Understanding threats to Brassica crops: A case study
Study Results.
Camera Trapping.
Herbivory.
Black Rot.
There were eight camera traps set up along the wildlife corridor at the beginning of the survey. Each week, we went over the pictures taken and replaced the memory card. In all 24,077 images were taken over a span of four weeks. During the survey, only one image of a groundhog was taken.
The video on the right is a clip of 392 pictures from the eighth camera which was facing the direction opposite our study site. This is the camera on which the groundhog was captured.
Below is a small collection of images that were taken during the survey. From left to right is a dog, groundhog, humans, and grass.
Over the course of four weeks, there was relatively little herbivory damage in the study plot. Only one crop type (Kohlrabi) was consitently affected by the presence of groundhogs and other small mammals. Other Brassica crops showed the signs consistent with small mammal herbivory, including Collards and Black Kale. Unlike the Kohlrabi, both of these crops became less impacted over the course of the study.
Before the study began, we believed that a higher presence of herbivory would be observed in the crop rows that were closest to the wildlife habitat. This was because groundhogs do not often venture further than 100 feet from the entrance of their burrow. As the mammal likes to remain under cover during the majority of the day, as well as within close proximity to their burrow it was predicted that they would remain within the rows closest to the wildlife habitat.
This was not the pattern that was observed. The groundhogs ventured into the middle sections of the field, avoiding the three rows of Daikon Radish closest to the habitat area. Currently we are unsure of the reasoning behind this pattern.
Over the course of four weeks, there was a consistent amount of black rot damage within the Brassica crops. Though many of the crops were affected by black rot disease, one crop type (Gai lan) was noticeably more impacted.
Before the study began, we believed that there was likely to be a correlation between the movement of small mammals, specifically groundhogs, and the presence of black rot. This meant that we expected the black rot to be more prevalent in the areas with higher signs of herbivory damage.
However, this was not the pattern observed. The presence of black rot seemed to be most concentrated in the Gai lan crop, and slowly spread out to affect more each week. The Gai lan acted as the epicenter for the disease, as the spread of black rot occured in a concentric pattern away from that crop type.
On each of the maps, the darker red marks the areas of the plot highly impacted by herbivory while the green is less impacted. White was not affected at all.
The image on the left is of Kohlrabi, the most affected crop type.
As in herbivory damage, the Daikon Radish was the least impacted by the presence of black rot. This is likely because it is the least suceptible, due to its underground growth.
In each of the maps depicting the spread of black rot disease the darker red color marks a higher concentration and impact on that particular section of crop. The light green is least impacted, while the yellow colors are inbetween green and red.
The image to the left is of Gai lan, the crop most impacted by black rot.