Biocontrol of Maize Weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), in Maize over a Six-Month Storage Period.

Food security is contingent upon increasing crop yields but also upon reducing crop losses to post-harvest pests and diseases. Weevils are particularly important agents of post-harvest losses in grain crops. A long-term evaluation of a biocontrol agent, Beauveria bassiana Strain MS-8, at a single dose of 2 × 109 conidia kg-1 of grain was formulated in kaolin as a carrier at levels of 1, 2, 3, and 4 g kg-1 of grain and screened against the maize weevil, Sitophilus zeamais. After six months, the application of B. bassiana Strain MS-8 at all levels of kaolin significantly reduced the maize weevil populations compared to the untreated control (UTC). The best control of maize weevil was observed in the first 4 months after application. Strain MS-8 applied in a kaolin level of 1 g kg-1 performed the best, resulting in the lowest number of live weevils (36 insects/500 g of maize grain), the lowest level of grain damage (14.0%), and the least weight loss (7.0%). In the UTC the number of live insects was 340 insects/500 g of maize grain, the level of grain damage was 68.0%, and weight loss was 51.0%.

Fall Armyworm Infestation and Development: Screening Tropical Maize Genotypes for Resistance in Zambia.

Knowledge of fall armyworm (FAW) (Spodoptera frugiperda J.E. Smith) rearing, infestation and development and precision screening protocols are preconditions for the successful introgression of resistance genes into farmer-preferred varieties. We aimed to determine FAW developmental stages, screen tropical maize and select resistant lines under controlled conditions in Zambia. Field-collected FAW samples constituting 30 egg masses and 60 larvae were reared using maize leaf- and stalk-based and soy- and wheat flour-based diets at 27 ± 1 °C, 60 ± 5% relative humidity and 12 h day length. The resulting neonates were separated into sets A and B. The life cycles of set A and field-collected larvae were monitored to document the FAW developmental features. Set B neonates were used to infest the seedlings of 63 diverse tropical maize genotypes. Egg, larva, pupa and adult stages had mean durations of 2, 24, 20 and 12 days, respectively. Test maize genotypes revealed significant differences (p < 0.05) based on FAW reaction types, with lines TL13159, TL02562, TL142151, VL050120 and CML548-B exhibiting resistance reactions, while CML545-B, CZL1310c, CZL16095, EBL169550, ZM4236 and Pool 16 displayed moderate resistance. These genotypes are candidate sources of FAW resistance for further breeding. This study will facilitate controlled FAW rearing for host screening in the integration of FAW resistance into market-preferred maize lines.

Short- and Long-Term Evaluation of a Fixed Dose of Beauveria bassiana Strain MS-8 Diluted in Various Doses of Kaolin as a Powder Formulation Applied to Rice Grains to Control Almond Moth, Ephestia cautella Walker (Lepidoptera: Pyralidae).

Short-term and long-term evaluation studies were conducted against Ephestia cautella on rice grains, using Beauveria bassiana Strain MS-8 formulated in various doses of kaolin as an active carrier. In the short-term study (45 days), a fixed dose of 0.03 g conidia kg-1 of grain of Strain MS-8 was formulated in kaolin at doses of 0.3, 0.5, 1, and 2 g kg-1 of grain. These formulations were evaluated for their effects on larval mortality and the number of adults emerged. The highest level of larval mortality (90.0%) and the lowest numbers of adults emerged (1.6 insect/100 g of rice grain) were caused by Strain MS-8 in a kaolin dose of 2 g kg-1. However, Strain MS-8 in a kaolin dose of 1 g kg-1 performed well for the same parameters. In the long-term evaluation study (180 days), the same dose of Strain MS-8 was formulated in kaolin at doses of 0.5, 1, 2, and 3 g kg-1 of grain. These formulations were then evaluated against the levels of webbed grain, grain damage, and weight loss. The lowest levels of webbed grain (2.0%), grain damage (3.0%), and weight loss (1.8%) were caused by Strain MS-8 in kaolin at a dose of 3 g kg-1, although Strain MS-8 in kaolin doses of 1 g and 2 g kg-1 also performed well for the same parameters. The highest levels of webbed grain (15.0%), grain damage (30.0%), and weight loss (9.0%) were observed in the untreated control treatment (UCT).

