Nutritive value, fermentation characteristics, and in situ disappearance kinetics of ensiled warm-season legumes and bahiagrass.

This study determined the nutritive value, ensiling characteristics, and in situ disappearance kinetics of bahiagrass (Paspalum notatum Flügge 'Tifton 9'), perennial peanut (Arachis glabrata Benth. 'Florigraze'), annual peanut [Arachis hypogaea (L.) 'FL MDR 98'], cowpea [Vigna unguiculata (L.) Walp. 'Iron clay'], and pigeonpea [Cajanus cajan (L.) Millsp. 'GA-2']. All forages were harvested at maturity stages that optimized dry matter (DM) yield and nutritive value. After harvest, forages were wilted to 45% DM, and 4 replicate bales of each legume and 8 bales of bahiagrass were wrapped in polyethylene and ensiled for 180 d. After each bale was opened, the forage was thoroughly mixed, and representative subsamples were taken for laboratory analysis and in situ incubation. Wilting and ensiling decreased the rumen-undegradable protein, water-soluble carbohydrate, crude protein (CP), and in vitro true digestibility (IVTD) of bahiagrass, perennial peanut, and cowpea, and increased their neutral detergent fiber (NDF) concentrations. Among haylages, CP concentration was greatest for annual peanut, followed by perennial peanut and cowpea, and least for bahiagrass. In contrast, NDF concentration was greater in bahiagrass than in legumes. Pigeonpea had the greatest NDF concentration among legumes and lowest IVTD of all haylages. All haylages were aerobically stable for at least 84 h, but pH was lower in perennial peanut and cowpea than in pigeonpea. Ammonia-N concentrations tended to be greater in legume haylages than in bahiagrass haylage. Butyrate concentration was greater in annual and perennial peanut than in bahiagrass. Total VFA concentration was greater in annual and perennial peanut and cowpea haylages than in bahiagrass haylage. Undegradable DM fractions were greater and extent of DM degradation was lower in bahiagrass and pigeonpea than in other haylages but lag time and degradation rates did not differ. Annual and perennial peanut and cowpea haylages were as aerobically stable and had greater CP, IVTD, and extent of degradation than did bahiagrass haylage; therefore, they are promising forages for dairy cow diets in the southeastern United States.

Intake, digestibility, and nitrogen retention by sheep supplemented with warm-season legume haylages or soybean meal.

The high cost of commercial supplements necessitates evaluation of alternatives for ruminant livestock fed poor quality warm-season grasses. This study determined how supplementing bahiagrass haylage (Paspalum notatum Flügge cv. Tifton 9) with soybean [Glycine max (L.) Merr.] meal or warm-season legume haylages affected the performance of lambs. Forty-two Dorper x Katadhin lambs (27.5 +/- 5 kg) were fed for ad libitum intake of bahiagrass haylage (67.8% NDF, 9.6% CP) alone (control) or supplemented with soybean meal (18.8% NDF, 51.4% CP) or haylages of annual peanut [Arachis hypogaea (L.) cv. Florida MDR98; 39.6% NDF, 18.7% CP], cowpea [Vigna unguiculata (L.) Walp. cv. Iron clay; 44.1% NDF, 16.0% CP], perennial peanut (Arachis glabrata Benth. cv. Florigraze; 40.0% NDF, 15.8% CP), or pigeonpea [Cajanus cajan (L.) Millsp. cv. GA-2; 65.0% NDF, 13.7% CP]. Haylages were harvested at the optimal maturity for maximizing yield and nutritive value, wilted to 45% DM, baled, wrapped in polyethylene plastic, and ensiled for 180 d. Legumes were fed at 50% of the dietary DM, and soybean meal was fed at 8% of the dietary DM to match the average CP concentration (12.8%) of legume haylage-supplemented diets. Lambs were fed each diet for a 14-d adaptation period and a 7-d data collection period. Each diet was fed to 7 lambs in period 1 and 4 lambs in period 2. Pigeonpea haylage supplementation decreased (P < 0.01) DM and OM intake and digestibility vs. controls. Other legume haylages increased (P < 0.05) DM and OM intake vs. controls; however, only soybean meal supplementation increased (P = 0.01) DM digestibility. All supplements decreased (P = 0.05) NDF digestibility. Except for pigeonpea haylage, all supplements increased (P < 0.01) N intake, digestibility, and retention, and the responses were greatest (P = 0.04) with soybean meal supplementation. Microbial N synthesis was reduced (P = 0.02) by pigeonpea haylage supplementation, but unaffected (P = 0.05) by other supplements. Efficiency of microbial protein synthesis was unaffected (P = 0.05) by diet. Ruminal ammonia concentration was increased (P = 0.01) by all supplements, but only soybean meal and annual peanut haylage increased (P < 0.03) plasma urea-N concentrations. Perennial peanut, annual peanut, and cowpea haylages are promising protein supplements for growing lambs.

