- IFP & Organics
- Change Log
Even when pollination conditions and tree vigour are satisfactory, spray thinning apples always involves calculated risks. Inadequate fruit removal is a more common result than excessive thinning. However, some years natural fruit set may be poor and applying a fruit thinning spray may excessively reduce final fruit set and crop load.
Recommended products include naphthalene acetic acid (NAA) (Fruitone L, Fruitone N), 6BA (Cilis or MaxCel) and carbaryl (Sevin XLR) alone or in combination to reduce fruit set of apples.
All fruit management practices, and spray thinning in particular, may require adjustment to work well in your orchard. Keep careful records of your spray thinning results in order to make appropriate adjustments for each block and to ensure improved fruit quality. When possible, leave some trees untreated for comparison purposes.
Reducing initial fruit set by blossom thinning will increase the amount of return bloom the following spring as well as improve fruit size and crop load in the current season. A foliar nutrient spray applied during bloom has proven effective in this regard. Descriptions of the specific effects of the nitrogen and sulphur containing fertilizer, ammonium thiosulphate (ATS) are found under Fruit Tree Nutrition. Note the precautions listed for the use of this chemical.
Apply NAA products from 7 to 12 days after Sevin XLR is effective between 10 and 25 days after full bloom and even later in some seasons. The effective timing for a NAA product and Sevin XLR mixture is between 15 and 20 days after full bloom. Cilis or MaxCel, used alone or in combination with Sevin XLR, should be applied when king fruitlets are 5 to 10 mm in diameter, a period that may extend 7 to 21 days after full bloom.
The extent of fruit development at the time of spraying is an important consideration and in seasons when post-bloom weather is consistently warm and bright these thinners should be applied early in their recommended period. If the weather is cool and fruit development is slow they should be applied later.
When used by itself, Sevin XLR results in good fruit thinning when the largest fruits are 10-15mm in diameter and the outlook is for several days of bright and warm weather. Temperatures should reach 20° C or higher within 5 days of application.
NAA products used alone should be applied when the largest fruit are 8 -10 mm in diameter and air temperatures are at least 10° C. Best uptake of NAA occurs under slow drying conditions (cloudy, humid).
When applying the mixture of an NAA product and Sevin XLR, apply when the conditions are most suitable for Sevin XLR.
Naphthalene acetic acid (NAA) (Fruitone L, Fruittome N) used alone tends to be less effective than Sevin, but when mixed with Sevin XLR will strongly promote fruit thinning. NAA, however, applied somewhat earlier than Sevin XLR or the Sevin XLR plus NAA mixture, may prove adequate and is worthy of consideration, particularly where Sevin-induced mite build-ups have been experienced. NAA can be applied to all varieties but caution is required with Red Delicious. NAA products may over-thin non-spur Red Delicious and spur-type strains may exhibit “pygmy apples”. Use at least 2250 L/ha (900 L/acre) to achieve good wetting and thorough coverage and use a surfactant with a NAA product. See the following table for the suggested rates. This is a general suggestion and growers are encouraged to experiment with NAA products. Apply higher rates on hard-to-thin varieties and lower rates on easy-to-thin varieties.
Carbaryl (Sevin XLR ) is effective on all varieties, including Red Delicious. Sevin XLR is now registered for use as an apple fruit thinner and should be selected over older formulations since it is less hazardous to bees. However, Sevin XLR can harm predatory mites. For that reason, Amid-Thin should be given first consideration for post-bloom thinning of all varieties except Red Delicious. Application of Sevin XLR to Red Delicious trees that have not reached full bearing can result in over thinning. The thinning effect of Sevin XLR and full extent of drop may not be evident for 3-4 weeks after application. Sevin XLR has a relatively low solubility in water. It is very important to apply Sevin XLR in at least 1700 L/ha (680L/acre).
NOTE: Sevin XLR can only be applied for thinning once per season. Re-entry interval 12 h - 14 days depending on orchard contact activity. PHI is 75 days for thinning rate application. Consult the label for mixing and application instructions for hard to thin varieties.
