Weed Foliage Research Articles

Mass multiplication of Trichoderma asperellum on conifer needles and weed foliage

The impact of hazard by chemical fungicides has necessitated the development of safe and eco-friendly bio-fungicides. Trichoderma asperellum is one of the potent biocontrol agents and for its cost-effectiveness large scale production on several agricultural and industrial wastes has been tested so far. Forest fire due to highly inflammable pine needles and invasion of weeds are considered as a major cause of biodiversity loss in forests of NW Himalaya. Therefore, in the present work, the potential of forest wastes like needles of five conifer species and foliage of three noxious weeds along with some commonly used substrates were evaluated for the mass production of T. asperellum. Amongst all the screened substrates, the highest spore count was recorded on Pinus roxburghii needle powder supplemented with yeast extract and potato dextrose broth. Therefore, authors recommend the use of P. roxburghii needles for the mass multiplication of Trichoderma species as a replacement for useful agro-wastes.

Sparrow Preferences for Winter Cover Crops in California's Central Coast

Agriculture in many regions of the world has reduced bird habitat and abundance, and altered avian community structure. A study was conducted on an organic research farm over two winters (Oct to Mar) in an intensive agricultural region of Salinas Valley, CA to determine how cover crop variety and planting density influenced birds. Cover crops were rye (Secale cereale), a mixture of rye and legumes (Vicia spp., Pisum sativum), and a mustard mixture (Brassica juncea, Sinapis alba). White-crowned Sparrows (Zonotrichia leucophyrs), Savannah Sparrows (Passerculus sandwichensis) and Song Sparrows (Melospiza melodia) were observed both years in the study field. Bird droppings in cover crops were quantified and dissected to determine dietary preferences, and sparrow movement when flushed was determined. Dropping number and weight per m2 were at least 10 times greater in mustard than in rye and in the legume-rye mixture. Droppings were dominated by leaf tissue in mustard versus arthropod tissue in rye and legume-rye. Within cover crop variety, plant density did not have a clear or consistent effect on sparrows. Sparrows flushed from cover crops usually settled in mustard. The White-crowned Sparrow fed on mustard leaves and apparently on weed foliage under mustard. The arthropod-dominated droppings in rye and legume-rye cover crops were consistent with the food preferences of Song and Savannah Sparrows. The White-crowned Sparrow’s clear preference for mustard cover crops is likely due in part to their high dietary needs for sulfur-rich amino acids during the prenuptual molt. This paper provides novel information to help farmers and others understand the cover crop preferences of sparrows, and ways that farmers might use mustard cover crops as trap crops to reduce White-crowned Sparrow feeding damage on winter and spring vegetable crops. It also provides evidence of ecosystems services that these sparrows provide by feeding on weed tissue in winter cover crops.

Host plant-mediated effects of elevated CO2 and temperature on growth and developmental parameters of Zygogramma bicolorata (Coleoptera: Chrysomelidae).

Mexican beetle, Zygogramma bicolorata Pallister (Coleptera: Chrysomelidae) is a potential weed control biocontrol agent in Australia, India and other countries. Its grubs and adults feed on the leaves of parthenium weed, Parthenium hysterophorus and check the further growth of the plant. Experiments were conducted to understand host plant-mediated effects of elevated temperature and elevated CO2 on biocontrol agent Z. bicolorata. Food consumption, utilization, ecological efficiency and life-table parameters of Z. bicolorata were studied in grubs and adults stage up to diapause. Reduction of leaf nitrogen in parthenium weed foliage with a significant increase in carbon and C:N ratio was recorded at elevated CO2. Elevated CO2 and temperature had no effect on adult longevity before diapausing. Duration of egg's hatching, specific stages of grub and pupa of Z. bicolorata were significantly longer when beetles fed on leaves grown under elevated CO2 but these parameters decreased significantly on leaves grown under elevated temperature. Significantly high consumption rates with low growth and digestion conversions were observed under elevated CO2 and/or in coupled with elevated temperature. Elevated CO2 and temperature-grown parthenium weed foliage also had a significant effect on Z. bicolorata intrinsic rate of increase (R), finite rate of increase (λ), mean generation time (T), and gross reproductive rate. Changed quality of parthenium weed leaves in elevated CO2 and temperature levels resulted in the increase of consumption, slower food conversion rates, increase in developmental period with reduced reproduction efficiency of Z. bicolorata. Our results indicate that the reproduction efficiency of Z. bicolorata is likely to be reduced as the climate changes, despite increased feeding rates exhibited by grubs and adult beetles on parthenium weed foliage.

