Horticultural Cropping Systems Research Articles

A Systematic Review and Quantitative Synthesis of the Efficacy of Quaternary Ammonium Compounds in Disinfesting Non-fungal Plant Pathogens.

This quantitative review and systematic analysis of the effectiveness of quaternary ammonium compounds (QACs) in disinfesting non-fungal plant pathogens in agricultural and horticultural cropping systems is a complementary follow-up to a previous study that evaluated the efficacy of QACs against fungal plant pathogens. In the present study, a meta-analysis involving 67 studies was conducted to assess the overall efficacy of QACs against plant pathogenic bacteria, oomycetes and viruses, and to identify factors associated with observed differences in product efficacy. Across all studies, QACs resulted in a significant (P < 0.0001) reduction in either disease intensity or propagule viability with a mean Hedges' g (g+) of 1.75, indicating that overall QAC treatments were moderately effective against non-fungal pathogens. Significant differences in product efficacy were observed between organism types (P = 0.0001), with QAC interventions resulting in higher efficacy (P = 0.0002) against oomycetes ( g+ = 4.20) than against viruses ( g+ = 1.42) and bacteria ( g+ = 1.07), which were not different (P = 0.2689) from each other. As a result, bacterium and virus types were combined into a composite set (BacVir). QAC intervention against BacVir resulted in significant differences in efficacy within categorical moderator subgroups for genus (P = 0.0133), target material (P = 0.0001) and QAC product generation (P = 0.0281). QAC intervention against oomycetes resulted in significant differences in efficacy only for genus (P < 0.0001). For the BacVir composite, five random effects (RE) meta-regression models were significant (P = 0.05), where models with dose and time, dose and genus, time and genus, dose and target; and time and target accounted for 62%, 61%, 52%, 83% and 88%, respectively, of the variance in true effect sizes (R2) associated with . For oomycetes, three RE meta-regression models were significant (P = 0.05), where models with dose and time; dose and genus, and time and genus accounted for 64%, 86% and 90 %, respectively, of R2 associated with g+. These results show that while QACs are moderately effective against non-fungal plant pathogens, the observed variability in their efficacy due to dose of active ingredient and contact time of these products can be influenced by organism type, genus within organism type, the target being treated, and the generation of QAC products.

Differential immune responses in new and old fruit fly-parasitoid associations: Implications for their management.

The oriental fruit fly, Bactrocera dorsalis (Hendel), and marula fruit fly, Ceratitis cosyra (Walker), are major fruit-infesting tephritids across sub-Saharan Africa. Biological control of these pests using parasitic wasps has been widely adopted but with varying levels of success. Most studies investigating host-parasitoid models have focused on functional and evolutionary aspects leaving a knowledge gap about the physiological mechanisms underpinning the efficacy of parasitoids as biocontrol agents of tephritids. To better understand these physiological mechanisms, we investigated changes in the cellular immune responses of C. cosyra and B. dorsalis when exposed to the parasitic wasps, Diachasmimorpha longicaudata (Ashmaed) and Psyttalia cosyrae (Wilkinson). We found that B. dorsalis was more resistant to parasitisation, had a higher hemocyte count, and encapsulated more parasitoid eggs compared to C. cosyra, achieving up to 100% encapsulation when exposed to P. cosyrae. Exposing B. dorsalis to either parasitoid species induced the formation of a rare cell type, the giant multinucleated hemocyte, which was not observed in C. cosyra. Furthermore, compared to P. cosyrae-parasitized larvae, those of both host species parasitized by D. longicaudata had lower encapsulation rates, hemocyte counts and spreading abilities and yielded a higher number of parasitoid progeny with the highest parasitoid emergence (72.13%) recorded in C. cosyra. These results demonstrate that cellular immune responses are central to host-parasitoid interaction in tephritid fruit flies and further suggest that D. longicaudata presents greater potential as a biocontrol agent of B. dorsalis and C. cosyra in horticultural cropping systems.

