Accumulation of fumonisins B1 and B2 in freshly harvested Brazilian commercial maize at three locations during two nonconsecutive seasons

Fifty-six Brazilian commercial maize cultivars were examined for FB₁ and FB₂ accumulation after two non-consecutive growing seasons. During the 94/95 growing season 35 cultivars were planted at three locations in the state of São Paulo, Brazil. All samples (total of 105) were contaminated (0.10 g/g–6.58 g/g FB₁ and 0.04 g/g–2.15 g/g FB₂). During the 97/98 growing season, 8 of the cultivars used during 94/95 and 21 others were replanted at the same locations. All 87 samples were contaminated (1.15 g/g–43.80 g/g FB₁ and 0.08 g/g–11.65 g/g FB₂). One cultivar accumulated significantly less fumonisins in all locations during both growing seasons, indicating that some degree of selection may be possible even in climates that favor F. moniliforme (verticillioides) infection of maize. The presence of water surplus in soil from kernel maturity to harvest correlated with concentrations of FB₁ in the grain for the 8 cultivars planted during both seasons at three locations. Observed trends indicated that water excesses and deficits from silking to harvest increased fumonisin levels. The difference in the incidence of FB₁, FB₂, and FB₁ + FB₂ was significant between growing seasons, planting locations and between cultivars. Neither the level of hybridization, nor the type of endosperm, nor the length of the vegetative cycle showed any effect on the FB₁ contamination.This revised version was published online in October 2005 with corrections to the Cover Date.     

Fumonisins production by Fusarium proliferatum strains isolated from asparagus crown

The present work deals with the capability for producing fumonisin by Fusarium proliferatum strains isolated from asparagus in China. Fifty of F. proliferatum strains were randomly selected and incubated on cultures of maize grain and asparagus spear, respectively. Fumonisin levels (FB₁ and FB₂) were determined by high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). The results showed that all 50 strains produced fumonisins in maize culture within a wide range of concentrations, 10–11,499 μg/g and 2–6,598 μg/g for FB₁ and FB₂, respectively. On culture of asparagus spear,48 strains (96%) produced fumonisins in the range 0.2–781.6 μg/g and no detected to 40.3 μg/g for FB₁ and FB₂, respectively. All of F. proliferatum strains produced much higher levels of FB₁, FB₂ and total fumonisins (FB₁ + FB₂) in maize grain culture than in asparagus spear culture. Meanwhile, fumonisin B₃ (FB₃) was identified in all maize culture extracts and most of asparagus spear culture extracts. This is the first study carried out the fumonisin-producing ability of F. proliferatum strains isolated from asparagus in China. The information obtained is useful for assessing the risk of fumonisins contamination in asparagus spear. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Leaching and crop recovery of15N from ammonium sulphate and labelled maize (Zea mays) material in lysimeters at a site in Zimbabwe

The fate of¹⁵N-ammonium sulphate fertilizer that was applied to four lysimeters in the 1990/91 summer was studied over three consecutive growing seasons during which either maize or wheat was grown. Aboveground portions of¹⁵N-labelled maize plants from the first harvest were applied to four other lysimeters at 5 t ha^–1. Two lysimeters in each of the sets of four were assigned a low and a high moisture treatment using irrigation. In both moisture treatments, plant recovery of fertilizer-¹⁵N in the first season was 27% and a further 2% was recovered by plants during the next two seasons. During the second and third seasons, total recovery of¹⁵N by aboveground plant portions from lysimeters that received¹⁵N-labelled maize material was equivalent to 2.5% of applied fertilizer-¹⁵N. This corresponded to ca. 18% recovery of the¹⁵N added in maize material. Leaching of fertilizer-N over the three growing seasons did not exceed 0.3% in total. During the first season, a maximum of 0.25 kg N ha^–1, equivalent to 0.25% of the applied fertilizer-N, was leached in the high moisture treatment. This represented 1.8% of the nitrate load in leachates. Less than 0.002% of the applied fertilizer-N was leached in the low moisture treatment during the first season.     