Sevin XLR and Fruitone L or N (NAA) mixtures effectively thin Spartan, McIntosh, Golden Delicious, and Spur Red Delicious apples when applied 15 – 20 days after full bloom. This combination may be questionable for non-spur Red Delicious as it removes more fruit than either chemical applied singly. The suggested rates for each material are listed in the following table. This spray should be applied with at least 2250 L/ha (900 L/acre) of water to achieve good wetting and thorough coverage. To increase or decrease the activity of NAA plus Sevin XLR mixture, increase or decrease the amount of NAA product in the mixture. Do not alter the rate of Sevin XLR.
Cilis or MaxCel and Sevin XLR mixtures for post-bloom thinning and Cilis or MaxCel for mild thinning and fruit size enhancement. Cilis or MaxCel will increase the fruitlet thinning activity of carbaryl on a wide range of apple cultivars. Cilis and MaxCel contain 1.9% 6-benzyladenine (also known as N-(phenyl-methyl)-1H-purine-6-amine, or 6BA), a natural plant hormone that functions as a mild fruit thinner when applied when the king fruits are between 5 and 10 mm in diameter. Unlike Accel, Cilis and MaxCel can be applied at rates higher than 100 ppm, as such significant thinning can be achieved with these products. The addition of carbaryl to Cilis or MaxCel will increase the amount of thinning activity at any rate, reducing the amount of Cilis or MaxCel necessary to achieve adequate thinning results. Cilis or MaxCel applications can begin at Petal Fall or 6 mm, follow up applications may be necessary to achieve the desired thinning results.
For fruit thinning and the promotion of return flowering, apply Cilis or MaxCel by airblast sprayer in combination with Sevin XLR. Applications made when the king fruits are about 10 mm in diameter have given good results. Use sufficient spray volume to achieve complete coverage. Slow drying conditions found in the early morning or late evenings will increase uptake of the active ingredients. Daytime temperatures in the 20° to 27° C range during the week following spraying will optimize the amount of thinning and fruit size achieved with the Cilis or MaxCel plus carbaryl combination.
Unlike Accel, Cilis and MaxCel can be used in spray thinning programs with Fruitone L or N; although, the use of Fruitone L or N on Fuji or Reds should still be avoided to prevent the retention of pygmy fruit.
The use of Cilis or MaxCel alone to achieve some fruitlet thinning and increase fruit size may require two applications. The timing is when the king fruit is about 5 mm in diameter and again 7-10 days later.
While local experience is still being gained, mature bearing trees of all new cultivars will, likely, require thinning to maintain annual production and achieve good fruit quality. The following comments and suggestions are for those growers thinning Gala, Fuji, Jonagold, Ambrosia and Aurora Golden Gala:
Gala apple blooms over a long period and young trees have a tendency to flower on one-year wood. Fruit size of Gala is small to medium. An aggressive thinning program will improve fruit size and ensure an adequate return bloom. Sevin XLR is the most suitable material but trials with Amid-Thin alone or followed by Sevin XLR could be considered. Use the rates listed in the table. Combinations of Sevin XLR and Cilis or MaxCel may also help improve size of Gala. Multiple spray thinning applications may be necessary to achieve adequate thinning.
Ambrosia will need a fairly aggressive thinning program to achieve the desired size ranges. Most growers will apply one or more blossom nutrient sprays followed by post bloom thinners that may include Sevin XLR and Cilis or MaxCel. Some growers have found Ambrosia may be thinned very easily, grower experience in individual blocks will help to prevent crop reductions due to over thinning. Where over thinning has occurred in the past, growers are advised to try a nibble approach, using multiple applications of thinners to achieve the desired level of thinning.
Aurora Golden Gala is another variety that needs aggressive thinning to achieve good fruit size. Several blossom nutrient sprays followed by post bloom thinners such as Sevin XLR and/or Cilis or MaxCel sprays will be necessary. Reports from Ontario indicate that applications of Promalin may assist with thinning and improve the shape of the fruit from young trees.
Jonagold is a triploid cultivar that should be relatively easy to thin. Sevin XLR is suggested on a trial basis. Use the rates listed in the table.
Fuji is often very difficult to thin and growers will need to consider an aggressive thinning program. Bloom thinning sprays followed by several post bloom sprays that could include Sevin, Cilis or MaxCel and Fruitone L or N.
