Yield and forage quality of glandular-haired alfalfa under alfalfa weevil (Coleoptera: Curculionidae) and potato leafhopper (Hemiptera: Cicadellidae) pest pressure in Virginia

Cultivars of glandular-haired alfalfa, Medicago sativa L., such as '54H69', are currently available and marketed as being resistant to potato leafhopper, Empoasca fabae (Harris) (Hemiptera: Cicadellidae). 54H69 and a standard, nonglandular-haired alfalfa 'Choice' were evaluated at two locations in Virginia over a 3-yr period. Dry matter yields and concentrations of crude protein and acid detergent fiber were compared at the first, second, and third harvests. Overall, the two cultivars produced similar dry matter yields of comparable forage quality in the absence of insecticides at both locations in each year. Untreated 54H69 did not produce greater dry matter yields than untreated Choice under either light or heavier potato leafhopper pest pressure. Concentrations of crude protein did not vary between the two cultivars at any harvest. Some differences in concentrations of acid detergent fiber were detected between cultivars, but these differences were not consistent among years, harvests, or between locations. Further comparisons between untreated 54H69 and treated Choice were made, but few significant differences were detected in dry matter yields or forage quality. An economic analysis for the study indicated that a grower planting 54H69 would realize less net revenue than a grower planting Choice, largely because of the seed premium for the glandular-haired cultivar and the evident need to treat 54H69 with insecticide for control of alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae), and potato leafhopper.     

A degree-day model of sheep grazing influence on alfalfa weevil and crop characteristics

Domestic sheep (Ovis spp.) grazing is emerging as an integrated pest management tactic for alfalfa weevil, Hypera postica (Gyllenhal), management and a degree-day model is needed as a decision and support tool. In response to this need, grazing exclosures with unique degree-days and stocking rates were established at weekly intervals in a central Montana alfalfa field during 2008 and 2009. Analyses indicate that increased stocking rates and grazing degree-days were associated with decreased crop levels of weevil larvae. Larval data collected from grazing treatments were regressed against on-site and near-site temperatures that produced the same accuracy. The near-site model was chosen to encourage producer acceptance. The regression slope differed from zero, had an r2 of 0.83, and a root mean square error of 0.2. Crop data were collected to achieve optimal weevil management with forage quality and yield. Differences were recorded in crude protein, acid and neutral detergent fibers, total digestible nutrients, and mean stage by weight. Stem heights differed with higher stocking rates and degree-days recording the shortest alfalfa canopy height at harvest. The degree-day model was validated at four sites during 2010 with a mean square prediction error of 0.74. The recommendation from this research is to stock alfalfa fields in the spring before 63 DD with rates between 251 and 583 sheep days per hectare (d/ha). Sheep should be allowed to graze to a minimum of 106 and maximum of 150 DD before removal. This model gives field entomologists a new method for implementing grazing in an integrated pest management program.     

Rumen Fungi and Forage Fiber Degradation

The role of anaerobic rumen fungi in in vitro forage fiber degradation was determined in a two forage × two inoculum source × five treatment factorial design. Forages used as substrates for rumen microorganisms were Coastal bermuda grass and alfalfa; inoculum sources were rumen fluid samples from a steer fed Coastal bermuda grass hay or alfalfa hay; treatments were whole rumen fluid (WRF), WRF plus streptomycin (0.2 mg/ml of rumen fluid) and penicillin (1.25 mg/ml of fluid), WRF plus cycloheximide (0.5 mg/ml of fluid), WRF plus streptomycin, penicillin, and cycloheximide, and McDougall buffer. Populations of fungi as shown by sporangial development were greater on bermuda grass leaves than on alfalfa leaflets regardless of inoculum source. However, endogenous fungal populations were greater from the alfalfa hay inoculum. Cycloheximide inhibited the fungi, whereas streptomycin and penicillin, which inhibit bacterial populations, resulted in an increase in numbers of sporangia in the alfalfa inoculum, suggesting an interaction between bacteria and fungi. Bacteria (i.e., WRF plus cycloheximide) were equal to the total population in degrading dry matter, neutral-detergent fiber (NDF), acid-detergent fiber (ADF), and cellulose for both inocula and both forages. Degradation of dry matter, NDF, ADF, and cellulose by anaerobic fungi (i.e., WRF plus streptomycin and penicillin) was less than that due to the total population or bacteria alone. However, NDF, ADF, and cellulose digestion was 1.3, 2.4, and 7.9 percentage units higher, respectively, for bermuda grass substrate with the alfalfa versus bermuda grass inoculum, suggesting a slight benefit by rumen fungi. No substantial loss of lignin (72% H₂SO₄ method) occurred due to fungal degradation. The most active fiber-digesting population in the rumen was the bacteria, even when streptomycin and penicillin treatment resulted in an increase in rumen fungi over untreated WRF. The development of large numbers of sporangia on fiber may not indicate a substantial role as digesters of forage.     

