Effects of Initial Infestation Levels of Callosobruchus maculatus (F.)(Coleoptera: Chrysomelidae) on Cowpea and Use of Nicotiana tabacum L.Aqueous Extract as Grain Protectant

This study determined the effects of initial infestation of cowpea seeds （Ife brown variety） with different insect densities （0, 2, 4 and 6 pairs per 50 g seeds） of Callosobruchus maculatus （F.） and evaluated the effects of aqueous leaf extract of Nicotiana tabacum L. on C. maculatus in the laboratory. It was observed that adult beetle population increased significantly （p〈0.05） with increase in insect density. The increase in population of beetles and corresponding weight loss of the seeds in different levels of infestation showed that the cowpea variety was susceptible to beetle infestation, emergence and survival of progeny. Significantly more adults emerged on higher infestation compared to lower and no infestation. In Nigeria, Nicotiana tabacum L. is a locally available plant, with known insecticidal properties. The plant leaf extract was easily extracted with water and confirmed its effectiveness as a protective agent for stored cowpea seeds. Experiment was conducted to assess the effects of aqueous extracts ofN. tabacum at 0, 0.1, 0.2 and 0.3 mL＂ 50 g-1 cowpea seeds on C. maculatus. Data was recorded and showed varying levels of effectiveness against C. maculatus. Result showed that seed appearance was dependent on levels of insect population, while N. tabacum aqueous extract exerted effects on survival of C. maculatus. Aqueous leaf extract of N. tabacum probably contained some insecticidal properties which might have significantly conferred beetle mortality and reduced beetle emergence leading to a decrease in seed weight loss.

Evaluation of Insecticidal Potential of Capsicum chinense Jacq. and Aframomum melegueta K. Schum. Against Trogoderma granarium Everts(Coleoptera: Dermestidae) in Groundnut

The insecticidal potential of seed powders of Capsicum chinense Jacq. （Solanaceae） and Aframomum melegueta K. Schum. （Zingiberaceae） was tested against Trogoderma granarium （Coleoptera： Dermestidae） in the laboratory at （28±2）℃ and 70%± 5% relative humidity. The seed powders were tested at the rates of 0.0%, 0.5%, 1.0% and 1.5% （w/w） of groundnut seeds replicated three times. At the highest rate of treatment, C. chinense caused 56.7% and 76.8% larval mortality at 3 and 7 days post treatment （DPT） respectively while A. melegueta exerted 53.4% and 73.8% larval mortality at 3 and 7 DPT, respectively. Results showed that insecticidal potential of the seed powders against adult mortality of T. granarium and seed damage followed similar trend. The various rates of C. chinense seed powder performed better than .4. melegueta seed powder in causing larval and adult mortality and in reducing seed damage. The activity of the seed powders on mortality of the insect, seed weight loss and seed damage were exposure time and rate dependent. A significant reduction （p〈0.05） in seed weight loss and seed damage was recorded among the treatments and maximum reduction was observed in the seeds treated with the highest rate of C. chinense seed powder. Percentage seed damage significantly （p〈0.05） decreased with increase in the rate of treatment while the highest seed weight loss and seed damage were obtained in the control. The study showed that C. chinense seed powder had higher activity against the test insect pest than .4. melegueta seed powder. The two seed powders had high bio-activity against the insect and therefore could be used in formulating environment friendly plant-derived insecticide.

Identification of damaged corn seeds using air-coupled ultrasound

Corn,an important staple in many countries around the world,is subject to a very inefficient germination rate due to worm-damaged seeds.However,air-coupled ultrasound is a rapid,safe and widely accepted method for the early detection of such damage.In this study,the current effectiveness and future prospects of this technique for identifying damaged seeds were explored.The presented procedure started with drawing a sample of 810 seed particles,consisting of 400 that were intact,400 manually damaged and 10 damaged by worms.Then the principal component analysis(PCA)method was used to reduce the dimensions of air-coupling ultrasonic information and extract the top ten principal components.Finally,a KNN decision tree by using SIMCA software and a Fisher recognition model by using MATLAB software were constructed.The pattern recognition was established by using KNN,which has the most accurate recognition rate.The correct recognition rate of modeling for the front and back data of the intact particles was 98%and 100%,respectively;and for the manually damaged particles,99%and 97%,respectively.The results show that the model developed by using air-coupled ultrasonic data can classify corn seed particles both with and without holes to provide a basis for the development of a seed selection system,which has a significant role in improving the clarity and the germination rate.

Constraints on treeline advance in a warming climate:a test of the reproduction limitation hypothesis

Aims Several mechanistic hypotheses have been developed to explain the existence of alpine treelines worldwide.The reproduction limita-tion hypothesis(RLH)postulates that reproductive processes such as seed production and dispersal are restricted in treeline envi-ronments,thereby limiting the establishment of new individuals in advance of extant treelines.Despite its popularity,no study has tested this hypothesis in a comprehensive fashion.In this experi-ment,we attempted to answer whether there are enough viable seeds being dispersed beyond treeline for sexually mediated tree-line advance,and what the implications of climate change might be on these processes.Methods We established 30 plots across two aspects(north vs.south)and three elevational habitats(forest,treeline and tundra)in a white spruce(Picea glauca)boreal forest-alpine tundra ecotone in south-west Yukon,Canada.In each plot,tree characteristics,seed produc-tion and predispersal damage were measured.Additionally,eight dispersal trays were positioned in each plot to measure seed rain,and germination trials with and without predation exclosures were constructed in a subset of plots to quantify dispersal and germina-tion success.Important Findings Results were highly variable both temporally and spatially.In 2014,a mast year,69%of adult trees produced cones compared to 0.4%in the following year.Higher density of trees in forest plots compared to treeline and tundra resulted in greater seed production at lower elevations.Across all plots,88%of seeds were damaged before dispersal or were not viable.Treeline plots had significantly greater predispersal damage.Seed rain was greater in south-facing plots than north-facing plots.Less than 2%of seeds produced on the landscape were dispersed into Tundra plots,located 50 m above treeline.There was a net movement of seeds from the north-facing slope to the south at our study site,likely due to prevailing winds during the dispersal period.Germination counts were more than double on north-facing slopes and one-third higher inside exclo-sures.Cumulatively,the results provide some evidence for the RLH.Collectively,the high amount of predispersal damage and non-viable seeds,variability associated with dispersal and significant seed predation can functionally influence treeline dynamics.These findings suggest that global treeline distribution models,which rely largely on temperature,may not be entirely accurate for predicting treeline advance-at least at finer temporal scales.Many stochas-tic factors need to align temporally for successful advance,which is likely to result in a lag of many decades between the period of temperature amelioration and an increased number of trees beyond extant treelines.