Category: Threats

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Potato pest heads west

070627.Globodera-Pallida-IGlobodera pallida cysts. Cysts are the egg-engorged bodies of dead female nematodes. Eventually, the cysts dislodge from a plant root and the eggs hatch. Image courtesy Zafar Handoo, ARS.

American agricultural scientists have confirmed the presence of the pale potato cyst nematode (Globera pallida) in soil in Idaho. This is the first time it has been reported in the US, although it has been in Canada for at least a year. The report from USDA makes much of the skilled science needed to distinguish G. pallida from a close relative, the tobacco cyst nematode, (G. tabacum), and we applaud that. What it doesn’t say is that economic losses amount to roughly 2 tonnes per hectare for every 20 eggs per gram of soil. Total losses can approach 80% in the case of heavy infestations. the main means of control is to grow resistant varieties. In the UK this resulted in the rise of Maris Piper, a potato that, in my opinion, is little better than wet blotting paper.

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European corn borer not so boring

Jeremy had a post recently on how to keep track of emerging pests and diseases. Certainly services like ProMED-mail and HealthMap are incredibly valuable. But perhaps even better would be a way to predict what a disease might do before it actually does it, for example as a result of climate change. That’s what some Czech researchers have done for the European corn borer, a pest of maize. ((There’s also an assessment of the risk of spread to new areas in a recent study of the root-parasite Orobanche crenata, but that paper did not specifically consider climate change in any detail.)) They modelled its life cycle on the basis of daily weather data, both current, to see if the model fit reality, and possible future, to predict what the pest might do under different climate change scenarios. The result was that the corn borer will cover the entire agricultural area of the country by 2040-2075, by which time “maize is expected to partly replace traditional cereals (e.g. winter wheat, rye, etc.).” That’s a frightening prospect. Better start planning – and breeding – for it now. ((A recent paper on wheat spot blotch in the East Gangetic Plains of India, Bangladesh and Nepal describes how breeding has made good resistant varieties available, but adds that climate change is tilting the playing field in favour of the disease, which means that breeders can’t afford to rest on their laurels.))

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Earthworms, nematodes, bananas

There’s an interesting paper in the latest Pedologia. Researchers grew Cavendish bananas in all combinations of with and without an endoparasitic nematode, and with and without  an earthworm. They found that the banana plants did better when there were earthworms around, which slightly alleviated the root damage done by the nematodes and made more nutrients bioavailable. This is a great illustration of the importance of having an understanding of agricultural biodiversity as a whole, in the sense of all the different organisms — including crops, pests, symbionts, whatever — that interact in a farming landscape, affecting each other’s performance. These kinds of interactions are what organic agriculture aims to maintain, and why silver bullets rarely work.