The invincibility of genetically modified crops may be starting to crumble under its own weight, with Syngenta (NYSE: SYT) being the latest biotech to stress-test their resilience.

Last week, I noted how an Australian farmer was suing a neighboring farmer for contaminating his organic fields with Monsanto's (MON) GM seed, potentially changing the dynamic in how fields can be protected. Rather than go after the seed giant itself, which has never lost a case, suing the individual farmers who've caused the cross-contamination may cause Monsanto to become a pariah among seed buyers.

Source: SXC.hu.

Now both Bunge (BG 2.83%) and Cargill, the biggest U.S. grain exporter, have said they will refuse to accept Syngenta's latest crop of GM corn for export because it will be rejected by China. Although the seeds containing the Agrisure Duracade trait were approved for planting by the FDA last year, making this year's crop the first containing them, it hasn't been approved by Europe or China. In December, China refused acceptance of 665,000 metric tons of corn and byproducts because it tested positive for the presence of MIR162, or Agrisure Viptera, a genetically modified insecticide not approved for import.

The exporters have said they don't want either of them until China approves the genetic modifications, and last month the National Grain and Feed Association and North American Export Grain Association sent Syngenta a letter asking the company to immediately shut down commercialization of both Agrisure Viptera and the new Agrisure Duracade corn unless and until it gets an international seal of approval. While the trade associations support the creation of GM crops, they don't do so if the economic harm they'll create will crush their farmers.

Interestingly, Syngenta acknowledges that many U.S. grain elevators have long posted signs saying they didn't want to accept Viptera corn, so the biotech says the letters aren't really any new stance by the industry, just a long-held position that it's otherwise chosen to ignore. Yet the backlash against genetic modification of food continues to mount. There's a certain illogic to the notion that we can spray seed with poison that kills everything around it but still allows it to germinate and grow. The resulting crops are also sprayed, only to be harvested, sold, and consumed later on.

Although farmers understand that even if Syngenta's corn crop is refused by the European Union or China, there are still other countries that will accept them. The risk is that some GM corn will end up in good shipments thus spoiling the whole batch  if they're tested and found -- and that's too big of a risk to assume.

Consider France is poised to reimpose a ban on Monsanto's MON 810 maize, and that includes insect-resistant maize developed jointly by DuPont (DD) and Dow Chemical (DOW) that the rest of Europe will be forced to accept. Although 19 of the 28 EU members voted against the GM corn, the confederation's weighted voting system meant it still passed. Russia is also considering a complete ban on GMO products.

Syngenta maintains demand for its new Agrisure Duracade seed is strong, particularly in North America, but it's clear resistance is building. Despite the pro-GMO crowd's mantra of "it's all safe, move along, nothing to see here," several seed companies have declined to license the trait from the biotech because of export concerns and scientists see the likelihood of superbugs developing from their proliferation just as they've witnessed the development of superweeds due to the over application of Monsanto's Roundup herbicide.

The problem for Syngenta is one for the industry as a whole, and though they've got their finger in the dike at the moment, leaks are springing up around them everywhere and the whole structure may soon collapse.