Spray deposition, adjuvants, and physiochemical properties affect benzobicyclon efficacy

AbstractBenzobicyclon is a new pro-herbicide being evaluated in the Midsouth United States as a post-flood weed control option in rice. Applications of benzobicyclon to flooded rice are necessary for efficacious herbicide activity, but why this is so remains unknown. Two greenhouse experiments were conducted to explore how herbicide placement (foliage only, flood water only, foliage and flood water simultaneously) and adjuvants (nonionic surfactant, crop oil concentrate, and methylated seed oil [MSO]) affect herbicide activity. The first experiment focused on importance of herbicide placement. Little to no herbicidal activity (<18% visual control) was observed on two- to four-leaf barnyardgrass, Amazon sprangletop, and benzobicyclon-susceptible weedy rice with benzobicyclon treatments applied to weed foliage only. In contrast, applications made only to the flood water accounted for >82% of the weed control and biomass reduction achieved when benzobicyclon was applied to flood water and foliage simultaneously. The second experiment concentrated on adjuvant type and benzobicyclon efficacy when applied to foliage and flood water simultaneously. At 28 days after treatment, benzobicyclon alone at 371 g ai ha−1 provided 29% and 67% control of three- to five-leaf barnyardgrass and Amazon sprangletop, respectively. The inclusion of any adjuvant significantly increased control, with MSO providing near-complete control of barnyardgrass and Amazon sprangletop. Furthermore, we used the physiochemical properties of benzobicyclon and benzobicyclon hydrolysate to derive theories to explain the complex activity of benzobicyclon observed in our study and in field trials. Benzobicyclon applications should contain an oil-based adjuvant and must be applied to flooded rice fields for optimal activity.

Evaluation of Steam Application for Weed Management in Citrus

Abstract. In this study, a weed steamer was developed, and several steam treatments were utilized to maintain and control the growth of weeds in a citrus grove. Two factors affecting the steam treatment were studied: (i) tractor speed (low, 1.2 km/h; and high, 1.7 km/h); and (ii) steam flow rate (low, 15 L/h; and high 53 L/h). The weed control treatments included various combinations of steam flows and tractor driving speeds, a post-emergent herbicide (paraquat) treatment, and an untreated check for comparison purposes. Randomized experiments were conducted to evaluate the efficacy of each application. It was found that steam applications at high flow rate provided 93%-97% burndown damage of the weed foliage within 3 days after application. Weed re-growth was observed in steam applications, especially with low flow-rate applications. The combination of low tractor speed and high steam flow-rate was the most effective of the steam treatments tested (84% total weed burndown at 12 days after application). This treatment was found effective in controlling weeds like goatweed and sedges. Florida pusley was the least affected by steam due to its prostrate growth nature that prevents an adequate coverage of steam on the entire plant. Based on the observations from this study, the steam application has the potential to be a non-chemical and sustainable strategy for weed management in citrus tree rows. Keywords: Citrus production, Herbicide, Steam application, Weed control.