Efficacy of Biopesticides in the Management of the Cotton Bollworm, Helicoverpa armigera (Noctuidae), under Field Conditions.

Cotton is one of the most valuable materials in the world, popularly used in the clothing industry and other products. However, its production is limited by the high infestation of insect pests. A study was conducted to evaluate the effects of different biopesticides on the control of the African bollworm (Helicoverpa armigera) under cotton field conditions. Four biopesticides-namely, Eco-Bb® (Beauveria bassiana), Bb endophyte (Beauveria bassiana), Bolldex® (Nucleopolyhedrovirus), and Delfin® (Bacillus thuringiensis)-were evaluated and compared with the pyrethroid Karate® (lambda-cyhalothrin) and an untreated control against H. armigera. Field trials were conducted at the Agriculture Research Council, Rustenburg, in the North West Province of South Africa during the 2017 and 2018 cotton seasons. The results revealed that in plots sprayed with Karate® and Bolldex®, the numbers of H. armigera were significantly reduced compared to the untreated controls. Plots treated with Bolldex® had the lowest number of damaged bolls in 2017, while those treated with Karate® had the lowest number of damaged bolls in 2018. All treated plots had significantly fewer damaged bolls when compared to the controls. A seed cotton yield of 5987 kg/ha was recorded in the plots that were treated with Bolldex®-significantly higher than the yields from plots treated with Eco-Bb®, Delfin®, and Bb endophyte-in 2017. However, the yield in treatments with Eco-Bb®, Delfin®, and Bb endophyte was lower than that from the untreated controls during this season. In 2018, plots treated with Bolldex® had the highest yield, at 6818 kg/ha, which was not different from the other treatments. The highest average seed cotton yield of 6400 kg/ha was recorded in the plots treated with Bolldex®, followed by Karate®. In summary, the efficacy of different biopesticides against H. armigera varied significantly, while the synthetic pesticide (Karate®) and Bolldex® resulted in more consistent control of this pest. The results suggest that biopesticides may, however, have the potential for use in the sustainable control of cotton bollworms as part of integrated pest management programmes, although further work is required to support this hypothesis.

Understanding the Determinants of Food Security among Rural Farming Households in Rwanda.

Despite Rwanda's impressive economic success over the last decade, household food insecurity persists, particularly in rural areas. Empirical evidence is therefore deemed necessary to inform policies addressing food insecurity, hunger and poverty in general. This study examines household food security and its determinants in the rural areas of Southern and Northern provinces of Rwanda. Using cross-sectional data collected from 534 farming households, we estimated household food security status by Food Consumption Score (FCS) and Food Insecurity Experience Scale (FIES) and applied ordered Probit model to identify drivers of household food security. The results indicate that a significant proportion (74.4%) of households had an acceptable FCS, but 36.52% of the farming households experienced moderate and severe food insecurity when assessed with FIES. Ownership of livestock was identified as a key determinant of food security using both metrics, which affirms the importance of combating hunger and food insecurity in Rwanda through their 'one cow per household policy' and recommends that this policy be strengthened.

Assessing the genetic diversity of cowpea [Vigna unguiculata (L.) Walp.] germplasm collections using phenotypic traits and SNP markers.

BACKGROUND: Productivity of cowpea [Vigna unguiculata (L.) Walp] in sub-Sahara Africa is curtailed by a lack of farmer-preferred and improved cultivars and modern production technologies. The objectives of the study were to determine the extent of genetic diversity present among a collection of cowpea accessions from Zambia and Malawi using phenotypic traits and single nucleotide polymorphism (SNP) markers and, to select distinct and complementary parental lines for cultivar development. One hundred cowpea genotypes were evaluated for agronomic traits in two selected sites in Zambia, using a 10 × 10 alpha lattice design with two replications. Ninety-four of the test genotypes were profiled with 14,116 SNP markers. RESULTS: Number of pods plant- 1 (NPP), pod length (PDL), and number of seeds pod- 1 (NSP), were significantly (p < 0.05) affected by genotype × environment interaction effects. Genotypes such as CP411, CP421, CP645, CP732, Chimponongo, and MS1-8-1-4 exhibited higher grain yield of > 1200 kg/ha with excellent performance in yield components such as NSP, PDL, HSW and GYD. Grain yield had significant (p < 0.05) associations with NPP (r = 0.50), NSP (r = 0.46) and PDL (r = 0.42) useful for simultaneous selection for yield improvement in cowpea. The SNP markers revealed gene diversity and polymorphic information content of 0.22 and 0.17, respectively, showing that the tested cowpea accessions were genetically diverse. Test genotypes were classified into four genetic groups irrespective of source of collection allowing selection and subsequent crosses to develop breeding populations for cultivar development. CONCLUSIONS: Genotypes Bubebe, CP411, CP421, CP645, Chimponogo and MS1-8-1-4 were identified to be the most genetically divergent and high yielding making them ideal parental lines for breeding. This study provided a baseline information and identified promising cowpea genetic resources for effective breeding and systematic conservation.

