Challenges of Organic ArableFarming3rd module: Monitoring, preventive and curativemeasures for pest and disease management
Module description andobjectives Increasing the resilience of a cropping system is a major goal for organicfarming in order to maintain productivity and crop health. In order to designorganic production systems that are more resilient to disease and pest attacks, itis essential to provide a range of component strategies and combine differentapproaches, including new plant protection products, decision support systemsand cropping systems adapted to specific crops and conditions. The objective of the module is to deliver a set of measures to be applied byorganic farmers in order to efficiently manage diseases and pests, with anemphasis on system resilience and prevention. Special attention will be givento the replacement of copper compounds. Tools provided will offer somealternative methods in disease and pest control.
Module outlineIntroduction1 – The concept of plant health in organic agriculture2 – Resilience of cropping systems3 – Disease control3.1 Preventive measures3.2 Cultural measures3.3 Plant protection products3.4 Challenges of the replacement of coppercompounds4 – Pest management4.1 Crop habitat management for pest control4.2 Cultural pest management4.3 Insecticides5 – Practical examples of pest and disease managementFuture prospects in disease and pest control in organic arable farming
IntroductionIn organic agriculture, all preventive measures to support plant health andproductivity should be exploited first, before implementation of direct controlmeasures. Since the occurrence of diseases depends on many factors (e.g.cultivar susceptibility, pedoclimatic or general weather conditions, etc.), therisk and virulence of diseases may vary in different environmental conditionsand cropping systems.Organic farmers face the same potentially severe pest problems as theircolleagues in integrated pest management (IPM) and conventional cropfarming. However, approaches to manage insect pests are different. In organiccropping systems farmers are supposed to apply preventive measures to keeppests abundance under damaging levels, thus minimizing the need for directand curative pest control.Here is very important to take into account regional and cultural differences aswell as the economic realities and the local regulatory framework.
1. The concept of plant healthin organic agricultureThe figure above illustrates the importance of the holistic approach in organicfarming. We should take in consideration that not every farm can implement the entireknow-how of disease and pest prevention. Sometimes, lowering a risk may enhancethe risk for another disease and pest to arise. Eventually, certain weather conditions,the development of resistance, and other factors may lead to disease and pestoutbreaks even when all possible preventive measures have been taken into account.
2. Resilience of croppingsystemsIncreasing the resilience of a cropping system involves the increase in theecosystem diversity through the establishment of non-crop habitats andbiotope networks.Secondly, farmers can reduce damages by rotating crops, increasing cropdiversity, planting at the right time, harvesting, transplanting, weedmanagement, choice of resistant varieties, and by avoiding growing areaswith high pest and diseases pressure.The combination of all these measures creates a broad and solid basis forhealthy plant development, while direct control measures can be applied incase of threatening pest and diseases outbreaks.
3. Disease control3.1 Preventive measuresPrevention is a key strategy for organic producers, since diseases can rapidlyspread and their control can be difficult if farmers only resort to organicpesticides.For several crops and diseases, the risk of infections by plant pathogenscan be lowered by the use of less pathogen-susceptible, tolerant andresistant varieties. However, resistant varieties are not available for alldiseases.Local participative breeding programs for cultivars for niche markets arevery interesting (Lammerts van Bueren et al., 2015).Seeds infested with pathogens are a major source of disease outbreaks inmany arable crops. This can be avoided by the use of certified seeds. Whenseeds are produced on farm, they should be inspected and, if infested, theyneed to be treated by appropriate methods such as heat or PPPs suitable fororganic farming.
3.2 Cultural measuresThe implementation of optimal crop rotations is another important measure toreduce the risk of disease build-up. In cases of pathogens that can survive forseveral years in the soil, rotation breaks of several years for the same crop arenecessary. For example, to avoid infection with Sclerotinia sclerotiorum insoybean or other legumes, cultivation breaks of at least 4 years should beperformed for these crops and other host plants of the pathogen, such assunflower and rape seed.Tillage, such as deep ploughing after harvest, is a general measure to reduceinoculum for the next season, e.g. for infection structures of S. sclerotiorum orfor pathogens causing seedling diseases in sugar beet. However, tillage choicewill be influenced by soil type and trade-offs with soil organic matter storage,greenhouse gas emissions and weed management. We should also keep in mindthat deep ploughing is in conflict with soil conservation and such aspects needto be considered as well.
