Scientists warn EPA on Monsanto corn rootworm (Reuters) - A group of plant scientists is warning federal regulators that action is needed to mitigate a growing problem with biotech corn that is losing its resistance to plant-damaging pests. The stakes are high - corn production is critical for food, animal feed and ethanol production, and farmers have increasingly been relying on corn that has been genetically modified to be toxic to corn rootworm pests. "This is not something that is a surprise... but it is something that needs to be addressed," said Joseph Spencer, a corn entomologist with the Illinois Natural History Survey, part of the University of Illinois. Spencer is one of 22 academic corn experts who sent a letter dated March 5 to the Environmental Protection Agency telling regulators they are worried about long-term corn production prospects because of the failure of the genetic modifications in corn aimed at protection from rootworm. Monsanto introduced its corn rootworm protected products, which contain a protein referred to as "Cry3Bb1," in 2003 and they have proved popular with farmers in key growing areas around the country. Biotech corn sales are a key growth driver of sales at Monsanto. The corn rootworm product is supposed to reduce the need to put insecticides into the soil, essentially making the corn plants toxic to the worms that try to feed on their roots. But plant scientists have recently found evidence that the genetic modification is losing its effectiveness, making the plants vulnerable to rootworm damage and potentially significant production losses. The scientists said in their letter to EPA that the situation should be acted upon "carefully, but with a sense of some urgency." As concerns have mounted over the last year that Monsanto's rootworm-protected products were losing their effectiveness, Monsanto has said the problem is small and has said the products continue to provide corn farmers with "strong protection against this damaging pest." Monsanto, the world's largest seed company, has recommended growers rotate the corn with its biotech soybeans, use another of its biotech corn products and use insecticides to try to address the problem. "Rootworm performance inquiries in 2011 were isolated to less than 0.2 percent of the acres planted with Monsanto rootworm-traited corn hybrids," said Danielle Stuart, a Monsanto spokeswoman. In all of these cases, Monsanto is working very closely with the farmer and has provided best management practices for the upcoming season on each of these fields.  The problems with insect resistance have been reported in parts of Illinois, Iowa, Minnesota, Nebraska and South Dakota. Continuing to plant a failing technology only increases the resistance development risk, the scientists said in their letter. Moreover, they say, the rootworm-protected BT corn is being planted in areas that have no need for it, often because there are few alternative seed options. Scarcity of non-BT corn seed is a concern, they said. Using insecticides along with the biotech corn as Monsanto has advised is not a good approach, according to the scientists, because it elevates production costs for farmers and masks the extent and severity of the building insect resistance. "Recommendations to apply insecticides to protect transgenic Bt corn rootworm corn strikes us as a clear admission that the Cry3Bb1 toxin is no longer providing control adequate to protect yield," the scientists wrote. "When insecticides overlay transgenic technology, the economic and environmental advantages of rootworm-protected corn quickly disappear," the scientists wrote. EPA Office of Pesticide Programs Director Steven Bradbury, who the letter was addressed to, could not be reached for comment. Reporting By Carey Gillam;editing by Sofina Mirza-Reid