Effect of annual and/or biennial burning of seed alfalfa stubble on populations of alfalfa weevil and pea aphid

The effects of five burning treatments of alfalfa (Medicago sativa L.) stubble combined with two insecticide treatments on populations of alfalfa weevil, Hypera postica (Gyllenhal), and the pea aphid, Acyrthosiphon pisum (Harris) were evaluated over an eight year period. The effects of the burn treatments were dependent on insect species, time of burn and year. Immature alfalfa weevil population levels were significantly reduced by the burn-every-autumn treatment in 3 of the 8 years, in 2 out of 8 years by the burn-e very-spring treatment, and by the alternate-year-burn treatment in 1 out of 4 years. Burning had little or no effect on pea aphid populations.     

Nutritional quality and yield of seedling alfalfa established with a barley companion crop and weeds

Alfalfa (Medicago sativa L.) was established with barley (Hordeum vulgare L.) and weeds to determine the effect of weed management treatments on yield and nutritional quality of alfalfa and companion crop and weeds. Alfalfa+barley and alfalfa+wild oat (Avena fatua L.) had much higher yields in August of the first year than alfalfa alone. Total yields for the first three harvests were similar for alfalfa established weed free, with broad leaf weeds, wild oat or green foxtail (Setaria viridis L.). Protein contents in forage from the August harvest were 228, 196, 117 and 181 g/kg dry matter (DM) in weed free alfalfa, alfalfa plus broadleaf weeds, alfalfa plus wild oat, and alfalfa plus green foxtail, respectively. Alfalfa+barley had higher total in vitro gas production than pure alfalfa, which is correlated with the digestibility of the forage. Total in vitro gas production indicated that alfalfa+barley+weeds had slightly lower digestibility than weed free alfalfa+barley. However, alfalfa with a high percentage of redroot pigweed (Amaranthus retroflexus L.), wild oat or green foxtail had similar or higher in vitro gas production than pure alfalfa. The results from this experiment support a previous economic study that indicated herbicide application for weed control in seedling alfalfa was not necessary.     

Host effects of glandular-haired alfalfa on alfalfa weevil (Coleoptera: Curculionidae) and potato leafhopper (Homoptera: Cicadellidae) populations in Virginia

Cultivars of glandular-haired alfalfa, Medicago sativa L., such as '54H69', are currently available and marketed as being resistant to potato leafhopper, Empoasca fabae (Harris). Between 2000 and 2002, studies were conducted to compare the effects of '54H69' and a standard, nonglandular-haired alfalfa cultivar, 'Choice', on alfalfa weevil, Hypera postica (Gyllenhal), and potato leafhopper populations at Campbell and Montgomery counties, Virginia. '54H69' had no effect on alfalfa weevil populations. At each location, densities of alfalfa weevil in '54H69' and 'Choice' were similar, but pest pressure was higher at Campbell Co. than at Montgomery Co. and always exceeded the economic threshold before insecticide was applied. Densities of potato leafhopper also did not differ between '54H69' and 'Choice' in any year at the two locations. Insecticide treatment effectively reduced potato leafhopper densities in the two cultivars, although populations were below the economic threshold at both locations when the insecticides were applied. Overall, postinsecticide treatment comparisons showed that the densities of alfalfa weevil and potato leafhoppers were similar or higher in untreated '54H69' compared with insecticide-treated 'Choice'. In addition, there were no differences in seasonal dry yields between '54H69' and 'Choice' in any year at either location. Our results indicate that the glandular-haired alfalfa '54H69' does not provide acceptable resistance to potato leafhopper and also does not offer a yield advantage to growers in Virginia.     

