Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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PUMPKIN RESPONSE TO HALOSUFSULFURON, FOMESAFEN, AND TERBACIL.
R.B. Batts, North Caroline State Univ., Raleigh, A.W. MacRae, University of Georgia,
Tifton, and J.B. Beam, North Carolina Cooperative Ext. Service, Lincolnton.
ABSTRACT
Pumpkin trials were conducted in Iron Station and Edenton, NC and Blairsville,
GA in 2006 to determine crop tolerance and yield response of ‘Magic Lantern’ and
‘Appalachian’ pumpkin to halosulfuron (Sandea 75 DF), fomesafen (Reflex 2 SC) and
terbacil (Sinbar 80 WP). Sandea was applied preemergence (PRE), postemergence
(POST) or post-directed (P-DIR) at 0.5, 0.75, or 1.0 oz/A. Reflex and Sinbar was
applied PRE at 1 or 2 pt/A and 3 or 6 oz/A, respectively. For comparison purposes, a
hand-weeded control was included.
Injury data were combined across cultivars at all locations and across both North
Carolina sites. Compared to the hand-weeded control, Sandea applied PRE, POST,
and P-DIR injured pumpkin 37-51, 33-37, and 18-20%, respectively, in North Carolina 2
wks after treatment (WAT). In contrast, injury seen in Georgia ranged from 5-7%, 19-
32%, and 0% when applied PRE, POST, and P-DIR, respectively. Optimum growing
conditions were prevalent in Georgia for the duration of the growing season, limiting
injury from herbicide application. Similar results were observed with Reflex and Sinbar
applications in North Carolina causing 26-56 and 84-98% injury, respectively, while in
Georgia these applications only caused 4-13 and 16-65% injury. Severe injury from
Sinbar applications resulted in a reduction in pumpkin stand. Sandea P-DIR had the
least amount of injury at all locations, while the PRE timing was most injurious in North
Carolina and POST was most injurious in Georgia. PRE injury was expressed as crop
stunting, while POST and P-DIR injury appeared as discoloration in the terminals of the
plants.
As with injury, yield data were combined across cultivar at all sites and across
both North Carolina locations. When compared to the hand-weeded control in North
Carolina, yield reduction (total weight) from Sandea treatments ranged from 10 to 25%
with no trend for rate or timing of application. Yield reduction from the high rate of
Reflex and both rates of Sinbar were greater than any other treatment in North Carolina.
Similarly, these three were the only treatments to have greater plant stand reduction
compared to the nontreated control. In Georgia, the two Sinbar treatments were the
only treatments with reduction in yield compared to the nontreated control. The only
reduction in plant stand was with the high rate of Sinbar.
Based on these data, Sandea appears to be relatively safe to pumpkins,
especially in heavy weed situations where some injury is acceptable. However, Sinbar
appears to be too injurious, especially if heavy or excessive rainfall follows a PRE
application.
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