Production and use of homemade dry manure-based tea in fertigation systems in North Africa

AbstractOrganic matter water extract, or so-called ‘tea’, may be used to correct nutrient deficiencies in crops or enhance their defense systems. Such tea mixtures are prepared locally by Mediterranean farmers to offset a multitude of constraints, particularly a scarcity of organic manure or high synthetic input costs. However, the diverse range of tea production and usage practices and farmers' underlying rationales have yet to be thoroughly studied. Yet locally they constitute real alternatives that allow farmers to maintain their income levels while reducing reliance on chemical inputs. The main objective of this study was to gain insight into farmers' rationale and practices regarding the production of homemade dry manure tea (HMT) in North Africa, while also highlighting the benefits perceived by farmers. Nearly 50 interviews with farmers were thus conducted in three irrigated cropping areas in Morocco, Algeria and Tunisia. Our results showed that HMT is widely used in intensified family horticultural cropping systems that usually rely on drip irrigation and chemical fertilization. The analysis of farmers' practices revealed that HMT was generally made from aged manure that was pure or consisted of a mixture of sheep, cow or poultry dung. The production protocol varied in terms of drenching techniques, maceration time, container volume and type, and filtration techniques. Farmers applied the derived tea via the drip irrigation system, regularly or with a limited number of applications. The analysis of farmers' rationales and perceptions regarding HMT clearly highlighted that they felt that these practices played a positive role. HMT was considered to improve vegetative growth, yield and, to a lesser extent, soil properties. These benefits could in turn lead to decreased use of synthetic fertilizers by farmers, while boosting their income. The increased understanding of HMT and the underlying rationales showcased in this study could help scientists better analyze and assess these practices in the future. The findings could also facilitate improvement and wider dissemination of these practices to achieve more sustainable irrigation systems in the intensified irrigated cropping areas that abound in North Africa.

Opportunities to reduce nitrous oxide emissions from horticultural production systems in Canada

Horticultural systems, specifically vegetable production systems, are considered intensive agricultural systems as they are characterized by high nitrogen (N) fertilizer application rate, frequent tillage, and irrigation operations. Accordingly, horticultural production in temperate climates is prone to N losses — mainly during post-harvest (during fall and winter) or pre-plant (spring) periods — such as N2O emissions and nitrate leaching. The risk for N losses is linked to low crop N use efficiency (NUE) combined with a narrow C:N and high N content of crop residues. Here we reviewed the studies conducted in Canada and similar climates to better understand the risk of N2O emission and potential agronomic management strategies to reduce N2O emissions from horticultural systems. Current knowledge on N2O emissions from horticultural systems indicate that increasing crop NUE, modifying the amount, type, time, and rate of N fertilizer inputs, and adopting cover crops in crop rotations are some of the effective approaches to decrease N2O emissions. However, there is uncertainty related to the efficiency of the existing N2O mitigation strategies due to the complex interactions between the factors (soil characteristics, type of plant species, climatic conditions, and soil microbial activity) responsible for N2O production from soil. Little research on N2O emissions from Canadian horticultural systems limits our ability to understand and manage the soil N2O production processes to mitigate the risk of N2O emissions. Thus, continuing to expand this line of research will help to advance the sustainability of Canadian horticultural cropping systems.

Municipal organic waste compost replaces mineral fertilization in the horticultural cropping systems, reducing the pollution risk

