1997 WEED SCIENCE WORKGROUP REPORT

University of California, Davis
November 12-13, 1997

Breakout Sessions

	Trees and Vines
	Aquatic Weeds
	Vegetable Crops
	Non-Crops
	Agronomic
	Turfgrass
	Ornamentals

Trees and Vines

Aquatic Weeds

Reporter: Lars Anderson

Research Accomplishments:
Results in 1997: a) Tested injection systems for using copper-based herbicides to control Egeria densa in the Sacromento delta. Delta; b) Dr. Spencer obtained good suppression of hydrilla sprouting with acetic acid applied a soil-drench; c) investigated interaction of Egeria and coontail in controlled tank; d) assessed viability of Egeria fragments produced during mechanical harvesting in the Sacramento delta.

What is currently being done: a) Analyzing levels of fluridone in non-target emergent plants at Clear Lake; b) comparing efficacy of "biological" products with "claims" for improving pond/lake conditions; c) determining partitioning of fluridone between water column and pore-water.

Extension Accomplishments:
Current Solutions: Projected funded to support Egeria management with Ca. Dept. of Boat. Waterways: ID's of several accessions of M. spicatum and RAPDs run on same. Use of Hydrothal 191 for algae control shown effective when copper products failed due to extreme water hardness.

Publications status: Assisted in IPM drafts for aquatic weed manual; drafts of updated chapter for Ca. Weed Sci. Soc. book; plus papers on American pond weed, hydrilla tubers (acetic acid)

Planning Accomplishments:
What are the problems: Efficacy of sonar in flowing water (Egeria in the Delta); control of Spartina alterniflora; frogbit? ; spread of M. spicatum at Lake Tahoe; algicides needed. Future research needs: Effects on M. spicatum on nutrient cycling at Lake Tahoe; improving efficacy of Garlon on parrot feather

Future extension needs: Handbook for aquatic weed control in California Need good slide set for Ca. aquatic weeds (including rice)

How will goals be accomplished: a) project funded to survey and due pilot mech. (dredge) removal of M. spicatum at Tahoe; proposal for studies on cutting and use of Roundup on Spartina alternaflora (with Dr. Don Strong)

Who is going to do the work: L. Anderson or Dave Spencer

Training Accomplishments:
Meetings held: Several lectures on aquatic weeds presented by L. Anderson, D. Spencer (e.g. PAPA; Son. City Parks; Target); 3-unit courses on Aquatic Plant Biology and Management taught by L. Anderson

Return to top of page

Vegetable Crops

Reporter: Tom Lanini

Artichokes
A shift toward annual varieties is occurring in the Salinas Valley growing area. Pronamide (Kerb) may be lost and therefore a search for alternatives is occurring. Harry Agamalian is evaluating Pendimethalin (Prowl) and Artichokes have shown good tolerance.

Carrots
Kurt Hembree is examining Pendimethalin (Prowl) for use in carrots (? Or was it Harold Kempen). Results to date show carrot has good tolerance.

Cilantro
Although no work is currently being done on this crop, it was thought that cilantro should be included with Chinese parsley and therefore allow the use of prometryn (Caparal).

Cole crops
Several herbicides have been evaluated for selectivity in cole crops by Harry Agamalian, including metolachlor (Dual), napropamide (Devrinol), and propachlor (Ramrod). Metolachlor was found to be a bit too phytotoxic to the broccoli, propachlor had good safety, and napropamide was too persistent and also was slightly phytotoxic (@ 2lb/a). Prefar (bensulide) and Dacthal (DCPA) were used as standards in these trials. The objective of these studies was to find a replacement for Dacthal.

Harry Agamalian has been looking at the carryover of halosulfuron (Permit). Of the crops planted 100 days after halosulfuron application, tomatoes and peas were tolerant, alfalfa cotton, radish, and carrots were intermediate, and lettuce, broccoli and onions were killed. Milt McGiffen did a similar study and found cool season vegetables to be susceptible (lettuce, broccoli, spinach, and cabbage) and warm season crops to be tolerant (melons, squash, peppers, carrots, snap beans, and okra). It was also noted that cabbage was the most sensitive species, but was safe to plant at 6 months after application. Harold also noted that in an Imperial Valley test, alfalfa was tolerant to halosulfuron treatments made 2 months before planting.

