Florence V. Dunkel

The efficacy of linalool, a major component of freshly-milled Ocimum canum Sims (Lamiaceae), for protection against postharvest damage by certain stored product Coleoptera

Abstract Linalool was present at 8.6 ± 0.9 mg/g in the dried leaves of Ocimum canum Sims, an annual mint used in Rwanda to protect against postharvest insect damage. Direct exposure of adults of Zabrotes subfasciatus (Bohem.) to milled, dried O. canum leaves resulted in 100% mortality of males and 50% mortality of females after 48 hr. Dose-response curves for linalool were completed with adult Z. subfasciatus, Acanthoscelides obtectus (Say), Rhyzopertha dominica (F.), and Sitophilus oryzae (L.) using a filter paper bioassay. The LC 50 values were: 428 μg/cm 2 for Z. subfasciatus ; 405 μg/cm 2 for A. obtectus ; 428 μg/cm 2 for R. dominica ; 427 μg/cm 2 for S. oryzae . Knockdown was occasionally followed by recovery at doses less than the LC 50 for all species. There are significant differences in the LC 50 and LT 50 values for male and female Z. subfasciatus . At the lower dosages hyperactivity rarely preceded moribundity and mortality where these occurred, while at higher dosages hyperactivity occurred soon after initial exposure and preceded imminent death. A concentration increase from 250 to 750 μg/cm 2 , representing a tripling of dosage, spanned th 10–100% response mortality for all species at 24 hr. Air-exposure of linalool-treated papers (500 μg/cm 2 ) for up to 24 hr significantly decreased toxicity to both sexes of Z. subfasciatus . Quantitative analysis showed the only significant decrease in the amount of linalool to occur after 0.25 hr, and this did not fully correlate with the resulting decrease in efficacy against both sexes of Z. subfasciatus . The results are discussed in terms of the efficacy of using O. canum for the protection against loss due to insects in the traditional food storage systems of Rwanda.

Dried leaves from Rocky mountain plants decrease infestation by stored-product beetles

Leaves of two highly aromatic plants,Artemisia tridentata (Nutt.) andMonarda fistulosa L., prepared according to a patented process, inhibited oviposition by the Mexican bean weevil,Zabrotes subfasciatus (Boheman), in beans at concentrations less than 1% w/w. Both plant species were less effective against the rice weevil,Sitophilus oryzae L., in wheat, with onlyM. fistulosa exhibiting any concentration-dependent activity. The maximal control achieved against this species was less than 50% at 3% w/w. Two less aromatic plant species,Balsamorhiza sagittata (Pursh.) Nutt. andGeranium viscosissimum Fisch. and Mey., caused only low levels of inhibition against both insect species. Volatiles probably caused the response toA. tridentata andM. fistulosa, while the asymptotic concentration dependence for the less volatile plant material was likely caused by behavioral factors related to the physical presence of foreign particulate matter in the foodstuff. Chemical analysis indicated that most of the volatile components from the dried leaf material from all species were terpenoids, with camphor (9.7 mg/g) and 1,8-cineole (4.0 mg/g) being most abundant inA. tridentata and carvacrol (26.3 mg/g) being most abundant inM. fistulosa.

Contact and Fumigant Efficacy of Powdered and Intact Ocimum canum Sims (Lamiales: Lamiaceae) Against Zabrotes subfasciatus (Boheman) Adults (Coleoptera: Bruchidae)

Abstract The efficacy of powdered and intact dried leaves of Ocimum canum Sims were determined against adult Zabrotes subfasciatus (Boheman) in dried Pinto beans. The finely-powdered dried leaves suppressed oviposition completely at 2% w/w, with an EC 50 of 0.45% w/w. None of the concentrations of intact dried leaves caused a reduction in population, but, increasing concentrations did cause a weak but significant increase in fecundity. At 5% intact leaves (w/w) the number of eggs, hatched eggs and adult F 1 progeny were 110, 110 and 111% of those for the control, respectively. Additional experiments determined that 1% powdered leaves (w/w) in pinto beans caused 100% mortality of adult Z. subfasciatus in 48 h. An assessment of the fumigant toxicity of powdered O. canum leaves indicated that 24 g/l had an LT 50 of 8.15 h. Linalool is the major chemical present in extracts of O. canum leaves. Neat linalool, however, at the amount which is extractable from 24 g of powdered O. canum leaves (207 mg/l) had an LT 50 of 26.0 h. Linalool sorbed onto oat proteinaceous microparticles at 0.85% w/w (the concentration in powdered O. canum leaves) at 1% w/w in beans caused only 24 ± 10% and 56 ± 7% contact mortality of female and male adult Z. subfasciatus at 48 h, respectively. However, fumigation trials with this preparation at 24 g/l had an LT 50 of 83 h, which is very similar to that for the powdered leaves. Thus, the fumigant toxicity of powdered O. canum leaves can be explained by the gradual release of linalool from the powdered material. The contact toxicity evidently involves other chemical constituents. In addition to linalool present at 8.6 ± 0.9 mg/g (previously reported), powdered leaves of this supply of O. canum also contained β-caryophyllene at 0.8 ± 0.1 mg/g and α-bergamotene at 3.4 ± 0.4 mg/g dry weight. These three compounds represented 97.2 ± 0.3% of the material extracted from these dried leaves and probably adequately account for both the fumigant and contact toxicity.