Biological characterization of the entomopathogenic nematode, Steinernema innovationi: a South African isolate.

Entomopathogenic nematode species perform differently under different environmental conditions; therefore, the authors investigated the biological and environmental characteristics that could optimize performance of Steinernema innovationi. The authors studied the effect of temperature on infectivity and reproduction, the foraging behavior and host range. Thermal activity was optimal between 22 and 25°C. Highest infective juvenile (IJ) yields in last instar Galleria mellonella were observed at 22°C (333,014 IJs/g) and 25°C (354,165 IJs/g). An average of 26% of the IJs infected G. mellonella larvae at depths of 15 cm within 24 hr. Steinernema innovationi IJs raised greater than 95% of their body off the substrate and moved in a circular pattern, but did not jump. The hosts, Acheta domesticus, Chilo partellus, and Plutella xylostella showed the least susceptibility. All other hosts, [Eldana saccharina, Sesamia calamistis, Tenebrio molitor, G. mellonella, Cydia pomonella] suffered 100% larval mortality. Pupal mortality ranged from 47 to 68%. An LC50 and LC70 of 3 and 31 IJs/larva, respectively, were calculated for Agrotis ipsilon. The results indicate that S. innovationi is adapted to moderate temperatures. Furthermore, to the author's knowledge this is the first report of a nematode (particularly from 'glaseri group') that shows cruiser-type behavior in movement, but also nictates.Entomopathogenic nematode species perform differently under different environmental conditions; therefore, the authors investigated the biological and environmental characteristics that could optimize performance of Steinernema innovationi. The authors studied the effect of temperature on infectivity and reproduction, the foraging behavior and host range. Thermal activity was optimal between 22 and 25°C. Highest infective juvenile (IJ) yields in last instar Galleria mellonella were observed at 22°C (333,014 IJs/g) and 25°C (354,165 IJs/g). An average of 26% of the IJs infected G. mellonella larvae at depths of 15 cm within 24 hr. Steinernema innovationi IJs raised greater than 95% of their body off the substrate and moved in a circular pattern, but did not jump. The hosts, Acheta domesticus, Chilo partellus, and Plutella xylostella showed the least susceptibility. All other hosts, [Eldana saccharina, Sesamia calamistis, Tenebrio molitor, G. mellonella, Cydia pomonella] suffered 100% larval mortality. Pupal mortality ranged from 47 to 68%. An LC50 and LC70 of 3 and 31 IJs/larva, respectively, were calculated for Agrotis ipsilon. The results indicate that S. innovationi is adapted to moderate temperatures. Furthermore, to the author's knowledge this is the first report of a nematode (particularly from 'glaseri group') that shows cruiser-type behavior in movement, but also nictates.

Pepo aphid-borne yellows virus: a new species in the genus Polerovirus.

Pepo aphid-borne yellows virus (PABYV) has been proposed as a putative representative of a new species in the genus Polerovirus in the family Luteoviridae. The genomes of two South African (SA) isolates of cucurbit-infecting PABYV were described in this record. Total RNA, extracted from a pattypan (Cucurbita pepo L.) and a baby marrow (C. pepo L.) leaf samples, was subjected to next-generation sequencing (NGS) on the HiSeq Illumina platform. Sanger sequencing was subsequently used to authenticate the integrity of PABYV's genome generated from de novo assembly of the NGS data. PABYV genome of SA isolates consists of 5813 nucleotides and displays an organisation typical of poleroviruses. Genome sequence comparisons of the SA PABYV isolates to other poleroviruses support the classification of PABYV as a new species in the genus Polerovirus. Recombination analyses showed that PABYV and Cucurbit aphid-borne yellows virus (CABYV) shared the same ancestor for the genome part situated between breaking points. Phylogenetic analyses of the RNA-dependent RNA polymerase and the coat protein genes showed that SA PABYV isolates shared distant relationship with CABYV and Suakwa aphid-borne yellows virus. Based on our results, we propose that PABYV is a distinct species in the genus Polerovirus.

