Designing strategies to control grey mould in strawberry cultivation using decision support systems

Grey mould is one of the major diseases in strawberry cultivation. Fungicides to control Botrytis cinerea are applied frequently during flowering and sometimes at harvest. Reduction of pesticide use is one of the major aims of the Dutch government. Implementation of a Decision Support System (DSS) helps to achieve this goal. Pin point timing of fungicide application can possibly improve the efficacy of the treatment and reduce the number of spray applications. Predicted weather data to forecast infection risks are used by most DSS’s. However in strawberry cultivation irrigation is a daily practice. The effect of overhead irrigation on the Botrytis infection risk is unknown. This is one of the reasons that strawberry growers infrequently use DSS’s. Therefore adaptation of the model to agricultural management is necessary. Under low disease pressure DSS BoWaS controlled Botrytis fruit rot 62% better then routine applications of fungicides, with a 50% reduction of fungicide input. Adding an irrigation or a disease pressure sub-routine did not improve the model under low disease pressure. BoWaS based on disease pressure and weather resulted in better control of grey mould then the weather based BoWaS, under high disease pressure. Adding an irrigation rule did not improve the model further. Using the modified BoWaS reduced fungicide input with 36% compared to routine applications with the same efficacy

Strategies to control late blight in potatoes in Europe

In Europe an aggressive genetically diverse population of potato late blight is present which regularly causes problems in all potato growing regions. It is therefore of the utmost importance that blight is managed in an integrated way by combining a range of measures. Hygiene measures can keep the number of primary sources of inoculum low. In a number of European countries campaigns are ongoing to increase the awareness of growers to reduce the risk of early inoculum sources such as dumps, volunteers and infected seed. The use of varieties with stable resistance for foliar and tuber blight is also a part of an integrated control strategy. In intermediate resistant varieties possibilities are investigated to reduce the input of fungicides. Fungicides still have a key role to play in the integrated control of late blight. In order to optimize the use of fungicides it is important to know the effectiveness and type of activity of the active ingredients to control blight. The use of fungicides should be targeted by using information on infection conditions based on weather data, disease pressure and fungicide characteristics. Decision Support Systems (DSS) can be used to integrate and organize all the available information required for decisions to control late blight

Effect of spore density, cultivar resistance and Phytophthora infestans isolate on tuber blight under field conditions

Survival of P. infestans in soil was limited to 5 weeks at high inoculum density. With a ten fold dilution of the infection pressure survival of P. infestans in soil was limited to two weeks. Differences between isolates concerning survival in the soil were small. From these experiments we conclude that survival of P. infestans in soil depended on spore density rather than P. infestans isolate used. Tuber blight infection rate depends on density of the sporangia in the soil, tuber blight resistance of the cultivar and to a lesser extent the P. infestans isolate used. Isolate of type EU 13 A2 was not more aggressive to tubers than IPO 428-2, regardless of the resistance level of the cultivar used. A mixture of isolates was found to be more aggressive than two single isolates tested on cultivar Bintje only. Thus measures to avoid infection of the soil with P. infestans sporangia lower the tuber blight infection risk, especially on the susceptible cultivar Bintj

Hou valse meeldauw eronder

Onlangs is een aantal uienrassen geïntroduceerd met resistentie tegen valse meeldauw. Maar zolang deze en andere ziekten nog niet zijn uitgebannen, blijven preventie en accurate bestrijding de sleutelwoorden. Het PPO-AGV zet de belangrijkste aantastingen op een rijtje. Valse meeldauw staat met stip op één

Experimental control strategies reducing the fungicide input at a practical scale

Phytophthora infestans is the most devastating disease in potato cultivation. Chemical control is necessary to ensure a healthy crop. At the same time Dutch governmental policy asks for a reduction of the environmental impact of potato late blight control by 75% in 2012 as compared to 1996-1998. The aim of the experiments was to compare Decision Support Systems with different approaches to blight risk management for their ability to reduce the fungicide input without compromising control efficacy. Considerable savings, up to 81% when compared to weekly, full dose rate, spray schedules, can be achieved by using information on cultivar resistance, length of the critical period and disease pressure to decide whether or not to spray. The subroutine calculating the potential for viable transport of spores is only effective on resistant varieties as the threshold was exceeded with every critical period on less resistant cultivars. Implications of the experimental control strategies for agricultural practise are discusse

