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. 45:202-213.
Sclerotinia Rot of Carrots
Sclerotinia rot of carrot (SRC), caused by Sclerotinia sclerotiorum, is one of the most economically important diseases of carrots. Losses to this disease can occur from pre-harvest epidemics, originating in the field, or from post-harvest outbreaks caused by infected carrots entering storage. Post-harvest outbreaks are particularly devastating, with storage losses of some commercial growers reported as high as 50% in Canada.
“Typically, in Prince Edward Island (PEI), where about 300 ha of carrots are grown, losses in storage due to SRC occur in most years. In 2006, losses due to SRC cost carrot growers in PEI approximately $500,000. In 2007, losses in storage of approximately 25% (valued at $350,000) occurred, and yet, 2007 was not considered a year with high disease pressure. After witnessing the serious disease pressure and crop losses occurring at the local vegetable co-op first hand, our research teams initiated a program to examine potential post-harvest control options for SRC in storage.
Based on the results of our studies, fludioxonil (Scholar) was found to be an excellent tool for managing SRC in storage. …In 2008 and again in 2009, Scholar 50WP (a product currently registered in Canada for post-harvest control of some fruit diseases) received emergency registration in Canada for post-harvest use by carrot growers for control of SRC in storage. Feedback from growers in PEI indicated that the post-harvest use of fludioxonil in 2008 prevented the type of losses due to SRC experienced in previous years.”
Peters, R. D., et al.
Affiliation: Agriculture and Agri-Food Canada.
Title: Post-harvest Application of Fludioxonil for Control of Sclerotinia Rot (Sclerotinia sclerotiorum) of Carrots in Storage.
Source: Carrot Country. Winter 2009. Pgs. 12-15.
Bean rust usually is observed first as discrete pustules which are filled with cinnamon-brown spores, which leave a dusty brown streak when rubbed. The last bean rust epidemic in North Dakota in the 1990s caused in excess of $10 million in crop losses. Following the introduction of rust-resistant dry bean varieties produced through crop breeding, rust was not a problem until 2008 when a new race appeared which could overcome the resistance. Since the new race was first detected, rust has re-appeared every year. However, the disease has caused little damage due to frequent fungicide applications for white mold (most of the fungicides applied for white mold have some efficacy against rust).
“Between 1996 and 2008, bean varieties with resistance to rust made the threat of a bean rust epidemic in North Dakota very low. However, in 2008 a new race of the pathogen was identified in North Dakota. The new race has the ability to cause disease on the only commonly used effective resistance gene in common varieties. In 2010, the new race spread throughout North Dakota and into northwestern Minnesota. With the spread of the new race, the region is at risk again for the multimillion dollar yield losses caused by bean rust decades ago.
A fungicide application can be a very effective tool for rust management… In rust trials conducted between 2009 and 2011, all fungicides tested reduced rust severity… Because of this, a secondary benefit to a fungicide for white mold (which occurs at early bloom, R1-R2) is that the application may offer some measure of rust protection.
A fungicide application is most effective soon after the disease is found, making scouting for the disease critical.”
Authors: Markell, S., Olson, L., and Acevedo, M.
Affiliations: NDSU Department of Plant Pathology
Title: Dry edible bean rust
Source: Plant Disease Management. NDSU Extension Service. January 2012. Available at: http://www.ag.ndsu.edu/pubs/plantsci/pests/pp1601.pdf