Municipal waste compost was evaluated under open field conditions for replacing synthetic fertilizers in a vegetable three-year succession. Three compost rates, 45 t ha–1, 30 t ha–1 and 15 t ha–1 (dry matter), and compost at 15 t ha–1 combined with 25%, and 50% of the full synthetic nitrogen rate, were compared to full and none synthetic nitrogen fertilizations. Crop succession was: tomato followed by endive in the first year; eggplant and, then, broccoli in the second year; tomato and, then, endive/broccoli, in the third year. The application of compost at a dose of at least 30 t ha–1 or at 15 t ha–1 with the addition of 25% of the full synthetic nitrogen rate, in Spring-Summer cycle, sustained growth and yield at levels comparable with those of synthetic nitrogen fertilization. However, only a very poor residual effect of the compost soil treatment on the yield of Autumn-Winter crops, was observed. Monitoring of nitrate content into the soil during cropping seasons, a reduction of the risk of groundwater pollution was displayed due to nitrates released by compost, respect to synthetic nitrogen fertilizer. The cumulative effects of compost application on soil properties were detected at the end of the field trials, registering changes in chemical parameters analysed, except for phosphorus and boron.&#x0D; Highlights&#x0D; - Municipal solid organic waste compost (MSWC) integrated with N fertilizers can sustain vegetable production. - MSWC (at least 30 t ha–1 d.w.) replaced synthetic fertilizers for tomato and eggplant productions. - N fertilizer integration to the compost residual effect is necessary to sustain endive and broccoli productions. - MSWC (at 15 t ha–1 d.w.) needs 25% of N integration to reduce the gap with plant only fertilized with N fertilizer. - MSWC preserved soil quality and avoided accumulation of undesired metals, such as Cu and Zn.

Semiochemical-mediated host selection byXylosandrusspp. ambrosia beetles (Coleoptera: Curculionidae) attacking horticultural tree crops: a review of basic and applied science

AbstractExotic ambrosia beetles (Curculionidae: Scolytinae) in the tribe Xyleborini include destructive pests of trees growing in horticultural cropping systems. Three species are especially problematic:Xylosandrus compactus(Eichhoff),Xylosandrus crassiusculus(Motschulsky), andXylosandrus germanus(Blandford). Due to similarities in their host tree interactions, this mini-review focuses on these three species with the goal of describing their host-selection behaviour, characterising associated semiochemicals, and assessing how these interactions relate to their management. All three of theseXylosandrusspp. attack a broad range of trees and shrubs. Physiologically stressed trees are preferentially attacked byX. crassiusculusandX. germanus, but the influence of stress on host selection byX. compactusis less clear. Ethanol is emitted from weakened trees in response to a variety of stressors, and it represents an important attractant for all three species. Other host-derived compounds tested are inconsistent or inactive. Verbenone inhibits attraction to ethanol, but the effect is inconsistent and does not prevent attacks. Integrating repellents and attractants into a push–pull management strategy has been ineffective for reducing attacks but could be optimised further. Overall, maintaining host vigour and minimising stress-induced ethanol are keys for managing these insects, particularlyX. crassiusculusandX. germanus.

Importance of drive-row vegetation for soil carbon storage in woody perennial crops: A regional study

Increasing the carbon (C) content of agricultural soils can help mitigate rising atmospheric CO2 concentrations, improve soil health and increase crop yield. Unlike annual cropping systems, soils planted to perennial woody crops, such as vineyards and orchards, are left undisturbed for many years making them particularly amenable to soil C storage. Here, we used a regional sampling campaign of over 80 commercially-managed sites across the Okanagan Valley, in the southern interior of British Columbia, Canada, to examine the spatial distribution of soil C under irrigated perennial woody crops. Using this living lab approach, we collected soils from the crop and drive rows of apple and cherry orchards, and vineyards subjected to a wide range of real-life management regimes (e.g., for weed and pest control, fertilizer application, etc.). Sites were selected with soils belonging to five surficial deposit classes, representing 40% of the mapped agricultural land area. Soil C was spatially heterogeneous across all the sites, with the surface soil (0–15 cm) of drive rows containing more C than the soil in adjacent crop rows. Clear differences emerged among cropping systems, despite the variation in management practices applied by individual growers. Drip-irrigated apple orchards showed the greatest spatial heterogeneity, with C concentrations of 2.9% in the drive row and 1.8% in the crop row, while vineyard and cherry orchard soils showed the least, with differences between crop and drive rows of approximately 0.3%. Higher C concentrations in the drive rows appeared to be the result of recently assimilated/less processed litter and fine root C inputs from the shallow-rooted understory vegetation. This was confirmed using stable isotope analysis: drive row soil C was significantly 13C depleted compared to the crop row soil, to a depth of 30 cm. Overall, cherry orchards contained the most C (70 Mg C ha−1 to a depth of 30 cm), vineyards the least (48 Mg C ha−1), and apple orchards were intermediate (66 Mg C ha−1). A recent land-use survey in 2015 determined that 8501 ha of agricultural land in the Okanagan Valley was planted to apples, cherries or grapes, and that large shifts in crop land area have occurred since the previous survey, conducted in 2006. We estimate that apple orchards currently hold approximately 199 Gg C, vineyards 188 Gg C and cherry orchards 110 Gg C. Marked differences in soil C storage between the cropping systems, despite the fact some were less than 10 years old, suggests that soils in this region are responsive to changes in crop and associated management practices over relatively short time periods. We conclude that the drive rows of vineyards offer the greatest scope for increased soil C storage among woody perennial horticultural cropping systems in the Okanagan Valley but that ‘long-term’ soil carbon storage may not be possible in these soils.

