Identifying Herbicides for Use During Zoysiagrass Sprigging Identifying Herbicides for Use During Zoysiagrass Sprigging

Weed control after planting warm-season grasses in the spring can be critical for acceptable establishment of the stand. However, many herbicide labels can be unclear on sprigging restrictions before or after the application of a product. Research was conducted on the growth effects of pre-and postemergence herbicides applied at or near the day of ‘Innovation’ zoysiagrass sprigging. Preliminary data from this study shows granular (Ronstar G) and liquid (Ronstar Flo) formulations of oxadiazon caused the least amount of injury to zoysiagrass.


Identifying Herbicides for Use During Zoysiagrass Sprigging
Dani McFadden and Jack D. Fry

Summary
Weed control after planting warm-season grasses in the spring can be critical for acceptable establishment of the stand.However, many herbicide labels can be unclear on sprigging restrictions before or after the application of a product.Research was conducted on the growth effects of pre-and postemergence herbicides applied at or near the day of 'Innovation' zoysiagrass sprigging.Preliminary data from this study shows granular (Ronstar G) and liquid (Ronstar Flo) formulations of oxadiazon caused the least amount of injury to zoysiagrass.

Rationale
There are limited preemergence herbicides labeled for application at the time of zoysiagrass (Zoysia spp.Willd) sprigging.To our knowledge, no research has been conducted to evaluate how pre-and postemergence herbicides affect the establishment of zoysiagrass when applied at or near the time of sprigging.

Objective
The objective of this field trial was to determine if commonly used preemergence herbicides influence the establishment of Innovation zoysiagrass sprigs.

Study Description
A field study was conducted at the Olathe Horticulture Research and Extension Center in Olathe, KS, in the summer of 2021 to investigate the effects of pre-and postemergence herbicides on Innovation zoysiagrass establishment.The experiment was arranged in a randomized complete block design with four replicates.Herbicide treatments included a nontreated, seven single active ingredient treatments, and two combination postemergence herbicide treatments applied after weed emergence in experimental plots, for a total of 40 individual experimental plots (Table 1).Zoysiagrass sod was cut on July 9, 2021, at a 1:10 ratio for sprigging with four equally spaced furrows created for sprigs to be evenly spread into each 4-× 8-ft experimental plot (Figure 1).Preemergence herbicide treatments (all containing a single active ingredient) were applied immediately after sprigging; while two postemergence treatments were applied on August 2, 2021, after grassy and broadleaf weed emergence.On July 30 and August 16, 2021, 1 lb of N/1000 ft 2 was applied to the entire study area using a 16-0-8 and 46-0-0 (N-P 2 O 5 -K 2 O) fertilizer, respectively.Supplemental irrigation was applied on the study plots throughout the duration of the growing season to prevent stress.Data collection included: NDVI (normalized difference vegetation index) measurements, turfgrass vigor, percent establishment, and digital % green cover.Turfgrass vigor was a visual estimate of green color, stolon expansion, density, etc., that reflected the relative speed as the sprigged plot developed into mature sod.All data for each of the ratings were subjected to ANOVA in SAS (9.4) using the GLIMMIX procedure to determine those factors which were significant (P ≤ 0.05) and means were separated according to Tukey's Honest Significant Difference (HSD).

Results
The data revealed many similarities among treatments for the last three rating dates.Zoysiagrass vigor rated at 33, 49, and 63 days after sprigging (DAS) had low to unacceptable vigor for all treatments (vigor ratings ranged from 2.75 to 5.25).At 77 DAS, sprigs treated with liquid oxadiazon resulted in turf with acceptable vigor, which was significantly better than untreated sprigs.By 63 DAS no treatment had reached > 50% cover of the experimental plot (Table 3); granular and liquid oxadiazon along with the two postemergence combination treatments had the highest establishment (33%, 29%, 29%, and 26%, respectively).Digital images were analyzed using SigmaScan to find the total amount of digital percent green cover in the middle of each experimental plot.Due to significant weed populations in untreated plots, percent green cover was significantly higher.SigmaScan analysis revealed an average digital % green cover of 19 and 15 in the granular oxadiazon and liquid oxadiazon experimental plots, respectively (Table 4).No other herbicide treatment reached > 14% mean green cover by 93 DAS.Considerable weed pressure in untreated plots affected vigor, establishment, and skewed the digital green cover data.Innovation zoysiagrass was slow to establish from sprigs, likely affecting preliminary results.Research is ongoing and results after complete establishment will be reported in the future.

Brand names appearing in this publication are for product identification purposes only.
No endorsement is intended, nor is criticism implied of similar products not mentioned.Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.

a
Zoysiagrass vigor was rated on a 1 to 9 scale ( 1 = dead, 6 = acceptable, and 9 = maximum vigor).b Preemergence herbicides (oxadiazon to prodiamine) applied immediately after sprigging on July 9, 2021.Combination herbicides applied on August 2, 2021.c DAS = days after sprigging.d Means followed by the same letter in a column are not significantly different according to Tukey's Honest Significant Difference (P < 0.05).Means are averages over replication, n = 4.

Table 1 .
Herbicides evaluated for effects on zoysiagrass when sprigged the same day of application at the Olathe Horticulture Research and Extension Center in Olathe, KS

Table 2 .
Vigor of Innovation zoysiagrass at intervals after herbicide application on sprigs at the Olathe Horticulture Research and Extension Center, Olathe, KS, in 2021

Table 3 .
Establishment of Innovation zoysiagrass sprigs at intervals after herbicide application at the Olathe Horticulture Research and Extension Center, Olathe, KS, in 2021 Means followed by the same letter in a column are not significantly different according to Tukey's Honest Significant Difference (P < 0.05).Means are averages over replication, n = 4. e Quinclorac + sulfentrazone + 2,4-D + dicamba applied on August 2, 2021.

Table 4 .
Mean digital percent green cover of herbicide treatments applied after sprigging Innovation zoysiagrass at the Olathe Horticulture Research and Extension Center, Olathe, KS, in 2021 Digital percent green cover was evaluated in SigmaScan (Hue: 48-110, Saturation: 0-100) using digital images taken with a camera light box.Evaluations were on a 0 to 100% scale (0% = no green cover, and 100% = complete green cover in the image).b Preemergence herbicides (from oxadiazon to prodiamine) applied immediately after sprigging on July 9, 2021.Combination herbicides (treatments 9 and 10) applied on August 2, 2021.Means followed by the same letter in a column are not significantly different according to Tukey's Honest Significant Difference (P < 0.05).Means are averages over replication, n = 4.
a c DAS = days after sprigging.d