Sustainability of European winter wheat- and maize-based cropping systems: Economic, environmental and social ex-post assessment of conventional and IPM-based systems

In order to ensure higher sustainability of winter wheat and maize production in Europe, cropping systems featuring different levels of Integrated Pest Management (IPM) need to be tested in the field and validated for their sustainability before being adopted by farmers. However, the sustainability evaluation of cropping systems is difficult to perform effectively due to the complex economic, social and environmental dimensions of sustainability. Within the EU research project PURE, nine long-term experiments were conducted in various European regions from 2011 to 2014, comparing two IPM levels against the conventional system (CS) in winter wheat- and maize-based cropping systems. IPM1 encompassed some pesticide use in semi-diverse crop rotations while IPM2 favoured reduced- and non-chemical methods in diverse rotations. The modified DEXiPM (DEXi Pest Management) model for arable cropping systems was used for ex-post assessments to compare the economic, environmental and social sustainability of these systems. The assessments showed that in six out of nine trials the CS was overall unsustainable because of low evaluation of the environmental sustainability that was mainly due to high pesticide use and simplified crop rotations where the choice of crops is primarily market-driven. In contrast, six IPM1 and five IPM2 systems could be classified as sustainable, achieving ‘medium’ or ‘high’ scores for all three sustainability dimensions. Differences in the socio-economic conditions across countries and/or climatic and soil conditions across experimental trials highlighted that IPM is based on general principles that must be adapted to address specific local conditions. Overall, IPM systems included more diverse crop rotations and practices compared to the CS, promoting IPM-based strategies with less pesticide use but also a reduced reliance on pesticides that could partially compensate for any yield reductions by the savings on pesticide and application costs. It is recommended that the results of the study should be disseminated to policy-makers, advisors and farmers and that their implementation should be considered on a regional level. Regional policies to encourage the adoption of more sustainable systems based on IPM principles, as well as better support by more closely involving the regional advisory services for the general implementation of IPM is further recommended. Ex-post analysis with DEXiPM also identified the constraints of the IPM1 and IPM2 systems evaluated as not sustainable. These were related to i) environmental issues for those IPM1 systems that still relied mainly on pesticide use and had less diverse crop rotations, and ii) economic issues for IPM2 systems, mainly due to the choice of less profitable crops in the rotation, as well as to yield penalties caused by the very low pesticide use or replacing pesticides with less effective non-chemical methods. The identification of these constraints is a valuable input to the local and regional discussion on how to adopt IPM and develop more sustainable cropping systems

Summer epidemics of apple scab : The relationship between measurements and their implications for the development of predictive models and threshold levels under different disease control regimes

A 2-year study on epidemic progress of apple scab was conducted at Randwijk, the Netherlands, in 1998 and 1999. The summer epidemic caused by conidia was studied instead of the well-described spring season epidemic originating from ascospores. The aim was to investigate relationships between disease measurements, i.e. disease incidence and severity measures of apple scab, and their implications for the development of predictive models and threshold levels. The study characterized good relationships between the measurements on cultivar Jonagold using regression analyses in three disease control regimes (untreated, organic and integrated). For fruit quality prediction, the relationship between fruit incidence (I (f) ) and leaf incidence (I (l) ) in the organic control regime was given by I (f) = 1.966 + 0.402 x (I (l) ) (R (2) = 0.92). As a result of low level of disease in the integrated control regime, shoot incidence (I (s) ), with higher values than leaf incidence, was better suited for prediction. The relationship was given by I (f) = -0.162 + 0.028 x (I (s) ) (R (2) = 0.91). For the integrated control regime, disease threshold levels were constructed for timing of the final fungicide application. If an apple grower wants to keep fruit infection under 1% incidence (harvest scab threshold), the timing of the final fungicide application (action threshold) should correspond to 4% shoot scab incidence at the beginning of August. The results are compared with similar studies and their biological interpretation is discussed

Effects of integrated control measures on earthworms, leaf litter and Venturia inaequalis infection in two European apple orchards