Innovative Soil Management and Micro-Climate Modulation for Saving Water in Peach Orchards

Microclimatic and soil management studies emphasize that roofing above the canopy or soil mulching contributes to reduce water losses from horticultural cropping systems and, at the same time, to increase water use efficiency. The aim of this 2-year on-farm study, carried out on a late ripening peach (cv. California) orchard, was to investigate the combined effect of water supply (full or deficit irrigation, DI), incoming light (hail or shading net), and soil management (tilling or mulching) on: microclimate; fruit growth; yield; irrigation water use productivity (WPI); and soil water stress coefficient (Ks). Shading hail net reduced air temperature (−1°C), wind speed (−57%), solar radiation (−32%), while increased relative air humidity (+9.5%). Compared to the control treatment (hail net coverage, soil tillage, and full irrigation), the innovative management (DI + shading hail net + mulching) reduced seasonal volumes of irrigation water (−25%) and increased both final yield (+36%) and WPI (+53%). Saving water resources without losing yield is an achievable goal by peach orchards growing under the Mediterranean climate if the DI agro-technique is adopted conjointly with shading hail net and soil mulching.

Salinity as eustressor for enhancing quality of vegetables

Abstract Vegetable crops show variable responses to stressful conditions with physiological, biochemical, metabolic and morphological changes that occasionally lead to changes in chemical composition and visual appearance of the final products. Eustressors are various biological, physical or chemical stressful factors that trigger the signaling pathways leading to a higher bioactive compounds content and quality attributes of plant products. Therefore, its application could be a useful tool in modern horticulture towards fulfilling the agro-food industry and consumers’ demands for high quality and functional vegetable products. Salinity is considered an chemical eustressor which has been proved to affect both physical quality and chemical composition of various vegetable commodities. The present review focuses on the application of an eustress in particular salinity as chemical eustressor towards quality improvement of various vegetable crops, with special interest in quality attributes such as physical quality (color, texture, visual appearance and firmness), flavor and nutritional value (aroma, taste), health promoting properties (antioxidants and bioactive compounds). Moreover, the physiological mechanisms behind the responses of plants to salinity and the functions that directly or indirectly affect vegetable quality will be elucidated, while a case study on tomato where salinity eliciting has been extensively applied will be presented in order to highlight the benefits of this technique. Finally, this review concludes with remarks about the efficiency and valorization of this technique in advanced horticultural cropping systems, as well as with prospects and research breakthroughs that have to be considered in order to make production of high added value products feasible.

English

English

New Trends in the Fertigation Management of Irrigated Vegetable Crops

The use of fertigation, coupled with micro-irrigation, has continued to increase since it was first introduced in horticultural cropping systems. This combination provides a technical solution whereby nutrients and water can be supplied to the crop with high precision in terms of time and space, thereby allowing high nutrient use efficiency. However, the correct estimation of crop nutrient and water needs is fundamental to obtaining precise plant nutrition and high nutrient use efficiency in fertigated cropping systems. This paper illustrates the state-of-the-art and new perspectives for optimal nutrient management of vegetable crops cultivated under fertigation regimes. An overall description is reported for the most valuable technologies and techniques based on simulation models, soil testing, plant testing, and related decision support systems that can be adopted for efficient fertigation. However, it should be highlighted that only a few of the above technologies and techniques are practically available and/or easy to use by growers. Therefore, much more attention should be paid in the future to the transfer of research knowledge to farmers and technical advisors.