Onions
Harry Agamalian has looked at metolachlor (Dual), pendimethalin (Prowl), bensulide (Prefar), and propachlor (Ramrod) for use in onions. Propachlor has shown the best selectivity and has also controlled yellow nutsedge. Pendimethalin and metolachlor were too phytotoxic.

Kurt Hembree has examined flaming with good tolerance when onions were at the two to three leaf stage.

It was suggested that enfuric would be a good product to have labeled in onions and garlic.

Spinach
Both metolachlor (Dual) and propachlor (Ramrod) have been examined by Harry Agamalian for safety and weed control in fresh market spinach. A concern with fresh market spinach is the need to avoid leaf burn that occurs with Spinaid (phenmediphen). Propachlor at 2, 4, or 6 lb./a was very safe on spinach. Triflusulfuron (Upbeet) was also evaluated at 0.03, 0.05, and 0.07 lbs./a with spinach yields being 93%, 76%, and 73% of the untreated, weed free control, when applications were made at the 2 leaf stage.

Currently, Betamix (phenmediphan + desmediphan) is not labeled for spinach but is weak on burning nettle, and Roneet (cycloate) is labeled for preemergence treatments.

Steve Fennimore has volunteered to write the Spinach pest management guidelines.

Tomatoes
Kurt Hembree is currently evaluating rimsulfuron (Shadeout) in processing tomatoes. He is looking at both preemergence and early postemergence treatments at rates between 0.375 to 0.5 oz/a. Control of nightshades is fairly good, but does not control most grasses or lambsquarters. In addition to weed control ratings, he is also comparing hand weeding times on these treatments for an economic evaluation of treatment effectiveness. Kurt is also looking at Frontier as a layby treatment in place of trifluralin (Treflan). Frontier is providing better control of nightshade than is Treflan.

Kurt Hembree has been looking at the timing of irrigation to incorporate rimsulfuron (Shadeout). He has looked at various times between application and irrigation and found that applications made within 5 to 7 days provided good weed control but waiting longer than this resulted in some loss of activity.

Harold Kempen noted that rimsulfuron is not yet federally labeled or into the 45-day comment period required by DPR and thus the chances of having this material for 1998 is in doubt. Harold also noted that carryover could be a problem on onions, cotton was OK, and that carrots had not been evaluated.

Mariano Battista and Tom Lanini have been looking at ways to predict future weed species and locations within a field. Studies have compared seedbank, previous year's seedlings, or previous year's seedrain as predictors of current weeds. Seedbanks have been the most accurate, but increased sampling is required for increases in precision. This work is continuing.

Tom Lanini has been looking at a biocontrol agent for dodder control in tomatoes. The pre-emergence treatments have been very effective; however, even the controls had good control, as white flies appear to be moving the spores of the fungi from plot to plot. More isolation is needed to determine the formulation which will work best. Postemergence treatments have not been effective, perhaps due to the dry conditions at the time of application, not being conducive for spore germination or survival. Work is continuing on the Heinz tomato variety H9492, which has show to be resistant to dodder.

Enrique Herrero and Jeff Mitchell have been looking at no till planting of tomatoes into dying mulches. To date, the mulches have not adequately suppressed weeds and some optional weed control measures may need to be implemented.

David Slaughter has been looking at using a video guided sprayer, which is able to spot treatment in the row. Vision recognition of the tomatoes slows the process limiting speed of the current machine to less than 1 mph, but a new transgenic purple tomato may improve recognition and increase speed.

A publication on resistance management was thought to be needed to prevent resistance buildup with all the new ALS herbicides coming into the market.

