MaxCel has been authorised in The Netherlands since 2008 for fruit thinning in apple.
Formulation
Originally, MaxCel was formulated as VBC-30001. For the current application, the formulation of MaxCel has been changed slightly. The surfactant is replaced by another surfactant with a better aquatic profile. This new formulation, coded VBC-30127, was tested in comparison with the
authorised formulation VBC-30001 in order to prove comparability in effectiveness and phytotoxicity of both formulations. For apple and pear resp. 12 and 4 bridging studies were conducted with both formulations.
Apple
In apple, a total of 32 GEP efficacy trials have been carried out in the Maritime (24) and North East Climate Zone (8) between 2001 and 2011 with MaxCel. The product being either formulated as VBC-30001 or VBC-30127. The trials in the North East Climate zone (Poland) are used as supportive
trials.The studies covered efficacy and crop safety for different dose rates ranging from 0.375 to 2.0%. All studies were carried out on commercially important apple varieties in EU Central:
‘Braeburn’, ‘Brookfield Gala’, Çox Orange’, ‘Elstar’, ‘Gala’, ‘Gala Must’, ‘Galaxy’, ‘Golden Delicious’,
‘Jonagold’, ‘Jonagored’, ‘Najdared’ and ‘Pinova’. Applications were undertaken at king fruit diameters ranging from 10 mm (BBCH 65-67) to 14 mm (BBCH 72). Assessments were made on fruit set, fruit number per tree, fruit weight, fruit size, yield and return bloom in the year after application.
Bridging studies
In order to prove comparability in effectiveness and phytotoxicity of the authorised formulation (VBC-30001) to the new (adapted) formulation of application (VBC-30127) 12 bridging studies in apple were conducted with both formulations.
These bridging studies were conducted in 2009, 2010 and 2011. In 8 Maritime climate zone trials VBC-30001 was applied at dose rates of 0.5% and 0.75%, and VBC-30127 at dose rates of 0.5%, 0.75%, 1% and 1.5%. In 4 North East climate zone trials, both VBC-30001 and VBC-30127 were applied at dose rates 0.75% and 1.5%.
The trials with dose rates of 1% and 1.5% were used to assess phytotoxicity only.
Effectiveness trials
In 16 effectiveness trials conducted in the Maritime Climate Zone between 2001 and 2008, MaxCel (VBC-30001) was tested at the claimed dose rate range of 0.375-0.75% for its fruit thinning effect in apple. The lowest dose rate of 0.375% was laid out in 13 trials, 0.5% in 15 trials and 0.75% in 16 trials.
The effectiveness of MaxCel was compared to the effectiveness of different reference products based on naphthyl-acetic-acid (NAA). In Poland in 2010, 4 supportive effectiveness trials were laid out with 0.375, 0.5 and 0.75%, in comparison to. a reference product based on naphthyl-acetic-acid (NAA).
Pear
In pear, a total of 10 GEP efficacy studies have been carried out. These studies covered efficacy and crop safety for different dose rates ranging from 0.5 to 2.0%. MaxCel was either formulated as VBC-30001 or VBC-30127. The study conducted in 2004 used VBC-VBC-30001 and tested the 1.0% dose rate only. In 2011, five studies tested VBC-30127 only and applied a dose rate range of 0.5, 0.75, 1.0 or 2.0%. In addition, in 2011 four studies applied VBC-30127 at 0.5, 0.75, 1.0 or 2.0% and VBC-30001 at 0.75% to compare efficacy and crop safety. The high dosage of 2.0% was employed for phytotoxicity assessment only.
One trial had to be cancelled because of a severe Psylla infestation. One trial was performed in Poland and can be used as supportive.
All studies were carried out with the most important pear cultivar ‘Conference’. Applications were undertaken at king fruit diameters ranging from 7 mm (BBCH 69) to 12 mm (BBCH 72). In the majority of the studies (9 of 10) MaxCel was applied at 10 to 12 mm (BBCH 71-72).
As no chemical pear thinner is registered in EU Central, MaxCel was compared in all ten effectiveness studies with an untreated control. The majority of the 2011 studies (7x) used hand thinning after June drop as a reference treatment. The study conducted in 2004 used a reference treatment
containing the active substance ethephon. At this time ethephon was used as a thinner on pome fruit (apples) and to follow EPPO guidelines it was used as a reference treatment in the Belgium study.
The remaining two studies had no reference treatment.
Assessments were made of fruitset, number of fruit removed by hand thinning, mean fruit weight, amount (%) of large fruit and yield (fruit number) at-harvest.
8.1 Efficacy evaluation
In 2 trials in the Maritime Climate Zone, both VBC-30001 and VBC-30127 were included at a dose rate of 0.5%. In addition, in 6 trials in the Maritime Climate Zone and in 4 trials in the North East Climate Zone (Poland), both VBC-30001 and VBC-30127 were included at a dose rate of 0.75%. In all trials both formulations of MaxCel were compared for their effectiveness as a fruit thinning agent in apple. In all trials, for all variables assessed (fruit set, fruit number per tree, yield, mean fruit weight, fruit size, red blush colour and return bloom in the year after application), generally the two
formulations gave comparable efficacy. The type of formulation appeared not to influence efficacy.
