Fungicide Spraying is Critical for African Potato Production

African Potato Fields Fungicide Treated (L) Untreated (R)

African Potato Fields Fungicide Treated (L) Untreated (R)

Potato consumption has increased dramatically in Sub-Saharan Africa in the past ten years as more people have moved to cities and have diversified their diets. Potato production has increased to meet the demand through the planting of more fields with potatoes which are encroaching on forestland. Potato yields remain low in Africa primarily due to damage from the late blight disease. Increasing farmer knowledge about late blight and the importance of fungicide recommendations could dramatically increase potato yields.

“Potato cultivars grown in Uganda have low levels of general resistance to late blight. As such, most commercial potato farmers rely on fungicide applications for control of Phytophthora infestans, the causal agent of late blight.

Potato has become an important staple and cash crop in the highlands of eastern Africa. These areas experience moderate temperatures (about 15–22°C) and receive relatively high amounts of rainfall (>1200 mm per year) that are favourable for potato production. However, these same conditions favour severe epidemics of late blight, and as such, late blight is a major limitation to potato production in high humid elevations.

In Uganda, potato late blight has been a serious problem since the introduction of the crop into the country in the early 1900s… During the 1990s, six varieties with resistance to late blight were released. However, resistance to late blight in these cultivars has since been overcome and significant yield losses experienced. Additionally, susceptible varieties are still greatly desired by farmers due to their good agronomic characteristics. Invariably, fungicides must be used to ensure disease control.”

Authors: Kankwatsa, P., et al.
Affiliation: Department of Crop Science, Makerere University, Uganda.
Title: Efficacy of different fungicide spray schedules for control of potato late blight in Southwestern Uganda.
Source: Crop Protection. 2003. 22:545-552.

Do You Want Nematodes with Your Fries?


Nematode-Damaged Potato

Farmers in Oregon and Washington grow 12 billion pounds of potatoes every year. 90% of this production is for processing into potato chips and fries. 80-90% of the potato acres in Oregon and Washington are fumigated every year to reduce populations of nematodes which are microscopic parasitic worm-like animals that live in the soil and penetrate potatoes underground. Females feed just under the potato skin and deposit 200 to 1000 eggs. Brown spots become evident when the eggs are laid. Growers fumigate the soil to reduce the nematode populations because of the potential for rejection of the potatoes for processing into consumer products.

Columbia root-knot nematode (CRN) infects and develops in potato tubers but does not cause yield loss. Columbia root-knot nematode causes quality defects such as galling on the surface and small brown spots surrounding adult females when peeled. The external and internal defects render tubers unacceptable for fresh market sales and internal defects are unacceptable for processing. For processed potatoes, if between 5% and 15% of the tubers in a field have visual defects the whole-field crop can be substantially devalued or rejected. Based on USDA 2010 yields and prices, the average gross value of potatoes in Idaho was $6,921/ha. The rejection of a potato crop grown on an average 52.6-ha center-pivot-sprinkler-irrigated field represents a loss of $364,000. The potential for dire financial consequences from the presence of CRN in potato tubers is taken very seriously by producers.

Because potential for crop rejection exists with low population levels at planting, fields with any CRN must be treated with a preplant fumigant, nonfumigant nematicides, or both.”

Authors: King, B. A., and J. P. Taberna, Jr.
Affiliation: USDA, Agricultural Research Service, Kimberly, ID
Title: Site-Specific Management of Meloidogyne chitwoodi in Idaho Potatoes Using 1,3-Dichloropropene; Approach, Experiences, and Economics
Source: Journal of Nematology. 2013. 45[3]:202-213.

French Government Policies to Reduce Pesticide Use Will Lower Food Production


Pesticide Spraying: French Vineyard

French farmers spend several billion Euros on pesticides each year. A large number of pesticide treatments are made to crops in France: wheat (4), sugarbeets (4), rapeseed (6), potatoes (17), apples (36) and vineyards (7-22). The French government has announced a policy to reduce the use of pesticides by 50%. The French National Institute for Agricultural Research (INRA) estimated the impacts on crop production as a result of the pesticide use reductions.

