the precise timing of sprays within 24 to 36 h after flower opening. In 1999, cool weather delayed the application of hormone-type thinners, which were intended for at bloom comparison with pollination/fertilization. Pollination inhibitors applied in bloom and hormone thinners applied at petal fall or 8 mm fruit diameter caused good fruit thinning. Ethephon applied in bloom did not cause thinning of `Empire' fruit, but Sevin + Accel + Oil caused good fruit thinning when applied in bloom. Sevin + Accel + Oil increase fruit diameter and did not affect fruit russet. Ethephon applied at 22 mm fruit diameter at water rates of 935 L/ha or 3741 L/ha and chemical rates of 21.5 L/ha or 42.9 L/ha did not cause significant fruit thinning. In 1998, pollination inhibitors and hormone-type growth regulators caused flower and fruit thinning of `Starkrimson'/MM111/106 trees. Good thinning occurred with both pollination inhibitors and ethephon treatments; but Sevin + Accel + oil was not as effective. Thinex caused the most side russet. Treatments that thinned generally caused increased fruit diameter. In 1999, return bloom was promoted by early thinning, but ethephon did not appear to promote return bloom beyond the thinning effect. In 1998, endothall caused good thinning of `York'/MM.111 with a minimum of foliage injury. Fruit diameter was increased. Thinning with endothall in 1998 greatly increased return bloom in 1999, but trees were slightly over thinned. Fruit injury caused by carbaryl was almost non-existant in 1999 in two tests having over 25 carbaryl treatments that compared different formulations and adjuvants for thinning and injury. Some very slight, non-significant injury, may have occurred with three of nine formulations tested when trees were shaded. Shading trees for 1 day in conjunction with carbaryl sprays also did not promote injury. In a previous year, shading trees promoted carbaryl injury. A tank mix of Oil with either 50WP, 80WP, XLR, or 4L formulations caused 3 to 8% of the fruit to show injury at a very low intensity. However, in an adjoining block, Sevin + Accel + Regulaid caused injury to >50% of the fruit when applied the same day as the other experiments. Further investigations on this problem are in progress.