Host selection behavior of Bagrada hilaris (Hemiptera: Pentatomidae) on commercial cruciferous host plants

A series of host-choice tests were conducted under greenhouse conditions to evaluate the host selection behavior of the Bagrada bug, Bagrada hilaris on commercial cruciferous seedlings. In addition, a separate choice test was conducted to investigate the selection behavior of B. hilaris adults for broccoli plants of various growth stages: cotyledon, 1-leaf, 2-leaf, and 4-leaf plant stages. In comparing host selection among the commercial seedlings, observations on host attractiveness, host acceptance and host susceptibility of the cruciferous cultivars to B. hilaris adults were measured by recording numbers of adults per plant, the time at which feeding damage was first observed, and the time plant mortality occurred for each cultivar, respectively. Results showed that significantly more adult B. hilaris were attracted to a commercial radish cultivar than all other hosts, followed by red and green cabbage. Measurements of host acceptance varied among the cruciferous cultivars, however in terms of feeding damage, alyssum, arugula and broccoli appeared to be relatively less acceptable hosts for B. hilaris. Similarly, all host plants were susceptible to B. hilaris feeding damage and plant mortality varied among cultivars. In the broccoli growth-stage trials, experiments were designed in a similar fashion except that the experiment was conducted in plastic cages. A greater number of B. hilaris adults were attracted to 4-leaf-stage broccoli than other growth stages, but feeding damage was observed more quickly on cotyledon-stage plants. The implications of these findings for developing alternative pest management approaches for B. hilaris in commercial cruciferous crops are discussed.     

Spatiotemporal Distribution of Chinavia hilaris (Hemiptera: Pentatomidae) in Peanut-Cotton Farmscapes

The green stink bug, Chinavia hilaris (Say) (Hemiptera: Pentatomidae), is a pest of cotton in the southeastern United States, but little is known concerning its spatiotemporal distribution in agricultural farmscapes. Therefore, spatiotemporal distribution of C. hilaris in farmscapes where cotton fields adjoined peanut was examined weekly. Spatial patterns of C. hilaris counts were analyzed using SADIE (Spatial Analysis by Distance Indices) methodology. Interpolated maps of C. hilaris density were used to visualize abundance and distribution of C. hilaris in crops. For the six peanut-cotton farmscapes studied, the frequency of C. hilaris in cotton (94.8%) was significantly higher than in peanut (5.2%), and nymphs were rarely detected in peanut, indicating that peanut was not a source of C. hilaris into cotton. Significantly, aggregated spatial distributions were detected in cotton. Maps of local clustering indices depicted patches of C. hilaris in cotton, mainly at field edges including the peanut-to-cotton interface. Black cherry (Prunus serotina Ehrh.) and elderberry (Sambucus nigra subsp. canadensis [L.] R. Bolli) grew in habitats adjacent to crops, C. hilaris were captured in pheromone-baited stink bug traps in these habitats, and in most instances, C. hilaris were observed feeding on black cherry and elderberry in these habitats before colonization of cotton. Spatial distribution of C. hilaris in these farmscapes revealed that C. hilaris colonized cotton field edges near these two noncrop hosts. Altogether, these findings suggest that black cherry and elderberry were sources of C. hilaris into cotton. Factors affecting the spatiotemporal dynamics of C. hilaris in peanut-cotton farmscapes are discussed.     

