Azoxystrobin, tebuconazole, pyraclostrobin, chlorothalonil + flutolanil, and chlorothalonil fungicide programs were evaluated on selected peanut cultivars for the control of early leaf spot (ELS) and southern stem rot (SSR) in 2000, 2001, and 2002. A peanutcotton-peanut rotation was followed and the plots were irrigated as needed. Virugard and Georgia Green were planted in all 3 yr. The late-maturing line Southern Runner was planted only in 2000 and was replaced with Florida C-99R in 2001 and 2002. Since the ranking of fungicide programs for ELS and SSR control and yield response was similar over peanut cultivars, data for each variable in 2000, 2001, and 2002 were pooled. The • 0.34-kg ai/ha azoxystrobin and pyraclostrobin programs gave better ELS control than the season-long chlorothalonil standard in 1 yr. However, SSR control and yield response to pyraclostrobin was similar to the chlorothalonil standard. Significant reductions in SSR damage and higher yields were obtained with 0.34-kg ai/ha azoxystrobin program in all 3 yr. When compared to the chlorothalonil standard, the 0.47-kg ai/ha azoxystrobin program gave superior SSR control in 2000 and 2001, but significantly better ELS control and higher yield were obtained only in 2001. Tebuconazoletreated peanuts had similar ELS ratings to those recorded for the chlorothalonil standard and azoxystrobin programs in 2000 and 2001, but the ELS ratings for the former program were significantly higher in 2002. While tebuconazole reduced SSR damage compared with chlorothalonil alone, the azoxystrobin and chlorothalonil + flutolanil programs controlled SSR significantly better than tebuconazole in at least 1 yr. Also, the 0.34-kg ai/ha azoxystrobin program significantly increased yield above that of the chlorothalonil standard more consistently than did tebuconazole. Relatively few differences in disease control or yield response were noted between the two chlorothalonil + flutolanil programs, but both increased yield above that of the chlorothalonil standard. By maturing about 2 wk before Georgia Green, Virugard may have escaped some ELS and SSR damage, which may have contributed to its higher yield. There are indications that the late-maturing Florida C-99R has partial resistance to ELS but not SSR. Georgia Green proved more susceptible to both diseases than Virugard

Efficacy of azoxystrobin (Heritage 50W™) was assessed over a range of application rates and intervals for the control of powdery mildew (Erysiphe polygoni) and Cercospora leaf spot (Cercospora hydrangea) on bigleaf hydrangea (Hydrangea macrophylla) ‘Nikko Blue’. Rooted hydrangea cuttings were transplanted in a pine bark/peat mixture. In 1998 and 1999, azoxystrobin at 0.16 g ai/liter and 0.32 g ai/liter, as well as 0.24 g ai/liter myclobutanil (Eagle 40W™) and 0.84 g ai/liter thiophanate methyl (3336 4.5F™), greatly reduced the incidence of powdery mildew compared with the untreated control where 75% of the leaves of were infected by the causal fungus. When applied at 1-, 2-, and 3-week intervals, both rates of azoxystrobin were equally effective in both years in preventing the development of powdery mildew on bigleaf hydrangea. In 1998, all fungicides except for thiophanate methyl protected bigleaf hydrangea from Cercospora leaf spot. In the last two trials, the incidence of powdery mildew increased significantly as the application rate for azoxystrobin decreased from 0.16 to 0.04 g ai/liter and the application interval was lengthened from 1 to 3 weeks. In general, all rates of azoxystrobin applied on a 3-week schedule failed to provide the level of powdery mildew control needed to produce quality bigleaf hydrangea for the florist and landscape market. When applied at 2-week intervals, myclobutanil was equally or more effective in controlling powdery mildew than any rate of azoxystrobin applied on the same schedule. When compared to the untreated controls, significant reductions in the incidence of powdery mildew on bigleaf hydrangea were obtained with weekly applications of paraffinic oil. No symptoms of phytotoxicity were associated with the use of any of the fungicides screened.

Reaction of selected shrub and ground cover roses to black spot, Cercospora leaf spot, and powdery mildew, as well as the impact of fungicide inputs on the control of the above diseases, was assessed from 1999 through 2003 in a simulated landscape planting in Brewton, AL. Chlorothalonil at 1.25 g ai/liter was applied at 2- and 4-week intervals from mid-March until October to randomly selected plants in each replicate. An unsprayed control was also included in each replicate. Although black spot was the predominate disease observed, a number of rose selections suffered from objectionable Cercospora leaf spot-induced leaf spotting and premature defoliation. Few mixed outbreaks of black spot and Cercospora leaf spot on a single selection were seen. In all years, significant differences in the reaction of rose selections to black spot and Cercospora leaf spot were noted. Of the roses damaged by black spot, the least leaf spot and defoliation were noted on the unsprayed Ice Meidiland®, Mystic Meidiland®, Red Cascade™, ‘Hansa’, ‘Pink Grootendorst’, ‘Pink Pet’, and to a lesser extent Carefree Wonder™ and Pearl Sevillana™. In a residential planting, monthly applications of chlorothalonil or other recommended fungicide would be needed to protect the above rose selections from a destructive black spot outbreak. ‘Betty Prior’, Bonica®, Cherry Meidiland®, First Light™, Kent™, Jeepers Creeper™, ‘Livin’ Easy™, Lilian Austin™, ‘Nearly Wild’, ‘Nozomi’, Butterfly rose, Ralph's Creeper™, Raven™, Royal Bonica™, ‘Sea Foam’, Sevillana™, and Sweet Chariot™ were susceptible to black spot. While black spot did not appreciably damage Carefree Delight™, Flower Carpet®, White Flower Carpet®, Fire Meidiland®, Fuchsia Meidiland®, Happy Trails™, ‘Petite Pink Scotch’, Polar Ice™, R. wichurana, The Fairy™, and ‘Therese Bugnet’, considerable Cercospora leaf spot development occurred on all of the above rose selections. Of these roses, Polar Ice™, Fuchsia Meidiland®, and Fire Meidiland® exhibited the highest resistance to Cercospora leaf spot and may not require any fungicide inputs to maintain plant health and vigor. Magic Carpet™ and Knock Out™ roses, which were susceptible and resistant to black spot, respectively, as well as Flower Carpet®, and White Flower Carpet® appeared to be poorly adapted to the hot and sometimes dry summer weather patterns of South Alabama. In nearly all years, chlorothalonil gave better control of both diseases when applied on a 2-week than on a 4-week schedule. Significant chlorothalonil-induced leaf burn was seen on First Light™, Flower Carpet®, ‘Hansa’, Happy Trails™, Magic Carpet™, Mystic Meidiland™, ‘Nozomi’, and Raven™. Consistent powdery mildew development was found only on ‘Therese Bugnet’ and to a lesser extent on Red Cascade™ and ‘Petite Pink Scotch’. Canopy spread of the roses that were heavily damaged by black spot and Cercospora leaf spot often was often reduced in size when compared with that of adjacent chlorothalonil-treated plants of the same selection. In contrast, little if any increase in growth was obtained with fungicide inputs for the more disease resistant rose selections.