Braeburn and Granny Smith are easy to thin and many growers do not chemical thin these varieties. If thinning is needed, a lower rate of Sevin XLR could be used.
Trees planted strictly for pollination may be thinned more severely and otherwise managed to insure reliable flowering. Since crabapple pollinizers flower mainly on one year wood, pruning shortly after bloom helps to maximize return bloom and can be used to control the size and shape of these trees.
|SPRAY THINNING OF APPLES – HORMONE MATERIALS
per 1000 L
0.5 - 3.22 L
0.2 - 1.3 L
All varieties. Apply 0.5 - 3.22 L/ha for to spindle to super spindle trees. Apply 0.5 - 2.15 L/ha to all other tree density plantings. Do not spray trees which have not reached full bearing. REI: 12 h - 14 days.
Cilis or MaxCel
0.5 - 3.22 L
2.5 to 6.25 L
0.2 - 1.3 L
1 to 2.5 L
2.35 L to 5.88 L
All varieties. See rates above.
All varieties. Apply higher rates for hard to thin varieties.
McIntosh, Spartan, Golden Delicious,
Spur Red Delicious (and hard to thin new varieties)
McIntosh and Spartan apple trees are prone to excessive preharvest fruit drop. This problem can be reduced by applying ReTain (AVG) or naphthalene acetic acid (NAA). Since NAA may result in over mature fruit at harvest time, growers are not encouraged to use this product. The BC Tree Fruits Cooperative will not accept fruit treated with NAA for stop drop. If you plan on using an NAA product, consult your packinghouse field service prior to application.
ReTain contains 15% aminoethoxyvinylglycine (AVG), a biologically derived inhibitor of ethylene production in plants. In tree fruits it delays preharvest drop of all apple varieties prone to this problem, delaying water core development, slowing fruit ripening (e.g., softening, starch degradation) and reducing fruit cracking of Gala and other varieties. Treated apple trees can be harvested later than normal without risk of fruit drop or internal quality deterioration. There are also reports of improved fruit firmness and reduced incidence of storage scald after CA storage.
ReTain is applied four weeks before normal anticipated harvest (i.e., this timing may be as early as 3 weeks before actual harvest). Experience has shown that applications slightly later than 4 weeks before harvest do not significantly affect performance. Note that in some years the development of red colour is delayed after the application of Retain in treated Galas and Spartan blocks.
Each package of ReTain contains 333 grams of material, or 50 grams active ingredient. The label rate for all apple cultivars is 125 g active ingredient (2.5 packages) per hectare (50 g/acre = 1 package/A) applied with enough water to thoroughly wet the fruit and foliage (about 900 L/ha, 80 gallons imp/acre). To achieve good coverage and efficient use of the product, tree row volume principles (see page 11-13) should be used. A properly calibrated and maintained sprayer and the addition of an organosilicone wetting agent, Sylgard 309 at 0.05%-0.1% by volume (500 - 1000 ml/1000 L) are essential ingredients of the application protocol. When high temperature (in excess of 32 degrees C) weather conditions prevail or are anticipated, the 0.05% v/v rate is recommended. Absorption of ReTain is improved by slow drying conditions. Avoid weather conditions where spray drift onto non-target crops could occur. Do not spray if rain is forecast within the next 8 hours.
Since the benefits of ReTain relate to the inhibition of natural ethylene production, it should not be mixed with NAA or ethephon, which increase ethylene production in apple fruits.
These products require uniform coverage and are most effective when applied in a high volume spray not less than 2250 L/ha or 900 L/acre. Uptake of NAA is best under warm, but slow drying conditions.
NAA takes effect about two days after application and will be effective in reducing fruit drop for a period of approximately 10 days.
Treatment with NAA promotes ripening of apples. Therefore, application earlier than one week before anticipated harvest, double spraying or late harvesting may result in soft apples at harvest.