Fiber-optic immunosensor for mycotoxins

Evanescent wave-based fiber-optic immunosensors were studied for the detection of fumonisins and aflatoxins in maize. Two formats, competitive and non-competitive, were used. A competitive format was used to measure fumonisin B1 (FB1) in both spiked and naturally contaminated maize samples. Fumonisin monoclonal antibodies were covalently coupled to an optical fiber and the competition between FB1 and FB1 labeled with fluorescein (FB1-FITC) for the limited number of binding sites on the fiber was assessed. The signal generated in the assay was inversely proportional to the FB1 concentration. For samples, the concentration causing an inhibition of binding by 50% (IC50) was dependent upon the clean-up procedure used. Simple dilution of methanolic maize extracts yielded an assay with an IC50 equivalent to 25 microg FB1 g(-1) maize with a limit of detection of 3.2 microg g(-1) maize. Affinity column clean-up yielded an assay with an IC50 equivalent to 5 microg FB1 g(-1) maize (limit of detection 0.4 microg FB1 g(-1)). An HPLC method and the immunosensor method agreed well for naturally contaminated maize samples except when large amounts of other fumonisins that cross-react with the immunosensor were present. The second sensor format, for the mycotoxin aflatoxin B1 (AFB1), was a non-competitive assay using the native fluorescence of this mycotoxin. Because the fluorescence of AFB1 itself was detected, the response of the sensor was directly proportional to the toxin concentration. The sensor, while capable of detecting as little as 2 ng ml(-1) of AFB1 in solution was technically not an immunosensor, since the attachment of aflatoxin specific antibodies was not required. Sensors of the formats described have the potential to rapidly screen individual maize samples but require coupling with a clean-up technique to be truly effective.     

Genetic and environmental influence on maize kernel proteome

Comparative targeted compositional analysis is currently an important element in the safety assessment of genetically modified plants. Profiling methods have been suggested as nontargeted tools to improve the detection of possible unintended effects. In this study, the capability of 2-dimensional electrophoresis to detect significant differences among seven conventional maize (Zea mays) cultivars grown in six different locations in Germany during two consecutive seasons was evaluated. Besides maize genotype, both geographic location and season had a significant effect on protein profiles. Differences as high as 55- and 53-fold in the quantity of specific proteins were recorded, the median observed difference being around 6- and 5-fold between the genotypes and growing locations, respectively. Understanding the variation in the quantity of individual proteins should help to put the variation of endogenous proteins and the novel proteins in the genetically modified plants in perspective. This together with the targeted analyses the profiling methods, including proteomics, could also help to get a deeper insight into the unintended alterations that might have occurred during the genetic modification process.     

Biomass Yield and Quality of Reed Canarygrass under Five Harvest Management Systems for Bioenergy Production

Reed canarygrass, Phalaris arundinacea L., produces high biomass yields in cool climates and wetlands. The number and timing of harvests during a growing season directly affect biomass yield and biofuel quality. In order to determine optimum harvest management, seven cultivars of reed canarygrass were planted in field experiments at Ames, IA; McNay, IA; and Arlington, WI in the upper Midwestern USA and harvested once in autumn or in winter, twice in spring + autumn or spring + winter, or three times during the season as hay. Biomass yield varied considerably among harvest treatments, locations, and years, ranging up to 12.6 Mg ha^?1. Dry matter percentage ranged from 37% for spring-harvested biomass to 84% for overwintered biomass. The three harvest hay and two harvest spring + autumn managements produced the highest biomass yield compared to other systems, but the advantage, if any, of hay management was small and probably does not justify the cost of additional fieldwork. More mature biomass, such as that found in the single harvest systems, had higher fiber concentrations. Overwintered biomass had superior biofuel quality, being low in P, K, S, and Cl and high in cell wall concentration. However, winter harvest systems had lower yield than autumn harvest and in some years, no harvest was possible due to lodging from snow compaction. The main limitation of a two harvest system is the high moisture content of the late spring/early summer biomass.     

Metabolite profiling of maize grain: differentiation due to genetics and environment

A comparative metabolite profiling approach based on gas chromatography-mass spectrometry (GC/MS) was applied to investigate the impact of genetic background, growing location and season on the chemical composition of maize grain. The metabolite profiling protocol involved sub-fractionation of the metabolites and allowed the assessment of about 300 distinct analytes from different chemical classes (polar to lipophilic), of which 167 could be identified. A comparison, over three consecutive growing seasons, of the metabolite profiles of four maize cultivars which differed in their maturity classification, was carried out using principal component analysis (PCA). This revealed a strong separation of one cultivar in the first growing season, which could be explained by the immaturity of the kernels of this cultivar compared with others in the field trial. Further evaluations by pair-wise comparison using Student’s t-test and analysis of variance (ANOVA) showed that the growing season was the most prominent impact factor driving variation of the metabolite pool. An increased understanding of metabolic variation was achieved by analysis of a second sample set comprising one cultivar grown for 3 years at four locations. The applied GC/MS-based metabolite profiling demonstrated the natural variation in maize grain metabolite pools resulting from the interplay of environment, season, and genotype.     