Effect of particle size of alfalfa hay and reconstitution with water on intake, digestion and milk production in Holstein dairy cows

Twenty-four lactating Holstein dairy cows (12 first lactation and 12 multiparous; day in milk = 11 ± 5 days) were allotted to a randomised complete block design in a 2 × 3 factorial with four replicates per treatment to evaluate the effects of two methods of alfalfa feeding (dry and reconstituted to achieve a theoretical dry matter (DM) content of 350 g/kg) and three geometric mean (GM) particle sizes of alfalfa (9.13, 4.51 and 1.20 mm) on performance of dairy cows for a period of 28 days. Diets were offered for ad libitum intake as total mixed rations (TMR). The GM particle size, its standard deviation, and the values of physical effectiveness factor of alfalfa and TMR decreased as alfalfa particle size decreased. Reduction of particle size and reconstitution of alfalfa increased the bulk density and the functional specific gravity of alfalfa and rations. Reduction of particle size decreased insoluble dry matter, water-holding capacity, and hydration rate of alfalfa. As particle size decreased, the amount of physically effective NDF in the ration (g/kg) decreased but the daily intake of physically effective NDF (kg/day) increased. Reduction of particle size and reconstitution increased dry matter intake (DMI) and ruminal passage rate, but reduced NDF and ash digestibilities, ruminal pH, N-NH3, milk fat, total chewing activity, rumination and eating time, total and ruminal mean retention time, and time delay of marker. Increased functional specific gravity, from reduced forage particle size and the reconstitution of alfalfa, was the most important factor influencing DMI, milk composition, and chewing activity.     

Hypera postica [Col.: Curculionidae] and its natural enemies in Maryland and West Germany — 1971

A comparative study of field populations ofHypera postica (Gyllenhal), the alfalfa weevil, and its natural enemies was conducted in Maryland and West Germany in 1971. Populations of alfalfa weevil larvae peaked at 231/.09 m² in Maryland versus 45/.09 m² in West Germany. The ichneumonid parasiteBathyplectes curculionis (Thomson), and the eulophid,Tetrastichus incertus (Ratzeburg), were recovered in both Maryland and West Germany.Bathyplectes anurus (Thomson) was recovered only in West Germany, and the braconid,Microctonus colesi Drea, was recovered only in Maryland. A review of the agricultural practices and climatological conditions indicated that these factors may contribute to the regulation of the alfalfa weevil in West Germany and the United States. This paper is the 2nd in a series of 3 studies on the biology, ecology and biological control of the alfalfa weevil from 1966–1979.     

Ruminal microbial populations and fermentation characteristics in bison and cattle fed high- and low-quality forage

Ruminal microbial populations and fermentation products were compared between two ruminally cannulated bison (375 kg) and two ruminally cannulated Hereford steers (567 kg) on alfalfa or prairie hay diets. Differential media were used to enumerate carbohydrate-specific bacterial subgroups. Voluntary dry matter intake was higher (P=0.006) for cattle than for bison fed alfalfa, but prairie hay intake was not different (P=0.16) between the two species. Volatile fatty acid concentrations, pH, and ruminal ammonia were similar between bison and cattle on both diets. Total anaerobic bacteria and xylanolytic bacterial counts were higher (P<0.02) in bison than in cattle fed alfalfa. However, with the prairie hay diet, no differences in bacterial counts on any medium were observed between ruminant species. Both bison and cattle possessed a mixed A-B protozoan population with nearly identical protozoan numbers and distribution of genera. The similarities between bison and cattle consuming either high-or low-quality forage suggest that any differences in putative forage digestibility between the species are not due to differences in microbial counts.     