Organic No-Till Systems in Eastern Canada: A Review

For more than a decade, studies have aimed to adapt the agronomy of organic no-till systems for the environmental conditions of Eastern Canada. Most research on organic no-till practices in Eastern Canada has been conducted in the province of Québec, where 4% of farms are certified organic, and results from these trials have been published in technical reports available in French. The objective of this review was to revisit previous research work on organic farming in Eastern Canada—the majority of which has been published as technical reports in the French language—in order to highlight important findings and to identify information gaps. Cover crop-based rotational no-till systems for organic grain and horticultural cropping systems will be the main focus of this review. Overall, a few trials have demonstrated that organic rotational no-till can be successful and profitable in warmer and more productive regions of Eastern Canada, but its success can vary over years. The variability in the success of organic rotational no-till systems is the reason for the slow adoption of the system by organic farmers. On-going research focuses on breeding early-maturing fall rye, and terminating cover crops and weeds with the use of bioherbicides.

Use of the Nitrogen Index to assess nitrate leaching and water drainage from plastic-mulched horticultural cropping systems of Florida

Water quality in Florida is significantly impacted by nitrate (NO3-N) leaching losses from agriculture in a large part of the state. Horticultural crops are planted across large areas of Florida on coarse sandy soils with low soil water retention and soil organic matter, increasing the potential for NO3-N leaching. Nitrate leaching losses from the root zone of vegetable cropping systems can negatively impact groundwater. New tools such as the Nitrogen Index (N-Index) are able to quickly assess N use efficiency and losses via NO3-N leaching from agricultural systems. Furthermore, the N-Index provides technical information about N losses pathways tied to agricultural management practices with a great level of confidence; this information has been used by researchers, growers and policymakers as a decision support system. However, the current version of the N-Index that has been used for different field crops has not been calibrated to be used in plastic-mulched horticultural cropping systems. The aim of this work was to calibrate and validate the N-Index for plastic-mulched horticultural cropping systems of Florida. This study found that the N-Index tool accurately identified and ranked the risk of N losses in the evaluated horticultural systems. The N-Index was calibrated for Florida's plastic-mulched horticultural cropping systems using a sensitivity analysis. The adjusted N-Index was validated using compiled data of vegetables grown under plastic mulching systems during three consecutive seasons. Results from these studies suggest that the N-Index can be an easy-to-use tool capable of assessing nitrogen management practices for vegetable systems. The tool can be used to guide nutrient managers in the implementation of best nitrogen management practices that could contribute to reduced NO3-N leaching losses from vegetable systems in Florida, contributing to a smaller environmental footprint and conservation of water quality.

Conservation Horticulture in Mango Orchards: Comparative Effects of Conventional and Conservation Management Practices on Soil Properties of an Alfisol under Seasonally Dry Tropical Savanna Climate