“The results demonstrated that the commitment of the Environment Round Table to a 50% reduction of pesticide use from current levels is a difficult target to achieve. During an average year similar to 2006, this could correspond to the results of a simulation under which all French farming would switch to integrated production: the reduction in pesticide use would then be estimated at 50% in arable crops, 37% in viticulture, 21% in fruit orchards and 100% in grasslands; drops in yield (in value terms) would then be observed, estimated at 12% for arable crops, 24% for viticulture and 19% for fruits (based on 2006 prices).”

Author: INRA
Affiliation: INRA
Title: Ecophyto R&D – which options to reduce pesticide use?
Source: Ecophyto R&D. January 2010. Pgs. 1-8.

Stopping the Nematode Threat to Potatoes with Fumigation


PCN Damage (right)


PCN cyst hatching

Cyst nematodes are a huge potential threat to potato production in the US. Nematodes are microscopic unsegmented worms. Roots of infected plants contain minute, white bodies of females. When a female dies, its cuticle forms a protective cyst containing 200 to 500 eggs. Cysts containing viable eggs can persist in the soil for up to 20 years. When potatoes are planted, root exudates stimulate juvenile nematodes to emerge from eggs. The juveniles locate and enter potato roots. They cut through cell walls and feed. Infection with nematodes reduces root biomass, which can lead to stunting of plants, yellowing and wilting of foliage and small tubers. Heavy infestations often results in total crop loss. Potato cyst nematodes are widespread in many countries, but only two localized infestations have occurred in the US. The latest infestation, found in Idaho in 2006, has led to a strict treatment program with fumigants.

“Two species of potato cyst nematode are found in the United States: Globodera pallida, the pale cyst nematode (PCN), was first found in Idaho in 2006, whereas the golden nematode, G. rostochiensis (GN), was first found in New York in 1941. Both species are regulated under a Federal Domestic Quarantine Order (USDA-APHIS) and parallel State Rules (Idaho State Dept. of Agriculture, New York State Dept. of Agriculture), and eradication effects are underway.

While some resistance to PCN is present in potato varieties grown in Europe and elsewhere in the U.S., there is no resistance in most of Idaho’s signature russet varieties.

The presence of G. pallida in Idaho has been viewed with alarm by other states and countries that import Idaho potatoes and other farm products. After the initial Idaho PCN detection in 2006, markets for Idaho fresh potato products and nursery stock were lost for Canada, Mexico, and Korea. Japan temporarily closed the market for all U.S. potatoes, and continues to disallow Idaho shipments. Consequently, eradication of PCN is a top priority for the Idaho potato industry, including the Idaho Potato Commission, the Idaho State Department of Agriculture, and USDA-APHIS. Millions of dollars have been spent in Idaho in eradication efforts. A critical component of this work has been treatment of infested fields with the fumigant methyl bromide (MeBr), which has been ongoing since the spring of 2007. Lab tests conducted after each treatment indicate a 95% viability reduction after one year’s fumigation, and over 99% viability reduction after successive treatments.”

Author: Dandurand, L. M.
Affiliation: University of Idaho, Moscow
Title: Novel Eradication Strategies for Pale Cyst Nematode
Source: Potato Progress. September 16, 2013. Volume XIII, Number 10.

Czech Republic: Unsprayed Potatoes Completely Destroyed

Late Blight Destroyed Field

Late Blight Destroyed Field

Spanish explorers brought the potato to Europe from the Americas in the 16th century. A fungus causes a disease of potatoes known as late blight. Infected potatoes emit a distinctive unpleasant odor due to decay of plant tissue. Late blight first appeared in Europe in 1845 and had devastating consequences, particularly in Ireland. Today potato growers in Europe spray fungicides to prevent late blight infections. In the Czech Republic, 1.6 billion pounds of potatoes are grown annually and growers typically spray fungicides seven times yearly. 2011 was an ideal year for late blight development in the Czech Republic with devastating results for unsprayed potatoes….

