Post-harvest Grain Research Articles

Effect of Insecticidal Plant Materials, Lantana camara L. and Tephrosia vogelii Hook, on the Quality Parameters of Stored Maize Grains

The effect of ground powders of two tropical plants, Lantana camara L. and Tephrosia vogelii Hook, on the level of insect damage and the grain quality parameters of stored maize were evaluated for five months. The evaluations were aimed at generating natural product treatments suitable for post-harvest grain protection and as sustainable alternatives to synthetic insecticides in the control of the maize weevil, Sitophilus zeamais Motschulsky. Three rates (1.0, 2.5 and 5.0% w/w) of each plant powder, a synthetic insecticide, Actellic Super 2% dust at 0.05% w/w and an untreated control were used as treatments. Results showed that the plant powders significantly minimised the magnitude of depression in percent grain moisture content albeit at a lesser rate with high concentration and had no effect on the percent germination of maize grains when compared to the controls. The botanical treatments and synthetic insecticide were equally effective in reducing insect damage by 25%, but the level of damage was independent of the concentration applied. Grain colour and odour were unaffected by the botanicals. Results are discussed with regard to the use of botanicals by small-scale farmers as cost-effective and sustainable alternatives to synthetic insecticides in maize grain storage. Key Words: botanicals, indigenous knowledge, grain storage, grain quality parameters, synthetic insecticides, insect damage, seed viability, food safety Journal of Food Technology in Africa Vol.9(1) 2004: 29-35

Major heretofore intractable biotic constraints to African food security that may be amenable to novel biotechnological solutions

The input costs of pesticides to control biotic constraints are often prohibitive to the subsistence farmers of Africa and seed based solutions to biotic stresses are more appropriate. Plant breeding has been highly successful in dealing with many pest problems in Africa, especially diseases, but is limited to the genes available within the crop genome. Years of breeding and studying cultural practices have not always been successful in alleviating many problems that biotechnology may be able to solve. We pinpoint the major intractable regional problems as: (1) weeds: parasitic weeds ( Striga and Orobanche spp.) throughout Africa; grass weeds of wheat ( Bromus and Lolium) intractable to herbicides in North Africa; (2) insect and diseases: stem borers and post-harvest grain weevils in sub-Saharan Africa; Bemesia tabaci (white fly) as the vector of the tomato leaf curl virus complex on vegetable crops in North Africa; and (3) the mycotoxins: fumonisins and aflatoxins in stored grains. Abiotic stresses may exacerbate many of these problems, and biotechnological alleviations of abiotic stress could partially allay some predicaments. Some of these constraints are already under study using biotechnological procedures, but others may require longer-term research and development to alleviate the problems. Despite the huge impacts of post-harvest weevils and of mycotoxins in grains, these issues had not been given high priority in national biotechnological programs, possibly due to a lack of knowledge of their immensity. The need for public sector involvement is accentuated for cases where immediate profits are not perceived (e.g. lowering mycotoxin levels in farmer utilized grain, which does not increase yield) but where the public weal will gain, and will be invaluable, especially where the private sector supplies genes already isolated.

Optimal On-Farm Grain Storage by Risk-Averse Farmers

Most previous research on post-harvest grain storage by farmers has assumed riskneutral behavior and/or made restrictive assumptions about underlying price probability distributions. In this study, we solve the optimal on-farm storage problem for a risk-averse farmer under more general assumptions about underlying price distributions. The resulting model is applied to Michigan corn farmers and findings show, contrary to the all or nothing risk-neutral rule, risk-averse farmers will spread sales out over the storage season. As farmers become more risk averse, the optimal strategy is to sell more grain at harvest and spread sales over the storage season, even though this practice reduces expected return. This result is more consistent with observed farmer behavior than the all or nothing risk-neutral rule.

Efficacy of powder and essential oil from Chenopodium ambrosioides leaves as post-harvest grain protectants against six-stored product beetles

Abstract Powder and essential oil obtained from dry ground leaves of Chenopodium ambrosioides were tested under laboratory conditions (25±1°C, 70–75% r.h.) for their ability to protect grains from damage by six insect pests, Callosobruchus chinensis , C. maculatus , Acanthoscelides obtectus , Sitophilus granarius , S. zeamais and Prostephanus truncatus . The insects were reared and tested on whole maize grain for S. zeamais and P. truncatus , whole wheat for S. granarius , green peas for C. chinensis , mung bean for C. maculatus and white bean for A. obtectus . The powder prepared from dry leaves of C. ambrosioides was mixed with grains at different dosages ranging from 0.05–0.80% (wt/wt) for C. chinensis , C. maculatus and A. obtectus and from 0.8–6.4% (wt/wt) for S. granarius , S. zeamais and P. truncatus . The dosage of 0.4% killed more than 60% of all the bruchids 2 days after treatment, while a dosage of 6.4% induced total mortality of S . granarius and S. zeamais within the same exposure time. All levels of the dry ground leaf concentrations inhibited F1 progeny production and adult emergence of the tested insects. The dosage of 0.2 μl/cm 2 of the essential oil killed 80–100% of the beetles within 24 h except C. maculatus and S. zeamais , where this dosage induced only 20% and 5% mortality, respectively. These results indicate a scientific rationale for the use of this plant in grain protection by local communities in the western highlands of Cameroon.

