Across the corn belt depending on time of year | The naturally occurring biocontrol nematode population in a field is totally dependent on the pre agriculture fauna and flora of that field before it was placed in agricultural production, a dramatic environmental change. Some natural environments are void of biocontrol nematodes because they didn’t evolve there or were never introduced. The second issue is not all species of biocontrol nematodes are suitable for effective pest control of agricultural insects.
Let me give you an example. NY was almost entirely white pine forest before it was completely deforested for European immigrants to build houses and clear for farm land. In a mature white pine forest, the active soil layer is just a few inches thick and the most common biocontrol nematode in NY completely resides in the top 2” of soil. Convert the field from white pine forest to agriculture and the soil active layer increases from 8-12”. The native biocontrol nematode still only lives in the top 2” leaving a large area for pest insects below the area colonized by the native nematode. While these native nematodes kill a few rootworms when they occur in the top 2”, most rootworms feed on corn roots below 2” deep and therefore escape the naturally occurring nematodes.
The ideal biocontrol nematode needs to cruise through the top 12” to be effective on rootworm. That particular species is exceedingly rare in nature, but is a perfect fit for that disrupted artificial environment called an agricultural production row crop field. When introduced into an agricultural field planted to a single crop and a large number of susceptible host insects it establishes fine and persists fine as long as it is an agricultural field or pasture. Abandon the field and let it return to mature forest, the agricultural adapted biocontrol nematode probably goes extinct.
Hope this answers your question, because your statement about most fields do not support biocontrol nematodes is incorrect. Convert the field to agriculture and introduce the appropriate biocontrol nematode, and we get pest control. BTW, this rare nematode we are introducing to your field is naturally occurring in MN, but you have to look for it in the correct natural environment. |
Biological Control of Rootworm - A link to a recent presentation