To minimize the adverse effect of NAA and to avoid excessive fruit drop after the effective stop-drop period for NAA has been exceeded, apply NAA products no earlier than 10 days prior to anticipated harvest completion date.
|STOP-DROP APPLICATION FOR APPLES *
Time to Apply
Duration Effectiveness from Time of Application
445 -832 g
4 weeks before the start of the anticipated harvest of the treated fruit
37 to 40 days after application (7-10 days after the beginning of normal harvest of untreated fruit)
OR in exceptional circumstances
NAA 3.1% powder (Fruitone N) or liquid (Fruitone L)
2 days before expected drop, but not earlier than 10 days before anticipated harvest completion date.
10 days from
date of application
See Pesticide Application Equipment.
Red Delicious apples produced in some locations may lack the “typiness” demanded by certain markets.
Perlan and Promalin are mixtures of benzyladenine and two gibberellins; their application can improve fruit shape when applied as king blossoms are opening.
To improve fruit shape, apply Perlan or Promalin at a rate of 1.25 - 2.3 L/ha (500 - 900 mL/acre) in a medium volume spray (2250 L/ha) (900 L/acre) or 125 mL/100 L (567 mL/100 gal imp). Addition of a registered surfactant should prove beneficial.
1. Perlan and Promalin are known to thin apple blossoms. Weak or frost-injured flowers appear to be particularly susceptible. On such trees, Perlan or Promalin usage may also increase the amount of thinning achieved with a subsequent blossom thinning spray.
2. Where spur vigour is low or where the king blossoms have been damaged by frost, the fruit lengthening response to Perlan or Promalin may be negligible.
3. Do not apply Perlan or Promalin if rain is expected within 6 hours.
ReTain is a plant growth regulator that has been shown to extend flower viability in cherries by reducing ethylene production in cherry flowers and delaying flower and stigmatic senescence. Due to this effect, flowers that last longer have a higher likelihood to be successfully pollinated, and increased pollination results in a higher yield. Research has shown that ReTain works best if used before poor pollinating conditions, including wet, cool, windy weather or low honey bee activity, or on varieties that tend to be shy-bearing.
For Sweet Cherry fruit set, use 1 pouch/0.4 ha (1 pouch/ac.). Make a single application of ReTain during bloom. Efficacy requires thorough coverage of the product on the flower buds and flowers. Use appropriate water volume based on tree size. Applications between balloon stage to first bloom are more effective than earlier or later applications. Do not apply after petal fall. Do not apply when fruit are present. ReTain on cherries is not meant to be used as a harvest management aid.
The normal harvest period for sweet cherries can be delayed 5 to 7 days and several aspects of fruit quality can be improved by a single spray of gibberellic acid applied about 3 weeks before normal harvest (the straw-yellow stage of fruit maturity).
This treatment delays red colour development, increases fruit firmness and fruit size, and delays the period of maximum sensitivity to rain splitting. Gibberellic acid-treated fruit is less likely to develop the postharvest disorder known as “cherry pitting”.
There are now four registered products containing gibberellic acid - Activol, Falgro, Florgib 4L, GroSpurt GS-4 and ProGibb 40 SG.
Activol contains 0.92 g of gibberellic acid per tablet. Dissolve 20 tablets in 1000 L water (20 ppm) and apply as a foliar spray 21 days before expected harvest. The fruit is usually in straw-coloured stage. Do not harvest with 21 days of harvest. Research in BC has shown ripening is delayed 4-5 days.
Falgro contains 1g of gibberellic acid in each tablet. To prepare the recommended spray concentration of 20 ppm active ingredient, dissolve 20 Falgro tablets in 1000L of water (9 tablets per 100 gal imp). Add 250 ml of Agral 90 non-ionic surfactant per 1000L (113ml/100gal imp). Apply as a high volume spray (see page 11-15) to full foliage wetness.
Make one application of 20-50 ppm (50-125 mL/100 L) when the fruit is light green to straw coloured in sufficient water to ensure thorough wetting (to point of run-off). PHI - 7 days.
ProGibb contains 40 percent active ingredient or 1 gram of active ingredient (GA) for every 2.5 grams of product. To make a 20 ppm concentration spray mixture, add 50 grams of ProGibb for every 1000 litres of water (22.5 grams per 100 gal imp). Apply as a high volume spray (see page 11-15) to full foliage wetness.