Biodegradation of Chlorpyrifos, Malathion, and Dimethoate by Three Strains of Bacteria Isolated from Pesticide-Polluted Soils in Sudan.

This study was done to identify pesticide-biodegrading microorganisms and to characterize degradation rates. Bacillus safensis strain FO-36bT, Bacillus subtilis subsp. inaquosorum strain KCTC13429T, and Bacillus cereus strain ATCC14579T were isolated from pesticide-polluted soil in Sudan, separately incubated with each pesticide with periodic samples drawn for GC and GC-MS. Pesticide biodegradation followed a biphasic model. α and ß half-lives (days) of chlorpyrifos, malathion, and dimethoate in B. safensis culture were 2.13, 4.76; 2.59, 5.66; and 9.5, 11.0, respectively. Values in B. subtilis and B. cereus cultures were 4.09, 9.45 and 4.33, 9.99 for chlorpyrifos; 2.99, 5.36 and 2.43, 4.71 for malathion; and 9.53, 15.11 and 4.16, 9.27 for dimethoate. No metabolite was detected in B. subtilis cultures, whereas a few were detected from B. safensis and B. cereus cultures. Bacterial efficiency can be ordered as B. safensis > B. subtilis > B. cereus for chlorpyrifos and B. cereus > B. subtilis > B. safensis for malathion and dimethoate.

Effects of Selected Diazotrophs on Maize Growth.

Laboratory, greenhouse, and field experiments were conducted at the University of KwaZulu-Natal, Pietermaritzburg, South Africa in the 2010/2011 and 2011∖2012 seasons to study the effects of eight strains of diazotrophic bacteria on the growth and yield of maize. Maize seeds were treated with Bacillus megaterium (V16), Pseudomonas sp. (StB5, A3, A6, and A61), Burkholderia ambifaria (V9), Enterobacter cloacae (L1) and Pantoea ananatis (LB5), aiming to stimulate plant growth, and maintain or increase yields while reducing the need for N fertilization. All the diazotrophic bacteria increased germination of maize seed, and Pseudomonas sp. (StB5) and B. megaterium (V16) significantly increased shoot length. Pseudomonas sp. (StB5), B. megaterium (V16), E. cloacae (L1), B. ambifaria (V9), and Pseudomonas sp. (A3) very significantly increased root length and seed vigor index. Under greenhouse conditions, plants treated with diazotrophic bacteria developed more leaf chlorophyll and greater dry weight, albeit not significantly (n.s.). In a field trial in 2010/2011, application of the best five diazotrophic bacteria, with or without 33% N-fertilizer, had no significant effect on germination, grain yield, dry weight, plant height and leaf chlorophyll. In the 2011/2012 growing season, at 60 days after planting (DAP), all the diazotrophic bacteria increased plant dry weights to equal that of the fertilized control (33%N-fertilizer) (n.s.). After inoculation with the diazotrophs alone increased plant heights (n.s.), and chlorophyll contents (n.s.). With the addition of 33%N-fertilizer at planting, the diazotrophs still caused increases of chlorophyll content relative to the control with 33%N (n.s.). It may be concluded that the tested diazotrophs alone may be beneficial for use on maize growth.

Nutritional and Sensory Evaluation of Injera Prepared from tef and Eragrostis curvula (Schrad.) Nees. Flours with Sorghum Blends.

