Saber Miresmailli

Environmental impact and sustainability of feedstock production

This project will inform the broader biofuel and environmental communities of the potential ecosystem consequences and benefits of the extensive deployment of perennial feedstock crops in land currently supporting row-crop agriculture, and will guide efforts to reduce unforeseen negative impacts of these feedstocks.

Volatilization of individual components of botanical products

In previous studies we have shown that essential oil-based pesticides are non persistent and break down noticeably faster than conventional chemical pesticides (Miresmailli and Isman, 2006). We have also found that some constituents in a chemically-complex essential oil have synergistic effects on efficacy of the mixture against pests and these effects do not necessarily depend on their relative abundance in the mixture (Miresmailli et al., 2006). These and many similar experiments conducted in laboratories are based on the assumption that after application, all the constituents of the essential oil mixtures are available and functioning at the same time. However, our recent observations suggest a different scenario.We analyzed a sample of an insect repellent with an ultra-fast gas chromatograph (zNose™) and noticed that different constituents are released from the mixture at different times. In some cases, certain compounds were not released until another compound completely left the mixture.The new ultra-fast GC enables us to analyze chemicals in an extremely short time (30 seconds for most of the compounds) with a greater sensitivity compare to regular GC (PPT versus PPM). The device is battery operated and can be used for field research. The suitability and reliability of this new technology for field work has been confirmed by some well known scientists in the field of plant volatile analysis (Kunert et al.2002. Journal of Separation Science 25, 677-684, Miresmailli et al. 2010 submitted). Now - with this new technology- we can have a better understanding of the behavior of individual components of botanical pesticides and find the optimum time frame when all the important constituents are available at desirable concentrations.

Miresmailli S., Bradbury R., and Isman M.B. 2006. Comparative toxicity of Rosmarinus officinalis L. essential oil and blends of its major constituents against Tetranychus urticae Koch (Acari:Tetranychidae) on two different host plants. Pest Management Science, 62: 366-371

Miresmailli S., Isman M.B. 2006. Efficacy and persistence of rosemary oil as an acaricide against twospotted spider mite on greenhouse tomato (Acari: Tetranychidae). Journal of Economic Entomology, 99(6): 2015-2023

A new approach towards pest management

Translating plant’s signals

Pest management programs are based on several practices among which pest identification and population monitoring are very important ones. Even in recent years, developing new control methods has been the center of attention for many researchers and far less has been done to develop more effective detection and identification tools that are the first steps for any pest control program. Like other organisms, cultivated plants produce many symptoms and signals in response to biotic stress (viz. pathogen infection or herbivore attack).

Detecting these signals at an early stage could be a key factor for successful pest control. Plants emit a wide array of volatiles, some of which are novel, when infected with pathogens or attacked by pests. Emission of these volatiles is part of an indirect defense mechanism that can help the plant to attract predators and parasitoids that will attack pests. Pests themselves or their presence / feeding symptoms have been the center of attention for most current pest monitoring practices. However, in this project I suggest a novel approach to pest monitoring by shifting the attention from the pest to the plant.

If interpreted correctly, plant driven volatile chemical signals can provide more accurate information about the health of the plant. By using well-developed mechanical olfaction technology (known as the ‘electronic nose’), we can follow these chemical cues to locate crop problems be-fore they become visible to the naked eye of human scouts. This could enable a grower to take early action, preventing pest or disease dispersion and further damage by controlling the problem right at the source.

Electronic noses are special biosensors that are able to detect different types of volatile chemicals at various concentration based on their sensitivity. These sensors are used mostly in food processing plants to measure the quality of meats and other food products. They also have many applications in military and anti-terrorism practices (by detecting explosives). The sensors can be programmed to detect specific volatiles and monitor changes in the concentration and quality of these volatiles. Electronic chemosensors are very sensitive and can detect chemicals in concentrations as low as parts per trillion.

In order to use biosensors in pest control programs, we need to have a database of plant volatiles emitted in response to pests and diseases. First we should collect plant volatile chemicals, analyze them and select a set of com-pounds as indicators. After documenting the variability of indicator compounds emitted from clean and infested plants, we can select the best sensor(s) to detect these variations and report changes. Based on these reports and a database, initial pest problems can be localized and appropriate action taken.

It is a fact that plant driven volatiles might vary due to several biotic (pests, diseases) and abiotic (light,temperature, moisture, stress) factors. Therefore, the pest induced-plant volatile data-base will be designed in such a way that enables me to segregate pest induced signals from non-pest induced signals and also can provide a flexible and robust range of acceptable signals. Many techniques have been developed in recent years (i.e. Neural net-works, fuzzy logic, discriminant analysis, data mining, pattern recognition, etc.) which allows creation of such intelligent databases.

As Part of my PhD project, I assessed the suitability of herbivore-induced plant volatiles as indicators of cabbage looper (Trichoplusia ni, Noctuidae) infestation on tomato plants for developing a pest monitoring system inside tomato greenhouses. From volatile blends of infested tomato plants, four compounds have been selected as T. ni infestation indicators: (Z)-3-hexenyl acetate, (E)- β-ocimene, limonene and β-caryophyllene.

Laboratory results indicated significant quantitative differences in the emission level of these indicator chemicals from infested plants compared to clean plants. Research greenhouse trials confirmed these results and also indicated that these differences are detectable six hours after initiation of infestation. The research greenhouse trials also indicated that is it possible to obtain information about T.ni population density, their location within the plant canopy and their feeding duration.

A survey was conducted inside a commercial greenhouse. Indicator chemical emission levels, pest infestation status, environmental factors and operational practices were recorded. Pest infestation was found to have significant effect on the emission of indicator chemicals.

A portable gas chromatograph (zNose) was used for most phases of this research. This instrument was found suitable for fieldwork and monitoring rapid changes in the emission levels of plant volatiles.

In general, these four chemical volatiles were found to be suitable indicators of cabbage looper infestation in greenhouse tomato plants.