Organic fruit production in the Netherlands

Apples and pears are the most important organic fruit crops in the Netherlands. Smaller crops, such as berries and grapes for wine production are up and coming. Around 50% of the total Dutch organic fruit production is exported. To be able to facilitate organic fruit growers, Wageningen UR and the Louis Bolk Institute carry out a variety of research aimed specifically at organic fruit production. Hot topics are the prevention and control of scab and black rot and the development of new varieties. The report contains sector facts, sector aspirations, current affairs and research projects

Singular nonlinear H∞ optimal control problem

The theory of nonlinear H∞ of optimal control for affine nonlinear systems is extended to the more general context of singular H∞ optimal control of nonlinear systems using ideas from the linear H∞ theory. Our approach yields under certain assumptions a necessary and sufficient condition for solvability of the state feedback singular H∞ control problem. The resulting state feedback is then used to construct a dynamic compensator solving the nonlinear output feedback H∞ control problem by applying the certainty equivalence principle

Development of a protocol that allows safe consumption of the hypoallergenic apple cultivar Santana

The apple (Malus ×domestica) cultivar Santana was shown to have a low allergenicity in a previously reported clinical trial. A protocol was developed to validate these results outside a clinical setting and to market the Santana as a hypoallergenic apple for large-scale consumption. This protocol was designed to ensure safe consumption of the Santana by consumers suffering from apple allergy. We tested the protocol in a pilot in 100 supermarket stores and evaluated in an internet-based survey with 295 respondents. Forty-one percent of the consumers with an apple allergy did not have an allergic reaction to the Santana. Only five percent of the allergic consumers that tried the Santana reported a strong allergic reaction. In concordance with this, the majority (78%) of the mild apple allergic consumers appreciated the Santana. The developed protocol is considered suitable for safe consumption of the Santana providing that information about the possibility of having an allergic reaction among consumers with a mild apple allergy is added to the label

Reducing russeting of organically grown Elstar to increase quality

Sales organisations indicated that opportunities for organic apples sales can increase when quality increases, in particular reducing the amount of russeting. The use of copper is probably the most important factor for russeting. Therefore a worst case scheme was compared with a scheme with reduced copper application. Furthermore, there was a particular interest in the effects on russeting of potassium bicarbonate (Armicarb) because this product might be an important element in a copper free fungicide scheme. Application of Armicarb was investigated on wet or dry canopy and effects of two different dosages were studied. All the schemes were compared with a worst case organic fungicide scheme with copper. The experiment was done on two year old Elstar trees because Elstar is the most important organically grown cultivar in the Netherlands. Effects of the schedules on russet and scab control were evaluated. At harvest no effects were found on scab. Between the different schemes with copper no differences were found in amount of russet. Only the highest dosage of Armicarb (10 kg/ha) and the schedules with Armicarb on a wet canopy gave more russet compared with the worst case scheme. Also effects on fruit rot were evaluated

Chemical thinning of 'Conference' pears

The increasing difference in the market value of small and larger sized ‘Conference’ pears (>65 mm) and the high labour costs for hand thinning, makes it interesting for growers to find a cheaper and reliable method for thinning pear trees. In 2007, 2008 and 2009 trials were carried out to test the thinning efficacy of several chemicals. Fruit set was only significantly reduced by a two-fold application of ammonium thiosulphate (ATS) or by a tankmix application of 6-benzyladenine (BA) and 1-naphtalene acetic acid (NAA). Unfortunately, russeting of ‘Conference’ pears was augmented by the treatments with ATS during bloom. Tankmix applications of NAA + BA, applied at an average fruit diameter of 8.8 mm, resulted in a severe overthinning of the trees in 2008. However, the same treatments applied at an average fruit diameter of 14.7 mm had much less of a thinning effect. In 2009 adequate thinning was obtained with lower concentrations of BA+NAA applied at 8-10 mm fruit diameter. Surprisingly, the reduction in fruit set by BA+NAA did not result in a proptional increase in the average fruit weight at harvest. In some treatments average fruit weight was even reduced compared to that of the hand-thinned trees, a size-reducing effect that was attributed to NAA. In conclusion, BA+NAA seems to thin ‘Conference’ pears more strongly than BA alone. However, the addition of NAA to BA has the disadvantage of a diminishing effect on the increment of fruit size, i.e. fruit size increased less than expected on basis of the reduction in crop load. Additional research will be carried out to further optimise the developmental stage, weather conditions, and concentrations at which a BA and NAA must be applied to obtain the desired level of thinning and gain in yield percentage of fruits over 65 mm in diameter

Reducing russeting of organically grown Elstar to increase quality

Sales organisations indicated that opportunities for organic apples sales can increase when quality increases, in particular reducing the amount of russeting. The use of copper is probably the most important factor for russeting. Therefore a worst case scheme was compared with a scheme with reduced copper application. Furthermore, there was a particular interest in the effects on russeting of potassium bicarbonate (Armicarb) because this product might be an important element in a copper free fungicide scheme. Application of Armicarb was investigated on wet or dry canopy and effects of two different dosages were studied. All the schemes were compared with a worst case organic fungicide scheme with copper. The experiment was done on two year old Elstar trees because Elstar is the most important organically grown cultivar in the Netherlands. Effects of the schedules on russet and scab control were evaluated. At harvest no effects were found on scab. Between the different schemes with copper no differences were found in amount of russet. Only the highest dosage of Armicarb (10 kg/ha) and the schedules with Armicarb on a wet canopy gave more russet compared with the worst case scheme. Also effects on fruit rot were evaluated

Verleden boven Water Erfgoed, identiteit en binding in de IJsselmeerpolders

Legene, S. [Promotor]Kolen, J.C.A. [Copromotor

Samenwerking Wageningen UR met Koppert Biological Systems

Wageningen UR werkt in haar onderzoeksprogramma’s samen met het bedrijfsleven. In dit artikel een nadere kennismaking met een van deze partners: Koppert Biological Systems. Koppert Biological Systems ontwikkelt systemen voor natuurlijke bestuiving en biologische/geïntegreerde gewasbescherming voor bedekte en onbedekte teelten