Injera is a fermented, sour bread consumed as a staple food in Eritrea and Ethiopia. The bread can be prepared from various cereals but tef [Eragrostis tef (Zucc.) Trotter] is the most preferred ingredient. This study assessed the acceptability of injera prepared using grains of a closely related but underutilized grass, Eragrostis curvula (Schrad.) Nees. The nutritive value of the grains was compared and the sensory attributes of injera made from flours of tef (control) and E. curvula, each combined with 0, 5, and 10% of sorghum flour, were assessed using a tasting panel. Nutrient analysis showed that E. curvula contains more than double the amount of crude protein found in tef. E. curvula also contains higher fat, dietary fiber and mineral nutrients than tef. Injera made of E. tef and E. curvula flours showed non-significant differences in taste, texture, appearance and overall acceptability. This suggest that E. curvula has the potential to serve as a novel source of gluten-free flour for human consumption. Agronomically viewed, growing E. curvula could be more advantageous for smallholder farmers on marginal lands because the species is a perennial that can produce a seed harvest twice a year, unlike tef, which is annual crop. It also tolerates acidic soils better than tef.

Genome sequence analysis of two South African isolates of Moroccan watermelon mosaic virus infecting cucurbits.

Moroccan watermelon mosaic virus (MWMV) has been prevalent in cucurbits in the Republic of South Africa (RSA) since it was first reported in 1987. However, full genome studies of the South African isolates have never been conducted previously. The full genome of two MWMV isolates infecting cucurbits (Cucurbita pepo L.) in the province of KwaZulu-Natal, RSA, was compared with the genome of the Tunisian isolate in this communication. The genome sequences of the RSA MWMV isolates were elucidated using next-generation sequencing and Sanger sequencing. The analyses performed included nucleotide and amino acid sequence comparison, determination of the genetic distances, detection of potential recombination, and phylogeny. The genome sequences of the RSA MWMV isolates were found to be 9719 nucleotides long, excluding the poly(A) tail. Sequence homology, genetic distances, and phylogenetic analyses indicated close relationships between the RSA isolates. This record will contribute to building up the MWMV isolate sequences from the different countries where the virus occurs, a useful step toward understanding MWMV evolution.

Levels of pesticides residues in the White Nile water in the Sudan.

Twenty-two commonly used pesticides were monitored during autumn, winter, and summer of 2004-2005 in 27 water samples from three sites along the White Nile in Sudan (former Sudan). Sites were selected to reflect pesticides gathered from drainage canals in central Sudan and from upstream sources. Collected samples were extracted and subjected to gas chromatographic analysis. Pesticides levels were measured in nanograms per liter. Pesticides residues were detected in 96 % of the samples with a total residue burden of 4132.6 ng L(-1), and an overall mean concentration and range of 50.99 and not detected-1570 ng L(-1), respectively. Ororganochlorines were the most frequently detected contaminants, which were found in 70 % of the samples, causing a total burden of 2852.8 ng L(-1), followed by pyrethroids 15 % of the samples, with a total burden of 926.5 ng L(-1). The tested herbicides were detected in ˂4 % of the samples with a total burden of 353.3 ng L(-1), while organophosphorus levels were below the detection limit. The most frequent contaminants were the following: heptachlor and its epoxide (52 % of samples), followed by DDTs (dichlorodiphenyltrichloroethanes) (DDT and DDE, in 19 % of the samples), cypermethrin and fenvalerate (in 11 % of the samples), and pendimethalin (in <4 % of the samples). Residues of hexachlorocyclohexane (HCH) isomers (α, ß, γ and δ), endosulfan (α and ß), p, p-DDD, λ cyhalothrin, deltamethrin, and oxyfluorfen were not detected in the analyzed samples. Generally, levels were least in autumn, and followed by summer and winter. Sources of contamination might include agricultural lands in central Sudan and upstream sources. Both recent and old contaminations were indicated.

Effect of surfactants and temperature on germination and vegetative growth of Beauveria bassiana.

Three non-ionic surfactants: Tween20, Tween80 and Breakthru (®) were screened for their effects on spore germination and mycelial growth rates and for their influence on three isolates of Beauveria bassiana spore germination at various temperatures. Tween20 and Tween80 were compatible with all the B. bassiana isolates in the germination studies, but inhibited germination at higher surfactant concentrations, irrespective of the conidial concentrations . Breakthru (®) had an inhibitory effect on germination even at the lowest concentration of 0.1% on all the B. bassiana isolates. The effects of the surfactants on spore germination did not correspond with their effects on colony growth. Conidial viability within the same formulation declined significantly with increases in temperature, irrespective of the surfactant. The optimal temperature for conidial germination of B. bassiana isolates was approximately 25 °C with an upper limit at 30 °C. Isolate 7320 was identified as the least affected by the different surfactants. This isolate was able to germinate rapidly in a broad temperature range of 25-30 °C after 24 h, this characteristic being an essential factor in controlling house fly populations in poultry houses.