Spatiotemporal Distribution of Chinavia hilaris (Hemiptera: Pentatomidae) in Corn Farmscapes

The green stink bug, Chinavia hilaris (Say) (Hemiptera: Pentatomidae), is a pest of cotton in the southeastern United States but little is known concerning its spatiotemporal distribution in corn cropping systems. Therefore, the spatiotemporal distribution of C. hilaris in farmscapes, when corn was adjacent to cotton, peanut, or both, was examined weekly. The spatial patterns of C. hilaris counts were analyzed using Spatial Analysis by Distance Indices methodology. Interpolated maps of C. hilaris density were used to visualize abundance and distribution of C. hilaris in crops in corn–peanut–cotton farmscapes. This stink bug was detected in six of seven corn–cotton farmscapes, four of six corn–peanut farmscapes, and in both corn–peanut–cotton farmscapes. The frequency of C. hilaris in cotton (89.47%) was significantly higher than in peanut (7.02%) or corn (3.51%). This stink bug fed on noncrop hosts that grew in field borders adjacent to crops. The spatial distribution of C. hilaris in crops and the capture of C. hilaris adults and nymphs in pheromone-baited traps near noncrop hosts indicated that these hosts were sources of this stink bug dispersing into crops, primarily cotton. Significant aggregated spatial distributions were detected in cotton on some dates within corn–peanut–cotton farmscapes. Maps of local clustering indices depicted small patches of C. hilaris in cotton or cotton–sorghum at the peanut–cotton interface. Factors affecting the spatiotemporal dynamics of C. hilaris in corn farmscapes are discussed.     

Incidence of cabbage maggot (Diptera: Anthomyiidae) infestation and plant damage in seeded Brassica fields in California's central coast

The temporal incidence of cabbage maggot, Delia radicum L. was investigated using three exclusion cage experiments, one each during spring, summer and fall, in broccoli fields as well as two surveys, one each in three broccoli fields, and sixteen turnip plantings in central coast of California. In the cage experiments, sets of broccoli plants were exposed to natural populations of D. radicum flies for ∼14-d periods after plant emergence throughout the growing season. For the surveys, soil, root samples, and yellow sticky traps were collected every week from broccoli fields to determine number of eggs, maggots, feeding-injury and adults. Only roots were sampled from turnip plantings to determine feeding-injury. In all three cage experiments, feeding injury from D. radicum maggot was less during the first 14-d than ∼15–28 d after plant emergence (DAE). In the summer and fall, feeding injury by D. radicum was less during 29–42 and 43–56 DAE than it was 15–28 DAE. In the survey of broccoli fields, a greater number of D. radicum eggs were detected starting the fourth week after planting (WAP). Similarly, an increase in number of D. radicum maggots and feeding injury was observed at fifth and sixth WAP, respectively. However, adults were abundant throughout the growing period. In the turnip survey, increase in injury from D. radicum feeding did not appear until the fifth WAP. Overall, these studies indicate that increased incidence of D. radicum was delayed by about two to three weeks after plant emergence. The implications of these results for timing of insecticide application for D. radicum in the central coast of California are discussed.     

Dormant season foliar sprays of broad-spectrum insecticides: An effective component of integrated management for Diaphorina citri (Hemiptera: Psyllidae) in citrus orchards

Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a global pest of citrus and vector of Candidatus Liberibacter, a bacteria that causes huanglongbing or greening, a devastating disease of citrus. Mature citrus trees are dormant in winter and produce most new shoots in spring, followed by sporadic canopy growth in summer and fall. Young shoots are required for oviposition and nymphal development, but adults can survive and overwinter on hardened leaves. Surviving adults reproduce in spring shoots and their progeny are probably responsible for a large portion of disease spread as they disperse to search for food. Therefore, foliar sprays of broad-spectrum insecticides applied to mature trees in winter were evaluated in a commercial citrus orchard as tactic to reduce pest populations and insecticide use in spring and summer when beneficial insects are most active. A single spray of chlorpyrifos (2.8 kg a.i. ha⁻¹) in January 2007 reduced adult psyllids an average of 10-fold over six months compared to untreated trees. The following year, differences with the untreated control averaged 15-fold for over five months following a single spray of chlorpyrifos, fenpropathrin (0.34 kg a.i. ha⁻¹), or oxamyl (1.12 kg a.i. ha⁻¹) applied in January. Spiders, lacewings and ladybeetles were equally abundant during the growing season in both treated and untreated trees both years (P = 0.05). Thus foliar sprays of broad-spectrum insecticides before spring growth suppressed D. citri for five to six months, with no detectible impact on key natural enemies. This tactic has been widely adopted to control the psyllid in Florida, in some cases area-wide. Additional sprays during the growing season should be based on scouting and targeted at adults before anticipated new flush.     