Using food for different purposes: female responses to prey in the predator Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Abstract.  1. Although predatory insects often feed on diverse prey, their reproductive activity may be linked most strongly to a more restricted range of prey. The propensity of adult females of the ladybird beetle, Coccinella septempunctata L., to attack two natural prey species, pea aphids [ Acyrthosiphon pisum (Harris)] and alfalfa weevil larvae [ Hypera postica (Gyllenhal)], was compared, and the degree to which ladybird egg production depends on consumption of aphids vs. weevils was assessed.
2. Coccinella septempunctata females more readily attacked aphids than weevil larvae. This was true regardless of whether females had fed previously on aphids or on weevil larvae.
3. When females were provided with few to many aphids daily, or few aphids plus an excess number of weevil larvae, their rates of egg production depended primarily on the number of aphids consumed.
4. Addition of weevil larvae to diets of limited numbers of aphids increased egg production, but only modestly. Thus, consumption of weevil larvae may have served mostly for self-maintenance, thereby enabling females to use for egg production more of the nutrients and energy obtained from limited consumption of aphids.
5. The females' linkage of egg production primarily to aphid rather than weevil consumption may be adaptive, as their offspring are much less able as larvae to survive and mature on a diet of weevils rather than aphids.     

Impact of Bemisia whiteflies (Homoptera: Aleyrodidae) on alfalfa growth, forage yield, and quality

A 3-yr project was initiated in 1993 to examine the effects of insecticides and sustained whitefly, Bemisia argentifolii Bellows & Perring [aka. B tabaci Gennadius (Strain B)], feeding on alfalfa plant growth and vigor in greenhouse cage studies, and to determine the impact of natural Bemisia whitefly populations on alfalfa forage yields and quality in a large-plot field experiment. Alfalfa plant growth and vigor after exposure to imidacloprid and a mixture of fenpropathrin and acephate insecticides did not differ from untreated plants in the greenhouse. Consequently, foliar and soil applied insecticides were used to manipulate whitefly densities on alfalfa plants to measure whitefly feeding effects on plant growth and forage yield. Heavy whitefly densities on untreated alfalfa plants in the greenhouse resulted in significant reductions in relative growth rates and net assimilation rates as compared with imidacloprid-treated plants that were maintained relatively whitefly-free. Reductions in alfalfa plant growth measured between infested and treated plants were proportional to whitefly densities. Field plot results derived from three crop seasons were relatively consistent with our greenhouse trials. Both experimental approaches clearly showed that alfalfa plants exposed to high densities of whitefly immatures and adults grew at a significantly slower rate and produced less foliage. As a result of reduced growth rates, alfalfa maturity in the naturally infested plots was estimated to be approximately 7-10 d behind managed plots. Delays in maturity resulted in significant reductions in forage yields of 13-18% during August-September harvests when whitefly populations reached peak abundance. Whitefly feeding stresses also effected hay quality through the reduction of crude protein content and contamination of foliage with honeydew and sooty mold. The status of the Bemisia whiteflies as an economic pest to alfalfa is clearly evident from these studies, but the damage potential of whiteflies in the southwestern United States appears to be restricted to one or two harvest periods during the summer coinciding with peak adult populations and their dispersal from alternate host crops.     

Molecular and morphological identification of the alfalfa weevil larval parasitoids Bathyplectes anura and Bathyplectes curculionis to estimate the rate of parasitism

BioControl - The alfalfa weevil (Hypera postica Gyllenhal, Coleoptera: Curculionidae) is a major pest of alfalfa crops. Chemical control measures are inefficient, but the larvae are often infested...     

Farm-Scale Cost of Producing Perennial Energy Cane as a Biofuel Feedstock

Energy cane varieties are high-fiber sugarcane clones which represent a promising feedstock in the production of alternative biofuels and biobased products. This study explored the crop establishment and whole farm production costs of growing energy cane as a biofuel feedstock in the southeastern USA. More specifically, total production costs on a feedstock dry matter biomass basis were estimated for five perennial energy cane varieties over alternative crop cycle lengths. Variable production costs for energy cane production were estimated to be in the $63 to $76 Mg^?1 range of biomass dry matter for crop cycles through harvest of fourth through sixth stubble crops. Total production costs, including charges for fixed equipment costs, general farm overhead, and land rent, were estimated to range between $105 and $127 Mg^?1 of feedstock biomass dry matter material.     