Products derived from the leaves of Ocimum kilimandscharicum (Labiatae) as post-harvest grain protectants against the infestation of three major stored product insect pests

AbstractThe bioactivity of materials from the leaves of Ocimum kilimandscharicum was tested against Sitophilus zeamais Mots chulsky (Coleoptera: Curculionidae), Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) and Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae) in maize and sorghum grains in the laboratory. Exposure of adults of the three insect species to dried ground leaves and essential oil extract of O. kilimandscharicum induced 100% mortality after 48 h. Fresh and dried whole leaves were not toxic to Sitophilus zeamais or R. dominica. Grains treated with dried ground leaves and essential oil extract caused significant reductions in the number of progeny and survival rate of all three pest species tested. There was no adult survival or progeny production in grains treated separately with each of the two materials at doses of 25.0 g (dried ground leaves) and 0.3 g (essential oil) per 250 g of grain, respectively. Unlike R. dominica and Sitotroga cerealella, grains treated with fresh leaves enhanced the feeding activity of Sitophilus zeamais. Ground leaves and the essential oil, however, protected the grains against feeding by all three species, resulting in lower weight loss and number of damaged seeds compared with untreated grains. All the plant materials were repellent to S. zeamais with the essential oil extract applied at 0.3 g/250 g of grain evoking the highest repellent action. There was, however, considerable variation in the repellency of the materials against R. dominica and Sitotroga cerealella. The results are discussed in terms of the efficacy of O. kilimandscharicum for protection against loss due to insects in traditional grain storage in developing countries.

Study of an Expert System on Preservation of the Quality of Post-Harvest Grain: Planning of Storage Technical Route

The planning space is represented on 3 different abstraction levels : grain, operation, and silo. The planning is hierarchical and non linear and involves several techniques of artificial intelligence : causal diagnosis of grain quality at grain level ; selection of the storage operations needed to preserve grain quality at operation level ; ordering the selected operations, allocating and reasoning on resources, at silo level.The main originality of this study lies in the introduction of a preventive approach to stored grain management which is guided by the preservation of the grain quality.

Plant tissue tests for predicting nitrogen fertilizer requirements in spring wheat

Application of nitrogen (N) at sowing (basal N) alone is not always adequate for maximum yield and quality formation in wheat (Triticum aestivum L.). Because uptake and utilization ofN by the plant is influenced by many environmental and varietal factors, supplementary N may be needed during the growing season, too. Additional N can be applied at particular stages of the plant’s development (phenology) to produce the best result from its use. The applicability of plant tissue N concentration as a diagnostic tool for measuring the N status of a wheat stand to guide economical use of additional N application was reviewed here. On the basis of grain protein concentration data, growers producing spring wheat with consistently low protein concentration are advised to pursue a more vigorous and better planned N fertilization programme in their crops. Plant tissue N testing provides a useful method for the producer to annually optimize wheat grain yield and grain protein concentration. Knowledge of both these ‘critical components’ as determined by pre-harvest N levels of plant tissue and post-harvest grain protein concentration can be utilized for making both basal and supplemental N fertilizer recommendations.

The stored grain ecosystem: A global perspective

Ecosystem principles and processes, such as biological succession, population dynamics, niche concept, limits to growth, and food webs apply to grain storage systems, as well as to forests, oceans, lakes, prairies, and preharvest agroecosystems. In 1989, Odum classified the food-storage system as a human-subsidized, solar-powered ecosystem, one of the four main ecosystems of the world. A grain storage ecosystem is a complex system that can be described in several scales. One may consider the storage structure and its contents as an entire system, or one may consider a group of storage structures as an archipelago of ecological islands linked by transportation and commerce. Government policies and consumer demands are part of the environment that must be considered in effective economic management of the stored grain ecosystem. The grain storage system is part of the postharvest ecosystem, a larger system which extends from harvest to consumption. An understanding of the interrelationship of biological and physical factors, and selection pressures in the system is essential to making sound decisions about the long term directions of postharvest research, as well as the daily management of grain and other food commodities in the postharvest system. In this paper, ecosystem principles are used to draw together progress which has been made in understanding: (1) the physical elements, defined in part by the structure, (2) the biological elements, including human society, and (3) the interrelationships of physical and biological elements in postharvest systems throughout the world. Suggestions given for future directions in ecosystem-based research on the postharvest grain system are drawn from systems in several areas of the world and include examples of reverse technology.

The ecosystem approach for apprehending the extent of postharvest grain losses

The grain bulk in its environment is presented as an ecosystem, comprising biotic (grain, insects, microflora) and abiotic (dockage, intergranular air, water vapors, storage structure) elements. The effect of the stored grain bulk environment and microenvironment on each of the system components is analyzed, and the possible implications of these effects in the cause or prevention of grain storage losses are discussed. The interrelation of the biotic and abiotic elements (variables) of this ecosystem, interacting with each other in causing storage losses, is also considered. It is suggested that the ecosystem approach for evaluating the potential loss of stored grain in a given storage site can be used not only to assess the present status of damage and the storability of grain, but also to indicate the steps needed to prevent losses.