A Hybrid Artificial Intelligence Model for Aeneolamia varia (Hemiptera: Cercopidae) Populations in Sugarcane Crops

Sugarcane spittlebugs are considered important pests in sugarcane crops ranging from the southeastern United States to northern Argentina. To evaluate the effects of climate variables on adult populations of Aeneolamia varia (Fabricius) (Hemiptera: Cercopidae), a 3-yr monitoring study was carried out in sugarcane fields at week-long intervals during the rainy season (May to November 2005–2007). The resulting data were analyzed using the univariate Forest-Genetic method. The best predictive model explained 75.8% variability in physiological damage threshold. It predicted that the main climatic factors influencing the adult population would be, in order of importance, evaporation; evapotranspiration by 0.5; evapotranspiration, cloudiness at 2:00 p.m.; average sunshine and relative humidity at 8:00 a.m. The optimization of the predictive model established that the lower and upper limits of the climatic variables produced a threshold in the population development rate of 184 to 267 adult insects under the agroecological conditions of the study area. These results provide a new perspective on decision-making in the preventive management of A. varia adults in sugarcane crops.     

Evaluation of seed treatment insecticides for management of the rice water weevil,Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), in commercial rice fields in Louisiana

The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most injurious insect pest in US rice production. Yield losses in excess of 25% can occur from severe infestations. Management demonstrations were conducted in the 2008, 2009, 2010, and 2011 growing seasons to evaluate the use of commercially available insecticides to control L. oryzophilus in commercial rice fields. The demonstration tests, conducted on farms throughout Louisiana, compared the efficacies of recently registered seed treatment insecticides to untreated controls and to foliar applications of pyrethroids. Efficacy was assessed by collecting root/soil core samples three to four weeks after application of permanent flood and counting numbers of larvae and pupae in core samples. Tests were replicated across locations in multiple rice-producing Louisiana parishes. Densities of larvae and pupae in core samples exceeded the larval threshold (three larvae or pupae per core sample) in over 80% of untreated plots/cuts, confirming the ubiquity and severity of this insect as a pest of rice. Use of chlorantraniliprole (Dermacor^® X-100, DuPont™ Crop Protection, Wilmington, DE), thiamethoxam (CruiserMaxx^® Rice, Syngenta^® Crop Protection, Greensboro, NC), and clothianidin (NipsIt Inside^®, Valent^® USA Corporation, Walnut Creek, CA) seed treatments significantly reduced L. oryzophilus infestation compared to untreated checks. Fewer larvae and pupae were observed in rice treated with chlorantraniliprole than in rice treated with other insecticides.     

Non-chemical agents provide tenable,eco-friendly alternatives for the management of the major diseases devastating Indian mustard (Brassica juncea) in India

