Field trials were conducted in Texas during 2001 at Pearsall and 2002 at Yoakum to determine cultivar responses to certain foliar and soilborne diseases in single row (91 cm) vs. twin-row (rows spaced 18 cm on 91-cm centers) patterns and sprayed four times with tebuconazole at 0.23 kg ai/ha or twice with azoxystrobin at 0.34 kg ai/ha. Azoxystrobin and tebuconazole controlled southern stem rot similarly. Tebuconazole controlled rust more effectively than azoxystrobin. In 2002, early leaf spot severity was high and disease control was less than desirable with both fungicides, but still better than the nontreated plots. Both fungicides reduced early leaf spot severity in the single and twin-row patterns when compared to nontreated plots. Early leaf spot severity in the nontreated plots was greater in the twin-row pattern compared to the single row pattern. Tamrun 96 yielded better than any of the other cultivars in the study and showed less southern stem rot than all other cultivars when averaged across fungicide treatments and row spacing. Tebuconazole and azoxystrobin increased yield compared to nontreated control. No significant differences in yield occurred between fungicide treatments. The twin-row pattern showed a yield increase compared to the single row pattern when averaged across cultivar and fungicide treatments.

Field studies were conducted at three locations in the south Texas peanut growing region to compare regular agricultural calcium with power plant byproduct calcium applied at planting or peanut pegging to runner peanut at rates of 560 to 1680 kg/ha. Both calcium sources decreased Rhizoctonia and Pythium pod disease development up to 62% when compared with the non-treated control and resulted in a yield increase over the non-treated control of up to 25%. When Rhizoctonia or Pythium was not a problem, no increase in peanut yield over the non-treated control was noted with any calcium application. Peanut grade (Total Sound Mature Kernels + Sound Splits) was increased at one location with the use of both calcium sources. Calcium, magnesium, and potassium content of foliage, hull, and kernel tissue was variable and was not related to calcium source.

Experiments were conducted from 1996 through 2001 in Georgia, North Carolina, and Texas to determine peanut response to the commercial plant growth regulator Early Harvest® (a commercial mixture of cytokinin, gibberellic acid, and indole butyric acid). Early Harvest (applied in the seed furrow) or Early Harvest TST (applied as a dry seed treatment) followed by four foliar applications (four-leaf peanut, initial pegging, 14 d after initial pegging, and pod fill), was compared to non-treated peanut in five, 13, and three experiments in these respective states. Early Harvest did not affect pod yield or gross economic value of peanut regardless of location, cultivar, or edaphic and environmental conditions. These data suggest that a spray program consisting of Early Harvest most likely will not improve pod yield or gross economic value of peanut.

Flumioxazin in combination with ethalfluralin provided early-season control of eclipta, pitted morningglory, and Texas panicum. Metolachlor plus flumioxazin failed to adequately control pitted morningglory (less than 80%), while flumioxazin did not control yellow nutsedge. Eclipta control with flumioxazin plus dimethenamid, imazethapyr, or metolachlor combinations were at least 99%. When flumioxazin was used in combination with dimethenamid, imazethapyr, or metolachlor, late-season yellow nutsedge control was greater than 70%. Late-season eclipta control was greater than 80% with flumioxazin alone, dimethenamid plus flumioxazin applied preemergence (PRE), ethalfluralin applied preplant incorporated (PPI) followed by (fb) flumioxazin at 0.07 kg/ha applied PRE, imazethapyr plus flumioxazin at 0.09 kg/ha applied PRE, metolachlor plus flumioxazin combinations applied PRE, or ethalfluralin applied PPI fb imazapic applied postemergence (POST). Late-season pitted morningglory control was less than 65% for all herbicide programs. Flumioxazin alone controlled no greater than 25% pitted morningglory, while ethalfluralin plus flumioxazin combinations controlled less than 48%. Late-season, flumioxazin alone controlled less than 70% Texas panicum, while ethalfluralin alone provided 84% control. All ethalfluralin plus flumioxazin combinations controlled 70 to 83% Texas panicum, while imazethapyr or metolachlor plus flumioxazin combinations controlled less than 70%. Yellow nutsedge control was greater than 70% with imazethapyr or metolachlor plus flumioxazin combinations.