Return to top of page

Non-Crops

Reporter: Joe DiTomaso

For a summary of progress in yellow starthistle control, see Appendix B. In addition to this extension paper, Joe DiTomaso, Guy Kyser, and Carri Benefield are preparing 4 additional manuscripts on yellow starthistle biology, chemical control, mowing, and burning. Much of this work is in collaboration with Farm Advisors, particularly Steve Orloff, Dan Marcum, Glenn Nader, and Ken Churches. In addition, new projects studying rangeland management and yellow starthistle control are in progress with Steve Orloff, Dan Drake, Dave Pratt, and Larry Forero. Many of these projects will be part of the doctoral work of Steve Enloe. Other projects include work on perennial pepperweed (Ph.D. dissertation of Mark Renz), pampasgrass and jubatagrass (MS research of Jennifer Drewitz and Alison Tschohl), and projects on barbed goatgrass (Adina Merenlender) and Scotch thistle (Dan Marcum). These projects have only been initiated within the past year, and results are not currently available.

The group indicated that additional work needed to be conducted on medusahead, Russian thistle, and alkali heliotroph.

Return to top of page

Agronomic

Reporter: Kurt Hembree

Sugar Beets
Research Accomplishments:
Robert Norris and Kurt Hembree discussed results of Liberty resistance sugar beet trials: glufosinate (Liberty) not as efficacious as Roundup resistant beets. Concern was expressed as to the low rates of Liberty tested. Liberty beets bolted and did not have rhizomania resistance. Early postemergence treatments of UpBeet provided excellent cocklebur and velvetleaf control if weeds were at the cotyledon stage of growth when treated and if they were properly identified. No new herbicides tested. Registration status of Stinger is still unclear. Steve Orloff said Vapam was not providing adequate control of kocia, lambsquarters, or pigweed. Further evaluations of Liberty beets will be conducted as well as economic comparisons of weed management options.

Extension Accomplishments:
California sugar beet growers are presently satisfied with the current extension activities. The IPM Guidelines need to be updated to include the newly registered herbicides.

Planning Accomplishments:
There are not any major problems associated with weed control. Most problems appear to be related to specific weeds in specific areas. Future extension tactics should include weed identification and timing of application.

Training Accomplishments:
None noted

Other areas of concern included developing resistance strategies and the importance of herbicide resistance management in adapting to sulfonylurea herbicides (like UpBeet) and in the future of Roundup.

Alfalfa
Research Accomplishments:
Trimmer provided a broader spectrum of control with less residual than Pursuit. It is also more effective on grass species. Wild oats, annual bluegrass, and canarygrass control needed.

Extension Accomplishments:
Ron Vargas, Mick Caneveri, Dan Putnam, Tim Prather, and Tom Lanini are working on a publication for interseeding (oats, burseam clover, etc.) in established alfalfa stands. It should be completed by mid-May, 1998.

Planning Accomplishments:
Dodder and Setaria species are the primary weeds of concern. The registration status of thiazopyr (Visor) for their control in alfalfa is not known. The registrant is not currently pursuing it. Training on weed identification and herbicide selection is needed. Kurt Hembree held a training session in 1996, but others are still needed.

Training Accomplishments:
None noted

Cotton
Research Accomplishments:
Roundup resistant cotton tested showed yellow nutsedge and annual weed control was best achieved at rates of I - 2 LB a.i./acre. Harold Kempen said it was weak on purple nutsedge in Kern County. BXN cotton being tested. Kurt Hembree is looking at visor for fallow bed weed control and subsequent plant-back restrictions. Tim Prather said the light activated sprayer gave excellent control of nutsedge in cotton in Corcoran, reducing spraying days from 3 to 1. Tim also said he seen good control of field bindweed using a propane flamer at 40 - 60 psi in 7" tall cotton. Cotton tolerance to flaming was good. Bermudagrass control was better if flamed twice and covered with soil through cultivation than with cultivation alone.

Extension Accomplishments:
None noted. Publications are current.

Planning Accomplishments:
Bladex will be phased out by the year 2000; other alternative herbicides need to be evaluated. The impact of flaming on beneficial insects needs to be looked at. Additional training on sprayer calibration and application for low use-rate herbicides (Staple) needed.

Training Accomplishments:
None noted.