3.3 Plant protectionproducts (PPPs)The use of PPPs authorized under organic farming is often the only way torestrict the spread of causal agents of diseases, thus helping maintainproductivity. The number of PPPs allowed in organic farming is small withrespect to the overall number of PPPs on the market.All PPPs sold and used in the European Union have to be registered (Regulation(EC) 1107/2009). Products registered for organic farming need additionalapproval (Regulation (EC) 834/2007).For many diseases, direct measures are not available. Hence, there is a strongneed for the development of new alternative compounds.We need to considered that the development of a compound, its registration andfinal market introduction generally takes much more than 10 years. This needs tobe considered by farmers, when planning strategies for disease and pest controland by decision-makers when discussing future policies.
3.4 Challenges of the replacementof copper compoundsCopper-based products are among the most used PPPs to control downy mildewsand many other diseases. To date, cupric fungicides or bactericides are still ofhigh importance in organic (and integrated) production systems.The European Union policies aim at the promotion of sustainable, quality-basedagricultural production and at limiting environmental risks especially regardingsoil contamination. Since copper can accumulate in soils (AGES, 2011) and haveadverse effects on the environment (Kula et al., 2002), there is an urgent need toreduce the dependency of organic (and low input) farming systems on copperuse.Currently, for organic farming, copper is registered in the EU until 2018.
3.4 Challenges of the replacementof copper compoundsThe maximum amount of copper allowed by the EC for use in arable crops (e.g.potatoes) is 6 kg/ha per year. On a national basis, countries and organic farmers’associations have restricted themselves to lower amounts of copper, such as e.g.a maximum of 4 kg/ha per year in Switzerland or 3 kg/ha per year in Germany.Some countries, such as the Netherlands, or organic associations like Demeterdo not allow the use of copper-based PPPs at all.Copper-reduced or copper-free production systems may be achieved by: Reducing the dependency of agricultural systems on PPP use by increasingthe intrinsic tolerance of the production system (e.g. use of diseaseresistant/tolerant cultivars and/or reduction of disease pressure); Providing decision support systems - DSS, (e.g. Öko-SIMPHYT or BioPhytoPRE) that facilitate optimal application of PPPs; Providing alternative compounds with a similar range of activity as copper.
3.4 Challenges of the replacementof copper compoundsWith respect to research on copper reduction/replacement, several internationaland national research projects were carried out or are in progress: Blight-MOP12 Repco13 CO-FREE14In organic arable crops, copper-based PPPs play a major role in the control of P.infestans on potato. Swiss organic farmers apply on average only 2.5 kg copperper hectare and year in potatoes, although the maximum permitted quantities are4 kg (Speiser et al. 2015). Their strategy for minimizing copper applicationsinvolves resistant cultivars, adaptations in crop management, optimized copperapplications and the use of alternative products.Here you will find how to reduce use of copper onpotato.
4. Pests managementIn arable farming, yield limitations are mainly due to diseases, insufficientnitrogen supply or weeds. Severe, unsolved pest problems only occur in oilseedrape (pollen beetle Meligethes aeneus, stem weevil Ceutorhynchus ssp., fleabeetle Psylliodes chrysocephalus) and in potato production (wireworms,mainly Agriotes spp. but also others from the family Elateridae). In all otherarable crops, insect pests rarely lead to severe yield losses.Interactions between cultural practices, biotic and abiotic factors have a hugeimpact on plant health: the use of direct control methods can have side effectson beneficial arthropods, thus adversely affecting ecosystem services neededfor pest prevention. The use of non-selective bio-pesticides should therefore belimited as much as possible.