Yield of maize as influenced by population densities of the root lesion nematode,Pratylenchus zeae

Under field conditions, population density of the root lesion nematode, Pratylenchus zeae in soil and roots of maize cv. Single Hybrid 10 fluctuated throughout its growing season and reached the peak in September, harvest stage of maize. There were negative correlations (r) between the population densities of P. zeae in maize roots and grain yield of maize according to the data collected at all growing seasons.     

Habitat of the corn leafhopper (Hemiptera: Cicadellidae) during the dry (winter) season in Mexico

Although the corn leafhopper Dalbulus maidis (DeLong and Wolcott) is the most important vector of maize pathogens in Latin America, little is known about how and where it overwinters (passes the dry season), particularly in Mexico. The objectives of this study were (1) to monitor the abundance of D. maidis adults throughout the dry season in maize and maize-free habitats and (2) to determine where and how D. maidis adults, exposed or nonexposed to the maize pathogen Spiroplasma kunkelii Whitcomb, overwinter in a maize-free habitat. Work for the first objective was done during the two consecutive dry seasons of 1999-2000 and 2000-2001; the second objective was done during the dry seasons of 2003-2004 and 2005-2006. During the dry winter seasons, D. maidis was prevalent as long as maize was present in irrigated areas. The leafhopper was found in 52 of the 58 irrigated maize fields sampled in Mexico at the end of the dry seasons of 1999-2000 and 2000-2001. However, leafhopper adults were not found in nonirrigated maize-free habitats at high elevation during the dry winter season (February, March, and April), although leafhopper adults were prevalent on perennial wild grasses in January after maize harvest. Additional experiments revealed, however, that corn leafhopper adults, although few in number, survived the entire dry season in these nonirrigated maize-free fields. Also, no detectable difference in survival existed between leafhoppers exposed and those not exposed to S. kunkelli during the two dry seasons in the maize-free habitat.     

Yield loss of faba bean (Vicia faba) due to chocolate spot (Botrytis fabae) in sole and mixed cropping systems in Ethiopia

Two field experiments were conducted during 2004 and 2005 cropping seasons at Adet Agricultural Research Center, Ethiopia to assess yield losses caused by chocolate spot(Botrytis fabae) of faba bean in sole and mixed cropping systems using two cultivars. Cropping systems were sole faba bean (FB), faba bean mixed with field pea (FB: FP), barley (FB: BA) and maize (FB: MA). Mancozeb was sprayed at the rate of 2.5 kg a.i/ha at 7-, 14- and 21-day interval to generate different levels of chocolate spot disease in all the four cropping systems, and unsprayed control was also included. The treatments were arranged in a randomised complete block design (RCBD) with four replications. FB: MA mixed cropping significantly reduced disease severity and the area under disease progress curve (AUDPC) and increased faba bean grain yield. The highest faba bean grain yield among the three mixed croppings under different spray schedules was obtained from FB: MA mixed cropping in both 2004 and 2005 (2.56 and 3.74 t/ha, respectively) cropping seasons. There were highly significant yield differences (P < 0.05) among the spray intervals of mancozeb in both seasons. The highest grain yield (4.9 t/h) was recorded from the 7-day spray interval in 2005. The unsprayed faba bean had a lower grain yield (1.9 t/ha in 2004 and 2.3 t/ha in 2005) compared to the sprayed plots. The highest relative yield loss (67.5%) was calculated in 2005 from FB: FP mixed cropping in unsprayed plots. The relative yield losses in the unsprayed plots were in the range of 35.8–41.5% in 2004 and 52.6–67.5% in the 2005 cropping season. Severity and AUDPC were inversely correlated with faba bean grain yield. Significant differences were recorded in the 100-seed weight and days to maturity (DM). The unsprayed plots had shorter DM ranging from 126 to 128.5 day (except FB: MA mixed cropping) in 2004 and 122–123.9 days in 2005. In the sprayed plots DM was relatively longer than the unsprayed plots. A higher seed weight was recorded in the sole FB (56 g) and FB: MA (55 g) mixed cropping, and the lowest value of 100-seed weight was recorded from FB: FP (53 g) mixed cropping. The productivity of the mixed cropping evaluated by land equivalent ratio (LER) exceeded that of sole cropping. Faba bean grain yield was highly influenced by the severity of chocolate spot. The disease affects the DM, forcing early maturing of the plants.     

