Weed Management Challenges in Vegetable Production

Ed Peachey Horticulture, OSU The Future of Weed s in Oregon

E. Peachey Horticulture Department Common themes

Weeds continue to adapt or introduce themselves The challenge of diversifying selection pressure The challenge of finding new tools Case studies Commodity coat tails ◦Sweet corn

Minor crop mire ◦ Brassica fresh processed and seed crops I. Weeds continue to adapt

Herbicide resistance • Kochia (Gly Res) • Horseweed (Gly Res) • Annual ryegrass   ACCase inhibitors, 1987 (Poast, Select)

GR kochia in a sugar beet field

Photo courtesy of J. Felix New introductions

Palmer amaranth

‘Pollinator seed mix may contain Palmer amaranth weed’, WSU warns Photo courtesy of Capital Press Sept, 12, 2017 ‘New’ introductions

Velvet leaf in squash Velvetleaf 1928 Yamhill County, cottonseed from the south. 2002 Manure from poultry farms near Aurora. August 10, 2017

Velvet leaf seeds

•Notched •1/8 in dia •10 to 52% survival after 4 years

Bish and Bradley, U. Of MO Velvet leaf control with POOR CONTROL GOOD CONTROL Outlook Command Reflex Dual Magnum Chateau Reflex Spartan Eptam Treflan Cobra Raptor Basagran II. The difficulty of diversifying selection pressure INTEGRATED WEED MANAGEMENT IWM: Multi-tactic or Multiple-stress

1. Sanitation/ prevention 2. Mechanical 3. Biological 4. Cultural 5. Chemical A few weeds of one species survive

Selection Pressure and Weed Shifts Weed Shifts: Cost of reduced tillage

Yellow nutsedge A weed shift in row crops

Black nightshade selectivity in table beets A unique individual of one species survives

Selection Pressure and Herbicide Resistance

A unique individual of one species survives

Selection Pressure and Herbicide Resistance Herbicide resistance in vegetable crops?

Annual ryegrass Glyphosate ACCase inhibitors, 1987 (Poast, Select) III. Challenge of Finding New Tools Herbicides o No new modes of action in 2 decades o Goldilocks herbicides: something that kills weeds but not too long o Finding supporting registrants o Engaging IR-4 (the minor crop registration program) Herbicide Screening

2018 23 herbicides 9 Brassicaceous, 6 other crops Two trials Reflex efficacy on green onion Supplements to herbicides? Cultivation Flame weeding Crop rotation Mechanical

Garford RoboCrop

Selectivity very good; dependent on accuracy of 34 February 25,positioning 2020 software

Yuma Grower Tour Jan 14 and 15, 2019 Text: 541-740-6712 Name and ‘Interested in Yuma tour” Flame weeding

Photo courtesy of

Selectivity dependent on emergence sequence of weeds and crops

February 25, 2020 37

Snap Bean Tolerance to Flaming Corvallis, 2018 12 5 gal/A 10 gal/A 11 Yield of check plot 10

9

8

7

Snap bean pod yield (t/A) pod beanSnapyield 6

5 12-8-4 % 30-24-15 % 44-37-32 % Percent of bean seedlings visible at flaming (total- hypocotyl extended-cotyledons unfolded)

Crop rotation Assumes there are crops to rotate to! Assumes rotation crop is not a weed in the next crop! Assumes there are different selection pressures that can be applied! The problem with crop rotations

Radish in squash Squash in beans Case Studies Crop classes and herbicide registrations Commodity coat tails ◦ Sweet corn, non transgenic (field corn) ◦ Snap beans (soybeans) ◦ Beets (sugar beets) Minor crop mire ◦ High value and risk crops ◦ Low acreage ◦IR-4 Minor Crops Program USDA Non-transgenic Sweet Corn Trends in Sweet Corn Production in OR (source: ODA)

Sweet Corn Acreage 10.1 tons/A (average) $95/ton 60000

50000 Total/A = $960

40000

30000 Acres

20000

10000 Total Sweet Corn Production 0 1955 1965 1975 1985 1995 2005 2011 500000 Year 450000 400000 350000 300000 250000

Tons 200000 150000 100000 50000 0 1955 1965 1975 1985 1995 2005 2011 Year Challenges in Sw Corn

Lots of herbicides labeled but….

• Cost!! • A little goes a long way • Pressure to apply Laudis/Impact (HPPD) late in season • Some varietal sensitivity to Laudis herbicides • Managing resistance to HPPD herbicides • MRL’s (Maximum residue limits) that limit use of HPPD herbicides INGREDIENT PRODUCT NAME Short-comings 1 2,4-D Formula 40 crop tolerance 2 Cadence ground water restrictions 3 Atrazine Aatrex 4l triazine resistance, water contam. 4 Basagran poor efficacy 5 Carfentrazone Aim EC 6 Stinger plant back 7 -p Outlook 8 Starane Ultra crop tolerance 9 Fluthiacet-methyl Cadet broadleaves only 10 Halosulfuron Sandea 11 Callisto 311 products 12 Nicosulfuron Accent crop tolerance 13 Prowl H2O lodging 14 S- Dual Magnum 15 Tembotrione Laudis no soil residual 16 Topramezone Impact, Armezon no soil residual

17 Pyroxasulfone Zidua crop tolerance 18 Thiencarbazone Capreno Herbicide + Laudis crop tolerance Why not genetic manipulation of sweet corn to improve weed control?