Monitoring the Dutch Phytophtora infestans population for virulence against new R-genes

New possibilities offered by marker assisted breeding and GMO breeding have sparked renewed international efforts to breed for durable potato late blight resistance. Phytophthora infestans is however known for its adaptability, a trait confirmed by recent discoveries on the structure of the P. infestans genome. One of the possibilities to enhance the durability of newly introduced host resistance is to monitor the pathogen population for virulence to new R genes, prior to - and after their introduction. The late blight control strategy should be adapted accordingly. The Dutch P. infestans population was monitored during the growing seasons 2006 – 2008. P. infestans isolates were collected from blighted production fields and from bait fields in which R gene containing potato clones were grown without fungicide protection. A selection of the P. infestans isolates collected were characterized for virulence to a range of new R genes using a detached leaf bio-assay. Virulence for all single R genes tested was found. When we focus on R genes Rpi-blb1 and Rpi-blb2, no virulence was found in 2006. One Rpi-blb1 virulent isolate was found in 2007. Another 2007 isolate was found to be virulent to Rpi-blb2. Depending on the genetic background in which Rpi-blb1 was placed 13 or 21 isolates were virulent in 2008. Depending on the genetic background in which Rpi-blb2 was placed 4 or 11 isolates were virulent in 2008. One isolate was found to infect the stacked Rpi-blb1 and Rpi-blb2 resistance genes in a detached leaf assay. From these findings it is recommended that monitoring systems should be part of future potato late blight control strategies. The resulting information on the dynamics of virulence within the local P. infestans population can then be used to enhance the durability of newly introduced host resistanc

Interpolation of multidimensional diabatic potential energy matrices

A method for constructing diabatic potential energy matrices by interpolation of ab initio quantum chemistry data is described and tested. This approach is applicable to any number of interacting electronic states, and relies on a formalism and a computational procedure that are more general than those presented previously for the case of two electronic states. The method is tested against an analytic model for three interacting electronic states of NH₃⁺

Literatuuronderzoek naar het optreden van Cylincrocarpon in de teelt van aardbeien : aangevuld met informatie over andere pathogenen betrokken bij het ziektecomplex Zwart wortelrot of “Black root rot”

Onderzoek naar kennis over Cylindrocarpon in de teelt van aardbeien in de wetenschappelijke literatuur. Informatie wordt verzameld over de levenswijze van de schimmel en mogelijke beheersmaatregelen. Naast Cylindrocarpon zijn ook andere schimmels en nematoden betrokken bij het zogenaamde “Zwart wortelrot” (ZWR) of “Black Root Rot” ziektecomplex. Summier is informatie over preventie, beheersing en bestrijding van deze bodempathogenen ook in het rapport opgenomen

Modelling coral calcification accounting for the impacts of coral bleaching and ocean acidification

© Author(s) 2015. Coral reefs are diverse ecosystems that are threatened by rising CO2 levels through increases in sea surface temperature and ocean acidification. Here we present a new unified model that links changes in temperature and carbonate chemistry to coral health. Changes in coral health and population are explicitly modelled by linking rates of growth, recovery and calcification to rates of bleaching and temperature-stress-induced mortality. The model is underpinned by four key principles: the Arrhenius equation, thermal specialisation, correlated up- and down-regulation of traits that are consistent with resource allocation trade-offs, and adaption to local environments. These general relationships allow this model to be constructed from a range of experimental and observational data. The performance of the model is assessed against independent data to demonstrate how it can capture the observed response of corals to stress. We also provide new insights into the factors that determine calcification rates and provide a framework based on well-known biological principles to help understand the observed global distribution of calcification rates. Our results suggest that, despite the implicit complexity of the coral reef environment, a simple model based on temperature, carbonate chemistry and different species can give insights into how corals respond to changes in temperature and ocean acidification