Around 30-40% of crops around the world are lost to insect pests thereby affecting the ability of the 500 million small-scale farmers around the world to contribute towards the goal of achieiving zero hunger and ending poverty. Reducing losses by just 1% could feed millions more people but many countries in the Developing World need support to implement biological control programmes to reduce food losses.
As part of CABI’s mission to help farmers grow more and lose less, we have been funded by USAID – via the United States Department of Agriculture (USDA) – to help Pakistan improve its sanitary and phytosanitary (SPS) systems and therefore open up its fruit and vegetables to more high-end global markets that were previously untapped. Currently these products only contribute 13% of the country’s export but improvements to its SPS capabilities could see this number rise significantly.
By Carol Ellison
It was back in the early 1990s, on my first field trip to Assam in North-east India, with invasion ecologist Dr. Sean T. Murphy, when I first encountered mikania growing as an invasive weed. Until then, I had only seen this vine in its Central and South American native range, where locating a population of the plant could sometimes take all day.
By Urs Schaffner
Over the last few years, biological invasions have become a regular topic in the news. Today the general public is probably better informed about the negative environmental and economic impacts alien invasive species can cause than ever before. However, concern about invasive species and the search for methods to sustainably manage them has a much longer history, dating back to the 19th century.
Genetically modified crops containing a toxin gene from the bacterium Bacillus thuringiensis have been used by farmers for 11 years now. These Bt crops were designed to give the plants resistance to important pests. But might they also be harming non-target invertebrates? A study by Steven Naranjo of the US Department of Agriculture’s Agricultural Research Service looks at the evidence and compares it with the impacts of the pesticides that would otherwise have been used.
Bt maize and cotton have been commercially produced on about 42 million hectares in 20 countries. Their potential non-target effects have been considered in over 360 published research papers. Naranjo, in his paper in CAB Reviews, looks across around 200 of these studies to draw conclusions.
Investigations found that the abundance of all non-target invertebrates was slightly lower for Bt crops than in non-Bt crops, but much higher in Bt crops than in non-Bt crops treated with insecticides. Using meta-analysis, a way of doing a meaningful comparison across different studies, Naranjo found that laboratory studies indicated negative effects of Bt on some non-target invertebrates, though these depended on how the trials were done and which invertebrates were being looked at. However, few harmful effects of Bt crops were shown in field studies. One factor may be that exposure to the Bt toxin is higher in the laboratory experiments than in the field. It was also clear that nontarget effects for insecticides are much greater than for Bt crops.
While Bt crops mean that some specialist parasitoids that would otherwise attack pests of maize have less to feed on, the overall levels of predation on pests have not been shown to drop. Naranjo believes Bt crops could enhance the role of biological control in integrated pest management.
Naranjo's paper emphasises that a key comparison to make is what would have happened without Bt crops. Bt maize and Bt cotton are believed to have led to a 136.6 million kg reduction in insecticide active ingredient, and rootworm-resistance crops will reduce the levels of insecticide present in the soil.
The paper, "Impacts of Bt crops on non-target invertebrates and insecticide use patterns" by Steven E. Naranjo appears in CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2009, 4, No. 011, 23 pp.
Download full CAB Reviews article