Strongarm/Peanut Questions (by Dr. Prostko)
Had a few questions about Strongarm (diclosulam) use in peanuts yesterday that I thought might be interesting to all:
1) In general, what application method is more effective for weed control in peanut (PPI or PRE)?
When averaged over 7 weed species, there was little difference in weed control between PPI and PRE applications of Strongarm (Table 1). However, in dryland production fields with minimal future rain predictions, PPI applications would be preferred.
Table 1. Application Method Effects on Residual Weed Control with Strongarm 84WG @ 0.45 oz/A in Peanut.1
| Weed | Control (%) | |
| Application Method | ||
| PPI2 | PRE3 | |
| sicklepod | 54 | 44 |
| Florida beggarweed | 78 | 87 |
| bristly starbur | 94 | 97 |
| purple nutsedge | 59 | 73 |
| yellow nutsedge | 78 | 78 |
| morningglory sp. (Ipomoea sp.) | 89 | 99 |
| smallflower morningglory | 94 | 96 |
| All (average) | 78 | 82 |
1Source: Grey et al. 2003. Peanut Science 30:27-34.
2PPI = preplant incorporated.
3PRE = preemergence.
Also very important to remember that Strongarm provides a much broader spectrum of weed control when applied PPI or PRE when compared to POST applications. However, the following 7 weeds are sensitive to Strongarm when applied POST: tropical spiderwort/Benghal dayflower; common cocklebur; common ragweed; bristly starbur; horseweed/marestail; morningglory sp.; and eclipta.
2) What application method is more effective for the control of tropical spiderwort/Benghal dayflower?
Data collected a few years ago in Grady Co. indicated that POST applications were more effective than PRE applications for the control of tropical spiderwort/Benghal dayflower (Table 2).
Table 2. Application Method Effects of Strongarm 84WG @ 0.45 oz/A on Benghal Dayflower/Tropical Spiderwort Control in Peanut.1
| Application
Method |
Control (%)2 | ||
| 46 DAP3 | 69 DAP | 114 DAP | |
| PRE4 | 75 cd | 68 b | 11 e |
| EPOST5 | 97 a | 90 a | 75 abc |
| LPOST6 | 88 ab | 78 ab | 60 c |
1Source: E.P. Prostko and J.T. Flanders, 2003, PE-24-03, Unpublished data.
2Means in the same column with the same letter are not significantly different according to DMRT (P=0.05).
3DAP = days after planting.
4PRE = preemergence.
5EPOST = early-postemergence, 17 days after planting (2’’ tall, 3 leaf stage).
6LPOST = late-postemergence, 31 days after planting (6” tall).