• Vast array of niche consumer markets • Trade barriers for PNW producers • ~600 commercial hybrids (here today and gone tomorrow) • Glyphosate and multiple herbicide-resistant weed populations are expanding at an alarming rate in other regions of the US 4- HHPD herbicides in corn

Mesotrione Callisto Topramezone Impact Tembotrione Laudis Bicyclopyrone in Acuron Tolpyralate Shieldex (ISK,7-27-17) Manuka oil (Tea Tree, NZ) Not registered or labeled oManuka tree oil contains leptospermone. oLeptospermone inhibits production of 4-HPPD o4-HPPD is needed for carotenoid synthesis oCarotenoids capture sunlight Bleaching symptoms Manuka oil Mesotrione (Callisto) is an analog of leptospermae Wild proso millet (in Super Sweet Jubilee, 2007) First year of use for HPPD herbicides Impact and Laudis 11.4 t/A

Impact + Outlook + Atrazine (Applied at V2) Untreated Corn sensitivity to 4-HPPD herbicides

Impact/ corn is very tolerant Armezone Laudis occasional symptoms includes safener Var. Captain Callisto Often causes injury Var. Merit + Bicyclopyrone ? Callisto Shieldex 400 SC now labeled  AI: Tolpyralate  ISK (Ishihara Sangyo Kaisha Corp)  Distributed by Summit Agro partners (Helena and Tenkoz) 2012-17 OSU Evalautions Tolpyralate rates tested: 1 oz/A typical use rate 2/3 to 3.9 oz/A Insecticide interactions (Lorsban) 8 Varieties Corn varieties tested 2012-17

Variety Genetics Company GSS 1477 SH2 Rogers Basin R SH2 Seminis Devotion SH2 (white) Seminis Owatonna SH2 Harris Moran Coho SE Harris Moran SC 1263 SU Seminis Jubilee SU Rogers Captain SU Snowy River Seeds Weed control, var. Jubilee (SH2) Junction City, 2016

100 90 Alone 80 + Atrazine % 70 weed 60 control 50 40 30 20 10 0 Tembotrione Topramezone Tolpyralate Bicyclo Mesotrione (0.082) (0.022) (0.027) (0.023) (0.094) Laudis Impact Shieldex - Callisto July 18, 5 weeks after treatment

Impact Shieldex Weed control with 4-HPPD herbicides in sweet corn, Junction City, 2018

1 Laudis V4 3oz $ 15 98

2 Laudis + V4 3oz $ 19 83 Atrazine V4 1qt 3 Impact V4 1oz $ 20 93

4 Impact + V4 1oz $ 24 96 Atrazine V4 1qt 5 Shieldex V4 1oz $ 8 92 6 Shieldex+ V4 1oz $ 12 98 Atrazine V4 1qt Shieldex Control Carryover concerns?

Herbicide Half life (days) Impact/Armezon 14 Laudis 14 Callisto 5-32 Shieldex Tolpyralate ½ to 2.6 Carryover potential of 4-HPPD herbicides

Tall fescue + crimson clover

Planted July 7 Implication for interseeding Picture November 4 Adapted for Roundup ready systems 3 functions

Herbicide Fertilizer Replaced glyphosate with HPPD inhibitor HPPD inhibitor injury to red clover Applied post-plant surface

Laudis Impact (1/2x) (2x) 0.041 lb ai/A 0.054 lb ai/A

The Minor Crop Mire (fresh market vegetable and seed crops) "The trouble with being optimistic is that some people will think you're illiterate." Nothing has more strength than dire necessity

Euripides Playwright, Athens, Greece c. 484-407 Todays adaptation to Euripides

What doesn’t kill you…..

Makes you stronger Representatives in the PNW

Brassicaceous crops ◦ Broccoli, cabbage, cauli, etc Cucurbits Carrots Quinoa

Herbicides Labeled for Brassicaceae

Prefar Command Dacthal Outlook Prescription for Lorox nightshades and lambsquarters Goal Trans Trans Trans Devrinol Dual Magnum Trans Trans Spartan Trans Treflan Outlook Herbicide for Transplanted Radish for Seed

1800 1600 1400 1200

Lbs 1000 seed/A 800 600 400 200 0 16 16+5 32 32+5 Outlook (oz/A) Radish grown for seed oOutlook has a ‘tolerance’ for radish • Registrant not interested because of liability. Radish grown for seed o Stinger labeled on radish grown for seed o Stinger cannot be used on Daikon radish • Seed rule does not include seed that may be consumed (radish sprouts) Radish grown for seed o Starane • Crop safety must be demonstrated • Weeds oShepherdspurse oNightshade What will it take to make these options viable?

3rd party registrations?

Improve crop safety by applying activated charcoal Effect of activated charcoal on crop safety (% of normal growth)

Sulfentrazone '+ Charcoal 100 80 60 40 20 0 Crop Tolerance to Summary Weeds will continue to introduce themselves and adapt Solutions will continue to emerge for commodity-related crops Specialty vegetable crops …….. Questions? Comments? Questions?

The art of agriculture

2/25/2020