Field studies were conducted in various peanut growing regions of Texas and Georgia to study peanut response to flumioxazin alone or in combination with dimethenamid or metolachlor. In south Texas during 1997, flumioxazin plus metolachlor resulted in greater than 45% peanut stunt, while flumioxazin plus dimethenamid caused ≤20% peanut stunt. This stunting was attributed to cool, wet growing conditions. Peanut yields in flumioxazin plus metolachlor-treated plots were reduced 58% from peanut in the non-treated check. In 1999 and 2000, flumioxazin plus dimethenamid or metolachlor resulted in 15% or greater peanut stunt, but stunting was not constant across weather conditions or locations. In west Texas and Georgia no peanut stunting with flumioxazin was noted. At the Levelland, TX location, flumioxazin at 0.07 kg/ha plus metolachlor at 1.1 kg/ha reduced peanut yield 32% when compared with the non-treated check; while at the Pearsall, TX location, metolachlor or dimethenamid at 1.1 kg/ha, flumioxazin at 0.07 kg/ha plus dimethenamid at 1.5 kg/ha, and flumioxazin at 0.1 kg/ha plus dimethenamid at 1.1 kg/ha reduced peanut yield 24 to 48% when compared with the non-treated check. No yield reduction was noted in Georgia.

Field studies were established in 1996 and 1997 in Atascosa Co. in south Texas to evaluate the response of six peanut cultivars to Rhizoctonia pod rot when sprayed with the fungicides azoxystrobin and tebuconazole. Compared to unsprayed plots, significant disease reduction occurred when cultivars were sprayed with either fungicide. Disease reductions were similar with both fungicides. Tamrun 96 displayed the lowest disease incidence both years with and without a fungicide application. Yields were significantly enhanced both years when either azoxystrobin or tebuconazole was applied to all six cultivars. Tamrun 96 was the highest yielding cultivar in 1996 when sprayed with azoxystrobin and in 1997 when sprayed with tebuconazole. Both fungicides improved grade (%TSMK) when compared to the unsprayed checks.

Field trials were conducted in Georgia, North Carolina, and Texas to evaluate the effects of preplant applications of 2,4-D, dicamba, tribenuron, and tribenuron plus thifensulfuron on peanut yield. Herbicides were applied 30, 15, 7, or 0 d before planting (DBP) in conventional production systems in Georgia and Texas, and 28, 21, 14, 7, and 0 DBP in no- and strip-tillage systems in North Carolina. Amine and ester formulations of 2,4-D did not affect peanut yield at any time of application in any state. Dicamba reduced peanut yield when applied at 0 DBP in two of seven trials. Tribenuron did not affect peanut yield regardless of preplant interval. However, tribenuron plus thifensulfuron reduced yields when applied at 7 DBP in one of five trials. These data suggest that 2,4-D, tribenuron, and tribenuron plus thifensulfuron can be safely used for preplant weed control in peanut when applied 7 DBP. Dicamba should be applied a minimum of 15 DBP.

Field studies were conducted to evaluate broadleaf signalgrass and southern crabgrass control and effect on peanut yield of clethodim alone and sequential applications with six broadleaf herbicides. When rated 9 wk after treatment (WAT), broadleaf signalgrass control with clethodim followed by (fb) acifluorfen, imazapic, or 2,4-DB 24 hr later did not differ from clethodim alone. When acifluorfen, acifluorfen plus bentazon, imazethapyr, imazapic, and lactofen were applied in a tank-mix with clethodim, broadleaf signalgrass control was less than 65%. Clethodim alone or clethodim plus 2,4-DB controlled 86 and 73% broadleaf signalgrass, respectively. When acifluorfen, acifluorfen plus bentazon, or imazethapyr was fb clethodim, signalgrass control was less than 72%. Southern crabgrass control was reduced in 2 of 3 yr from clethodim alone when acifluorfen was tank-mixed with clethodim. When other broadleaf herbicides were tank-mixed with clethodim, reduced crabgrass control was noted in only 1 of 3 yr. Where no POST herbicides were used, peanut yield was < 1600 kg/ha, while all plots which received a POST herbicide yielded over 2200 kg/ha.