4.1 Crop habitat managementfor pest controlA vast variety of measures and strategies are used for habitat management atfield level (Malézieux et al. 2009, Parolin et al. 2012):Intercropping and mixed cropping stand for the simultaneous growing ofdifferent harvested crop species in one field.Under-sowing crops, often clover, are sown with or after the main crop and arenot harvested; their most intensive growth occurs before covering the main cropor after harvesting it.Companion plants are non-crop plants grown within the fields for differentpurposes:1) Attraction and support of natural enemies by providing pollen and nectar(insectary plants)2) Repellence and/or interception insect pests (repellent plants) and3) Influence on nutrition and/or chemical defense of crop plants (Parolin etal. 2012).
4.1 Crop habitat managementfor pest controlIn cabbage production, inter- and cover cropping are implemented as efficientstrategy for Delia radicum prevention: oviposition of D. radicum issignificantly reduced in cabbage fields intercropped with clover, because nonhost plants interfere with host plant location of this specialist cabbage pest(Finch and Collier 2000, Meyling et al. 2013). If we keep higher weed numbersand diversity around organic farms, a similar effect can be achieved or thefollowing solutions can be used to keep beneficial arthropods in our field:Banker plants, mainly used in greenhouse production, are a mini-rearingsystem for natural enemies (Huang et al. 2011): They supply a non-pest prey(e.g. aphids which infest the banker plant but not the crop plant) andtherefore sustain the natural enemies within the greenhouse.Beetle banks – grass covered earth banks in the middle of the field – areshelter habitats that provide suitable over wintering sites for predatorycarabid and staphylinid beetles or spiders (Jonsson et al. 2008).
4.1 Crop habitat managementfor pest controlCover crops are sown after harvesting the main crop before sowing the newcrop mainly to prevent nitrogen leaching and soil erosion.Flowering strips usually consist of plants attractive for insects sown at fieldmargins and aim at attracting natural enemies by providing food and shelter.Barrier plants are also sown at field margins and aim at interceptingimmigrating pest insects (Parolin et al. 2012).Trap crops or trap plants are of preferred growth stage, cultivar or speciesand attract, divert, intercept, and/or retain targeted insects because they aremore attractive than the main crop (Parolin et al., 2012).
4.2 Cultural pest managementCultural control practices aim at prevention, avoidance or suppression of pestsby creating conditions that are detrimental to the pest or favorable to naturalenemies (Hill, 2014). Optimal and expedient implementation of culturalpractices requires in-depth knowledge of pest biology and careful long-termplanning.Cultural practices for pest control include crop rotation, sanitation, use ofhealthy seed and planting material, choice of adapted/resistant/tolerant cultivars,agronomic measures aiming to improve soil quality and functioning (minimumtillage, animal and green manure, compost) as well as agronomic measuresfavouring healthy plant development (irrigation, optimal nutrition, weedmanagement, row spacing) and adapted timing for planting or harvest in orderto disrupt the crop-pest phenological synchrony.
4.2 Cultural pest managementCrop rotation for pest control is useful against pests which have a narrow hostrange and a limited dispersal ability. For instance, maize rootworm (Diabroticaspp.) is efficiently controlled by a three-year rotation. Crop rotation is also animportant control method for the cabbage pest Contarinia nasturtii, whichoverwinters in the soil of the previous crop and migrates over less than 100 m.In addition, there are indirect effects of crop rotation on pest incidence: legumesin a crop rotation are an important source of nitrogen and nitrogen availabilityinfluences and often increases susceptibility of plants to pest damages.Fertilization can have a significant impact on pest occurrence. Examples fromfew studies follow: in cabbage production, lower densities of flea beetles,aphids, and caterpillars were observed on organically manured plants comparedto chemically fertilized and unfertilized plants (Arancon et al. 2005, Cullineyand Pimentel 1986). Phelan et al. (1995) showed that females of European cornborer preferred plants in conventional soils for oviposition.