Pear
In 3 trials in pear, both VBC-30001 and VBC-30127 were included at a dose rate of 0.75% and compared for their efficacy as a fruit thinning agent. In all three trials, for all variables assessed (fruitset, fruit number at harvest, fruit weight, hand thinning labour and fruit size), generally the two formulations gave comparable efficacy. The type of formulation appeared not to influence efficacy.
Overall conclusion bridging studies
The two formulatons VBC-30001 and VBC-30127 are comparable with regard to effectiveness when applied for fruit thinning in apple and pear. As a result, trial results with both formulations can be used complementary and the trial results with VBC-30001 are still acceptable for this application.
Dose justification Apple
In the trials MaxCel showed to have a significant effect on fruit thinning. The degree of thinning depended strongly on the apple variety used in the trials. On ‘easy to thin’ varieties generally 0.375-0.5% showed the best thinning results (reduction of fruit set, increase in fruit weight and size, increase of return bloom) while application of 0.75 and 1.0% resulted in over thinning. On ‘medium-hard to thin’ varieties a dose rate of 0.75% showed to have the best thinning effect, while lower dose rates showed a minor effect on reduction of fruit set, increase of fruit weight and size and increase in reduction of bloom. In 3 trials, 1.0% MaxCel was laid out. The higher dose rate did not improve fruit thinning compared to the dose rate range of 0.375-0.75%.
Overall, it can be concluded that the claimed dose rate range of 0.375-0.75% MaxCel is required for an optimal effect on fruit thinning in apple. The dose rate to be used depends strongly on the apple variety and the weather circumstances at and shortly after application (minimum temperature of 15
°C until 2-3 days after the application).
Pear
It was concluded that MaxCel thinning treatments up to 2.0% did not result in excessive over thinning. However, the period of cold weather following the applications in the 2011 trials will have had an influence on that. Results showed that the efficacy can be variable and to be safe the 1.0%
dose rate is concluded to be maximum. It should always be possible to fine-tune the fruit setting by (a reduced amount of) hand thinning. When taking into consideration the overall results, a dose rate range from 0.75 to 1.0% is found to be most appropriate to give a clear thinning effect and most of all, a positive influence on the pear size at harvest.
Effectiveness Apple
One application with 0.375-0.75% MaxCel at a fruit diameter of 8-12 mm reduced fruit set (fruit / 100 flower clusters) compared to the untreated control over all years and cultivars on average by 14%
(0.375%), 22% (0.5%) and 32% (0.75%). Accordingly, MaxCel thinned best at a dose rate of 0.75% but showed also good thinning effects at a dose rate of 0.5% in hard or moderate to thin varieties like
‘Elstar’, ‘Gala’ and ‘Golden Delicious’. The lowest dose rate of 0.375% often showed insufficient thinning effects but performed very well in easy to thin varieties like ‘Braeburn’.
The mean fruit weight was correspondingly increased by 7% (0.375%), 12% (0.5%), and 14% (0.75%) and the red blush colour was increased by 6% (0.375%), 7% (0.5%), and 1% (0.75%). Return bloom in the year following the MaxCel applications was clearly improved by 13% (0.375%), 19% (0.5%), and 119% (0.75%).
The reference products based on naphthyl-acetic-acid reduced fruit set (fruit / 100 flower clusters), increased average fruit weight, fruit colour, and return bloom when compared to the untreated control over all years and cultivars on average by 22%, 10%, 7% and 63%, respectively. The thinning effect of the reference products based on naphthyl-acetic-acid was generally comparable to the effect given by 0.5% MaxCel and less than the effect given by 0.75% MaxCel.
MaxCel also improved marketable yield per hectare, generally comparable to or somewhat higher than given by the reference products based on naphthyl-acetic-acid.
Overall, MaxCel showed to be an effective thinner in apple where it significantly improved fruit quality and return bloom. The thinning effect was significant in cultivars that are traditionally hard to thin such as ‘Elstar’ or ‘Gala’. The thinning effects given by MaxCel were generally comparable to or better than those given by the reference products based on naphthylacetic acid. It is therefore justified to apply for the proposed dose rate range of 0.375-0.75%.
Pear
Efficacy of MaxCel has been demonstrated at the proposed dose rates of 0.75-1.0%. The thinning effect in the trials was not very strong. However, the effects on fruit weight and the size of the fruits was obvious. Especially when combined with (less) hand thinning an increment of marketable yield (less poorly flavoured, small-sized fruits) may be expected after treatment with MaxCel.
A dose rate of 0.75% has proven to be effective. However, when combined with hand thinning, a clear dose rate respons is observed in the trials with stronger effects at increased dose rates. It may be desirable under certain circumstances to increase this dose rate to 1.0%, e.g. at inevitable sub-optimal (cold) weather conditions after application, very high fruit setting etc. It is therefore justified to apply for the proposed dose rate range of 0.75-1.0%.
