Potato Late Blight
The Washington Post is not known for publishing articles describing the benefits of pesticide use. However, in a recent article about the development of a biotech potato in Ireland, a Post reporter described the current use of fungicides to control the late blight fungus. In the 1840s the Irish peasant population depended almost entirely on the potato for their diets. The late blight fungus destroyed the Irish potato crop in 1845 and 1846 and a million people died. Today, the fungus is well-controlled with regular fungicide spraying, a point made by the Post reporter…..
“The disease has become even more damaging in the past five years with the arrival of new, highly aggressive strains. Unchecked, blight can destroy entire crops in just days.
From the end of May until harvest, farmers spray fungicides every seven to 14 days, depending on the weather.
Without the sprays, the potato fields of Ireland would echo the destruction that began in 1845, when the blight took hold in Flanders and moved like wildfire to the British Isles.
More than a million died of starvation and disease, and as many as another 2 million fled to Britain, North America and other lands.”
Author: Adrian Higgins
Title: Modified tuber is no small potato in Ireland
Source: The Washington Post, March 17th 2013
Colorado Potato Beetle
The native home of the Colorado Potato Beetle is the American West from which it has spread around the world eating potato plants. After adult beetles mate, each female deposits 500 eggs on a potato leaf. The larvae emerge and eat the leaves for about three weeks. Feeding by the beetles can defoliate plants, killing them, or significantly reducing their yields.
“The Colorado potato beetle (CPB), native to the south-west United States and Mexico, is the most important agricultural insect pest throughout North America, Europe and parts of Asia. … The beetle invaded China in the 1990s from Kazakhstan. Since then, it has spread eastwards by more than 40 km per year and is currently distributed throughout most of the northern Xinjiang Uygur Autonomous Region. Foliage damaged by the CPB is a serious threat to potato crops in northern Xinjiang.”
“The beetles consume the leaves of the potato plants, causing a 30-50% reduction in yield each year, with no gain at all in some fields. … Insecticide treatments are currently indispensable and effective in CPB control.”
“Increasing the scale of potato farming is now seen as an important measure in resolving the food crisis and overcoming poverty in provinces such as Gansu, the Inner Mongolia Autonomous Region and the Ningxia Hui Autonomous Region… where the acreage of potato crop reaches over 1 million ha. Therefore, controlling the damage and spread of the CPB has become an important issue in China.”
Authors: Zhaoxu Zhou, Jinhuan Pang, et al.
Affiliation: State Key Laboratory of Plant Genomics, Chinese Academy of Sciences, Beijing, China
Title: Evaluation of the resistance of transgenic potato plants expressing various levels of Cry3A against the Colorado potato beetle (Leptinotarsa decemlineata Say) in the laboratory and field.
Publication: Pest Management Science. 2012. 68(12):1595-1604.
Potato psyllids in the Pacific Northwest are spreading a new disease, Zebra chip. Beginning in 2011, psyllid feeding has spread a virus that reduces potato yields and renders tubers unmarketable with bands that darken when fried. Immediate spraying to control the insect vector is required.
“Researchers say populations of potato psyllids – vectors of zebra chip, a crop disease new to the region – are growing dramatically in the Columbia Basin.”
“Despite the increasing psyllid pressure during the past couple of weeks, Phil Hamm, an Oregon State University plant pathologist, believes the disease shouldn’t cause major problems for growers who stick with insecticide programs. … ‘When the region has psyllids, you treat,’ Hamm said.”
Author: John O’Connell
Headline: Psyllid populations growing dramatically
Publication: Capital Press. August 31, 2012.
The pathogen Phytophtera infestans causes a disease of potatoes called “late blight”. The pathogen grows in potato plants, breaking down cell walls so that it can use the nutrients found within them. Severely infected plants have an acrid odor which is the result of dying plant tissue. In the 1800s, Irish peasants subsisted almost entirely on potatoes. The late blight fungus arrived in 1845 and destroyed 40% of the Irish crop. In 1846, 100% of the crop was destroyed. Over 1.5 million Irish died of famine and a comparable number emigrated to America and other countries. Today, the fungus is still present in Ireland and would destroy the crop again if not for fungicides.