Two-, three-year studies were conducted to determine the effect of combining chemical (fungicide and urea) and non-chemical (leaf shredding) sanitation treatments on earthworm populations, leaf litter density (LLD), and leaf and fruit infections caused by Venturia inaequalis in Dutch and Hungarian integrated apple orchards from 2000 to 2002 and 2001 to 2003, respectively. The combined sanitation treatment included urea and captan sprays applied to the tree and to the orchard floor and the shredding of fallen leaves in the previous autumn and winter. The earthworm numbers were significantly higher in the sanitation treatment compared to the treatment without sanitation in 2001 and 2002 (P <0.05) at Randwijk (The Netherlands) and in 2002 and 2003 (P <0.05) at Derecske (Hungary). LLD decreased continuously from leaf fall in late autumn to mid-May the following spring at Randwijk, which was explained well by a linear function fitted to the LLD data, with R 2 values ranging from 0.82 to 0.99. Model coefficients for the sanitation plots were significantly different (P <0.05) from those of the non-sanitized plots in 2001 and 2002. At Derecske, LLD started to clearly decrease in both treatments from February 2001 and 2002 and from March 2003 to late spring, and this was explained well by an exponential function fitted to the LLD data, with R 2 values ranging from 0.80 to 0.97. Model coefficients for the sanitation plots were significantly different (P <0.05) from those of the non-sanitized plots only in 2002. In most years and at both sites, the sanitation treatment resulted in significantly lower (P <0.05) scab incidence on spur-leaf clusters compared to the treatment without sanitation. However, the sanitation effect on scab levels on older leaves and fruits was low and varied by year and location. The results are discussed in connection with the environmental conditions in the two countries

Efficacy and phytotoicity of lime sulphur in organic apple production

Curative and preventive efficacy and phytotoxicity of lime sulphur spray schedules, based on a warning system, were evaluated in the Netherlands during two growing seasons under field conditions. In most cases, lime sulphur treatments applied either curatively or preventively resulted in significantly lower scab damage on both the leaves and fruits compared to wettable sulphur treatments. However, all lime sulphur treatments showed high phytotoxicity values, reduced leaf size and had a tendency to a reduced yield quality compared to all other treatments. For curative schedules of lime sulphur on scab control, phytotoxicity and yield did not differ significantly from preventive schedules of lime sulphur. However, the use of a warning system combined with curative schedules of lime sulphur saved one and two lime sulphur sprays in 2000 and 2001, respectively, compared to the preventive treatments of lime sulphur. Our results demonstrated that a curative spray programme with lime sulphur at 0.75-2%, applied 35-45 h after predicted infection periods, can provide effective primary apple scab control, but no benefit in either yield or fruit quality was reached under organic growing conditions. Moreover, research herein clearly showed that organic growers are forced to find a balance between good efficacy and phytotoxic effects of lime sulphur

Overwintering of conidia of Venturia inaequalis and the contribution to early epidemic of apple scab

Overwintering of conidia of Venturia inaequalis associated with shoots and buds was determined, and the contribution to early spring epidemics of apple scab was evaluated during three consecutive seasons (1999 to 2001) in the Netherlands. Examinations of shoot samples collected before bud break showed that the percentage of shoots with superficial black fungal mycelia or conidia was above 65%, and the mean number of conidia on a 1-cm piece of shoot length ranged from 581 to 1,033. However, germination tests showed that the viability of conidia on shoots was less than 1.5%. No macroscopic scab lesions were detected on the scales of dormant buds. However, microscopic examinations of individual bud tissues demonstrated that the number of conidia was >3,000 per 100 buds in each year. The mean viability of conidia associated with buds ranged from 0.7 to 1.9% and from 3.7 to 10.5% for the outer and inner bud tissues, respectively. Results of field assessments at tight-cluster phenological stage showed that the percentage of infection caused by the viable overwintered conidia ranged from 0.3 to 3.8% in the various treatments. Our results indicated that conidia were unlikely to overwinter on the surface of shoots or outer bud tissues, where they were exposed to fluctuating environmental conditions, and, consequently, were unlikely to play a role in initiating an early epidemic of apple scab in the spring. However, our results indicated a risk from overwintered conidia in the inner bud tissues arising from a high level of scab the previous autumn. Therefore, orchards with high levels of apple scab, where ascosporic inoculum is much reduced, e.g., by sanitation, should be protected in early spring by means of fungicide treatment at green tip