India is a leading producer of oilseed Brassicas, contributing approximately 23 percent of the country's total oilseed production. In India, the Indian mustard [Brassica juncea (L.) Czern. & Coss.] crop is ravaged by various diseases, including Alternaria blight, white rust, downy mildew, Sclerotinia rot and powdery mildew, which can contribute to fluctuations in crop yields. A field experiment examining an integrated disease management system for Indian mustard (B. juncea) was conducted under the All India Coordinated Research Project on Rapeseed-Mustard (Indian Council of Agricultural Research or ICAR) during three crop seasons (2006–09) at 11 locations to assess treatments suitable for the management of crop disease. The data from the different locations and years regarding disease severity and incidence were pooled and analyzed. Seed treatments with freshly prepared Allium sativum bulb aqueous extract (1 percent w/v) resulted in significantly higher initial plant stands, across locations and years. Seed treatment with A. sativum bulb extract, followed by its use as a foliar spray, resulted in significantly reduced Alternaria leaf and pod blight severity, reduced white rust severity, fewer stag heads per plot, reduced downy mildew and Sclerotinia rot incidence, and reduced powdery mildew severity, across locations and years. The combination also provided significantly higher seed yields compared with the control across locations and years and was at par with treatment by chemical fungicides. The combination used in the present study was as effective as the combination of seed treatment with Trichoderma harzianum and foliar spraying with Pseudomonas fluorescens and T. harzianum. Economic returns were higher when using biorational treatments (A. sativum bulb extract, T. harzianum, P. fluorescens) compared with chemical fungicides. The combination of seed treatments with T. harzianum followed by its use as a foliar spray (17.22), and the similar combination of seed treatments and foliar spraying with the A. sativum bulb extract (17.18), resulted in a higher benefit to cost ratio. This eco-friendly technology can help oilseed Brassica growers in India safeguard the crops from major diseases and increase the stability and productivity of the Indian mustard crop.     

Field assessment of novaluron for sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), management in Louisiana sugarcane

On-farm field experiments were conducted in 2004 and 2007 to assess the suitability of novaluron, a chitin synthesis inhibitor, for sugarcane borer, Diatraea saccharalis (F.), management in Louisiana sugarcane (Saccharum spp. hybrids). Aerial insecticide applications reproducing commercial production practices were made when D. saccharalis infestation levels exceeded a recommended action threshold. In addition to decreased D. saccharalis infestations, 6.3 – 14.5-fold reductions in end of season injury, expressed as the percentage of bored sugarcane internodes, were observed in plots treated with novaluron. D. saccharalis control in novaluron plots was equivalent to (P > 0.05) or better (P < 0.05) than that achieved with tebufenozide, an ecdysone agonist that has been extensively used for over a decade on sugarcane. With a numerical trend of a 3.1-fold decrease in percent bored internodes, the pyrethroid gamma-cyhalothrin seemed less effective than the biorational insecticides in protecting sugarcane against D. saccharalis. Using continuous pitfall trap sampling, no measurable (P > 0.05) decreases in predaceous and non-predaceous soil-dwelling non-target arthropods were associated with insecticides. However, numerical trends for decreases in immature crickets associated with novaluron and gamma-cyhalothrin were recorded in 2007. Our data suggest that novaluron will fit well in Louisiana sugarcane integrated pest management.     

Re-evaluation of sugarcane borer (Lepidoptera: Crambidae) bioeconomics in Louisiana

The sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), is the key insect pest of sugarcane, Saccharum spp., grown in Louisiana. For more than 40 years, Louisiana sugarcane farmers have used a value of 10% internodes bored at harvest as the economic injury level (EIL). Three plant-cane studies were conducted to re-evaluate the long-standing sugarcane borer EIL level using the most recently released varieties of sugarcane. Varieties were exposed to artificially enhanced borer infestations; the experimental treatments consisted of borer control with insecticides or no control. Data were collected on infestation intensity, damage intensity, and associated yield losses. Crop yields from plots were obtained by mechanical harvesting, and losses were classified as field losses, e.g. losses of gross tonnage in the field and factory losses, e.g., losses that were realized at the factory as cane is being milled. Farm income is based on the product of these two measures of yield, i.e. cane yield×sugar yield. In our study, seasonal stalk-infestation counts did not reveal any indication of preference by the borer moths for a specific variety; infestation pressure was generally uniform within a season among the varieties that we planted. Significant differences were detected among the varieties for harvest percentage of internodes bored as well as yields between borer-controlled and non-controlled plots (P<0.05). In general, varieties were less susceptible to losses in the field (sugarcane yields) than in the factory (sugar yields). As a group, the most recent varieties released to Louisiana growers exhibit more tolerance to the borer than varieties grown 40 years ago. The percent reduction in sugar/ha loss per 1% internodes bored has decreased from an average of 0.74 for varieties grown in the 1960s to 0.61 as a mean for the newly released varieties. Although the cost associated with an insecticide application for sugarcane borer control has increased nearly 4-fold from 1971 to present, sugar yields have increased by approximately 60% allowing farmers to offset some of these increased costs. Our economic analysis indicates that the EIL of 10% internodes bored is too high, considering the high yielding potential and susceptibility of currently grown varieties. For the most at risk farmer, the tenant farmer, a more appropriate value for the EIL is 6% internodes bored. However, this EIL can be raised 12% if a resistant variety is grown.     

