Specifically, my Russet Burbank potatoes were accidentally infected with thrips and were recently sprayed with Overture 35 insecticide, twice. My latest hypserspectral reflectance measurements show a rise in reflectances for both controls and inoculated plants, when I should expect a drop in reflectances for my inocluated plants. Has anyone else seen this after using Overture, or know of research articles examining the effects of insecticides?
Hello Emily:
http://www.ncbi.nlm.nih.gov/pubmed/20429431
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=928204
I don't work with pesticides/fertilizers but with phosphates. I am not sure why you are expecting a drop in reflectance once that you have sprayed the insecticide, since you are actually adding a reflective material onto another. You should expect for new absorptions features, but not a reflectance drop, Is Overture a dark powder with little reflectance? It seems to me that the Overture spectrum is being added to the potatoes spectra...
Looking from afar, if you are measuring with a white light set up (artificial light directed to sample over a spectralon plate and the reflectance sensor at the same angle that the artificial light is) it might be that the light output changed from the first measurement to the second, but that means blaming the instrument and laboratory conditions. If you have a direct probe-to-sample setup (like using a leaf clip or mineral probe on a FieldSpec spectrometer) make sure that you are calibrating with the same spectralon plaque.
Hope this helps you out... Cheers
Emanuel,
That does make sense that the Overture would cause a rise in reflectance. When I said that I was expecting a drop, it is because the virus, fungus and pests I've infected my plants with are supposed to cause a drop in reflectance, not the Overture. I suppose my question is, are there any papers out there which explore how much of a rise in reflectance would occur after spraying with insecticides? I believe that the two links you provided will help a bit, so thank you!
One thing that didn't make sense to me though is that two of my reps were too young to be sprayed and were half dead because of the spraying during my latest reflectance measurements. With that kind of stress I would expect the reflectance to drop quite a bit from last week's when the plants were healthy. But, alas, they look just the same as the rest. Does anyone know if the residue from spraying would have a higher impact on reflectance than the plant stress would? Because that seems to be the case. Unless, of course, I'm missing something else altogether.
I think this is something that you will have to test yourself in your conditions. I would take a bunch of potato leaves and dip some in Overture and some not. I would do this for all the products (insecticide, fungicide, acaricide, herbicide, fertilizer) that you use. The problem may not be in the active, rather it could be with one or more of the "inert ingredients." An obvious candidate would be any UV protectants in the formulation components/adjuvants. Sometimes dyes are added for various reasons, and these could have an effect.
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