Beans
Research Accomplishments:
Ernie Roncoroni said black nightshade control was excellent when Frontier was used at up to 1.0 lb. a.i./acre. Weed control on bed shoulders was excellent where Frontier was used. Plant-back questions need to be answered. Trimmer (a Pursuit analogue) provided good control with shorter residual problems. Axium provided weaker control of black nightshade than a tank-mix of Sencor plus Dual. Hairy and black nightshade failures with Sonolan noted. FMC's 8426 provided good control of annual morning glory but injured beans. Permit shows promise for nutsedge control.

Extension Accomplishments:
None noted.

Planning Accomplishments:
Black and hairy nightshade are resulting in quality problems, while morning glory and nutsedge are causing competition problems, additional research needs to be done. Additional work with Frontier and Trimmer need to be continued. Injecting Eptam into irrigation water needs to be investigated for nightshade control.

Training Accomplishments:
None noted.

Cereals/Corn
Research Accomplishments:
Steve Orloff and Ernie Roncoroni said Roundup was hard on Roundup-resistant corn. Split applications were effective on johnsongrass. Liberty provided good weed control in young corn. Puma and Achieve both provided good weed control.

Extension Accomplishments:
None noted.

Planning Accomplishments:
Puma needs to be evaluated for canarygrass control in cereals. FMC's 8426 should be investigated. Avenge is only providing 25% control of wild oats, resistance is a concern. Hoelon registered on wheat, but not barley. Registration needs to be pursued.

Training Accomplishments:
None needed.

Return to top of page

Rice

No information was provided.

Return to top of page

Turfgrass

Reporter: Clyde Elmore

Research Accomplishments:
Finished Research:

1. Selective control of bermudagrass in cool season turfgrass. Herbicides containing triclopyr, fenoxaprop and ethafumosate were applied one or more times at intervals during the summer for suppression and control of bermudagrass. Tall fescue and perennial ryegrass were tolerant to these herbicides. Paper published: Weed Technology. 1997. A follow up paper will be published in California Agriculture.

2. Invasion resistance of perennial ryegrass and tall fescue to Kikuyugrass. Ryegrass or tall fescue was overseeded into Kikuyugrass to determine suppression. Tall fescue was more suppressive than ryegrass. Kikuyugrass plugs were planted into established tall fescue and perennial ryegrass and invasion and establishment was evaluated. Turf-type tall fescue reduced the invasion of Kikuyugrass over a 2-year period. Paper published in Weed Technology, 1997.

3. Smutgrass (Sporobolus indicus) has been controlled with wick applications of 33% glyphosate without injury to bermudagrass turf. Glufosinate, fenoxaprop, fluazifop or sethoxydim was effective sprayed over the grass but injury was severe on bermudagrass. Seedlings were controlled with all preemergence herbicides tested.

4. Kyllinga (perennial running sedge) has been controlled with 2 applications of halosulfuron (Manage) as a post emergence application.

5. Dallisgrass was controlled from seed with all preemergence herbicides tested.

6. Crabgrass has been effectively controlled with the preemergence herbicides pendimethalin, prodiamine, dithiopyr and the older materials. Post emergence applications of fenoxaprop have been effective on 2 to 3 leaf crabgrass when it is not stressed for moisture.

Research Work in progress:

1. Kyllinga control in turfgrass. Seedling control with preemergence herbicides.

2. Reduced rate preemergence herbicide applications in conjunction with overseeding of tall fescue turf in the fall.

3. Research being established to evaluate the potential of vigorous tall fescue and perennial ryegrass varieties of reducing the invasion of bermudagrass.

4. Cultural factors relating to Oxalis corniculata invasion and establishment.

Extension Accomplishments:
Publications:
Need to revise the Turfgrass Pest Manual. Add section on indicator weeds for various turf conditions. (Exp.) Annual bluegrass/crabgrass = frequent watering.

