Pigweed Control. Doug Shoup. Kansas State University. homa. ll Oklah

Transcription

1 Pigweed Control Doug Shoup Southeast Area Agronomist Kansas State University

2 Outline Identification/Competitiveness Genetic Variability Herbicide Resistance Manage Resistance

3 Identification Redroot pigweed Palmer amaranth Common waterhemp Short Hairs Long Petiole No Hairs Slender leaf Short petiole e

4 Identification Genetic diversity can generate different characteristics in populations

5 Pigweed Competition Palmer amaranth Common waterhemp Height from 6 to 10 ft tall Up to 500,000 seed/plant Soy yield losses up to 79% at 8 plants/3ft row Height from 6 to 9 ft tall Up to 2 million seed/plant Soy yield losses up to 56% at 8 plants/3ft row Redroot pigweed Height from 5 to 8 ft tall Up to 400,000 seed/plant Soy yield losses up to 38% at 8 plants/3ft row

6 Pigweed Pollination Redroot pigweed, smooth pigweed, and prostrate pigweed are monoecious Male and female parts on same plant Palmer amaranth and common waterhemp are dioecious plants Male and female parts on separate plants Amaranth can cross pollinate between species Potentially transfer resistance genes

7 Pigweed Pollen Shape Pollen shape differences between species Dioecious species generally more apertures Prostrate pigweed Common waterhemp Franssen et, al.

8 Herbicide Resistance Palmer and waterhemp have developed resistance across five herbicide MOA (Heap 2010) Dinitroaniline (Palmer) SC 1989 Triazine Resistance TX 1993 Palmer NE 1990 Waterhemp ALS Resistance KS 1991 Palmer IA 1993 Waterhemp PPO Resistance (Waterhemp) KS 2001 Glyphosate Resistance GA 2005 Palmer MO 2005 Waterhemp

9 Herbicide Resistance Inheritance ALS and triazine resistance in pigweeds are resistance by one major gene 100% resistance Waterhemp resistance to PPO herbicides is a major gene resistance PPO herbicide PRE PPO herbicide POST

10 Pollination and Multi Gene Resistance Monoecious resistance Dioecious resistance X Gene a Gene a Gene b Progeny have a+b genes X Gene b

11 Glyphosate Resistance Glyphosate Resistant Palmer Amaranth Stanley Culpepper, University of Georgia WeatherMax 88 oz at 1 inch WeatherMax 88 oz at 4 inch WeatherMax 88 oz at 12 inch

12 Glyphosate Resistant Waterhemp Biotype in NW MO Kevin Bradley, University of Missouri Continuous soybeans for many years, RR soybeans with at least one application of glyphosate since 1996 Waterhemp also ALS and PPO resistant, but not ti triazinei resistant it t

13 Kevin Bradley, U of M

14 Greenhouse Population Treatments: Pre: Pursuit (20x) Post: Atrazine (1x) + Cobra (1x) + Glyphosate (2x) Susc: ALS Susc: Atz Susc: PPO Susc: Gly Res: ALS Susc: Atz Susc: PPO Res: Gly Res: ALS Res: Atz Res: PPO Susc: Gly Field Population Treatments: Pre: Pursuit Post 2 : Atrazine Post 5 : Cobra + Glyphosate Bell, Tranel, Hager, U of Illinois

15 Herbicide Options for Amaranth Keep using ALS, triazine, PPO, and gyp glyphosate in combination Preemergence herbicide program in soybeans! Seedling growth inhibitors PPO herbicides as a preemergence Growth regulators in burndown applications Liberty Link soybeans Growth regulator and HPPD herbicides in corn are effective against amaranth spp. Use preemergence herbicides in sorghum and cotton

16 Future for Weed Management Genetically modified crops Liberty Link crops (currently available) 24D 2,4 D resistant corn and soybean from Dow with tentative release in 2013 ti Dicamba resistant soybean from Monsanto with tentative release in 2013 Isoxaflutole resistant soybeans (in development)

17 Summary Amaranthus species are a major challenge for all producers, but can be more of a watch out for no till producers Competitiveness of pigweeds can have a negative impact on yield Currently there is resistance to 5 different herbicide MOA in amaranth species Development of 4 in one population in IL Proper management against resistance is p g g important to keep our technology relevant

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