Chemical regulation of growth,yield, and digestibility of alfalfa and smooth bromegrass

In addition to enabling manipulation of plant growth and development, growth regulators have potential for increasing forage digestibility. This study focuses on the use of gibberellic acid (GA3), -naphthalene acetic acid (NAA), 6-benzylaminopurine (BA), o-benzylhydroxylamine (OBHA), and monocetyl phosphate (C16P) to alter growth, dry weight (DW) yield, and in vitro digestible dry matter (IVDDM) of forage grasses and legumes grown in a greenhouse. Screening experiments revealed that GA3, NAA, and OBHA at rates of 1.6, 160, and 0.51 g a.i. ha^–1, respectively, were more effective in altering regrowth of potted alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.) compared with other treatments. Subsequent experiments with increasing dosages of GA3, NAA, and OBHA on alfalfa and smooth bromegrass (Bromus inermis Leyss.) confirmed that these regulators can be used to manipulate forage growth. Increasing concentrations of GA3 increased growth and DW yield but decreased IVDDM, whereas high concentrations of NAA decreased growth and DW yield but increased IVDDM. OBHA treatments resulted in little or negative change in IVDDM. Results generally showed that plant growth regulators can be used to manipulate forage growth, but that there is a trade-off between herbage yield and digestibility of forage tissues.     

Effect of wheel traffic and green manure treatments on forage yield and crown rot in alfalfa (Medicago sativa)

Harvesting alfalfa damages crowns and increases the opportunity for entry of pathogens. Incorporation of green manures into soil increases population density of streptomycetes with broad pathogen antagonist activity. This study aimed to measure the impact of wheel traffic on forage yield and plant health and the effect of green manures to reduce disease. Buckwheat and sorghum-sundangrass were incorporated into soil 3 weeks before seeding alfalfa. Total bacteria, streptomycete, and pathogen antagonist densities were measured prior to planting green manures and alfalfa. Wheel traffic was applied 2 days after each forage harvest. Wheel traffic reduced forage yield 12 % to 17 % depending on year and location, significantly reduced plant counts, and increased crown rot compared to the no traffic control. Cultivar had a significant effect on yield, plant counts, and crown rot. Streptomycete density and pathogen antagonists increased when fall-sown green manure crops were incorporated in spring. Forage yields were significantly higher in plots with greater antagonist density when traffic was applied. Green manure treatments did not affect plant counts or crown rot. Mechanical wheel traffic reduces forage yield and increases disease. Green manure crops may provide benefits in alfalfa production systems by increasing pathogen antagonists.     

Nutritive value of papyrus (Cyperus papyrus,Cyperaceae), a tropical emergent macrophyte

Papyrus (Cyperus papyrus, Cyperaceae) covers large areas in tropical African wetlands. Analysis of its nutritive value has revealed that crude protein is higher in umbels than culms. Ruminai dry matter digestibility of papyrus is, however, higher in culms than umbels. Both the crude protein and ruminai dry matter digestibility decrease with increasing age of the plant. Values for crude protein and ruminai dry matter digestibility are similar to those reported for the range grasses that constitute the greatest percentage of forage in East Africa. In general, papyrus has some grazing potential and could be used as fodder especially in the dry season when other forage is scarce and of low nutritive value.     

An assessment of the effect of harvest time and harvest method on biomass loss for Miscanthus × giganteus

This study examines the amount of biomass loss occurring in Miscanthus × giganteus crop at harvest. The study assesses loss incurred as a direct result of the harvest systems employed to collect the material along with examining how the time of harvest effects the amount of loss occurring over the spring harvest window. Pre harvest losses of 4.8–5.1% were measured prior to harvest. There was no significant difference between pre harvest loss and post harvest loss when a self‐propelled forage harvester fitted with a maize harvesting header was used to harvest the crop. The use of a conditioner mower and baler significantly increased crop losses to 9.4–14.1%. This demonstrates that correct selection of the harvest system can significantly increase biomass recovery. Additional losses were measured at headlands when the mower/baler system was used, but headland losses will not occur when self‐propelled forage harvesters are utilized. Losses were significantly greater in the area beside the swath after the baler pass when compared to prior to baling. This study has shown that correct selection of harvest systems can significantly increase biomass recovery, with no significant difference in pre harvest loss or harvest loss occurring as a result of cutting the M. × giganteus crop at different dates during the harvest window (March 1st, March 25th, April 21st).     

