Lab 4: The JOY of estimating soybean damage

This weeks lab assignment was to look at two different ways of estimating plant damage in soybeans. Unfortunately, this did not mean that we were allowed out into the field but the “field” was brought to us.

We used two different types of qualitative methods:
The first one was to look at soybean plants and determine the types of damage to the plants and try to determine what type of insect caused that damage.

The early planted soybeans had already gone through senescence. So they were brown and dead looking. It was difficult to determine what kinds of damage the plant had sustained. It appeared like it had some root loss but this could have been caused by being ripped out of the ground. However, “real” root loss is caused by various grubs (beetle larvae). I would say that its too late to sample these plants again especially since its so difficult to see the damage.

On the other hand, the late planted soybeans were green and yellow and it was easier to find potential insect pest damage. Some of the leaves had “window paining” damage which is usually caused by caterpillars. There was chewing damage in the middle of the leafs which is indicative of bean leaf beetle feeding. Chewing damage in the leaf margins indicates the presence of grasshoppers and caterpillars.

Some of the soybean pods had round damage which indicates more caterpillar feeding. I think that the late planted plants coudl be sampled again and could benefit from a sampling of the pests that are in the field.

The second estimation method involved estimating soybean leaf damage. Sixty leafs were obtained from the KSU Ashland Research Farm and were placed in plastic sandwich bags. Each student was asked to estimate the percent of damage on the leaf and write it down in a grid. My leaf estimates ranges from 1-96%, the mean was 26.1, and the standard error was 25.4. The standard error is quite high but in this case where we are estimating damage it is quite possible that there would be that much variation in the estimates of leaf damage. The teacher and his students used a scanner and image analysis software to determine the actual leaf damage estimate. The then compared the students estimates to the actual leaf damage estimate.

The teacher posted the above graphs with the equations and R2 values at the below link if you are interested in the r2 values and linear equations.

http://ipdmanhattan.blogspot.com/2009_10_01_archive.html

The class r2 values range from 0.8447 to 0.6798. The r2 values indicate the fit between the observed (our estimates) and the model (the scanner). R2 values run from 0-1, where 1 indicates a "perfect" fit. So our estimates are fairly good to medium in range.

http://en.wikipedia.org/wiki/Coefficient_of_determination link for more information on r2 values

I did not "win" the prize for having the best r2 value but my r2 of 0.7801 was good enough for second place so I can't complain. Additionally, this indicates that my mean and standard error were very good and there was that much variation.

Experience rating:

So-so, I would rather have been outside and not in a lab but I did learn that my leaf estimation is decent.

On a non-lab related note. One of my friends heard the below song and suggested that I listen because "its me." I agree, and it does have one of my favorite insects in the title so if you like music and can handle metal then check it out. The video is not theirs but is done by a fan and he/she includes dragonfly slides so it is "educational" to a small degree.

Note that I FINALLY figured out how to embed videos into the blog!!!!!

This week we also turned in another bug byte so to see mine click on the below link:

http://ent612.wetpaint.com/page/convergent+ladybeetle