Why is a cornfield more vulnerable to insect and plant disease than a grassland?

Question

Why is a simplified community such as a cornfield usually vulnerable to harm from insects and plant disease than a more complex, natural community such as a grassland?

I have been trying to find the correct answer to this question, but after reading the book (crappy book) I cant find anything and I NEVER ask for homework help, but please someone. This is the last question and I cant even begin to formulate a somewhat correct answer!

Thanks for the great answers guys. I am a Computer Sciences major, and the environmental class is a requirement! I can logically get through most of this stuff on my own, but this one just eluded me!

Answer 1

Lets start with the grass land or, in the US, prairie. In a healthy prairie ecosystem, there is about 120 different plant species. All of the different species have different defense abilities to ward off disease and insects. Some actualy work to protect other species that cannot exist without one another!! Some natural insects of the prairie, such as the tiger beetle, help to protect the plants from invading insects that harm the plants. This is the short answer, but with a variety of plants, insects, and animals in a grassland, it is much more able to resist insect or disease problems.

In a field where there is just corn, one species, it is far more suseptable to insect and disease. There is no genetic diversity to resist a rust blite or other diseases. There are not natural insects that use the corn as a host, that can defend the plants from other insects; ie, root bore, etc. Without genetic diversity, a single species can easily be wiped out.

Answer 2

One of the major contributors is planting corn repeatedly in the same place.

Many disease pathogens survive in crop residue or in the soil. Thus, the risk of increased disease severity is higher when corn follows corn.

Unlike grasses, corn is also more nutrient dense and has more complex parts, making it more desirable to pests and more vulneralbe to fungus.

Another major difference is that a grassland is simply more diverse. There are bugs that eat other bugs and the plants that grow there tend to be hardier and more resistent (without human intervention).

Answer 3

A cornfield is a monoculture, all one crop, custom made for disease spread. In a grassland, the variety keeps the soil more fertile, and a monoculture depletes it, sucking all of certain nutrients out of the soil. If one plant gets a virus in monoculture, many get it. Not so true in a grassland.

Answer 4

Insects carry disease from one plant to another and they like sugar. Corn has the sugar they want as compared to grass that doesn't.

Answer 5

A cornfield is usually irrigated, and fertilized making its vegitation very lush and full of nutrition.....A native grass land is usually not irrigated or fertilized, therefor, its leaves and stocks have much less nutrition, and are not as attractive to pests...I hope this helps..