(Solanum ptycanthum)

PSI Electron Diverter (D/22)

Canada, Ontario
Eastern Black Nightshade (Solanum ptycanthum) is a dicot weed in the Solanaceae family.  In Ontario this weed first evolved resistance to Group D/22 herbicides in 2009 and infests Blueberries.   Group D/22 herbicides are known as PSI Electron Diverter (Photosystem-I-electron diversion).  Research has shown that these particular biotypes are resistant to paraquat and they may be cross-resistant to other Group D/22 herbicides.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

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QUIK STATS (last updated Jul 26, 2012 )

Common NameEastern Black Nightshade
SpeciesSolanum ptycanthum
GroupPSI Electron Diverter (D/22)
LocationCanada, Ontario
Contributors - (Alphabetically)Kristen Obeid, and Francois Tardif 
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Francois Tardif
Gramoxone Resistant Eastern Black Nightshade Confirmed in Ontario September 2010.

Kristen Callow (Ontario Ministry of Agriculture, Food and Rural Affairs) François Tardif, Peter Smith. (Department of Plant Agriculture, University of Guelph)

Eastern black nightshade (Solanum ptychanthum), was confirmed to be resistant to group 22 herbicides (bipyridiliums), specifically Gramoxone (paraquat) in Chatham-Kent recently. The total area infested is not known at this time; however, the resistant weed was found in a perennial horticultural cropping system.

Eastern black nightshade is a dicot weed in the Solanaceae family. In Ontario, this weed first evolved resistance to Group 2 herbicides in 2000 in corn and soybeans. Imidazolinone (Pursuit) resistant populations exist in many counties. Cross-resistance to other Group 2 herbicides is likely to exist. Source: Gramoxone (paraquat) resistance is of particular concern to Ontario producers, due to the reliance of this product in perennial horticultural production systems. There have been no known cases of paraquat resistant Eastern black nightshade anywhere else in the world (International Survey of Herbicide Resistant Weeds

Eastern black nightshade is known to be a hard to control annual weed. In perennial horticultural cropping systems, post spot or hooded sprayer applications of glyphosate, Ignite (glufosinate-ammonium) and Gramoxone (paraquat) are usually effective if done before the nightshade gets too big. Chateau (flumioxazin) and Aim (carfentrazone-ethyl) are two newer herbicides (both Group 14 - PPO inhibitors) that have shown good control of Eastern black nightshade. Chateau should be applied prior to weed emergence, whereas Aim should be applied as a post application.

As a general rule, rotating between herbicide groups or mode of actions is essential to prevent resistance development.

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Confirmation Tests

Greenhouse trials comparing a known susceptible Eastern Black Nightshade biotype with this Eastern Black Nightshade biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetic studies on Group D/22 resistant Eastern Black Nightshade have not been reported to the site.  There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature
Mechanism of Resistance

The mechanism of resistance for this biotype is either unknown or has not been entered in the database.  If you know anything about the mechanism of resistance for this biotype then please update the database.
Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes.  If you have any information pertaining to the fitness of Group D/22 resistant Eastern Black Nightshade from Ontario please update the database.
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Weed Management Program Lead - Horticulture
Ontario Ministry Of Agriculture Food & Rural Affairs
RR #2, 2585 County Rd. 20
Harrow, N0R 1G0, Ontario
Email Kristen Obeid
Web   : Web Site Link
Associate Professor
University Of Guelph
Department Of Plant Agriculture
2055 Radatz Ave
Guelph, N1G 2W1, Ontario
Email Francois Tardif
Web   : Web Site Link


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Ontario have been instrumental in providing you this information. Particular thanks is given to Kristen Obeid, and Francois Tardif for providing detailed information.
Herbicide Resistant Eastern Black Nightshade Globally
(Solanum ptycanthum)
Herbicide Resistant Eastern Black Nightshade Globally
(Solanum ptycanthum)
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Herbicide Resistant Eastern Black Nightshade Globally
(Solanum ptycanthum)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Canada (Ontario) CanadaOntario2000 Corn (maize), and Soybean flumetsulam, imazamox, imazethapyr, nicosulfuron, primisulfuron-methyl, prosulfuron, and rimsulfuron 7 ALS inhibitors (B/2)
190Solanum ptycanthumEastern Black Nightshade5211
2 Canada (Ontario) CanadaOntario2009 Blueberries paraquat 7 PSI Electron Diverter (D/22)
190Solanum ptycanthumEastern Black Nightshade5493
3 United States (Wisconsin) United StatesWisconsin1999 Soybean imazamox, and imazethapyr 45 ALS inhibitors (B/2)
190Solanum ptycanthumEastern Black Nightshade1170
4 United States (North Dakota) United StatesNorth Dakota1999 Soybean imazamox, and imazethapyr 45 ALS inhibitors (B/2)
190Solanum ptycanthumEastern Black Nightshade1196
5 United States (Illinois) United StatesIllinois1999 Soybean imazamox, and imazethapyr 45 ALS inhibitors (B/2)
190Solanum ptycanthumEastern Black Nightshade5184
6 United States (Michigan) United StatesMichigan2004 Blueberries atrazine 45 Photosystem II inhibitors (C1/5)
190Solanum ptycanthumEastern Black Nightshade5286
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