Effect of surfactants and temperature on germination and vegetative growth of Beauveria bassiana

Three non-ionic surfactants: Tween20, Tween80 and Breakthru® were screened for their effects on spore germination and mycelial growth rates and for their influence on three isolates of Beauveria bassiana spore germination at various temperatures. Tween20 and Tween80 were compatible with all the B. bassiana isolates in the germination studies, but inhibited germination at higher surfactant concentrations, irrespective of the conidial concentrations. Breakthru® had an inhibitory effect on germination even at the lowest concentration of 0.1% on all the B. bassiana isolates. The effects of the surfactants on spore germination did not correspond with their effects on colony growth. Conidial viability within the same formulation declined significantly with increases in temperature, irrespective of the surfactant. The optimal temperature for conidial germination of B. bassiana isolates was approximately 25 °C with an upper limit at 30 °C. Isolate 7320 was identified as the least affected by the different surfactants. This isolate was able to germinate rapidly in a broad temperature range of 25–30 °C after 24 h, this characteristic being an essential factor in controlling house fly populations in poultry houses.

Levels of organochlorine pesticides in the blood of people living in areas of intensive pesticide use in Sudan.

Ninety-six human blood samples were collected from six locations that represent areas of intensive pesticide use in Sudan, which included irrigated cotton schemes (Wad Medani, Hasaheesa, Elmanagil, and Elfaw) and sugarcane schemes (Kenana and Gunaid). Blood samples were analyzed for organochlorine pesticide residues by gas liquid chromatography (GLC) equipped with an electron capture detector (ECD). Residues of p,p'-dichlorodiphenyldichloroethylene (DDE), heptachlor epoxide, γ-HCH, and dieldrin were detected in blood from all locations surveyed. Aldrin was not detected in any of the samples analyzed, probably due to its conversion to dieldrin. The levels of total organochlorine burden detected were higher in the blood from people in the irrigated cotton schemes (mean 261 ng ml(-1), range 38-641 ng ml(-1)) than in the blood of people from the irrigated sugarcane schemes (mean 204 ng ml(-1), range 59-365 ng ml(-1)). The highest levels of heptachlor epoxide (170 ng ml(-1)) and γ-HCH (92 ng ml(-1)) were observed in blood samples from Hasaheesa, while the highest levels of DDE (618 ng ml(-1)) and dieldrin (82 ng ml(-1)) were observed in blood samples from Wad Medani and Kenana, respectively. The organochlorine levels in blood samples seemed to decrease with increasing distance from the old irrigated cotton schemes (Wad Medani, Hasaheesa, and Elmanagil) where the heavy application of these pesticides took place historically.

Effect of Storage Temperature and Duration on Survival and Infectivity of Steinernema innovationi (Rhabditida: Steinernematidae).

Entomopathogenic nematode species differ in their optimum storage temperature; therefore, we conducted a study on the survival and infectivity of the recently described Steinernema innovationi from South Africa at five storage temperatures (5°C, 10°C, 15°C, 20°C, and 25°C) over 84 d using 20,000 infective juveniles (IJ) in 25 ml aqueous suspension containing 0.1% formalin. Our results showed that survival was highest and most stable at 15°C, ranging from 84% to 88% after 84 d. Infectivity of IJ against Galleria mellonella larvae was >90% for all temperatures except for 5°C at which survival decreased to 10% after 84 d. In addition, we stored 2.5 million IJ on a sponge formulation in 15 ml of 0.1% formalin solution for 84 d at the optimum 15°C followed by 2 wk storage at 25°C. Storage of the IJ on a sponge formulation for 14 d at 25°C post 15°C storage for 84 d did not have a detrimental effect on IJ survival (87%) or infectivity to G. mellonella (95%).

Isolation and Screening of Bacteria for Their Diazotrophic Potential and Their Influence on Growth Promotion of Maize Seedlings in Greenhouses.