褐飞虱对氟虫腈和新烟碱类药剂的抗性动态变化

于2006-2008年采用稻茎浸渍法监测了我国主要水稻种植区大田褐飞虱种群对苯基吡唑类杀虫剂(氟虫腈)、新烟碱类及昆虫生长调节剂类杀虫剂(噻嗪酮)的抗性动态变化。结果表明,2008年褐飞虱对氟虫腈的抗性水平随其迁飞途径而出现急剧上升态势,其中,从我国南方稻区迁入长江中下游流域等6省10地种群和回迁至广东韶山、深圳两种群对氟虫腈抗性分别上升至中等水平抗性(15.0～32.5倍)和高水平抗性(66.9～73.7倍),明显高于2006年5省6地(2.6～5.8倍)和2007年9省11地(3.2～8.4倍)大田褐飞虱种群的抗性水平。上述结果预示2009年、2010年两年在全国稻区可能暴发褐飞虱对氟虫腈更高水平的抗性。自从2005年10-11月褐飞虱对新烟碱类的吡虫啉产生极高水平抗性(277～811倍)以来,近3年来抗性虽有一定程度下降,但仍处于高水平-极高水平抗性阶段,其中,2008年我国8省13地褐飞虱种群的抗性仍高达210.1～381.7倍。褐飞虱对其他的新烟碱类药剂噻虫嗪、烯啶虫胺和呋虫胺的抗性水平分别为2.0～15.8、0.7～4.8和0.6～2.8倍。褐飞虱对噻嗪酮为敏感到中等水平抗性(3.0～11.9倍)。近几年来大量、广泛使用氟虫腈防治褐飞虱和稻纵卷叶螟两类迁飞性害虫是褐飞虱对其暴发抗性的重要原因。因此,必须及时制定全国范围防治两类迁飞性害虫的交替轮换用药抗性治理对策方案,才能延缓褐飞虱抗性的再次暴发。     

Economic injury levels for Bemisia tabaci (Homoptera: Aleyrodidae) in cotton: impact of crop price, control costs, and efficacy of control

Field studies were conducted during 1993 and 1994 in the Imperial Valley, California and Maricopa, Arizona to examine relationships between densities of Bemisia tabaci (Gennadius) populations and cotton (Gossypium hirsutum L.) yields, and to estimate economic injury levels (EILs) for pest management application. Populations of B. tabaci were manipulated by applying different numbers of insecticide applications in replicated plots. Resulting insect populations and cotton lint yields were used to develop damage functions and to estimate EILs for all life stages in relation to variable cotton prices, insecticide costs, and pest control efficacy. Economic injury levels declined with increasing cotton prices and increased as the cost of control increased, however, these changes were relatively small, based on typical ranges in price and control costs. In contrast, the efficacy of control provided by insecticide applications had a large influence on EILs, with lower efficacies being associated with higher injury levels. We developed a multiple regression model that accounted for the dynamic changes in the EIL in relation to crop price, control costs, control efficacy, and potential yield. Based on average prices and reasonable control costs and efficacy, EILs ranged from 5.9–15.2 adults/leaf, 6.1–19.8 eggs cm⁻², and 1.7–4.7 nymphs cm⁻² of leaf area. Additional research is needed to more closely relate the costs of control to the suppression of insect populations, and to define economic thresholds that will enable pest managers to maintain pest populations below EILs.     