&lt;p&gt;Conservation horticulture is a new concept in management of soil health under perennial horticultural cropping systems. Experiments conducted reasonably over a long period on such soil management systems provide valuable information about sustainability of production systems. This paper reports the results of comprehensive investigations on soil chemical, physical, biochemical and biological properties of soils under conventional and conservation horticulture practices over a long period in drylnd mango orchards on Alfisols. Effects of conservation tillage, inter cropping and cover cropping on soil carbon fractions was measured by determination of loss on ignition, organic carbon (OC) and active carbon (AC). Soil biochemical properties were evaluated by measuring glomalin and extracellular enzymatic activities viz., dehydrogenase, urease, phosphomonoestrase and arylsulphatase and measurement of soil microbial biomass carbon (MBC) and carbon mineralization. Biological status was evaluated by estimating bacterial, actinobacterial and fungal populations, earthworms, micro arthropods and centipedes. Soil physical status was assessed by measuring bulk density, soil moisture status and infiltration rates.&lt;/p&gt;&lt;p&gt;Conservation horticultural practices improved the quality of soil, especially near the surface, by lowering the bulk density and enhancing infiltration rate. The soil aggregate formation and water stability have enhanced in plots with conservation practices because of higher production of glomalin compared with vegetable and orchard plots where conventional practices were followed. Relationship between measured infiltration and soil properties showed high average IRs in conservation plots due to high organic matter content, low bulk density values and enhanced exchangeable basic cations. Vegetable plots and conventional mango plots showed complete decline in earthworm and centipede population while plots with conservation practices showed a build-up of their population. Microbial and biochemical properties significantly improved in plots with conservation horticultural practices over orchard plots with conventional practices. Legumes as inter and cover crops were found to be superior in improving soil quality than sweet potato.&lt;/p&gt;

Local landscape heterogeneity affects crop colonization by natural enemies of pests in protected horticultural cropping systems

Conservation biological control of crop pests is considered a promising strategy in protected horticultural cropping systems. In Mediterranean regions, crop colonization by native predatory mirid bugs is frequent but highly heterogeneous among crop production sites. The contribution of landscape heterogeneity to the variability in colonization levels remains little explored, although it is a major driver of the abundance of natural enemies of pests in open field cropping systems. The goal of our study was to assess whether landscape heterogeneity (land-cover diversity, percent cover, and spatial configuration) at a local scale (up to 300m) affects colonization of protected crops by Macrolophus and Dicyphus mirids, and whether these effects are significantly greater or lower than those of crop management practices. In southern France (Roussillon) in 2010 and 2011, we collected data on mirid populations, pest infestation levels, crop management practices, and landscape heterogeneity within 300m buffers. We investigated relationships between natural enemies, farming practices, and landscape metrics using an algorithm for random forests combined with GLM analyses. Tomato crops were colonized the most by Macrolophus mirids in landscapes with fallow, suggesting that these semi-natural habitats contribute to mirid movements between protected crops and the surrounding landscape. In contrast, crop colonization by mirids was reduced by nearby orchard, which reflected either sink effects due to intensive management practices or dilution effects linked to herbaceous resources. Landscape composition and configuration had similar effects on mirid populations. Macrolophus and Dicyphus mirids responded the most to lanscape heterogeneity at different spatial scales (200–300 and 100m scales, respectively), possibly reflecting different dispersal abilities. However, effects of landscape heterogeneity on mirids were lower than those of crop management practices. Our study suggests that maintaining large areas of semi-natural habitats with ruderal vegetation typical of fallow is important to ensure colonization of protected crops by natural enemies of pests. Our findings emphasize that converting farms from conventional to organic production systems and adopting integrated plant management practices remain the most promising strategies to enhance populations of natural enemies in protected horticultural crops in Mediterranean regions.

Development of a lateral flow test to detect metabolic resistance in Bemisia tabaci mediated by CYP6CM1, a cytochrome P450 with broad spectrum catalytic efficiency

Cotton whitefly, Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) is a major sucking pest in many agricultural and horticultural cropping systems globally. The frequent use of insecticides of different mode of action classes resulted in populations resisting treatments used to keep numbers under economic damage thresholds. Recently it was shown that resistance to neonicotinoids such as imidacloprid is linked to the over-expression of CYP6CM1, a cytochrome P450 monooxygenase detoxifying imidacloprid and other neonicotinoid insecticides when recombinantly expressed in insect cells. However over-expression of CYP6CM1 is also known to confer cross-resistance to pymetrozine, an insecticide not belonging to the chemical class of neonicotinoids. In addition we were able to demonstrate by LC-MS/MS analysis the metabolisation of pyriproxyfen by recombinantly expressed CYP6CM1. Based on our results CYP6CM1 is one of the most versatile detoxification enzymes yet identified in a pest of agricultural importance, as it detoxifies a diverse range of chemical classes used to control whiteflies. Therefore we developed a field-diagnostic antibody-based lateral flow assay which detects CYP6CM1 protein at levels providing resistance to neonicotinoids and other insecticides. The ELISA based test kit can be used as a diagnostic tool to support resistance management strategies based on the alternation of different modes of action of insecticides.