Effects of routine late-season field operations on numbers of boll weevils (Coleoptera: Curculionidae) captured in large-capacity pheromone traps

Flat and cylindrical adhesive boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), pheromone traps captured significantly more (P < or = 0.05) boll weevils than the Hercon (Hercon Environmental, Emigsville, PA) trap during the late cotton-growing season, and larger adhesive areas were associated with higher captures; a flat plywood board collected the most boll weevils because it had the largest surface area. The flat board trap, chosen for measuring large late-season adult boll weevil populations common to the Lower Rio Grande Valley of Texas in 2000 and 2001, collected more (P < or = 0.05) weevils when deployed in proximity to natural and cultivated perennial vegetation, and mean numbers of captured boll weevils were higher (P < or = 0.0001) on the leeward sides of the board traps than on the windward sides. The board trap had an estimated potential capacity of approximately 27,800 boll weevils, and the large capacity of the board trap allowed for more accurate measurements of large adult boll weevil populations than the more limited Hercon trap. Measurement of adult boll weevil numbers after the routine field operations of defoliation, harvest, shredding, and stalk-pulling, demonstrated that large populations of boll weevils persist in cotton fields even after the cotton crop has been destroyed. Increases (P < or = 0.05) in the percentage variation of trapped boll weevils relative to the numbers collected just before each field operation were observed after defoliation, harvest, shredding, and stalk-pulling, but the percentage variations followed a quadratic pattern with significant correlation (P < 0.0001; 0.59 < adjusted r2 < 0.73). Numbers of adult boll weevils caught on board traps deployed at 15.24-m intervals on windward and leeward edges of cotton fields suggested that boll weevil populations in flight after field disturbances might be affected by large-capacity trapping.     

Endocarpic Microorganisms of Two Types of Windrow-Dried Peanut Fruit (Arachis hypogaea L.)

The endocarpic microorganisms of peanut fruit dried in either a random windrow (plants left as they fell from the digger) or an inverted windrow (plants inverted to expose fruit to sunlight) were different from that of freshly dug fruit. Chaetomium, Penicillium, Trichoderma, Rhizoctonia, and Fusarium were the dominant fungi found associated with shells (pericarp) of freshly dug fruit. The dominant fungi of shells of windrowed fruit included Chaetomium, Rhizoctonia, Fusarium, Sclerotium, and Alternaria. Seeds of freshly dug fruit were dominated by Penicillium and Aspergillus. The only dominant species in seed of windrowed fruit was Penicillium. Microorganisms were isolated from shells and seed of freshly dug fruit at a frequency of 79% and 52%, respectively. The percentage of infestation was reduced by drying in the field. This was particularly true of the inverted windrow. The proportion of shells and seed infested with a microorganism was reduced 13% and 36%, respectively, after field drying for 5 to 7 days in random and inverted windrows. Microorganisms were isolated much more frequently from shell pieces (73%) than from seed (36%).     

An Immunoassay Method for Detecting Microctonus aethiopoides (Hymenoptera: Braconidae: Euphorinae) Parasitism in the Alfalfa Weevil, Hypera postica (Coleoptera: Curculionidae)

A simple immunological assay was developed as an alternative to the dissection/visualization method for detecting the presence of the parasitoid, Microctonus aethiopoides Loan, in the alfalfa weevil, Hypera postica (Gyllenhal). The dot-blot assay was validated using laboratory-reared and field-collected adult weevils of known parasitization status. The dot-blot assay was also used to estimate the developmental stage of the parasitoid within parasitized adult hosts. The assay results can be used to forecast parasitoid emergence dates and estimate the parasitism rate of M. aethiopoides in alfalfa weevil populations.