Effectiveness of imidacloprid in combination with a root nitrogen fertilizer applied to tomato seedlings against Bemisia tabaci (Hemiptera: Aleyrodidae)

The whitefly Bemisia tabaci (biotype B) is a worldwide pest of vegetables and field crops. We tested the efficacy of imidacloprid (IM) with a root fertilizer ‘Root Feed (RF)’ (9% N, 7% Ca, 1.5% Mg and 0.1% B) sub-irrigated in the growing medium against the whitefly on tomato. Tomato seedlings (3–4 true leaves) were treated with 0, 3, 6 or 12 mg active ingredient (a.i.) seedling⁻¹ of IM and with RF (0, 0.02, 0.04 or 0.08 ml seedling⁻¹). The efficacy of 12 mg IM seedling⁻¹ was further evaluated in the greenhouse for 60 days. The survival of B. tabaci adults, nymphs, and egg production were negatively affected by the treatments in a dosage-dependent manner. Treatment of 12 mg IM seedling⁻¹ caused >60% adult and nymph mortality 50 days after treatment (DAT). The active ingredient of IM in tomato leaves also increased with the increase of IM dosage. The RF exhibited a limited effect on B. tabaci. However, the mortality of whitefly adults and nymphs treated with RF (0.02 or 0.04 ml seedling⁻¹) positively interacted with IM, and was greater than IM alone. In the greenhouse, 12 mg IM seedling⁻¹ greatly reduced the number of whitefly adults and increased the dry weight of the tomato plants at 30 DAT. In conclusion, application of 12 mg IM seedling⁻¹ on tomato seedlings before transplanting effectively controled B. tabaci for up to 50 days, and the efficacy of IM combined with 0.02 ml RF seedling⁻¹ performed even better. This could be a cost-effective method for managing B. tabaci on tomato and other vegetables.     

Economic implications of herbicide resistance and high labour costs for management of annual barnyardgrass (Echinochloa crus-galli) in Philippine rice farming systems

Implications of increasing labour costs and the development of herbicide resistance for profitable weed management in Philippine rice farming systems are investigated. The study employs RIMPhil (Resistance and Integrated Management in the Philippines), a bioeconomic simulation model developed to provide a comprehensive assessment of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus-galli) in rice crops. Results indicate that herbicide application will become increasingly economically attractive, relative to manual weeding, as labour cost increases. This is important since urban migration in the Philippines continues to increase the scarcity of rural labour. Results also show that the onset of herbicide resistance results in substantial losses in farm profit. It is worthwhile for farmers to take management actions to prevent or delay the onset of herbicide resistance, provided that these changes are effective and not too costly. The study highlights the complexity of decision making about integrated weed management on rice farms in the Philippines.     

Assessing the impact of areawide pheromone trapping,pesticide applications,and eradication of infested date palms for Rhynchophorus ferrugineus (Coleoptera: Curculionidae) management in Al Ghowaybah,Saudi Arabia

The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is a highly destructive pest of date palms, Phoenix dactylifera L. (Arecales: Arecaceae), in Saudi Arabia. Data spanning a six year period (2007–2012) from Al Ghowaybah, a 1104 ha date producing region in the Al Ahsaa Directorate in Saudi Arabia, were analyzed to assess the impact enhanced management efforts that commenced in Oct. 2009 had against this pest. Within six months of initiating the areawide management program significant reductions in the mean monthly number of weevils trapped and percentage traps with R. ferrugineus were detected. Mean monthly trap captures of R. ferrugineus and the percentage of traps capturing weevils declined significantly from 2009 to 2012 by an average of 65% and 90%, respectively, indicating that trapping and dispersal pressure was significantly reduced. By 2011, average monthly trap captures and percentage of traps with R. ferrugineus were significantly lower than all pre-management capture data and this was maintained through 2012 when data collection ceased. Additionally, over the period 2010–2012, insecticide application and palm eradication rates dropped by 91% and 89%, respectively. The total number of R. ferrugineus captured in 2012 declined by 86% when compared to total captures for 2010. At the end of 2012, the estimated infestation rate of date palms in Al Ghowaybah was 0.36%, which was below the economic threshold of a 1% infestation rate set by the Directorate of Agriculture supervising the program. It is concluded that the mandatory areawide management program that commenced in Oct. 2009 against R. ferrugineus in Al Ghowaybah had a significant and rapid impact against this pest.     