Eleven commercially grown peanut cultivars were evaluated for disease and yield response to two and four applications of tebuconazole under moderate disease pressure (< 12 hits/12.2 m) by southern stem rot ( Sclerotium rolfsii ). The incidence of southern stem rot was reduced in all cultivars when treated with two and four sprays of tebuconazole. Tamrun 96 and Southwest Runner had the lowest disease incidence. Cultivars responded with higher yields when sprayed with two and four applications of tebuconazole compared to the unsprayed plots. Peanut grade (SMK + SS) was not affected by tebuconazole. Georgia Runner and Tamrun 96 produced the highest grade while Southwest Runner was the lowest.

Field studies were conducted at 11 locations across south Texas from 1994 to 1997 to determine the activity of azoxystrobin against southern stem rot ( Sclerotium rolfsii Sacc.), Rhizoctonia pod rot ( Rhizoctonia solani Kuhn), early leaf spot ( Cercospora arachidicola Hori) and late leaf spot [ Cercosporidium personatum (Berk. & Curt.) Deighton]. Azoxystrobin at 0.22 to 0.45 kg/ha applied twice provided control of stem rot, Rhizoctonia pod rot, and leaf spot comparable to tebuconazole at 0.2 kg/ha applied four times. Peanut yield increases were evident with all fungicide treatments over the untreated check.

Peanut ( Arachis hypogaea L.) pod yield and response to early and late leaf spots [caused by Cercospora arachidicola S. Hori and Cercosporidium personatum (Berk. & M. A. Curtis) Deighton, respectively] were evaluated on six runner-type cultivars under four leaf spot spray programs using tebuconazole at 0.23 kg ai/ha and chlorothalonil at 1.26 kg ai/ha. The four leaf spot spray programs included unsprayed, 14-d schedule, 21-d schedule, and 28-d schedule. With the 14- and 21-d schedule, chlorothalonil was applied at the first and last applications with a maximum of four tebuconazole applications for the middle sprays. On the 28-d schedule, tebuconazole was applied four times. Under conditions of heavy leaf spot disease pressure where no fungicide was applied, Southern Runner and Georgia Browne were slightly less susceptible (although not significantly) to early or late leaf spot than Florunner, GK-7, Georgia Runner, or Sunrunner. Less leaf spot was present in the 14-d schedule compared to 21- or 28-d schedules. Although there was no yield difference between the 14-, 21-, or 28-d schedules, the plots sprayed on a 14-d schedule yielded 43% more than the unsprayed. When averaged across all spray schedules, Georgia Browne yielded 15% more peanuts than Georgia Runner.

Field experiments were conducted to determine the effect of the dimethylamine salt of 2,4-DB at 0.45 kg ae/ha applied at various times during the growing season on runner peanut growth, development, and pod yield. The herbicide was applied once at 30, 45, 60, 90, or 120 d after planting. Additional treatments included 2,4-DB at 0.45 kg/ha applied twice beginning at 30, 60, or 90 d after planting or applied three times beginning at 30, 45, or 60 d after planting. The dates of application were selected to expose plants to the herbicide during all stages of development from prebloom through early pod development. Peanut yield and grade were not affected by 2,4-DB regardless of application timing or numbers of applications.

Eight Texas and one Georgia breeding lines, four accessions from Burkina Faso (West Africa), and six runner and two spanish-type cultivars were compared for yield, grade, and susceptibility to Sclerotium rolfsii Sacc. for 3 yr under irrigated field conditions. The spanish-type cultivar Tamspan 90 and runner-type breeding line TX896100 (recently released as Tamrun 96) consistently had the lowest disease incidence for all 3 yr. Averaged over years, TX896100 was the highest yielding entry. Four breeding lines resulted in a 2 to 16% yield increase over Okrun, the highest yielding cultivar. The African accessions, in general, produced low yields and low grades with no advantages in disease resistance.