Interaction of Prodiamine and Flumioxazin for Nursery Weed Control

Both prodiamine and flumioxazin are used in the nursery production and landscape maintenance industries in the southeastern United States for preemergence weed control. Research was conducted to determine whether a tank mixture of these two herbicides would be more effective than either component applied alone. Prodiamine alone, flumioxazin alone, and a 72 : 28 (by weight) prodiamine–flumioxazin mixture were each applied at a series of rates to containers filled with a pine bark–sand substrate that is typical for nursery production in the southeastern United States. Our intent was to have a rate range that hopefully extended from ineffective to lethal for each treatment series. Subsequent to treatment, containers were overseeded with either large crabgrass, spotted spurge, or eclipta. Percent control was determined by comparing treated weed foliage fresh weight to that of the appropriate nontreated control at 6 and 12 wk after application. ANOVA followed by nonlinear regression was used to evaluate the interaction of prodiamine and flumioxazin when combined and to determine the rate of each treatment series required for 95% control (if applicable) for each of the three weed species. Results varied with weed species. The mixture was synergistic and more cost effective than either of the components applied alone in controlling spotted spurge. With respect to large crabgrass control, the mixture was additive and slightly more cost effective than the components. Eclipta could only be controlled with flumioxazin, and this control was antagonized by the addition of prodiamine.

Parasitic Hymenoptera Fauna on Agromyzidae (Diptera) Colonizing Weeds in Ecological Compensation Areas in Northern Italian Agroecosystems

Parasitoids (Hymenoptera) associated with agromyzid leafminers (Diptera: Agromyzidae) were studied in three rural farms located in northern Italy. The parasitoids were reared from mined foliage of weeds growing in field margins. We reared 998 Hymenoptera specimens, representing five families, 23 genera, and 53 species, from leafminers infesting weeds. Eulophidae was the most abundant family (67.64%), followed by Braconidae (28.86%), Eucoilinae (1.40%), Tetracampidae (1.40%), and Pteromalidae (0.7%). Braconids was the most species rich family, accounting for 28 species; eulophids were represented by 19 species, pteromalids by four species, and eucoilins and tetracampids by one species each. The dominant parasitoid was the eulophid Pediobius metallicus (Nees), representing 18.17% of the total, followed by Diglyphus isaea (Walker) (12.73%), and Neochrysocharis formosa (Westwood) (10.82%). The most abundant braconid parasitoid was Dacnusa maculipes Thomson (9.62%). More than 80% of parasitoids were recovered from 10 plant species: Cirsium arvense (L.) Scopoli, Plantago lanceolata L., Sonchus asper (L.) Hill, Papaver rhoeas L., Picris echioides L., Lactuca serriola L., Myagrum perfoliatum L., Ranunculus velutinus Tenore, Arctium lappa L., and Medicago sativa L. The retention and the management of wild plants within field margins can be crucial tools to enhance the populations of biological control agents of agromyzids and to conserve rare parasitic wasp species.

Parasitic Hymenoptera Fauna on Agromyzidae (Diptera) Colonizing Weeds in Ecological Compensation Areas in Northern Italian Agroecosystems

Parasitoids (Hymenoptera) associated with agromyzid leafminers (Diptera: Agromyzidae) were studied in three rural farms located in northern Italy. The parasitoids were reared from mined foliage of weeds growing in field margins. We reared 998 Hymenoptera specimens, representing five families, 23 genera, and 53 species, from leafminers infesting weeds. Eulophidae was the most abundant family (67.64%), followed by Braconidae (28.86%), Eucoilinae (1.40%), Tetracampidae (1.40%), and Pteromalidae (0.7%). Braconids was the most species rich family, accounting for 28 species; eulophids were represented by 19 species, pteromalids by four species, and eucoilins and tetracampids by one species each. The dominant parasitoid was the eulophid Pediobius metallicus (Nees), representing 18.17% of the total, followed by Diglyphus isaea (Walker) (12.73%), and Neochrysocharis formosa (Westwood) (10.82%). The most abundant braconid parasitoid was Dacnusa maculipes Thomson (9.62%). More than 80% of parasitoids were recovered from 10 plant species: Cirsium arvense (L.) Scopoli, Plantago lanceolata L., Sonchus asper (L.) Hill, Papaver rhoeas L., Picris echioides L., Lactuca serriola L., Myagrum perfoliatum L., Ranunculus velutinus Tenore, Arctium lappa L., and Medicago sativa L. The retention and the management of wild plants within field margins can be crucial tools to enhance the populations of biological control agents of agromyzids and to conserve rare parasitic wasp species.

