Weeds, Weed Control and PGRs Ronald N. Calhoun and Aaron D. Hathaway Department of Crop and Soil Sciences Michigan State University

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1 Weeds, Weed Control and PGRs Ronald N. Calhoun and Aaron D. Hathaway Department of Crop and Soil Sciences Michigan State University Almost 30 weed related projects were started or continued in The following report highlights and summarizes many of the research projects conducted by the turfgrass management program at MSU in In addition to the conventional product evaluation trials that are conducted for industry, many of our research projects have been developed in response to the specific needs of the Michigan turfgrass industry and directly supported by the MTF. As with any enterprise, the success of the turfgrass weed management research program is due to the efforts of the people doing the work. Best Management Practices for Weed Control in Lawn Cut Turf Common recommendations to LCO s and homeowners include mowing high and providing adequate fertility. Without proper management weed control will be at best, temporary. This study is examining mowing height, fertility, and postemergence herbicide treatment. Plots were maintained at two or four inches, and received either no fertility or 3 lb of nitrogen per 1000 ft 2 per year (holiday program 1# Memorial Day, ½# July 4, ½# Labor Day and 1# Thanksgiving). In October of 1998 plots were treated with Trimec, Confront or no herbicide. Broadleaf weed populations have been monitored since the beginning of the experiment. The re-infestation of white clover and dandelion has been slowest in the fertilized plots and those treated with Confront. Non-fertilized plots have proven to be an excellent environment for clover. The taller height of cut in conjunction with the holiday fertility program has not eliminated existing weeds. However, these management practices have proven to create a more competitive turfgrass stand that better resists re-infestation after a postemergence broadleaf herbicide application. Broadleaf herbicides (same treatments as 1998) were reapplied in October, Herbicide treatments were very effective in Both herbicides provided excellent control of clover and dandelion. This research indicates that cultural practices can decrease white clover and dandelion pressure by maximizing turfgrass competitiveness. Herbicide treatments provide profound but temporary remedy for weed infestation. Cultural practices were much more effective over time than herbicide treatment alone. Herbicides can be used to reduce weed infestations at a point in time but must be used in combination with improved cultural practices to maintain maximum turfgrass cover long-term.

2 Weed Garden In 1998 a weed garden was established at the south end of the turf center property. This display has been very useful for learning the identification of broadleaf and grassy weeds of turf. Proper identification is the first step to control. Although very labor intensive, the garden has been very useful during training sessions with extension agents, and visits from lawncare operators. The garden is a major component of the Weed ID workshop held on the afternoon of field day and has served as a ready source of plant material for the Turfgrass Pest Management class and Turfgrass Short Course, which are taught each fall. With the help of the MTF, exceptional progress was made in The number of specimens was increased and the quality of specimens was also improved. Due to the success of the weed garden, permanent plastic signs have been made to identify the plots year-round. Enough plant material has been generated that live plant samples were used for the Turfgrass Weed ID and Management Workshop at the 2005 MTF Conference. The weed garden has resulted in the development of a weed ID website based off of the images generated from the garden. The new website is The website design was created during the winter of Pictures and descriptions were added during the summer and fall of Students were able to use the website during fall semester. Over 300 pictures are included on the site. Users can search by common or scientific name and can also search by other known names. The dossier for each weed include information on habit, key identification features, look-a-likes, and cultural Pictures management recommendations Preemergence Crabgrass Trial # Preemergence Crabgrass Trial was conducted at the # The 2004 General Evergreen Cemetery in Lansing, Michigan. This site is located approximately two miles west of the Hancock Turfgrass Research Center and has a history or extremely heavy crabgrass pressure. 4, 3 N/M/YR from M 4, 3 N/M/Y Trimec The preemergence crabgrass treatments were applied on April 23, Commercially available products such as Pendulum 3.3EC, Pendulum 3.8CS, Dimension Ultra WSP, and Barricade were included in this trial as a stand alone treatments. This year, for the first time, there were several generic formulations of the previously mentioned products included in our trial. Record rainfall in May and June of this year facilitated excellent germination of crabgrass. Below average temperatures at the beginning of the summer delayed development of these plants. Warmer temperatures and additional rainfall in late July and August made for a nice finish to the season and yielded a very respectable crabgrass