GF-120 effects on fruit fly species (Diptera: Tephritidae) in Sahelian agroforestry-based horticultural cropping systems

Introduction. In the water-saving and income-generating agroforestry cropping systems developed and promoted by the ICRISAT in the Sudano-Sahelian zone of West Africa, particularly in Niger, fruits of domesticated Ziziphus mauritiana (apples of the Sahel) are severely damaged by fruit flies(Carpomya incompleta), and chemical pesticide application poses economic, environmental and human health problems. In the Bio-reclamation of Degraded Lands (BDL) system, apple of the Sahel is the main high-value crop, while in the Dryland Eco-Farm (DEF), it is grown alongside watermelon. Sclerocarya birrea (marula plum) is presently being investigated as a dryland tree species for fruit and oil production, either in orchards or such systems as BDL. Materials and methods. To complete preliminary results of earlier studies published elsewhere, we collected and incubated in 2010 ripe fruits of marula plum and water- melon in Sadore, Niger, where the above-mentioned agroforestry systems are developed, and we recorded emerging fruit flies. We also conducted a spot-spraying experiment (using GF-120) in an apple of the Sahel orchard in Niamey in 2010; we recorded undamaged and damaged fruits and incubated the latter. In the same orchard, we set up in 2011 a fruit fly trapping survey targeting the invasive species Bactrocera invadens (Chempac ® traps using methyl eugenol as the attractant). Results and discussion. The results showed that only Ceratitis cosyra emerged from marula plums, and only Dacus spp. from watermelon. The GF-120 spot-spraying experiment showed that C. incompleta was not attracted / intoxicated, contrary to Ceratitis spp. and Dacus spp.; the sprayed trees yielded significantly more mar- ketable fruits than unsprayed ones; only C. incompleta emerged from damaged fruit. Detection trapping revealed for the first time the presence of B. invadens in the Sahelian zone of Niger, including at the time of apple of the Sahel fruit production. Conclusion. This, alongside results of earlier studies, suggests a repellent effect of GF-120 on the monophagous C. incompleta species (Trypetinae), while it is attractive to oligophagous/polyphagous Dacinae fruit flies; some of them (e.g., Dacus spp.) damage watermelon, which is part of the DEF system, and produce fruit at the same time as the jujube tree. The prospects for harnessing these two opposite regulation pathways are discussed. Niger / Ziziphus mauritiana / Citrullus lanatus / pest control / Carpomya incompleta / Bactrocera invadens / Ceratitis / Dacus / control methods / integrated control / attractants / repellents

Interactions of Light Intensity, Insecticide Concentration, and Time on the Efficacy of Systemic Insecticides in Suppressing Populations of the Sweetpotato Whitefly (Hemiptera: Aleyrodidae) and the Citrus Mealybug (Hemiptera: Pseudococcidae)

The impact of light intensity on the uptake and persistence of the systemic neonicotinoid insecticides, imidacloprid and dinotefuran, were evaluated in poinsettia (Euphorbia pulcherrima Willd.) and yellow sage (Lantana camara L.). Insecticide residues were measured in leaves sampled from the treated plants at four time intervals after treatment to determine the relationship between insecticide concentration and efficacy against two insect pests: sweetpotato whitefly, Bemisia tabaci Gennadius, and the citrus mealybug, Planococcus citri Risso. The insecticides were evaluated at their respective label rate and at the comparable label rate of the other insecticide under two different light environments: ambient and shade. The uptake of dinotefuran into yellow sage was more rapid at both treatment rates than both rates of imidacloprid, resulting in higher percent mortality of whitefly nymphs (89.8-100) compared with imidacloprid (14.1-89.2) across all 4 wk. Additionally, plants that received both rates of dinotefuran had fewer whitefly pupae (< 1.0) at week 4 compared with imidacloprid-treated plants (23.7-25.3). The uptake of dinotefuran into poinsettia plants was also more rapid and resulted in quicker and higher percent mortality of whitefly nymphs (89.5-99.6) compared with imidacloprid (14.1-89.2) across all 4 wk. However, despite efficient uptake, the efficacy of both systemic insecticides was less for citrus mealybug where percent mortality values were <50% among all the treatments across the 4 wk. The use of the two systemic insecticides evaluated in regards to pest management in horticultural cropping systems is discussed.