Weed Control in Sericea Lespedeza with Imazethapyr

Field studies were conducted to determine the feasibility of using imazethapyr applied preemergence (PRE) and postemergence (POST) for weed control in sericea lespedeza. In the POST experiment, imazethapyr was applied at 0, 71, 142, and 213 g ai/ha to mature, recently mowed stands of sericea lespedeza. Regardless of rate, yellow nutsedge and cutleaf groundcherry control at 2 mo after treatment, as determined by weed foliage biomass relative to the nontreated plants, was 90 and 80%, respectively. Sericea lespedeza forage yield (weeds removed) was not reduced by POST-applied imazethapyr even at 213 g/ha. The same imazethapyr rates were used with newly seeded sericea lespedeza in the PRE-applied experiment. Imazethapyr at 71 g/ha provided at least 78% control of large crabgrass, stinkgrass, yellow nutsedge, sicklepod, and cutleaf groundcherry as well as maximum sericea lespedeza performance, as indicated by seedling height, weight, and stand count. Results indicated that imazethapyr can be used for either PRE- or POST-applied weed control in sericea lespedeza. However, margin of safety is greater with imazethapyr applied POST to mature stands than with PRE applications to germinating seeds.

Effects of Weeds on Selected Arthropod Herbivore and Natural Enemy Populations, and on Cotton Growth and Yield

Vegetative diversification with weeds can enhance natural enemy populations and suppress pest-related damage in various crops. Weedy and weed-free cotton (Gossypium hirsutum L.) plots were used to study the effects of weediness on selected herbivorous arthropod groups, including the boll weevil (Anthonomus grandis grandis Boheman), and natural enemies, boll weevil-induced injury to cotton squares, and cotton plant growth and yield in the Lower Rio Grande Valley of Texas, during 2000 and 2001. The presence of weeds was associated with greater populations of 9 of the 11 prey arthropod groups, and 9 of the 13 natural enemy arthropod groups counted in this study. These trends were mostly evident late in the season when weed biomass was greatest. Weed-free cotton harbored more cotton aphids (Aphis gossypii Glover), early in the season and silverleaf whiteflies (Bemisia argentifolii Bellows and Perring) later in the season than weedy cotton on some of the sampling dates. Diversity (Shannon’s index) within the selected arthropod groups counted in this study was significantly greater in dvac samples from the weed foliage than from weed-free cotton plants during both years, and diversity on weedy cotton plants was greater than on weed-free cotton plants during 2000. Boll weevil oviposition injury to squares was unaffected by weeds, but the higher weed-associated predator populations mainly occurred after most squares had become less vulnerable bolls. Weed competition resulted in lower lint yields of 89% and 32% in the 2 yr.

Methyl bromide alternatives in a bell pepper–squash rotation

Field studies were conducted to evaluate potential methyl bromide alternatives against multiple pests in a bell pepper ( Capsicum annum L.) – squash ( Cucurbita pepo L.) cropping sequence. Early in the growing season, the most effective treatments in suppressing purple nutsedge ( Cyperus rotundus L.) emergence through the polyethylene mulch were methyl bromide, methyl iodide, and chisel-injected 1,3-dichloropropene plus chloropicrin [1,3-D+C35 (chisel)]. However by the end of the season in 1999, only methyl bromide treatment had less purple nutsedge emerging through the polyethylene than the nontreated control. Each soil-applied treatment resulted in nematode-susceptible pepper plants with lower root-gall indices [ Meloidogyne spp. (root knot nematode)] than the nontreated control, while there were no differences among treatments with the nematode-resistant pepper cultivar. Total fungi isolated from soil was lower in all treated plots relative to the nontreated control, with the exception of methyl iodide. However, methyl bromide was the only treatment that was consistently effective against Pythium spp. and Fusarium spp. A treatment of metham prior to planting squash was beneficial in reducing root-gall indices in plots treated with 1,3-D+C35 (chisel) and methyl bromide prior to the pepper crop. Methyl bromide, methyl iodide, and 1,3-D+C35 (chisel) applied before pepper resulted in squash with lower root-gall indices than the nontreated control. Glyphosate applied between the first and second crop eliminated exposed weed foliage through the polyethylene mulch, possibly muting the effects of the second crop treatment on weed densities. Results of this study indicate that there are some potential methyl bromide alternatives available to growers for use in pest control, however there does not appear to be one broad-spectrum pesticide that will replace methyl bromide. Also, an effective control for nutsedge species within the pepper–squash cropping system is still elusive.