When applying either Falgro, Fruitsize or ProGibb apply at least 2250 L/ha (900 L/acre) of the spray mixture. Harvest the fruit at the desired shade of red skin colour. Falgro and FruitSize have a pre-harvest interval of 21 days; ProGibb has a pre-harvest interval of 28 days.
Peach - Apply 200 ppm (500 mL/100 L) twice per season (full bloom and fruit set) in sufficient water to ensure thorough wetting (to point of run-off).
Prune plum - Apply 40-125 ppm (100-312 mL/100 L) only once 4-5 weeks before expected harvest in sufficient water to ensure thorough wetting (to pint of run off).
Other stone fruit - Apply 40-80 ppm (100-200 mL/100 L) only once 3 weeks before expected harvest in sufficient water to ensure thorough wetting (to point of run-off).
Apple and Pear - Apply 10-50 ppm (25-125 mL/100 L) once only at early fruit set in sufficient water to ensure thorough wetting (to point of run off).
Apogee (27.5% prohexadione calcium) is registered growth control product for apples. Apogee acts within apple trees to inhibit the biosynthesis of gibberellin, which results in reduced vegetative growth. Suppression of growth may last from 2 – 5 weeks following application and does not affect growth in the following year. Apogee may cause the tree to retain more fruit, so more aggressive thinning programs may be required.
Apply Apogee with enough water to thoroughly cover the tree foliage. Apply the first spray at 5 cm growth stage, followed by a second application 14 -21 days later. Refer to the following table for application rates. Consult the label for more detailed information:
|APOGEE APPLICATION - APPLES
Apogee rate per 100L of dilute spray
Apogee rate per hectare
Medium to high vigour (split applications) (fire blight suppression)
Low to medium vigour (split applications)
Low vigour trees (single application)
810 – 1350 grams
To reduce fire blight secondary infections (shoot blight), apply Apogee at 2.5cm to 7.5 cm of shoot growth and apply at intervals of 14 – 21 days up to a maximum of 4 applications per season. Rates are the same as medium to high vigour growth in the table above. Apogee does not prevent blossom infection.
Raynox is a foliar product specifically designed to control sunburn. Raynox must be applied on its own and applications of pesticides, nutrients or ReTain should be made just prior to application or reapplication of Raynox, as the fresh coating of Raynox may interfere with absorption. Raynox dries in about one hour, avoid drift onto vehicles and housing, and wash machinery immediately after applying Raynox. Do not apply Raynox if the temperature will exceed 29°C during application. Apply at a rate of 23 L per hectare in 1000 L of water. or 9.5L /acre in 450L of water. The first application should be applied prior to a sun burning event or at the golf ball fruit size (42 mm) and reapplied every 2 to 4 weeks.
When Surround WP is applied to plants, a white particle-film is formed which is infrared- and UV-light reflective. Plant surfaces treated with Surround WP are cooler under summer heat-load. As a result, Surround WP may reduce sunburn and heat stress on fruit and foliage.
Begin applications of Surround WP soon after crop thinning and before the onset of hot conditions. Make initial applications at the high rate, 4 bags per 1000 L water per hectare (50 kg in 1000 L water, a 5% solution). To ensure thorough and even coverage, make follow-up applications at the lower rate, 2 bags per 1000 L (25 kg in 1000 L water, a 2.5% solution). Surround WP dries to a white haze on plant surfaces. Make low-rate applications to maintain the visible film.
Purshade is a new calcium carbonate (Lime) based spray product. Purshade leaves a protective film after application that reflects Ultra-Violet and Infra-Red radiation, lowering both plant and fruit surface temperatures, which in turn reduces sun induced disorders, such as sunburn. Begin applications once the fruit reach 19 mm, with follow up applications every 2 to 3 weeks. The first application should be made at the high rate, 30 L per hectare (12 L per acre); follow up applications can be made at the lower rate, 20 L per hectare (8 L per acre). Purshade should be applied as a low volume spray, as high spray volumes may cause pooling of the product and reduce efficacy.