Intake, digestibility, and nitrogen retention by sheep supplemented with warm-season legume hays or soybean meal.

The increasing cost of feed supplements necessitates evaluation of alternatives for ruminant livestock grazing poor quality warm-season grasses. This study determined how supplementing bahiagrass hay (Paspalum notatum Flügge cv. Pensacola) with soybean [Glycine max (L.) Merr.] meal or warm-season legume hays affected intake, digestibility, and N utilization by lambs. Dorper x Katadhin crossbred lambs (30.6 +/- 5.5 kg; n = 42) were fed bahiagrass hay (73.8% NDF, 8.1% CP) for ad libitum intake and supplemented with nothing (control), soybean meal, or hays of annual peanut [Arachis hypogaea (L.) cv. Florida MDR98; 46.2% NDF, 14.7% CP], cowpea [Vigna unguiculata (L.) Walp. cv. Iron clay; 62.2% NDF, 11.7% CP], perennial peanut (Arachis glabrata Benth. cv. Florigraze; 43.3% NDF, 15.2% CP), pigeonpea [Cajanus cajan (L.) Millsp. cv. GA-2; 78.6% NDF, 12.2% CP], or soybean (cv. Pioneer 97B52; 59.0% NDF, 13.5% CP). Legume hays were supplemented at 50% of total diet DM, and soybean meal was supplemented at a level (4.25% of diet DM) that matched the average dietary CP content (10.8%) of the legume hay-supplemented diets. The cowpea, pigeonpea, and soybean were harvested at respective maturities that maximized DM yield and nutritive value, and the peanuts were first cuttings. Diets were fed to 6 lambs per treatment for 2 consecutive 21-d periods. Supplementation with hays of annual and perennial peanut, cowpea, and soybean increased (P < 0.01) DMI vs. control, but apparent DM digestibility was only increased (P = 0.03) by supplementation with annual or perennial peanut hay. Compared with the control, N intake, digestibility, and retention were increased (P < 0.01) by supplementation with legume hay or soybean meal. Responses were greatest when annual or perennial peanut hays were fed. Ruminal ammonia concentration was increased (P < 0.01) by all legume hay supplements vs. the control. Microbial N synthesis and ruminally degraded OM were increased (P = 0.03) by perennial and annual peanut hay supplementation, but efficiency of microbial synthesis was not different (P = 0.52) among diets. Unlike other supplements, annual and perennial peanut hays increased DM and N intake and digestibility and improved microbial N synthesis; therefore, they were the best supplements for the bahiagrass hay under the conditions of this study.

Effects of Reduced Tillage, Resistant Cultivars, and Reduced Fungicide Inputs on Progress of Early Leaf Spot of Peanut (Arachis hypogaea).