Synthesis of spirothiohydantoin analogues of hydantocidin

Synthesis of Spirothiohydantoin derivatives of hydantocidin is described. The key feature of the synthesis was Spirothiohydantoin ring formation through an iminophosphorane intermediate. Spirothiohydantoin derivative 2 maintained comparable herbicidal activity to that of the natural compound except against fall panicum, when applied through a foliage of weeds at 1000 ppm. Surprisingly, its epimer 15 also demonstrated good herbicidal activity under the same condition, while 5-epi-hydantocidin 16 displayed fair activity.

Interferência de plantas daninhas na cultura da soja (Glycine max (L.) Merrill)

A soja constitui-se numa das principais culturas exploradas no País. Dentre os diversos problemas enfrentados na exploração da cultura, destaca-se a interferência de plantas daninhas. Neste trabalho, foram utilizados dados extraídos de vários experimentos desenvolvidos na Estação Experimental Agronômica da Universidade Federal do Rio Grande do Sul durante diversos anos, todos enfocando aspectos relacionados às plantas daninhas e seu controle. Procurou-se esclarecer alguns fatos relacionados com a convivência da soja x plantas daninhas e ficou claro que estas espécies vegetais exercem influência negativa no desenvolvimento da cultura, principalmente no rendimento de grãos. As espécies gramíneas são capazes de causar maiores danos do que as plantas daninhas dicotiledôneas. Dentre os métodos de controle empregados visando elevar o rendimento de grãos da soja, não há diferenças entre o uso de capinas, herbicidas aplicados no solo ou na folhagem. Desde que bem empregados, todos estes métodos são eficientes no controle de plantas invasoras.

Survey of Pathogenic Genera of Fungi on Foliage of Weeds in Mississippi

(1994). Survey of Pathogenic Genera of Fungi on Foliage of Weeds in Mississippi. Canadian Journal of Plant Pathology: Vol. 16, No. 1, pp. 25-29.

The Impact of Adjuvants on Herbicide Antagonism

Adjuvants are used to improve spray delivery, to increase spray retention on weed foliage, and to enhance foliar penetration by postemergence herbicides for increased herbicide efficacy. Numerous factors govern adjuvant efficacy, including the specific herbicide, plant species, and environmental conditions. Adding superior surfactants as adjuvants to a sethoxydim tank mix with Na-bentazon may overcome the Na-bentazon antagonsim of sethoxydim activity by facilitating increased sethoxydim absorption and by masking the antagonism similar to increasing the sethoxydim rate. Herbicides such as Na-bentazon contribute alkaline or alkaline earth cations that can form salts of a weakly acidic herbicide such as sethoxydim that are not absorbed readily by the plant. Adding abundant ammonium from ammonium sulfate or other sources may prevent and/or may overcome this antagonism.

Determination of Plant Proteinase Inhibitors by Agar Gel Radial Diffusion Assay 1

An agar gel radial diffusion assay for proteinases has been adapted for the assay of proteinase inhibitors from plants. It requires minimal equipment and produces results comparable to those obtainable with a conventional spectrophotometric technique (TAME assay). Insect gut proteinase preparations can be employed in the assay, as well as bovine trypsin. The assay should be useful in large-scale surveys of plant materials for inhibitor activity. Using it, we demonstrate that Jimson weed foliage contains a heat-labile inhibitor of bovine trypsin whose levels rise markedly in undamaged leaves 72 h after crushing injury to the cotyledons or leaves of the plant.