The stored grain ecosystem: A global perspective☆

Abstract 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.

Water quality and waterborne disease in the Niger River Inland Delta, Mali: a study of local knowledge and response.

This paper presents the findings of a study to assess patterns in local knowledge of and response to water quality and waterborne diseases in relation to seasonal changes in the Niger River Inland Delta. The study draws on field data collected in four villages along the Niger River in the Mopti region of Mali during September 2008. The major findings suggest: (1) water use behaviors and diarrheal disease management are influenced by the tremendous seasonal fluctuations in the riverine environment; (2) local awareness of the relationship between poor water quality, oral-fecal disease transmission, and waterborne disease is low; (3) interventions to mitigate the high incidence of childhood diarrhea and degraded water quality are limited by ongoing socio-economic, cultural, and environmental factors; and (4) womens level of health knowledge is socially and culturally dependent.

Toxicity and protectant potential of the essential oil of Tetradenia riparia (Lamiales, Lamiaceae) against Zabrotes subfasciatus (Col., Bruchidae) infesting dried pinto beans (Fabales, Leguminosae)

The essential oil of Tetradenia riparia had limited acute toxicity to adult Zabrotes subfasciatus, with females, which are larger, being less susceptible than males. However, freshly‐applied essential oil at a predicted concentration of 250 μg/cm2 of pinto bean surface completely suppressed the production of F1 adult progeny, with an EC50 of 72 μg/cm2. Eggs were sensitive to this preparation with an EC50 of 50 μg/cm2 of bean surface for F1 adult progeny per parental female. This concentration‐dependant effect upon the eggs was greatly enhanced by physical damage to the eggs during the treatment process, resulting in a population size 21 % of that achieved in controls. Larvae within the beans were well protected from the oil treatment with an EC50 of approximately 3980 μg/cm2 for F1 adult progeny per parental female. However, the EC50 for numbers of subsequent adult F2 progeny for these emergent F1 adults was 121 μg/cm2 of pinto bean surface. This value was similar to that for the freshly‐applied oil against adults, but the data followed a distinctly different distribution that was characterized by limited adult emergence during days 55–85. Emergence occurred even at extremely high concentrations, whereas no adults could emerge (because either no eggs were laid or none survived) for these concentrations when the treatment was directed at either the parental adults or eggs. The activity of the oil increased at 210 days post‐application with an EC50 of 23 μg/cm2 of pinto bean surface for hatched eggs per parental female at 25 days post‐inoculation. The essential oil is quite repellant to ovipositing females after this period of incubation with an EC50 of only 10 μg/cm2 of pinto bean surface. Volatiles emitted after this duration of incubation had a weak but significant effect on fecundity of females selecting untreated beans in a choice test. The essential oil had no effect on bean germination at 180 days. The logistic dose‐response transition equation, y = a + {b/[1 +(x/c)d]}, may better fit resulting population size estimates for experiments involving a ‘dose‐response’ than probit analysis, because midpoints can be determined for transitions in which partial suppression data are limited. We conclude that the essential oil of T. riparia may make an effective seed treatment against Z. subfasciatus at 1.7 1/to; but to be used as a treatment for beans for consumption, additional research must evaluate mammalian toxicity and palatability of these treated beans.