Pest Notes - Homeowner orientation

1. Spurge (prostrate and creeping)

2. Oxalis (creeping and yellow buttercup)

3. Nutsedge

Future Research Needs

1. English Daisy (Bellis perenne) has not been controlled well in coastal turfgrass areas (golf coarse). If cities such as San Francisco banns herbicides, then there will be a major influx of daisy in high maintenance turf.

2. Annual bluegrass has not been controlled well in bentgrass greens.

3. What is the potential for allelopathy with ryegrass or fescue? What weeds could be controlled?

Training Accomplishments:
Meetings:

1. Turfgrass field day - UC. Riverside (industry).

2. Bay Area Turfgrass and Landscape Field Day (industry)

3. Professional Turfgrass Research Update. UC Davis (industry)

4. OHECC Turfgrass Workgroup (University In-service Training)

Return to top of page

Ornamentals

Reporter: Clyde Elmore:

Research Results:

Container grown ornamentals:
Herbicides and mulches were evaluated in 5 gal containers with Rhapiolepis indica at South Coast Field Station and Davis. Pecan shell mulch reduced annual bluegrass number and dry weight in the container compared to the untreated control. The by-product corn gluten meal at the recommended rate had little affect on Poa annua at Davis or broadleaves at SCFS. The herbicide oxyfluorfen + oryzalin (Rout) was very effective for grass and broadleaf control at 2 + 1 lb./A. Geotextile collars around the plants reduced weeds but did not give complete control (weeds grew around the hole and cuts of the collar. Whenever Rout was combined with other treatments, control was excellent.

In container tests using Buxus, prostrate spurge was controlled with isoxaben, oryzalin, pendimethalin, combinations with oxyfluorfen and oryzalin or oxyfluorfen and trifluralin. Creeping spurge had a similar susceptibility to herbicides as prostrate spurge.

Landscape plantings:
Geotextile mulches and Biobarrier II was applied in woody landscape plantings. Weed control was excellent except for Washingtonia Palm seedlings.

Field Grown cut flowers:
Weed control studies were established in Limonium, Delphinium, Snapdragon and China Aster transplant plantings. Preemergence herbicides were evaluated on all crops. Mulches (finished "greenwaste", and rough "greenwaste" (6 weeks age) were applied after transplanting. Solarization was used at 4 or 6 weeks in the summer before transplanting. Post emergence herbicides were applied on Limonium only. Plant susceptibility varied by the herbicide and rate. Increased growth was observed with most plants in solarized plots. Both mulches gave good annual weed control but did not control field bindweed.

Current Work:Field grown flower studies are continuing with snapdragon, China aster and Delphinium at Davis, Bay Area Research and Extension Center (BAREC), and South Coast Research and Extension Center) SCREC. Bulb trials with Ranunculus and Dutch Iris will be established at BAREC and Davis.

Extension Accomplishments:

Meetings:

1. Bay Area Turfgrass and Ornamentals Field Day—(BAREC)

2. Training meeting for farm advisors at the same location.

3. Meeting to be held at SCREC in December. Publications:

4. Pest Notes

5. Spurge (Prostrate and Creeping)

6. Oxalis and Bermuda buttercup

7. Nutsedge

8. Weed control in the Landscape

Planning Accomplishments:

Future needs and problems:

1. Creeping spurge is becoming more of a problem in landscape plantings. There is need for information on control in the landscape.

2. There is the potential for loss of the herbicides oxyfluorfen and pronamide as well as DCPA (Dacthal). These would be major losses for the ornamental industry. New herbicides that may control nutsedge (halosulfuron and thiazopyr) also need to be evaluated.

3. Mulch: "greenwaste" has given good control, but must be evaluated for economics and feasibility for transplanting into the mulch, or it will not be a viable treatment.

4. Evaluation of Biobarrier II on perennial pepperweed in the landscape along Caltrans land.

Publication Needs:

1. Nursery Production Manual -In progress

2. Floriculture weed control Leaflet

Training accomplishments:

1. Meetings indicated above.

2. Participation in the Nursery Workgroup

3. Participation in the Floriculture Workgroup.

Return to top of page

Go to Table of Contents
Go to next document (Discussion of Priority Research and Extension Needs)