Apply 8 - 16 L of Parka in 800 - 1600 L of water per hectare (1% solution). Do not exceed 1600 L/ha per application. For best results, apply Parka in a two- application program with the first application at late straw color. Reapply in 7 – 10 days after the first application. Timing between first and second application may be lengthened depending on occurrence of rain events. Do not apply when the air temperature exceeds 29°C.
Applications of VaporGard form a protective barrier on the surface of the fruit that prevents or reduces the absorption of water into the fruit. Begin applications of VaporGard at pit hardening, 3 - 4 weeks prior to harvest, apply 9.4 L per hectare (3.75 L per acre), and make repeat applications on a 7 - 10 day schedule, as the activity of VaporGard is best within a few days of application. VaporGard must be applied during daylight hours and needs at least one hour of drying time prior to a rainstorm to be effective. VaporGard can be applied right up till harvest, as VaporGard has a zero day pre-harvest interval.
RainGard is a fruit protection product developed at Washington State University. The activity of RainGard is best within a few days of application, as full fruit coverage is necessary for adequate fruit protection, and coverage diminishes as the fruit grows. Begin applications at pit hardening, apply 23 L per hectare (9.5 L per acre), making follow up applications on a 7 day schedule. Raingard should be applied in 475 L per hectare (42 gal imp per acre), if applications of RainGard are made in higher water volumes per area, raise the application rate to maintain a 5% solution or 5 L per 100 L (23 L per 100 gal imp). Do not apply Raingard to fruit with visible residues (ie from certain nutrients, Wettable Powders, etc). Applications of other spray products should be made either prior to the application of RainGard or at least 4 days after the application of RainGard.
|Anti-transpirant, split protection. Retards normal moisture loss without interfering with plant growth or normal respiration
|Split protection. Binds with the lipid layer of the cherry skin
|3-4 weeks before harvest. Apply Vapor Gard at least one hour, during daylight, before rain – sunlight is need for the protective film to set. Re-apply every 7-10 days for maximum protection. 0 PHI.
|Begin application as 4 weeks PHI or straw; re- apply every 7-10 days for a total of 3 applications. Effective when dry.
|Apply at late straw color. Repeat 7-10 days later (may extend timing depending on rain). Do not apply within 5 days of harvest.
|Apply at 200 u.s. gallons/ acre
|Apply at 100-200 u.s. gallons/acre
|Apply at 100-170 u.s. gallons per acre. Do not exceed 170 u.s. gallons/acre.
|Pinolene (pine resin extract). Water emulsifiable concentrate.
|Fatty acids & vegetable esters.
|Phospholipids, carbohydrates & calcium
|Do NOT spray with pesticides. No surfactant needed.
|Can be tank mixed with pesticides. Do not tank mix with organosilicon surfactant.
|Do NOT add surfactants or stickers. Can be tank mixed with some fungicides. Do NOT tank mix with pinolene based products.
|3.8 L per acre
|0.8 u.s. gallons (3.0 L) for each 100 gallons/ acre. Keep a 0.8 % v/v dilution
|3.8 L or 1 u.s. gallon per acre.
Do not exceed 1% V/V final concentration. The rate could be halved for the second application if there is a concern about MRL.
|It does not expand with the fruits.
|Do not apply to fruit with visible residues. Coverage becomes thinner as cherries are growing.
|Somewhat permeable film. Does impair nutrient uptake. Do not apply when air temperature exceed 290C. Rainfast 24 hours.
Exposure of fruit to sunlight with good pruning practices will always give the best colour development. Other horticultural practices such as over-head irrigation and balanced nutrition can sometimes be helpful in apple colour development (see Fruit Tree Nutrition). Discuss the use of over-head irrigation with an irrigation specialist or horticulturist before applying this practice. Also consult a horticulturist if considering installing reflective ground fabric to aid in colour development.
BLUSH (5.25% prohydrojasmon) is a plant growth regulator for use on red apples to promote fruit colour development. Make 1-2 applications of 100-200 ppm at 7-14 day intervals, 7-28 days prior to anticipated harvest. It works best if climatic conditions allow an extended drying period. Apply in the morning or evening when temperatures are lower and humidity tends to be higher than during the day. Read the product label for more instructions on preparing concentrations (ppm) and application.