Handling and aflatoxin contamination of white maize in Costa Rica

Projects funded by International Development Research Centre (IDRC) of Canada and the European Commission have enabled the examination of more than 3000 samples of maize collected from all regions of Costa Rica at different stages, from the growing crop through storage to final sale, and at different water contents. Contamination with Aspergillus flavus was frequent and about 80% of samples contained more than 20 ng aflatoxins g-1 grain. Average contamination with aflatoxins in the Brunca Region was > 274 ng g -1 while that in other regions was < 70 ng g -1. Except in Brunca region, where it averaged 376 ng g -1, contamination of grain from commercial sources was slightly less than of that from farms (≤15 ng g-1). It appeared that samples kept on the cob after harvest contained almost no aflatoxin while shelled samples were frequently highly contaminated. Experiments were therefore done in Brunca and Huetar Atlantic Regions, utilising 34 experimental maize crops to study in detail the development of A. flavus and aflatoxin from before harvest, through postharvest treatment before drying and through storage for six months. A. flavus was isolated more frequently from maize shelled immediately after harvest than from that kept on the cob until it could be dried, and from more samples from the Brunca Region than from the Huetar Atlantic Region. Samples harvested with ≥18% water content often contained >70% of grains infected with A. flavus but sometimes there were few grains infected. As found in the initial survey, more aflatoxin contamination developed in shelled maize than in that handled on the cob during the period from harvesting to drying, especially if the delay was more than 5 days, and more in Brunca than in Huetar. Shelled grain contained 400–800 ng aflatoxin g -1 in Brunca but <100 ng g-1 in Huetar while grain kept on the cob contained <30 ng g-1, even with >18% water content. Incidence of Fusarium spp. exceeded 50% except where A. flavus colonized more than 80% of grains. This revised version was published online in June 2006 with corrections to the Cover Date.     

土壤-玉米系统中土壤呼吸强度及各组分贡献

用特殊设计的气体采集箱法对玉米生长期间潮土呼吸强度进行了测定。结果表明,施用150kgNhm^-2的裸地土壤CO2累积排放量是294g C m^-2,约为种植玉米土壤的一半。用根去除法测得的玉米对土壤呼吸的贡献率,苗期小于20％,拔节到收获期波动在30％-70％之间,全生长期平均为46％。玉米生长期间因土壤有机碳分解而释放出的CO2总量为2．94MgChm^-2,大约是0—40cm土层中土壤有机碳总储存量的8％,因此需要输入7．35Mghm^-2的碳含量40％的作物残留物才能平衡土壤中有机碳的损失,约为玉米收获时残留于土壤中根量的一倍,但与残留根量及玉米生长期间根系分泌到土壤的有机物量的总和相当,因此土壤中有机碳总体处于平衡状态。在玉米生长期间,施用氮肥可使土壤CO2排放量降低10％。土壤排放CO2主要受土壤温度的影响,温度效应Q10为1．90-2．88。     

HPLC determination of fumonisin mycotoxins in maize: a comparative study of naphthalene-2,3-dicarboxaldehyde and o-phthaldialdehyde derivatization reagents for fluorescence and diode array detection

Fumonisins are mycotoxins produced by various species of Fusarium and occur naturally in contaminated maize and maize-based foods. Ingestion of fumonisins has considerable health implications for humans and animals. Since fumonisins lack a useful chromophore or fluorophore, their determination in maize is routinely achieved via HPLC with fluorescence detection (FLD) after precolumn derivatization. This study optimized naphthalene-2,3-dicarboxaldehyde (NDA) derivatization of fumonisins in naturally contaminated maize following strong anion exchange (SAX) solid phase extraction (SPE) clean-up and utilizing diode array detection (DAD) as a practical alternative simultaneously to FLD. The limit of detection (LOD) for fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) with FLD was 0.11 ng, 0.50 ng and 0.27 ng, respectively, and with DAD it was 13.8 ng, 12.5 ng and 6.6 ng, respectively injected on column. The coefficient of variation (CV, n = 6) for FB(1), FB(2) and FB(3) in a naturally contaminated samples obtained with FLD was 2.6%, 1.8% and 5.3%, respectively, compared to 6.0%, 3.4% and 9.5%, respectively, obtained with DAD. Subsequently the optimized NDA derivatization was compared to the widely used o-phthaldialdehyde (OPA) derivatization agent as well as alternative sample clean-up with immunoaffinity column (IAC) by analyzing naturally contaminated maize samples (n = 15) ranging in total fumonisin (TFB = FB(1)+FB(2)+FB(3)) levels from 106 to 6000 μg/kg. After immunoaffinity column clean-up of extracted samples, the recoveries of spiked maize samples for NDA-FLD of FB(1), FB(2) and FB(3) were 62%, 94% and 64%, respectively. NDA proved to be an effective derivatization reagent of fumonisin in naturally contaminated maize samples following IAC clean-up, except for DAD at TFB levels below 1000 μg/kg. In contrast NDA derivatization following SAX clean-up produced results comparable to OPA only for levels below 1000 μg/kg. Aside from the difference in detection limits, FLD and DAD produced comparable results irrespective of the clean-up method or the derivatization agent.     