Field experiments were conducted in 2000 and 2001 on Georgia Green, Florida MDR-98, and C-99R peanut (Arachis hypogaea) cultivars in Tifton, GA, to determine the effects of tillage practices on early leaf spot (Cercospora arachidicola) epidemics under standard fungicide regimes and fungicide regimes with fewer applications. Leaf spot epidemics were suppressed in reduced tillage (strip-till) plots compared with conventional tillage plots and were suppressed in MDR-98 and C-99R cultivars compared with the standard runner-type cultivar, Georgia Green. Within tillage and cultivar combinations, leaf spot intensity typically was lower in plots treated with fungicides at standard intervals (seven total applications) than in those treated at extended intervals (four total applications). However, in most cases, leaf spot control in extended interval treatments in the strip-till system was comparable to that in the standard interval treatments in conventional tillage. Based on these results, the number of fungicide applications could be reduced without compromising control of leaf spot when reduced tillage is used, especially if combined with moderately resistant cultivars. Suppression of leaf spot epidemics in the strip-till plots did not coincide with higher yields in either year. In 2001, yields were lower in strip-till plots than in conventional tillage plots. Yields were typically higher in the cultivar C-99R than in Georgia Green, regardless of the tillage treatment.

First Report of Rhizoctonia solani AG-2-4 on Carrot in Georgia.

Anastomosis group-2-4 (AG-2-4) of Rhizoctonia solani Kühn was formally described in 2002 (1), but it was first collected in 1983 in Georgia from corn (Zea mays L.) exhibiting symptoms of crown and brace root rot. Although occasionally present on diseased corn roots, the role that isolates of AG-2-4 play in crown and brace root rot of corn is not specifically known (2). More recently, as part of a broad multi-year (1996 to 2000) survey of root diseases in field grown carrot (Daucus carota L.), isolates of R. solani AG-2-4 were recovered from diseased carrot plants in various stages of growth from fields of sandy loam soil at many locations in southern Georgia, including commercial fields in Coffee and Tift counties. During the 1996 to 2000 growing seasons, 123 isolates of Rhizoctonia sp. (including multinucleate and binucleate types) were collected from lesions on developing and mature carrot roots. Of these, 34% were AG-2-4, 10% were AG-2-2IV, 6% were AG-4, and 32% were binucleate Rhizoctonia sp. The remaining 18% were lost prior to AG typing. An additional 40 isolates were collected from carrot seedlings or soil and of these, 55% were AG-4, 18% were AG-2-2IV but none were AG-2-4. Virulence on carrot seedlings by two isolates of AG-2-4 (777R1P5-SL2 and 758C) was compared with virulence of isolates of AG-4, AG-2-2IV, AG-2-1, and binucleate Rhizoctonia sp. Carrot seeds soaked for 5 min in 0.5% NaOCl were planted in petri dishes containing moist autoclaved sandy loam soil. Each dish was inoculated in the center with a 10-mm-diameter disk cut from a 9-day-old potato dextrose agar (PDA) culture of the appropriate isolate. Petri dishes were placed in a 26°C incubator for 9 days, and then the seedlings were rated for disease. Virulence on mature carrot root tissue was also assessed on the same set of isolates. Cross sections of carrot roots (5 to 10 mm thick) were surface disinfested in 0.5% NaClO for 5 min. Three cross sections were placed on moist filter paper in sterile petri dishes and each was inoculated with a 5-mm-diameter disk of inoculum cut from 8- to 10-day-old cultures growing on PDA. All treatments were rated for damage following incubation on a lab bench at 21 to 24°C for 7 days. Isolate 777R1P5-SL2 caused moderate damage to seedlings but minimal rotting of mature carrot root tissue. Isolate 758C did no damage to either seedlings or root tissue. The AG-4 and AG-2-2IV isolates killed all seedlings and caused extensive rot on mature root tissue. The AG-2-1 isolate caused moderate damage to seedlings and mature root tissue, whereas isolates of binucleate Rhizoctonia sp. damaged neither seedling nor mature root tissue. These data suggest that some isolates of R. solani AG-2-4 may be capable of causing minor damage to carrot seedlings in the field in Georgia, but isolates of R. solani AG-4 and AG-2-2IV pose greater threat to seedlings and mature roots of carrot. Published data shows that isolates of AG-2-4 can kill seedlings of lettuce, cauliflower, and broccoli in the laboratory (1). R. solani AG-2-4 also may be capable of killing these crops in the field, all of which are grown commercially in Georgia. To our knowledge, this is the first report of R. solani AG-2-4 on carrot in Georgia. References: (1) D. E. Carling et al. Phytopathology 92:43, 2002. (2) D. R. Sumner and D. K. Bell. Phytopathology 72:86.