Poor soil fertility is one of the major constraints for crop production. Nitrogen is the most limiting nutrient for increasing crop productivity. Therefore, there is a need to identify diazotrophic inoculants as an alternative or supplement to N-fertilizers for sustainable agriculture. In the current study, a number of free-living diazotrophic bacteria were isolated from soils collected from maize rhizosphere and from leaves and roots of maize within the KwaZulu-Natal Province, Republic of South Africa. Ninety-two isolates were selected for further screening because they were able to grow on N-free media containing different carbon sources. Isolates that were very slow to grow on N-free media were discarded. The isolates were screened in vitro for diazotrophic potential tests for ammonia production and acetylene reduction. Ethylene (C2H4) production was quantified and ranged from 4 to 73 nmoles of C2H4h(-1) culture(-1). The top 20 isolates were re-screened on maize seedlings, and eight isolates significantly (P = 0.001) enhanced some growth parameters of maize above the un-inoculated control. Isolates that showed significant effect on at least two growth parameters were identified at species or genera level. In conclusion, selected diazotrophic isolates may be potentially beneficial but they should be tested more in greenhouse and field conditions with maize to confirm their potential for application as biofertilizers.

In vivo effect of selected medicinal plants against gastrointestinal nematodes of sheep.

Nematode resistance to anthelmintic drugs affects small ruminant production globally. This study evaluated in vivo effects of five plant extracts as alternative nematode treatments. Animals were divided into six groups. Each group was randomly assigned a treatment: Abamectin and Praziquantel (CAP) (positive Control), ethanol extracts of Ananas comosus (AC), Aloe ferox (AF), Allium sativum (AS), Lespedeza cuneata (LC) and Warburgia salutaris (WS). These were applied as an oral dose (100 mg kg(-1) BW), one dose per week per sheep for 42 days (Phase 1). From day 42 sheep were orally dosed for 3 consecutive days with the same treatments in the same groups (Phase 2). Rectal faecal samples were taken every 7 days up to day 63. Eggs per gram of faeces were counted in individual rectal samples, L3 larval stage was counted in faecal cultures, with four replicates per group. For plant extracts, EPG decreased (P < 0.001) with time and efficacy of plant increased (P < 0.001) with time. Ananas comosus and L. cuneata treatments had the highest efficacies of 58% and 61%, respectively, in Phase 1; and 77% and 81%, respectively, in Phase 2. Continuous treatment with these plants could further reduce nematode parasites and improve host health.

A survey of pre-harvest ear rot diseases of maize and associated mycotoxins in south and central Zambia.

Maize ear rots reduce grain yield and quality with implication on food security and health. Some of the pathogenic fungi produce mycotoxins in maize grain posing a health risk to humans and livestock. Unfortunately, the levels of ear rot and mycotoxin infection in grain produced by subsistence farmers in sub-Saharan countries are not known. A survey was thus conducted to determine the prevalence of the ear rot problem and levels of mycotoxins in maize grain. A total of 114 farmsteads were randomly sampled from 11 districts in Lusaka and southern provinces in Zambia during 2006. Ten randomly picked cobs were examined per farmstead and the ear rot disease incidence and severity were estimated on site. This was followed by the standard seed health testing procedures for fungal isolation in the laboratory. Results indicated that the dominant ear rots were caused by Fusarium and Stenocarpella. Incidence of Fusarium verticillioides ranged from 2 to 21%, whereas that of Stenocarpella maydis reached 37% on ear rot diseased maize grain. In addition, 2-7% F. verticillioides, and 3-18% Aspergillus flavus, respectively, were recovered from seemingly healthy maize grain. The mean rank of fungal species, from highest to lowest, was F. verticillioides, S. maydis, A. flavus, Fusarium graminearum, Aspergillus niger, Penicillium spp., Botrydiplodia spp., and Cladosporium spp. The direct competitive ELISA-test indicated higher levels of fumonisins than aflatoxins in pre-harvest maize grain samples. The concentration of fumonisins from six districts, and aflatoxin from two districts, was 10-fold higher than 2 ppm and far higher than 2 ppb maximum daily intake recommended by the FAO/WHO. The study therefore suggested that subsistence farmers and consumers in this part of Zambia, and maybe also in similar environments in sub-Saharan Africa, might be exposed to dangerous levels of mycotoxins due to the high levels of ear rot infections in maize grain.