4.2 Cultural pest managementPhysical methods of pest control include nets, fences, particle films, or inertdusts (Vincent et al. 2003). Crop netting is used in cabbage production againstC. nasturtii, D. radicum, Lepidoptera or flea beetles Phyllotreta sp. Althoughthis method is highly efficient, it has the disadvantage of excluding naturalenemies from the crop.In oilseed rape production, the good efficacy of inert dusts (i.e. clinoptilolithe)against pollen beetles was shown to increase yield by 23% (Daniel et al.,2013). Kaolin particle film technology has been developed for fruit production(Daniel et al., 2005) but was recently registered for pollen beetle control inSwitzerland (Dorn et al., 2014).Here you will find practical informationabout the use of rock dust against the rapepollen beetle.
4.2 Cultural pest managementDifferent other agronomic measures are used in order to reduce or avoid pestdamage:Certified seed and planting material are a prerequisite for healthy plantdevelopment.Adapted timing for planting or harvest can disrupt the crop-pestphenological synchrony; two examples follow: In areas with high pressure of the Swede midge (C. nasturtii),Broccoli is mainly produced in spring and autumn instead of summer.During summer, cauliflower which is less susceptible to the Swedemidge is produced as substitute. Damage by autumn oilseed rape pests, such as flea beetles (Psylloideschrysocephala) or Athalia rosae, is lowered by early sowing and bycreating conditions favorable for rapid plant development.
4.3 InsecticidesInsecticides for organic farming are of natural origin. For example:Neem can be used against Aleyrodes proletella, but the efficacy is onlysufficient if drop-leg technology for under–leaf application is used.Spinosad is used against different Lepidoptera larvae, thrips, C. nasturtii, and D.radicum.The advantage of most natural products lies in their lack of persistence andbioaccumulation in the environment, because they generally degrade faster insunlight, air and moisture than synthetic products.However, some insecticides used in organic farming (such as spinosad andpyrethrum) can have detrimental side effects on non-target organisms. Hence,all efforts to establish conservation biological control can be annihilated. Inorder to avoid negative impact of direct control measures on ecosystemfunctionality, selective methods for pest control should be preferred and thenecessity of applications should be carefully assessed.
4.3 Insecticides - BiorationalsInsecticides vary in their toxicity to people and to non-target organisms, and intheir potential ecological impact. The term “Biorational” has been recentlyproposed to describe those insecticides that are effective against the target pestbut are less detrimental to natural enemies.At the beginning the term was used to describe only those products derivedfrom natural sources, i.e. plant extracts, insect pathogens, etc. Later on, acommon way to define a biorational insecticide was “any type of insecticideactive against pest populations, but relatively innocuous to non-targetorganisms and, therefore, non-disruptive to biological control”.Here you will find the database that farmers can use by selecting Pest Type,Pest Name, Active Ingredient or Beneficial Organism or Pesticide Trade Nameto obtain a list of appropriate biorationals, their efficacy and possible sideeffects.
5. Example - PotatoSpecific problems for potatoes are Colorado potato beetles (Leptinotarsadecemlineata). Early-maturing varieties and quick emergence help prevent theinfestation by the beetle. Other preventive steps avoid both volunteer seeds toemerge and adjacent fields with potatoes in the last year. In addition,insecticides may be used to prevent economic losses in organic farming. Thecombination of Neem (NeemAzal-T/S) B.t.t. (Novodor FC) achieved goodcontrol of young larvae.Wireworms, the larvae stage of click beetles (Elateridae), are other seriouspotato pest. Different agronomic practices or the use of pheromone traps canreduce the damage of wireworms. Furthermore, between entomopathogenicfungi and the insecticide Spinosad, synergistic effects were observed.Here you will find a video that integrates manyaspects for control of wireworms in organicpotato cultivation.
All Cereals5. Examples - cereals DiseaseSolution Testing own seeds and ifneeded: Treatment with warm or hotwater or dressing withTillecur , Cedomon andCerall Certified seed 4, 5 Resistant varietiesBlotch (Septoria spp. )Take-all (Gaeumannomyces graminis)Powdery mildew (Erisyphe/Blumeria f. spp.)Rust (Puccinia spp.)Ergot (Claviceps purpurea)Here you will find booklet on the risks that mayoccur in the production of small grains, fromsowing to harvest and storage.