The effect of soil warming on bulk soil vs. rhizosphere respiration

There has been considerable debate on whether root/rhizosphere respiration or bulk soil respiration is more sensitive to long-term temperature changes. We investigated the response of belowground respiration to soil warming by 3 °C above ambient in bare soil plots and plots planted with wheat and maize. Initially, belowground respiration responded more to the soil warming in bare soil plots than in planted plots. However, as the growing season progressed, a greater soil-warming response developed in the planted plots as the contribution of root/rhizosphere respiration to belowground respiration declined. A negative correlation was observed between the contribution of root/rhizosphere respiration to total belowground respiration and the magnitude of the soil-warming response indicating that bulk soil respiration is more temperature sensitive than root/rhizosphere respiration. The dependence of root/rhizosphere respiration on substrate provision from photosynthesis is the most probable explanation for the observed lower temperature sensitivity of root/rhizosphere respiration. At harvest in late September, final crop biomass did not differ between the two soil temperature treatments in either the maize or wheat plots. Postharvest, flux measurements during the winter months indicated that the response of belowground respiration to the soil-warming treatment increased in magnitude (response equated to a Q ₁₀ value of 5.7 compared with ∼2.3 during the growing season). However, it appeared that this response was partly caused by a strong indirect effect of soil warming. When measurements were made at a common temperature, belowground respiration remained higher in the warmed subplots suggesting soil warming had maintained a more active microbial community through the winter months. It is proposed that any changes in winter temperatures, resulting from global warming, could alter the sink strength of terrestrial ecosystems considerably.     

QTL analyses of seed weight during the development of soybean (Glycine max L. Merr.)

At harvest traits such as seed weight are the sum of development and responses to stresses over the growing season and particularly during the reproductive phase of growth. The aim here was to measure quantitative trait loci (QTL) underlying the seed weight from early development to drying post harvest. One hundred forty-three F(5) derived recombinant inbred lines (RILs) developed from the cross of soybean cultivars 'Charleston' and 'Dongnong 594' were used for the analysis of QTL underlying mean 100-seed weight at six different developmental stages. QTL x Environment interactions (QE) were analyzed by a mixed genetic mode based on 3 years' data. At an experiment-wise threshold of a=0.05 and by single-point analysis 94 QTL unaffected by QE underlay the mean seed weight at different developmental stages. Sixty-eight QTL affected by QE that also underlay mean seed weight were identified. From the 162 QTL 42 could be located on 12 linkage groups by composite interval mapping (LOD>2.0). The numbers, locations and types of the QTL and the genetic effects were different at each developmental stage. On linkage group C2 the distantly linked QTL swC2-1, swC2-2 and swC2-3 each affected mean seed weight throughout the different developmental stages. The DNA markers linked to the QTL possessed potential for use in marker-assisted selection for soybean seed size. The identification of QTL with genetic main effects and QE interaction effects suggested that such interactions might significantly alter seed weight during seed development.     

华北旱地覆膜春玉米田水温效应及增产限制因子

为探求覆膜栽培春玉米旱作田土壤水温变化特征及其对玉米产量和水分利用效率(WUE)的影响,设计垄作覆膜、垄作裸地、平作覆膜、平作裸地(对照)4个处理的田间试验,对春玉米田各生育时段的土壤温度、土层水分、耗水结构及玉米产量进行了监测.结果表明：自播种到抽雄的生育前期春玉米田覆膜较裸地增温1～3 ℃,土壤积温增加155.2～280.9 ℃;延长生育期约5.9～10.7 d.自播种到成苗期覆膜保水效应显著,WUE较裸地提高81.6%～136.4%.春玉米成苗到拔节期正值该区域稳定干旱期,覆膜处理土壤供水层深达80～100 cm,干旱胁迫使WUE较对照降低17.0%～21.6%,产生奢侈耗水.春玉米小喇叭口期后进入雨季,各处理土体复水,并产生过饱渗漏,最终使收获期土体水分与播期持平,贮水丰富.垄作覆膜较裸地增产9.5%;平作覆膜不利于降水入渗而导致渍水,减产5.0%;垄作裸地与平作裸地差异不显著.以雨季前气象干旱期的土壤枯水与雨季后的土壤库水为特征的春玉米田水分供求时序失衡,限制了春玉米的高产.     