3 crop for Crabgrass populations were measured June 16 and August 25, The commercial standards included in this trial provided very good to excellent crabgrass control at both evaluation dates (Table 1). Most of the treatments provided acceptable control for Table 1: 2004 General Preemergence Crabgrass Trial Evergreen Cemetery, Lansing, Michigan, Michigan State University TRT Description Rate Crabgrass Cover lb ai/a 16-Jun 25-Aug 54 DAT 124 DAT 1 UNTREATED 11 ab 49 ab 2 DIMENSION ULTRA WSP d 1 f 3 DIMENSION ULTRA WSP d 1 f 4 PENDULUM d 10 ef 5 PENDULUM cd 9 ef 6 PENDULUM d 2 f 7 PENDULUM d 2 f 8 MANA-PRO d 3 f 9 MANA-PRO d 1 f 10 MANA-PRO d 0 f 11 BARRICADE d 5 f 12 BARRICADE d 7 f 13 BARRICADE d 1 f 14 MANA-PRO d 0 f 15 MANA-PRO d 0 f 16 MANA-PRO d 0 f 17 PENDIMETHALIN d 7 f 18 PENDIMETHALIN d 0 f 19 PENDIMETHALIN d 0 f 20 MANA-PRO d 0 f PENDIMETHALIN MANA-PRO d 0 f PENDIMETHALIN MANA-PRO d 0 f PENDIMETHALIN MANA-PRO d 0 f PENDIMETHALIN MANA-PRO d 0 f PENDIMETHALIN MANA-PRO d 0 f PENDIMETHALIN INTER PLUS II a 36 bcd 27 INTER PLUS II abc 44 abc 28 MANA-PRO d 14 ef INTER PLUS II MANA-PRO d 3 f INTER PLUS II MANA-PRO d 0 f INTER PLUS II MANA-PRO d 7 f INTER PLUS II TRIFLURALIN a 44 abc 33 TRIFLURALIN d 9 ef 34 MANA-PRO d 2 f

4 TRIFLURALIN MANA-PRO d 6 f TRIFLURALIN MANA-PRO d 0 f TRIFLURALIN MANA-PRO bcd 19 def TRIFLURALIN UNTREATED 18 a 62 a 39 UNTREATED 10 abc 46 abc 40 UNTREATED 12 ab 28 cde LSD (P=0.05) Means followed by same letter do not significantly differ (P=.05, LSD).

5 Proxy/Primo Initial Timing Study In the spring of 2004 we initiated a study to examine the best timing for Proxy/Primo tankmixes for Poa annua seedhead suppression. The study was conducted on a predominately Poa at Forest Akers Golf Course in East Lansing, MI. Treatments included combinations of Proxy at either 3 or 5 fl oz. per 1000 sq. ft. plus Primo at fl oz. per 1000 sq. ft. The objectives of this study were to determine the effect of initial treatment application timing and Proxy rate on seedhead suppression. Primo/Proxy treatments were made on April 5, 12, 17 and 26, 2004 and correlated to immediately after the second mowing (SM), 1 week after SM, 2 weeks after SM, and 3 weeks after SM. Repeat applications were applied on May 3 for all Primo/Proxy treatments. Embark was included in this trial as a comparison treatment and was applied on April 17. In general, earlier initial application timings provided better seedhead suppression than later timings. In addition, the 5 fl oz application rate of Proxy provided better results than the 3 fl oz rate. Table 2: Effect of Proxy rate on Poa annua seedhead suppression averaged over four application timings. Product Rate Clean Control Max Injury 1-9 Proxy + Primo Proxy + Primo Embark Check Table 3: Effect of initial application timing on Poa annua seedhead suppression averaged over two treatment rates. Date GDD 32 GDD 50 Clean Control Max Injury 1-9 Check Apr Apr Apr Apr