5. Examples - legumesLegume cultivation is subject to problems like “clover fatigue”, a generic termfor growth problems in clover. This phenomenon reduces the input of nitrogenfrom the grass-clover leys to the arable crops.The most used practice to tackle this problem is cultivation break to decreaseinfestation levels into the soil.Here you will find simple testing method thatcan be easily adopted by farmers to examinethe soil for legume-fatigue symptoms.
Grain legume crops5. Examples - legumes DiseaseSolutionIn legumes in case of soil fatigue, possiblepathogens are: Crop rotation Verticillium spp. Sclerotinia spp. Fusarium spp. Rhizoctonia spp. Fertilization with compost Cultivation of beneficialplants, e.g. biofumigationwith mustard (Brassicajuncae)Pests examples: Fava beans and peas can be infested by aphids andthrips, which usually remain below the economic threshold. Aphidscan be controlled by neem applications. Severe damage to fava beansand peas can be caused by the pea weevil Sitona sp., especially inspring and early-summer under hot and dry weather conditions. Inorder to limit their damages, intercropping peas with mustard orphacelia is effective.
CabbageCarrots5. Examples – carrots andcabbageDiseaseSolution Carrot leaf blight (Alternaria dauci) Black rot (Xanthomonas campestris) Clubroot (Plasmodiophora brassicae)Crop rotationResistant varietiesCertified seedFungicide: Cu-preparations,Serenade (Bacillus subtilisQST713)Blackrot: Avoidance of other cruciferaenearby Plant density 4 plants/mClubroot: Increase pH above 7 with lime In case of occurrence, cultivationbreak of all cruciferae for at least7 years
Future prospects in diseases and pestmanagement in organic arable farming Currently, organic farming still largely depends on varieties bred byconventional breeders. Nevertheless, further activities with respect tobreeding of varieties especially suitable for organic farming should beintensified. As pest and disease problems do not end at farm gates, a closer collaborationbetween neighbouring farmers could tackle pest problems at regional scaleand might increase the impact of conservation biological control and culturalmeasures. Regional control measures, especially for highly mobile pests, willplay a bigger role in future pest control. In order to fully exploit the benefits of functional agro-biodiversity, the use ofnon-selective insecticides that are also used in organic agriculture has to bereduced. This can only be achieved if tolerant and resistant cultivars areplanted.
Additional toolsHere some additional tools that concern this module, available in otherlanguages: Manual for potato management / German Agrometeo: decision support tool for pest prognosis and risk assessment /German / French / Italian Atlas of agricultural entomology - a knowledge base of pest insects / Italian Description of biological control agents and agro-environmental measuresfor plant protection / Polish ECOPHYTOPIC – The portal for integrated crop protection of arable crops/ French
References and futurereadingsAGES (2011). Forschungsprojekt Nr. 100537; 2. Zwischenbericht, 21. Dezember 2011; Kupfer alsPflanzenschutzmittel – Strategie für einen nachhaltigen und umweltschonenden Einsatz; 35-36.Arancon N.Q., Galvis P.A. and Edwards C.A. (2005). Suppression of insect pest populations anddamage to plants by vermicomposts. Bioresource Technology, 96, 1137-1142.Culliney T. W. and Pimentel D. (1986). Ecological effects of organic agricultural practices on insectpopulations. Agriculture, Ecosystems & Environment, 15, 253-266.Daniel C., Dierauer H. and Clerc M. (2013). The potential of silicate rock dust to control pollenbeetles (Meligethes spp.). IOBC wprs Bulletin, 96, 47-55.Daniel C., Pfamatter W., Kehrli P. and Wyss E. (2005). Processed kaolin as an alternative insecticideagainst the European pear sucker, Cacopsylla pyri (L.). Journal of Applied Entomology, 129,363-367.Dorn B., Jossi W., Humphrys C. and Hiltbrunner J. (2014). Screening of natural products in thelaboratory and the field for control of pollen beetles. Journal of Applied Entomology, 138, 109119.Finch S. and Collier R. H. (2000). Host-plant selection by insects – a theory based on‘appropriate/inappropriate landings’ by pest insects of cruciferous plants. Entomologiaexperimentalis et applicata, 96, 91-102.