Efficacy of selected registered fungicides and trifloxystrobin, was evaluated for the control of powdery mildew (Erysiphe pulchra) on container-grown flowering dogwood (Cornus florida). Bare-root trees were transplanted into a pine bark/peat moss substrate and maintained under a 47% shade cloth. All fungicide treatments significantly reduced the incidence of powdery mildew compared with the untreated control. During the trial period, the most consistent control of powdery mildew was given by azoxystrobin [Heritage® 50W] at 0.16 g ai/liter or propiconazole [Banner MAXX®] at 0.07 g ai/liter, respectively. In two of three years, myclobutanil [Eagle® 40W] at 0.24 g ai/liter was equally effective in controlling this disease as the above fungicides. Copper sulfate pentahydrate [Phyton 27®] at 0.74 g ai/liter gave similar control of powdery mildew in three of four years as propiconazole but was not quite as effective in controlling this disease as azoxystrobin. Paraffinic oil at 1% v/v [Sunspray Ultrafine Oil®] was slightly less effective in controlling powdery mildew than azoxystrobin or myclobutanil. However, no more than 6% leaves on the paraffinic oil-treated dogwood were colonized in any year by E. pulchra, compared with 75% colonization for the untreated controls. Although thiophanate methyl [3336™ 4.5F] at 0.84 g ai/liter and triadimefon [Bayleton® WSP] at 0.16 g ai/liter reduced powdery mildew incidence compared with the untreated control, the level of leaf colonization in three of four years was significantly higher than other fungicides. Trifloxystrobin [Compass™ 50W] at the 0.04 g ai/liter rate gave better control of powdery mildew when applied at 1- and 2-week intervals than on a monthly schedule. In contrast, the 0.08 and 0.16 g ai/liter rate of this fungicide were almost equally effective in controlling this disease at 1-, 2-, and 4-week intervals. When applied on the same schedule, myclobutanil (0.24 g ai/liter) gave the same level of powdery mildew control as all three rates of trifloxystrobin. In 1999, moderate to excellent control of powdery mildew with trifloxystrobin, propiconazole, and azoxystrobin resulted in a significant gains in tree dimensions and trunk caliper over those recorded for the untreated flowering dogwood. No symptoms of phytotoxicity were associated with the use of any of the fungicides screened.

In a simulated landscape planting in Brewton, AL, the impact of fungicide treatments on severity of Entomosporium leaf spot was assessed on 13 selections of Indian hawthorn, which range from highly susceptible to resistant to this disease. Chlorothalonil [Daconil 2787 4.17F] at 1.25 g ai/liter was applied at 2-and 4-week intervals to a randomly selected plant in each plot. The remaining plant in each plot was not sprayed and was the untreated control. From mid-winter to mid-spring in 1997, 1998, and 1999, fungicide applications were made over a 13-to 15-week period. When compared to unsprayed controls, reductions in the severity of Entomosporium leaf spot were noted on the fungicide-treated plants of nearly all selections, regardless of their susceptibility to Entomosporium leaf spot. As expected, disease severity was usually lower on those plants sprayed at 2-week rather than 4-week intervals. While chlorothalonil significantly reduced disease severity on the Entomosporium leaf spot resistant selections ‘Indian Princess’®, ‘Clara’, ‘Snow White’, ‘Olivia’™, and ‘Eleanor Tabor’™, only a limited reduction in the number of infected leaves in the canopy and perhaps a minor reduction in premature leaf loss were seen. In contrast, substantially less leaf spotting and defoliation on the selections such as ‘Spring Rapture’®, ‘White Enchantress’®, ‘Enchantress’®, ‘Heather’, ‘Harbinger of Spring’®, ‘Pinkie’, and ‘Bay Breeze’® were obtained with chlorothalonil, particularly when this fungicide was applied at 2-week intervals. When treated with chlorothalonil at 2-week intervals, disease severity on susceptible selections was, however, comparable to the damage levels observed on the unsprayed leaf spot resistant selections. When compared with costly and labor-intensive fungicide inputs, production and establishment of disease resistant selections is the preferred strategy for preventing destructive outbreaks of Entomosporium leaf spot on Indian hawthorn in the nursery and landscape.