A comparative study of plant volatiles induced by insect and gastropod herbivory

Insect and gastropod herbivores are major plant consumers and their importance in the evolution of plant defensive traits is broadly recognized. However, their respective effects on plant responses have rarely been compared. Here we focused on plant volatile emissions (VOCs) following herbivory and compared the effects of herbivory by caterpillars of the generalist insect Spodoptera littoralis and by generalist slugs of the genus Arion on the VOCs emissions of 14 cultivated plant species. Results revealed that plants consistently produced higher amounts of volatiles and responded more specifically to caterpillar than to slug herbivory. Specifically, plants released on average 6.0 times more VOCs (total), 8.9 times more green leaf volatiles, 4.2 times more terpenoids, 6.0 times more aromatic hydrocarbons, and 5.7 times more other VOCs in response to 1 cm2 of insect damage than to 1 cm2 of slug damage. Interestingly, four of the plant species tested produced a distinct blend of volatiles following insect damage but not slug damage. These findings may result from different chemical elicitors or from physical differences in herbivory by the two herbivores. This study is an important step toward a more inclusive view of plant responses to different types of herbivores.

Linking host plants to damage types in the fossil record of insect herbivory

Studies of insect herbivory on fossilized leaves tend to focus on a few, relatively simple metrics that are agnostic to the distribution of insect damage types among host plants. More complex metrics that link particular damage types to particular host plants have the potential to address additional ecological questions, but such metrics can be biased by sampling incompleteness due to the difficulty of distinguishing the true absence of a particular interaction from the failure to detect it---a challenge that has been raised in the ecological literature. We evaluate a range of methods for characterizing the relationships between damage types and host plants by performing resampling and subsampling exercises on a variety of datasets. We found that the components of beta diversity provide a more valid, reliable, and interpretable method for comparing component communities than do bipartite network metrics. We found the rarefaction of interactions to be a valid, reliable, and interpretable method for comparing compound communities. Both of these methods avoid the potential pitfalls of multiple comparisons. Lastly, we found that the host specificity of individual damage types is challenging to assess. Whereas some previously used methods are sufficiently biased by sampling incompleteness to be inappropriate for fossil herbivory data, alternatives exist that are perfectly suitable for fossil datasets with sufficient sample coverage.

Preliminary Analysis of Grains Bought from Four Markets in Kano State

The new order in world trade demands strict adherence to the rules of food quality and safety as an essential factor in the selection of raw materials for production since the quality of end products is dependent on that of the raw materials for its production. Therefore, in order to determine the quality of some agricultural grains bought from four markets (Yankaba, Dawanau, Tarauni and A. Rimi) in Kano State, Nigeria. These grains were examined for test weights, pest infestation, level of impurities, and germination potential to determine their export and processing standards. The results showed some difference among the different grains in term of weight, which can be attributed to their difference in physical properties. The result showed that there was some level of impurities present in grains sold in these markets, but no live adult insect was present in all the grain sample. The result also showed that cowpea from respective markets did not meet the standard economic threshold of insect egg free. Cowpea samples had the highest level of insect damage, an average of 2.9 % insect damage was observed. From the result, the average seeds germination in maize and sorghum samples was high (95 % and 88 % respectively) and acceptable according to recommended standards. Determining these terms is important to end users during purchasing, storage, consumption, exportation, and processing, as such will help to increase their knowledge about condition of agricultural produce in our various agricultural market for satisfactory purchasing. There are some food safety standards met by grains sold in these markets, and most commodities sampled too had standards that are either acceptable or unacceptable for consumption, export and processing purpose.

Storage Mycoflora in Sesame Seed Production in Benue State, Nigeria

Sesame (Sesamum indicum) is usually contaminated with many fungi where some of them are mycotoxigenic causing economic and health problems. This study investigated the percentage composition of fungi contamination of sesame seeds in Benue state Nigeria. Using direct plating technique; the study revealed twelve species of fungi contamination in sesame seed obtained in Benue State. The percentage occurrence of fungal isolates shows that Aspergillus flavus and A. niger were found in all the locations and their occurrence was significantly different (P≤0.05). The percentage contamination of Sesame samples collected from Otukpo LGA has the highest fungal (23.35%) contamination and was significantly higher (P≤0.05) from samples of other places whereas Sesame contamination from Gboko was the least with total percentage of (12.05%). In conclusion, considering the benefits of sesame, it is recommended that several treatments should be applied to reduce the levels of contamination in sesame seeds before consumption utilization such as environmental conditions leading to fungal proliferation (a high temperature, humidity, poor soil fertility, drought and insect damage). Also poor harvesting practices, unsuitable storage conditions, improper transportation, marketing and processing should be discouraged.

Generating and testing hypotheses about the fossil record of insect herbivory with a theoretical ecospace

A typical fossil flora examined for insect herbivory contains a few hundred leaves and a dozen or two insect damage types. Paleontologists employ a wide variety of metrics to assess differences in herbivory among assemblages: damage type diversity, intensity (the proportion of leaves, or of leaf surface area, with insect damage), the evenness of diversity, and comparisons of the evenness and diversity of the flora to the evenness and diversity of damage types. Although the number of metrics calculated is quite large, given the amount of data that is usually available, the study of insect herbivory in the fossil record still lacks a quantitative framework that can be used to distinguish among different causes of increased insect herbivory and to generate null hypotheses of the magnitude of changes in insect herbivory over time. Moreover, estimates of damage type diversity, the most common metric, are generated with inconsistent sampling standardization routines. Here we demonstrate that coverage-based rarefaction yields valid and reliable estimates of damage type diversity that are robust to differences among floral assemblages in the number of leaves examined, average leaf surface area, and the inclusion of plant organs other than leaves such as seeds and axes. We outline the potential of a theoretical ecospace that combines various metrics to distinguish between potential causes of increased herbivory. We close with a discussion of the most appropriate uses of a theoretical ecospace for insect herbivory, with the overlapping damage type diversities of Paleozoic gymnosperms and Cenozoic angiosperms as a brief case study.

On-Farm Grain Storage and Challenges in Bagmati Province, Nepal

Farmers in Nepal lose up to one-third of stored grain to pests and diseases. This results in food insecurity and loss of income. To mitigate these losses, farmers use several approaches including pesticide applications on stored grains. We interviewed 241 farmers in Bagmati Province, Nepal, to assess the current on-farm grain storage practices and challenges to improve postharvest management. The results show that rice was the most stored crop (median 1150 kg). About half of farmers stored for at least nine months and grain was mainly used for home consumption. Grain was stored by 66.5 and 69.8% of farmers in granaries (rice) and plastic drums (legumes), respectively. Insects were the most important challenge during storage, and farmers used pesticides to control them. Farmers were more likely to use insecticide on grain (p = 0.000) if they stored rice, used traditional granaries, and had insect damage during storage. The use of improved storage methods (e.g., hermetic bags) was very low for rice (3.5%). There is a need to improve on-farm grain storage by disseminating storage innovations to address postharvest challenges in important crops such as rice.