Diversity of Breadfruit (<Emphasis Type="Italic">Artocarpus altilis</Emphasis>, Moraceae) Seasonality: A Resource for Year-Round Nutrition<Superscript>1</Superscript>

Diversity of Breadfruit ( Artocarpus altilis , Moraceae) Seasonality: A Resource for Year-Round Nutrition. Breadfruit, Artocarpus altilis (Parkinson) Fosberg, is an important but underutilized staple crop cultivated throughout Oceania and much of the wet tropics. Indigenous peoples have selected and cultivated cultivars with different fruiting seasons to effectively extend fruit production for most of the year. In the present study, the seasonality of 219 breadfruit accessions originating from 17 Pacific island groups, the Seychelles, the Philippines, and Indonesia, and now growing in the National Tropical Botanical Garden’s (NTBG) Kahanu Garden, Hana, Hawaii, were evaluated. The predominant season of male flower production for most cultivars was from May to September, and fruit was produced most frequently between August and January. However, there were differences in the duration of the fruiting season from year to year and among cultivars. Over the 10-year period, 14 cultivars did not reliably produce fruit; most of this group were ‘ulu afa’ trees collected from Tokelau. About 24 cultivars exhibited very little seasonality and produced fruit throughout the year. The rest of the cultivars could be clustered into seasonality groups with characteristic fruiting patterns. Comparison of literature values indicates that unlike Hawaii, the breadfruit season in most locations begins around the date the sun reaches zenith prior to the summer months and extends throughout the summer months. Five cultivars asexually propagated from the NTBG collection growing in Kiribati (1°28′ N) exhibit similar fruiting patterns as in Hawaii, except that they begin 2–3 months earlier. These data predict that cultivars with complementary fruiting seasons in Hawaii may experience a temporal shift in their seasonality but will maintain their compatibility when cultivated in different locations and could enable year-round fruit production in many regions.     

Multi-trophic level interactions in a cassava-maize mixed cropping system in the humid tropics of West Africa

Multi-trophic level interactions in a mixed crop, involving cassava and maize, were studied in derived-savanna in Benin, West Africa. Two trials were planted, one during the short rainy season two months before onset of the dry season and one during the long rainy season in spring. Key pests under study on maize were the noctuid Sesamia calamistis Hampson and the pyralids Eldana saccharina Walker and Mussidia nigrivenella Ragonot, and on cassava, the exotic mealybug, Phenacoccus manihoti Matile-Ferrero and its encyrtid parasitoid Apoanagyrus lopezi De Santis. Both crops received insecticide treatments to assess the crop loss by a pest species. On maize, intercropping with cassava reduced egg and immature numbers of S. calamistis by 67 and 83%, respectively, as a result of reduced host finding by the ovipositing adult moth and of higher egg parasitism by Telenomus spp. Both trials showed similar effects on maize yields: on insecticide-treated maize, intercropping with cassava reduced maize yields by 9-16%, while on untreated maize the net effect of reduced pest density and increased plant competition resulted in zero yield differences; yield losses were lower in inter- compared to monocropped maize. For cassava, cropping system had no effect on parasitism by A. lopezi. Yield differences between mono- and intercropped cassava depended on time of harvest: they were large at the beginning and zero at final harvest. Land equivalent ratios were mostly > 1.5 indicating that a maize/cassava mixed crop, protected or unprotected, considerably increased the productivity per unit area of land.     

Effect of spacing in cow pea (Vigna unguiculata) on damage by the black cowpea moth, Cydia ptychora (Lepidoptera: Tortricidae)

Three indeterminate cowpea cultivars with different growth habits were each planted at four inter-row spacings in two different seasons at Ile-Ife, Nigeria, and at harvest assessed for Cydia ptychora damage. Damage by the moth increased with decreasing inter-row spacing much more in the erect and semi-erect cultivars, than in the semi-prostrate cultivar.