A total system approach to sustainable pest management.

A fundamental shift to a total system approach for crop protection is urgently needed to resolve escalating economic and environmental consequences of combating agricultural pests. Pest management strategies have long been dominated by quests for "silver bullet" products to control pest outbreaks. However, managing undesired variables in ecosystems is similar to that for other systems, including the human body and social orders. Experience in these fields substantiates the fact that therapeutic interventions into any system are effective only for short term relief because these externalities are soon "neutralized" by countermoves within the system. Long term resolutions can be achieved only by restructuring and managing these systems in ways that maximize the array of "built-in" preventive strengths, with therapeutic tactics serving strictly as backups to these natural regulators. To date, we have failed to incorporate this basic principle into the mainstream of pest management science and continue to regress into a foot race with nature. In this report, we establish why a total system approach is essential as the guiding premise of pest management and provide arguments as to how earlier attempts for change and current mainstream initiatives generally fail to follow this principle. We then draw on emerging knowledge about multitrophic level interactions and other specific findings about management of ecosystems to propose a pivotal redirection of pest management strategies that would honor this principle and, thus, be sustainable. Finally, we discuss the potential immense benefits of such a central shift in pest management philosophy.

Phylogenetic relationships of the pigeonpea (Cajanus cajan) based on nuclear restriction fragment length polymorphisms.

Nuclear restriction fragment length polymorphisms (RFLPs) were used to determine phylogenetic relationships in the genus Cajanus using 15 random genomic probes and six restriction enzymes. Twenty-four accessions representing 12 species of four genera (Cajanus, Dunbaria, Eriosema, and Rhynchosia) were examined to determine phylogenetic relationships in the genus Cajanus. Eriosema parviflorum was selected as the out-group. Sufficient RFLP polymorphisms were detected among species to resolve in-group taxa into distinct clusters. Topologies of trees from parsimony and similarity matrix analyses were similar but not identical, and clustering patterns agreed broadly with published phylogenies based on seed protein data and, to a lesser extent, data from cytology and breeding experiments. Accessions of cultivated C. cajan shared more DNA fragments with C. scarabaeoides than with C. cajanifolia. Inconsistencies in taxonomic relationships based on data from morphology, cytology, crossability, and RFLPs are discussed.

Biological Control of Yellow Nutsedge with the Indigenous Rust Fungus Puccinia canaliculata.

Yellow nutsedge (Cyperus esculentus L.) is a serious weed problem in the United States and other countries. An indigenous rust fungus [Puccinia canaliculata (Schw.) Lagerh.], pathogenic on yellow nutsedge, was released in early spring as a potential biological control agent. The fungus inhibited nutsedge flowering and new tuber formation. The fungus also dehydrated and killed nutsedge plants. The successful control of yellow nutsedge by a rust epiphytotic under experimental conditions demonstrates the potential use of the rust in an integrated weed management system.

Parthenocarpic Fruit Development from Grafted Ovaries of Cucuminis sativus L.

Reciprocal cleft and pistillate floral bud grafts were made between parthenocarpic ;Fertilla' and nonparthenocarpic ;MSU 713-5' cucumber (Cucumis sativus L.) lines to localize the site for stimulation of parthenocarpic fruit set. No fruit set on ;MSU 713-5' controls, scion grafted to ;Fertilla,' or rootstock with ;Fertilla' as the scion. ;Fertilla' controls, rootstock, and scions all produced parthenocarpic fruit when grafted to ;MSU 713-5.' When pistillate floral buds of ;MSU 713-5' were grafted to ;Fertilla,' no fruit were produced. However, individual immature pistillate buds of ;Fertilla' developed into mature fruits when grafted onto ;MSU 713-5.' Hence, the immature ovary is the site of stimulation for parthenocarpic fruit set in cucumber.