I don't agree that corporate farming with GM crops makes a country's staple foods more susceptible to parasites. If anything it's the opposite because one of the main goals of GM crop scientists is to develop varieties resistant to blights that are destroying the crops of subsistence farmers. They've saved poor countries from famine many times in this way. Most modern farms use a mixture of several slightly different varieties each with different genes for disease resistance, which makes it harder for parasites to spread or to wipe out a farm's entire yield.

It's definitely a cause for concern that cash crops are often lacking in biodiversity and don't fulfill some nutritional requirements, but we're talking about undeveloped countries where people are starving. I think we should worry first about helping these countries become self-sufficient in food production, and worry about the rest later. Personally I agree that the fruit and vegetables in chain grocery stores are bland, and I buy healthier and better-tasting produce at farmers' markets when I can, but this is a luxury. If it's a choice between McDonald's farms or famine, well, it's not even a choice. Also, if cash crops lack a certain nutrient, we can always provide nutrient supplements, which are dirt cheap compared to the cost of providing a starving country with food. This is another thing the developed world should be doing that it's a shame we aren't.