Czech Republic 2011. In 2011, the weather conditions were very favourable for the development of potato late blight. Rainfall in May, June and August was near the normal in the main production region; however, in July it reached 160 – 180% of the normal. The spread of foliage blight was intensive and the level of tuber infection was also severe. The first more important outbreaks in the potato production region were observed in the second decade of July; however, epidemic late blight spreading was very rapid and non-treated crops were completely destroyed in 2 – 4 weeks, based on locality and varietal susceptibility.”

Authors: Hansen, J. G., et al.
Affiliation: Aarhus University, Dept. of Agroecology, Research Centre Foulum.
Title: The Development and Control of Late Blight (Phytophthora infestans) in Europe in 2010 and 2011.
Source: Thirteenth EuroBlight workshop, St. Petersburg (Russia), 9-12 October 2011.

Zebra Stripes on Potato Chips? No Way.

Zebra Chip Disease

Zebra Chip Disease

5.4 billion pounds of potatoes are used to make potato chips in the U.S. every year. 50% of the potatoes grown in the U.S. come from the Pacific Northwest states of Washington, Oregon, and Idaho. The first appearance of a new potato disease known as “zebra chip” in the Pacific Northwest in 2011 caused great concern. The bacterium that causes zebra chip is transmitted to potato by an insect, the potato psyllid which transmits the bacterium within hours of colonizing a potato plant. Thus, psyllid controls must begin immediately upon detection of the insect in a field. The disease is not harmful to humans when they eat a potato chip, but the bacterium discolors the chips making them unmarketable. In regions where zebra chip has been a problem (Texas, New Zealand, Mexico, Honduras) entire fields have been abandoned.

“Potato producers and researchers, alike, were caught by surprise in late summer 2011 when zebra chip showed up for the first time in Washington, Oregon and Idaho, affecting most of the major cultivars grown in the region. Zebra chip, a disease spread by potato psyllids infected with the liberibacter bacterium, causes dark streaks in the tuber flesh. The discoloration is intensified when the infected tubers are processed into chips or fries. …At this point, the only way you’re going to control zebra chip is to manage your potato psyllids. …Nowhere where this thing has shown up, has it gotten better except by huge applications of insecticides.”

Authors: D. Keller
Affiliation: Field Editor, Potato Country.
Title: Zebra Chip Strikes Pacific Northwest.
Publication:  Potato Country. January 2012. 28-31.

Numerous Fungicide Sprays Needed in Brazil to Prevent Tomatoes and Potatoes from Rotting

Late Blight Tomatoes

Late Blight Tomatoes

The late blight fungus infects both tomatoes and potatoes. The fungus attacks all the aboveground parts of the plant. Infected foliage becomes brown, shrivels, and soon dies. When severe, all the plants in a field may be killed in a week. On tomato fruit, greenish brown greasy spots develop and can cover the entire tomato. Decaying vines can be identified by a foul odor. Environmental conditions in Brazil are ideal for the development of the disease.

“Tomato and potato are the most important vegetable crops in Brazil. During 2002, production of tomato and potato in Brazil totaled 3.6 and 3.1 million tons, respectively. The major producing areas are the south and southeast regions, in which 57.2% of the tomato and 92.3% of the potato are produced. Late blight, caused by Phytophthora infestans, occurs in both regions and is the most serious foliar disease of these crops. The environmental conditions in these regions also are highly favorable to late blight development, leading to severe crop losses if no control measures are adopted.”

“Due to favorable environmental conditions and high susceptibility to late blight, up to 20 and 15 fungicide sprays commonly are used in tomato and potato crops, respectively.”

Authors: A. Reis, F.H.S. Ribeiro, L.A. Maffia and E.S.G. Mizubuti
Affiliation: Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa-MG, Brazil
Title: Sensitivity of Brazilian isolates of Phytophthora infestans to commonly used fungicides in tomato and potato crops.
Publication: Plant Disease. 2005. 89(12):1279-1284.