“Without the routine use of fungicides, large-scale commercial potato production in Ireland would be impossible. The cool, damp climate, which favours the cultivation of the potato and limits problems with virus diseases, is also ideal for the spread of blight. … In warm, wet weather when the humidity is high, P. infestans will lay waste an unprotected crop. … To prevent such devastating losses, the potato industry in Ireland has long been reliant on a substantial annual usage of fungicides.”
Author: L.R. Cooke
Affiliation: Plant Pathology Research Division, Department of Agriculture for Northern Ireland
Title: Potato blight control in Ireland: a challenging problem.
Publication: Pesticide Outlook. 1992. 13(4):28-31.
Potato is a very popular vegetable crop in Myanmar and is essentially grown all year round. Phytophthora infestans, the fungus that caused the Irish Potato Famine in the 1840s, was first found in Southeast Asia in the late 1800s and has since been an annual widespread problem. Without fungicide protection, the disease spreads rapidly and can kill all the plants in a field within a few days.
“In Myanmar, late blight caused by Phytophthora infestans is the most destructive disease of potato. … High incidence and severity of potato late blight occur in this area because the crop can be found year-round at all stages of development, providing a constant source of primary inoculum.”
“At present, fungicide applications play a vital role in potato late blight control as resistant cultivars have not been widely available and adopted. … Fungicide is applied most frequently on post monsoon crops, which is when the weather conditions are ideal for late blight development.”
Author: M.M. Myint, Y.Y. Myint and H. Myint
Affiliation: Department of Plant Pathology, Yezin Agricultural University, Yezin, Myanmar
Title: Occurrence and growers’ perception of potato late blight in Kalaw Township, Myanmar.
Publication: Regional Workshop on Potato Late Blight for East and Southeast Asia and the Pacific Proceedings. 2004. 24-25 August, Yezin, Myanmar.
Organic growers are severely limited in the tools that they can use to fight fungal infections since they cannot use effective chemicals. One unhappy result was severe losses to diseases in the organic potato fields of Northern California last fall.
“John Crawford, part owner of Crawford Farms, Inc. for commercial farming and Cascade Farms for organic farming in Tulelake, said everyone across the county is two weeks behind on their potatoes. … The cool spring also contributed to problems with rhizoctonia disease… Rhizoctonia girdles the roots and the stem, then the plant withers and yield is reduced.”
“Rhizoctonia was a huge problem in Crawford’s conventional potatoes and crops would have a 100 percent infection rate. Now, with the new chemical compounds, he has good control. But Crawford said he continues to struggle with rhizoctonia in his organic potatoes. ‘It’s our worst enemy in organics because we really don’t have a natural compound that is very good at fighting it,’ he said, adding in one field of organic potatoes he estimates 75 percent are infected with rhizoctonia. … Crawford estimated at least a 20 percent yield loss from rhizoctonia damage.”
Author: Kathy Coatney
Title: Rhizoctonia and wilt create challenges for potato growers.
Publication: Ag Alert. September 14, 2011. p.18
The disease of potatoes known as ‘early blight’ occurs earlier in the season than the well-known ‘late blight’ disease. Early blight is a significant problem in Wisconsin and Minnesota potato fields. Fungicides have been used for over 100 years to protect potatoes from early blight. Recent research in Wisconsin shows that modern fungicides continue to be most effective with newer chemistries expected to continue effective control into the future.
“Potato early blight is a perennial and potentially destructive disease caused by the fungus Alternaria solani. Appropriately-timed, effective fungicides are necessary to limit yield and quality loss. In 2010, we evaluated 38 fungicide programs for early blight control at the University of Wisconsin Hancock Agricultural Research Station on ‘Russet Burbank.’ Programs included an untreated control, conventional and organic grower standard programs, and newer chemistries.”
“The highest yielding program was the Wisconsin conventional grower standard. Organic treatments were ineffective. Several newer chemistries and modified standard programs were effective. At this time, and in the registration pipeline, there are excellent fungicides for the control of potato early blight that will contribute to good fungicide resistance management practices.”
Authors: Kenneth Cleveland, Jamie Dobbs, Rosemary Clark and Amanda Gevens
Affiliation: University of Wisconsin-Madison, Dept. of Plant Pathology
Title: Evaluating the efficacy of fungicide programs for the control of potato early blight in the Central Sands of Wisconsin.
Publication: American Journal of Potato Research (2012) 89:32.