AN ECOLOGICALLY INTENSIVE APPROACH FOR THE DESIGN OF SUSTAINABLE HORTICULTURAL SYSTEMS IN THE TROPICS

Fruit and vegetable growers in the tropics are faced with crop protection issues resulting in food insecurity and low-income in low-input traditional agro-systems. In systems, pesticide-induced adverse impacts on human health and the environment may occur. Setting up an ecologically intensive horticulture by modifying agro-systems to mobilize natural regulation mechanisms taking ecological processes as a source of inspiration, has become a major challenge. This implies a shift from a tactical approach based on preventive and curative chemical treatments (agro-chemistry) to a strategic approach based on preventive and natural methods (agro-ecology) for the regulation of pests/pathogens infestations/infections. Horticultural cropping systems provide ideal frameworks for studying the effects of the planned introduction and management of plant species diversity (PSD), on pest and disease impact. The Cirad Omega3 Project builds on case studies representing a broad range of PSD levels, scales and deployment modalities, according to an a priori typology of pests and diseases based on their life-history traits. Obtained and anticipated outcomes of these studies concern both i) knowledge on ecological pest and disease regulation processes that can be mobilized in horticultural systems, ii) tools and methods for incepting and evaluating innovating pest and disease-resilient cropping systems. We present here the global approach and first results obtained within this framework regarding i) introduction of service plants with sanitizing/ allelopathic effect managed as green manure for reducing tomato bacterial wilt caused by Ralstonia solanacearum, ii) potential of trap crops/barriers for reducing infestation and damage of tomato fruit worms Helicoverpa armigera on okra in Niger and Helicoverpa zea on tomato in Martinique. Results of these case studies on non-specific disease and pests with respectively low and high dispersal ability, provide decision rules which help set up models to predict the impact of PSD deployment modes on the studied bio-aggressors or other pathogens/pests with similar life-history traits. (Resume d'auteur)

ARE AGROECOLOGICAL CROPPING SYSTEMS SUITABLE FOR TROPICAL HORTICULTURAL CROPS?

Nowadays, tropical horticulture is often characterized with a high use of chemicals (pesticides and fertilizers) that may led to both a diffuse and long term pollution of soils and water resources and an acute contamination of fruits and vegetables with pesticide residues. In FWI, this is the case for banana, and to a lesser extent for vegetable and citrus, whose intensive production had local ecological impacts that went beyond social acceptability. Today, new UE and French regulations require the reduction of the use of chemicals to ensure safe production and environment protection, hence enhancing the need for new cropping systems less dependent upon chemicals. Among different alternatives, the design of new horticultural cropping systems based on the concept of ecological intensification that prioritizes ecological processes for the management of horticultural agroecosystems, is a very challenging one. Our approach is both global and integrative, using multicriteria assessment tools. It is focused at the field and farm scales. We propose here a conceptual framework based on the concept of ecological intensification that prioritizes the enhancement of biodiversity and organic status nutrients availability in cropping systems; and illustrate this framework through three case studies in FWI : i) pest control in tomato and banana cropping systems through enhanced plant and insect biodiversity, increased food web complexity and feedback regulations, ii) phosphorus availability in banana potting experiments through earthworms activity , and iii) weed control through cover crops in citrus orchards. Ecological intensification, although at a preliminary stage, is a promising strategy to design sustainable horticultural cropping systems, even in high phytosanitary pressure conditions. (Resume d'auteur)