Consequences for biodiversity of reducing inputs to upland temperate pastures: effects on beetles (Coleoptera) of cessation of nitrogen fertilizer application and reductions in stocking rates of sheep

Current policies for upland pasture management in the UK encourage the integration of environmental objectives with livestock production through extensification of grazing systems. This study tested the hypothesis that a greater sward height in the summer would increase the diversity and abundance of grassland beetles (Coleoptera) as has been demonstrated for insects of indigenous grasslands. The hypothesis was tested with an experiment on an upland sheep pasture in mid‐Wales. Experimental treatments received different nitrogen fertilizer inputs (0 or 50 kg ha^?1), sheep stocking densities (12 or 9 ewes ha^?1) and average sward heights in summer were constrained to 3·5 or 5·5 cm by conserving surplus grass for silage in subplots. Five treatments, replicated in three randomized blocks, combined the two stocking densities and two sward heights without nitrogen fertilizer inputs, with the fifth combining the higher stocking density, shortest sward height and the nitrogen fertilizer input. Beetles were sampled with twelve pitfall traps in each of the fifteen plots from June to September in 1993 and 1995. In years 1 (1993) and 3 (1995) of the experiment, more Coleoptera species occurred in the tall sward (an average of nine species in addition to the forty‐one species present in the sward with the conventional sward height). Continuously grazed as opposed to ensiled subplots supported more beetle species but fewer individuals. Species composition of ground (Carabidae) and rove (Staphylinidae) beetles varied between treatments more than the arithmetic differences in species number. The experimental results supported the hypothesis but the benefits of taller swards to species diversity were small in the sown pastures of the study compared with indigenous upland grasslands (c. 33% fewer species). Inheritance effects of drainage, fertilizer and lime inputs, and the different species and management of cultivated pastures, may constrain the conservation benefits of altered pasture management compared with indigenous grasslands.     

Variability and estimating in fruiting of shea tree (Vitellaria paradoxa C.F. Gaertn) associated to climatic conditions in West Africa: implications for sustainable management and development

ABSTRACT

Shea tree (Vitellaria paradoxa) is one of the main native oil plants with high economic value in Africa. Its fruits are used for food, medicinal, cultural and exportation purposes. However, the lack of efficient tools to assess annual fruit production of the species limits the sustainable management of its resources. Therefore, production statistics are useful to organize the activities of the shea sector. This study aimed to (i) assess the interannual variation in fruit production along a climatic gradient in Burkina Faso, (ii) examine fruit production patterns according to climatic zones and tree size, (iii) assess the contribution of high-yielding trees in the annual potential production and (iv) develop allometric equations for estimating fruit yields of the species. The yield of 212 trees distributed across three climatic zones was monitored over four successive years. Within each climatic zone, fruit production was significantly different among years. Fruit production was positively and significantly correlated with tree size. The interannual variation in fruit production at tree individual level was higher in drier climatic conditions. The mean interindividual synchrony was less than 50% in each zone, suggesting a large range in fruit production patterns of the species. Annually, more than 55% of the total fruit production was supported by high-yielding trees. The best regression models for estimating fruit yields had R ² values of 69–73% with prediction errors ranging from ?7% to 4%. Our findings are useful tools for the planning of rational exploitation of shea tree’s resources and its sustainable management.