Storage Temperature of Neem Kernel Extract: Differential Effects on Oviposition Deterrency and Larval Toxicity of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

Abstract Neem has been used as an effective postharvest protectant for many crops. Neem is especially effective against the cowpea weevil, Callosobruchus maculatus (F.), a major pest of cowpeas. Although it is well known that azadirachtin A breaks down rapidly at high temperatures, the efficacy of neem kernel extract previously exposed to high temperatures for protecting stored pulses has not been conclusively investigated. Effectiveness of these materials would allow West African farmers to make a neem extract at their convenience and store it for later use. We found that neem kernel extract continued to reduce infestations of C. maculatus, after the neem kernel extract had been stored at high temperatures, including 2 wk at 50°C followed by up to 5 mo storage at 28°C. Neem kernel extract analyzed with high performance liquid chromatography revealed that azadirachtin A present in unheated or fresh neem kernel extract dissipated when stored at 50°C for 2 wk. Neem kernel extract heated to 28°C or above also lost effectiveness as an oviposition deterrent. However, the number of neem kernel extract-treated eggs that survive to become adults was significantly reduced even when the neem kernel extract was exposed to 50°C for 2 wk. We attribute the mortality we observed, which was maintained even when azadirachtin A was absent in neem kernel extract, to physical effects of the oil properties of neem kernel extract. We conclude that neem kernel extract can be stored at high temperatures for at least 5 mo without significant reduction in overall effectiveness.

The Potential for Entomophagy to Address Undernutrition

The use of insects as food for humans has the potential to substantially reduce undernutrition worldwide. The Food and Agriculture Organization of the United Nations estimates that 805 million people are undernourished, with a total food energy deficit of 67.6 billion kcal/day (84 kcal/day/person). Calculations in this article suggest that this deficit could theoretically be reduced or eliminated through edible insect rearing, utilizing organic side streams as feed, on 15,586 to 92,976 ha.

Effects of Steam-Distilled Shoot Extract of Tagetes minuta (Asterales: Asteraceae) and Entomopathogenic Fungi on Larval Tetanops myopaeformis

ABSTRACT Interactions of a biopesticidal formulation of steam distilled shoot extract of Mexican marigold, Tagetes minuta, and entomopathogenic fungi were evaluated for management of the sugarbeet root maggot, Tetanops myopaeformis (Röder). Shoot extract plus surfactant (E–Z Mulse) (=T. minuta oil) was used in a 65:35 ratio to test the hypothesis that this fungicidal and nematocidal biopesticide causes dose-dependent mortality and developmental arrest of T. myopaeformis but does not interfere with the action of entomopathogenic fungi when applied together. A soil-petri dish bioassay system was developed to test the hypothesis. For diapausing, nonfeeding but active 12-mo-old third-instar larvae, 0.5% T. minuta oil treatment (=0.325% active ingredient [AI]) was sufficient to prevent pupation without mortality, but 0.75% T. minuta oil treatment (=0.458% AI) was lethal for 93% of the test insects. The effect of T. minuta oil on fungal efficacy under simultaneous use was studied using a model system of two entomopathogenic fungi, Beauveria bassiana (Bals.) Vuillemin. TM28 and Metarhizium anisopliae variety anisopliae (Metsch.) Sorokin MA 1200, in a soil-based bioassay with larval sugarbeet root maggots. No adverse effects of T. minuta oil on action of entomopathogenic fungi and no synergy were found; an additive effect of the T. minuta oil and each fungal isolate separately was found.

Potential Use of Neem Leaf Slurry as a Sustainable Dry Season Management Strategy to Control the Malaria Vector Anopheles gambiae (Diptera: Culicidae) in West African Villages

ABSTRACT Larval management of the malaria vector, Anopheles gambiae Giles s.s., has been successful in reducing disease transmission. However, pesticides are not affordable to farmers in remote villages in Mali, and in other material resource poor countries. Insect resistance to insecticides and nontarget toxicity pose additional problems. Neem (Azadirachta indica A. Juss) is a tree with many beneficial, insect bioactive compounds, such as azadirachtin. We tested the hypothesis that neem leaf slurry is a sustainable, natural product, anopheline larvicide. A field study conducted in Sanambele (Mali) in 2010 demonstrated neem leaf slurry can work with only the available tools and resources in the village. Laboratory bioassays were conducted with third instar An. gambiae and village methods were used to prepare the leaf slurry. Experimental concentration ranges were 1,061–21,224 mg/L pulverized neem leaves in distilled water. The 50 and 90% lethal concentrations at 72 h were 8,825 mg/L and 15,212 mg/L, respectively. LC concentrations were higher than for other parts of the neem tree when compared with previous published studies because leaf slurry preparation was simplified by omitting removal of fibrous plant tissue. Using storytelling as a medium of knowledge transfer, villagers combined available resources to manage anopheline larvae. Preparation of neem leaf slurries is a sustainable approach which allows villagers to proactively reduce mosquito larval density within their community as part of an integrated management system.