Vol. 54—2000 - NorthEastern Weed Science Society

WEED MANAGEMENT WITH HALOSULFURON IN SUMMER SQUASH
B.W. Trader, H.P. Wilson, T.E. Hines, and H.E. HoWt!
ABSTRACT
Summersquash (Cucurbita pepo L.) is an economically importantvegetable crop in
Virginia Withthis interestin squashproductionthereis need foradditionalweed control
alternatives.Currentlythereareno postemergenceherbicidesregisteredfor controlof broadJeaf
weeds and yellow nutsedge (Cyperus esculentus L.) in squash. Both yellow nutsedge and
morningglory (Ipomoea spp.) areproblemsin squashproductiondueto theircompetitiveness
andinvasivenature. Halosulfuroncontrolsyellow nutsedgeandsuppressesannual
morningglories.Halosulfuronmay offer improvedweed controlin summersquash;however,the
effect of halosulfuronon squashhasnot beenstudiedextensively.
In 1999, field experiments were conducted at the Eastern Shore Agricultural Research
andExtension CenternearPainter,VA to investigateweed controland squashresponse to
haIosuifuron. Plots were 25 feet long and arranged in a randomized complete block design with
3 replications.'Monet'and'Tigress'were selectedas representativeyellow andzucchinisquash
cultivars, respectively. Ethalfluralin (0.56 Ib ai/A) and clomazone (0.156Ib ai/A) were applied
PRE to all plots except untreated controls. Halosulfuron wasapplied PRE and POST at 0.004,
0.008,0.016, and 0.0241b ai/A. Non ionic surfactant (0.25%) was included with all POST
treatments.
POSTtreatmentswere generallymoreinjuriousthanPREtreatments.'Monet'squashwas
injuted 10 to 25% by PRE treatments 2 wk after planting (WAP), but only minimal injury was
observed 4 WAP (0 to 3%). In contrast, injury from POST treatments was 16-35% 2 wk after
treatment (WAT). Injury to 'Tigress' zucchini from PRE treatments 2 and 4 WAP was 12 to 17%
and 1 to 4%, respectively. 'Tigress' was most sensitive to injuryfrom POST treatmentswith25
to 47% injury 2 WAT. POST treatments delayed maturity of 'Monet' and 'Tigress'. Although
yields were initially lower in squash treatedPOST, squash yields from fourth and later harvests
were equal to or significantly higher from squash treated POST than from squash treated PRE.
Morningg1ory control by PRE treatments averaged from 41 to 74% in both squash
cultivars. Control from POST haIosuifuron was significantly higher and ranged from 66 to goolo.
Annual momingglories were initially suppressed by POST applications but recovered and
interfered with later harvests. Yellow nutsedge control in the greenhouse 1 WAT with 0.004 IbiA
haIosuifuron was >gO%.
'Graduate Research Assistant, Professor, Research Specialist Senior, and Extension Specialist,
respectively, Virginia Polytechnic Institute and State University, Eastern Shore Agricultural
Research and Extension Center, Painter , VA 23420·2827.
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