Utilizing Pumpkins as a “Reverse” Trap Crop
in Rootworm Resistant Corn
In the world of agriculture, trap crops are normally used to lure pests away from a commercial crop by presenting the pest with a more attractive alternative. But when conducting research to develop new seed traits that provide better yield, drought resistance, or even insect resistance, trap crops can be used to test the performance of a new trait. The western corn rootworm beetle (Diabrotica virgifera virgifera) causes billions of dollars in damage to corn crops throughout the United States each year. Recent seed research has helped develop new corn varieties to combat this problem. These new varieties of corn have a protein (Bt protein) that causes stomach distress in adult western corn rootworm beetles that result in death. Thus, the pest resistance is literally bred into the seed, eliminating the need for harmful pesticides. This type of corn is considered to be rootworm resistant. Normally, in order to be able to “test” the performance of a specific rootworm resistant corn variety, a test plot has to be infested with western corn rootworm eggs manually. This tends to be costly and very labor intensive. The infested eggs then develop into larva, which feed on underground roots. Adult rootworms feed on the above ground tissue of the corn plant. Both the roots and the above ground tissue contain the Bt protein. The corn plant is then “harvested” prior to the pollination period in a process called a “root dig”. During a ‘root dig” the corn plant is cut off at approximately two feet above the ground, the roots are dug up and rinsed with a high power stream of water to expose the roots which are then rated for damage by the corn rootworm larva. Based on the data collected during the “root dig”, researchers are able to evaluate the effectiveness of the resistance that is bred into that variety of corn.
Root dig washing process is shown in picture on the left.
Diagram of corn root damage by corn rootworm beetles is shown in picture on the right.
HYPOTHESIS: What if one could utilize a “trap crop” to entice the adult western corn rootworm beetle to a test plot, allowing the adults to feed and eventually lay their eggs? I predict that by adding pumpkins (independent variable) as a trap crop in rootworm resistant corn will allow for a greater number of eggs (dependent variable) to be deposited in the test plot naturally versus the rootworm resistant corn without the trap crop, therefore eliminating the need for manual infestation. To test this hypothesis, we selected pumpkins to plant as a trap crop in a one acre square plot containing rootworm resistant corn. This would be the independent variable in this experiment. It is known that the adult western corn rootworm beetle is highly attracted to pumpkin vines and flowers. A second test plot of the same size (same farm) would be planted with the same variety of rootworm resistant corn without the pumpkin crop. The dependent variable would be the egg counts in both test plots. The control in this experiment would be utilizing acreage on the same farm. Special steps were taken to replicate the exact soil conditions by a pre-planting soil analysis; utilizing the same “batch” of chemical in herbicide spray applications, and the close proximity to each other to control factors such as precipitation, number of days with full sunshine, humidity, etc. This will aid in controlling the experiment’s internal validity and act as a guide in any subsequent replications of this experiment.
Adult western corn rootworm beetles are shown on a pumpkin flower in the picture on the left. Damage by rootworm beetles on a mature pumpkin shown in picture on the right.
Pumpkins were planted in the test plot # 2 in the spring of 2012...
References: (1) http://www.ars.usda.gov/sp2UserFiles/person/5648/PDF/ARIS 8-Sorghum as a Trap Crop for SGSB.pd
Tillman, P.G. 2006. Sorghum as a trap crop for Nezara viridula L. (Heteroptera: Pentatomidae) in cotton in the southern United States. Environmental Entomology. 35(3):771-783.
Tillman, P.G., Cottrell, T.E. 2012. Case Study: Trap crop with pheromone traps for suppressing euschistus servus (Heteroptera: Pentatomidae) in cotton. Psyche. DOI: 10.1155/2012/401703.
Rea, J. H., Wratten, S. D., Sedcole, R., Cameron, P. J., Davis, S. I. and Chapman, R.B. (2002), Trap cropping to manage green vegetable bug Nezara virdula (L.) (Heteroptera: Pentatomidae) in sweet corn in New Zealand. Agricultural and Forest Entomology, 4: 101-107. doi: 10.1046/j.1461 -
The Dow Chemical Company. Product Safety Assessment (PSA): Herculex RW Rootworm Protection. September 26, 2006. URL: http://www.dow.com/productsafety/finder/herculex.htm.
Please join StudyMode to read the full document