Conclusion
The product complies with the Uniform Principles because, in accordance with article 2.1, it is effective in fruit thinning and sizing in apple and pear, and improved return bloom in apple.
8.2 Harmful effects
8.2.1 Phytotoxicity Apple
Phytotoxicity assessments were made in 20 effectiveness trials and 12 bridging trials in apple conducted in the Maritime (24) and North East Climate Zone (8) between 2001 and 2011. In the trials, MaxCel was either applied once as VBC-30001 or as VBC30127 at the claimed dose rate range of 0.375-0.75% and at dose rates up to 1.0, 1.5 and 2.0%. The 1.0% dose rate was laid out in 2 trials, the double dose rate of 1.5% was laid out in 27 trials and the 2.0% dose rate was laid out in 2 trials.
In all trials, all dose rates of both MaxCel formulations did not cause any phytotoxicity to the crop and fruits and did not have a negative effect on fruit russeting. In addition, the MaxCel dose rates improved fruit quality (weight and size) and return bloom, compared to the untreated control. As a consequence, it can be concluded that MaxCel, when applied according to Good Agricultural Practices and according to the label recommendations, is safe to apple.
Pear
In six of nine studies some slight phytotoxicity symptoms were observed, esp. light discoloured and malformed young leaves. These symptoms disappeared during the season and did not have any negative effect on the final production and the commercial fruit quality.
Fruit russet was assessed in three of nine studies and showed a minor increase in the 2N rate in relation to the untreated control, but according to the reports this russeting was only a superficial bronzing russet which did not affect the external fruit quality and did not have any negative effect on the commercial value of the fruit.
Furthermore, fruit thinning efficacy, yield, fruit quality (weight, size, fruit russet) were evaluated to investigate any potential negative effects at double the intended recommended dose rate. The 2N rate showed a positive effect on fruit quality (weight and size). It can be concluded that MaxCel is safe to pear, in contrary, it has a positive effect on commercial fruit quality.
8.2.2 Yield
The influence of MaxCel on yield has been described in 8.1, Efficacy.
Effects on processing procedure
Two GEP studies, one from the Central Maritime zone (Germany) on the apple cultivars ‘Elstar’,
‘Golden Delicious’ and ‘Jonagold’ and one from the Southern climate zone (France) on the apple cultivars ‘Gala’, ‘Golden Delicious’ and ‘Granny’, were conducted to evaluate unintended effects on taint of processed apples. No significant differences were found in the taste of fresh apples, processed juice or compote for any cultivar treated wth 7.5 L MaxCel/ha (both formulations VBC-30001 and VBC-30127) when compared to an untreated control.
No studies are provided with pear, however because of the early season application timing and non-detectable residue levels at harvest, there is no reason to believe there would be any adverse effects on the juicing or cooking of treated pears.
Therefore, it is concluded that MaxCel, when applied according to Good Agricultural Practices and according to the label recommendations, is expected to have no negative effects on fruit processing procedures in apple and pear.
8.2.3 Effects on succeeding crops or substitution crops
Apple and pear are perennial crops and therefore succeeding crops will only occur infrequently.
However, in the event that the orchard is grubbed it is unlikely that there would have been an application of MaxCel shortly prior to the grubbing as orchards are generally replaced after harvest.
Nevertheless, in the worst case assumption that the orchard would be grubbed shortly after the application of MaxCel it is still unlikely that there would be any effect on the succeeding crop as 6-BA has been shown to have low impact on seedling emergence and vegetative vigour through available standard guideline studies (referred is to MII, Section 6, Point 8.12 and MIII, Section 6, 10.8.1).
Furthermore, it can be shown from soil metabolism and degradation studies that 6-BA degrades rapidly.
8.2.4 Effects on plants or plant products to be used for propagation Not applicable. Apple and pear orchards have fruit production purposes only.
8.2.5 Effects on adjacent crops
There has been no evidence of phytotoxicity to adjacent crops in field trials that have been conducted and presented in this Biological Assessment Dossier. This is further confirmed from a number of years of use of the product in countries where it has been registered for use on apple.
However, non-target plant toxicity studies have also been conducted according to the standard guidelines for vegetative vigour and seedling emergence studies (referred is to MII, Section 6, Point
8.12 and MIII, Section 6, 10.8.1). These studies confirm that under the labelled use conditions there is no unacceptable risk to adjacent crops.
Conclusion
The product complies with the Uniform Principles because it does not, in accordance with article 2.2., induce any unacceptable side effects on plants or plant products, when used and applied in
accordance with the proposed label.
8.3 Resistance
In general plant hormones are considered low risk substances for resistance development. In addition, MaxCel is applied only once per year. Therefore the application of these products poses no risk for resistance development.
Conclusion
The product complies with the Uniform Principles, article 2.1.3 as the level of control on the long term is not influenced by the use of this product because of the possible build up of resistance.
8.4 For vertebrate control agents: impact on target vertebrates Because no vertebrates are controlled, this point is not relevant.