References and futurereadingsHill S.B. (2014). Considerations for enabeling the ecological redesign of organic and conventionalagriculture: A social ecology and psychological perspective. In: Organic farming, prototypefor sustainable agricultures, S. Bellon and S. Penvern, Eds, Springer, Dordrecht (NL), pp. 401422.Huang N., Enkegaard A., Osborne L.S., Ramakers P.M., Messelink G.J., Pijnakker J. and MurphyG. (2011). The banker plant method in biological control. Critical Reviews in Plant Sciences,30, 259-278.Jonsson M., Wratten S.D., Landus D.A. and Gurr G.M. (2008). Recent advances in conservationbiological control of arthropods by arthropods. Biological Control, 45, 172-175.Lammerts Van Bueren E.T., Struik P. C. and Jacobsen E. (2002). Ecological concepts in organicfarming and their consequences for an organic crop ideotype. NJAS - Wageningen Journal ofLife Sciences, 50, 1-26.Lammerts van Bueren, E.T., Jones, S.S., Tamm, L., Murphy, K.M., Myers, J.R., Leifert, C. andMessmer, M.M. (2011). The need to breed crop varieties suitable for organic farming, usingwheat, tomato and broccoli as examples: A review. NJAS-Wageningen Journal of LifeSciences 58(3-4): 193-205.Malézieux E., Crozat Y., Dupraz C., Laurans M., Makowski D., Ozier-Lafontaine H., Rapidel B.,de Tourdonnet S. and Valantin-Morison M. (2009). Mixing plant species in cropping systems:concepts, tools and models: A review. In: Sustainable Agriculture, E. Lichtfouse, M.Navarrete, P. Debaeke, V. Souchère and C. Alberola, Eds, Springer, Dordrecht, pp. 329-353.
References and futurereadingsMeyling N.V., Navntoft S., Philipsen H., Thorup-Kristensen K. and Eilenberg J. (2013). Naturalregulation of Delia radicum in organic cabbage production. Agriculture Ecosystems &Environment, 164, 183-189.Palmer M.W., Cooper J., Tétard-Jones C., Srednicka-Tober D., Baranski M., Eyre M., Shotton P.,Volakakis N., Cakmak I., Ozturk L., Leifert C., Wilcockson S. and Bilsborrow P.E. (2013).The influence of organic and conventional fertilisation and cropprotection practices, precedingcrop, harvest year and weatherconditions on yield and quality of potato (Solanum tuberosum)in a long-term management trial. European Journal of Agronomy, Vol. 49: 83– 92.Parolin P., Bresch C., Desneux N., Brun R., Bout A., Boll R. and Poncet C. (2012). Secondaryplants used in biological control: A review. International Journal of Pest Management, 58, 91100.Phelan P.L., Mason J.F. and Stinner B.R. (1995). Soil-fertility management and host preference byEuropean corn borer, Ostrinia nubilalis (Hübner), on Zea mays L.: A comparison of organicand conventional chemical farming. Agriculture, Ecosystems & Environment, 56, 1-8.Speiser B., Mieves E. and Tamm L. (2015). Crop-specific copper applications by Swiss organicfarmers. Agrarforschung Schweiz 6(4), 160-165.Vincent C., Hallman G., Panneton B. and Fleurat-Lessard F. (2003). Management of agriculturalinsects with physical control methods. Annual Review of Entomology, 48, 261-281.
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The figure above illustrates the importance of the holistic approach in organic farming. We should take in consideration that not every farm can implement the entire know-how of disease and pest prevention. Sometimes, lowering a risk may enhance the risk for another disease and pest