Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The high cost of herbicides for weed control in crop fields in the Western Cape is a major cause of reducing farmers' net income. As chemical weed control became more difficult and expensive, it became necessary to focus on the technique of reducing weed impact, which does not only involve herbicide usage. Aspects such as tillage method, sowing date of crops, crop rotation, weed ecology and germination requirements, amongst other, may play a role in reducing weed impact. The first experiment was done to determine whether temperature and light had an effect on the germination of six selected weed species, namely Arctotheca calendula, Avena fatua, Bromus diandrus, Emex australis, Lolium temulentum and Raphanus raphanistrum. Seeds of the aforementioned weeds were collected from Langgewens during 2000 and stored at room temperature before being used in this study. The seeds were germinated in a germination cabinet at three temperature regimes namely 5 "C /15 "C, 10°C / 15°C and 10°C / 20°C. Most seeds showed a positive germination response at the 10°C / 15°C treatment, except for Emex australis and Lolium temulentum, which was believed to germinate throughout the year under favourable conditions. Among the germinated weed species, Avena fatua germinated best with a cumulative value of 90% as compared to Raphanus raphanistrum, which germinated least with a cumulative value of 12%. The second experiment was done to evaluate the effect of three growth regulators, namely gibberellic acid, hydroxylamine (auxin), and kinetin (cytokinin) to break dormancy and enable simultaneous germination of the six weed species mentioned above. Weed seeds were germinated in a germination cabinet at 20 °C using the test solutions of the aforementioned growth regulators. The germination was assessed after 3, 7, 10 and 14 days of incubation and the tetrazolium test for the viability of seeds was done for ungerminated seeds. The result obtained showed that no chemical/concentration proved to be successful in stimulating the germination of all species tested. As for example a high concentration of hydroxylamine increased germination of Emex australis to nearly 100% and inhibited germination of Raphanus raphanistrum to less than 12.5% at all hydroxylamine concentrations. The third experiment was conducted with the aim of determining the competitiveness of the six weed species mentioned above when grown together with wheat in order to decide when weed control will be cost-effective. An additive series experiment was conducted in a glasshouse. The influence of weed species on wheat plant height, tiller number at different growth stages, vegetative dry mass and gram mass was determined by using different varying weed densities. Weed densities, through reduction in number of tillers, reduced wheat grain yield. By increasing the density of wheat this competitive effect could be reduced. Different weed densities caused a significant difference in wheat plant height, tiller number, dry mass and grain mass. The results showed that species had a significant effect (p < 0.05) on wheat plant height during tillering, stem elongation and heading growth stages. Total wheat plant above-ground dry mass was significantly (p < 0.05) reduced by an increase in weed density. / AFRIKAANSE OPSOMMING: Die hoë koste van onkruiddoders vir onkruidbeheer in graangebiede van die Wes- Kaap is een van die hooffaktore wat graanprodusente se netto inkomste verlaag. Weens moeiliker en duurder chemiese onkruidbeheer en om die impak van onkruide te verlaag, het dit noodsaaklik geword om op die tegnieke te fokus wat nie die gebruik van chemikalieë insluit nie. Faktore wat in rol kan speel sluit bewerkingspraktyke, saaidatum van gewasse, wisselbou, ekologie en ontkiemingsvereistes van onkruide in. Die eerste eksperiment is gedoen om te bepaal of temperatuur en lig 'n effek het op die ontkieming van ses gekose onkruide, naamlik Arctotheca calendula, Avenajatua, Bromus diandrus, Emex australis, Lo/ium temulentum en Raphanus raphanistrum. Sade van die voorgenoemde onkruide is in 2000 op Langgewens versamel en by kamertemperatuur geberg voordat dit in hierdie studie gebruik is. Die sade is in 'n ontkiemingskabinet geïnkubeer by drie temperatuurreekse naamlik 5 oe / 15 oe, 10 oe / 15 oe en 10 oe / 20 oe. Die meeste sade het 'n positiwe ontkiemingsreaksie getoon na die 10 oe / 15 oe behandeling, met die uitsondering van Emex australis en Lolium temulentum, wat oënskynlik heeljaar salontkiem onder gunstige omstandighede. Avena fatua het die hoogste ontkiemingspersentasie oor alle spesies getoon met 'n kumulatiewe waarde van 90% en Raphanus raphanistrum die minste met 'n kumulatiewe waarde van 12%. Die tweede eksperiment is gedoen om die invloed van drie groeireguleerders, naamlik gibberelliensuur, hidroksielamien (ouksien) en kinetin (sitokinien), op die opheffmg van saadrus te ondersoek en om ook die gelyktydige ontkieming van bogenoemde ses onkruidspesies moontlik te maak. Onkruidsade is in 'n ontkiemingskabinet by 20 oe ontkiem deur gebruik te maak van toetsoplossings van bogenoemde groei-reguleerders. Die ontkieming van die sade is na inkubasie periodes van 3, 7, 10 en 14 dae geëvalueer en die tetrazoliumtoets VIr saadkiemkragtigheid is toegepas vir onontkiemde sade. Die verkreë resultate het getoon dat geen chemiekalie / konsentrasie die ontkieming van alle spesies suksesvol kon stimuleer nie. Hoë konsentrasies hidroksielamien het die ontkieming van Emex australis tot byna 100% verhoog en het die ontkieming van Raphanus raphanistrum geïnhibeer tot minder as 12.5% by alle hidroksielamien konsentrasies. Die derde eksperiment is uitgevoer met die doelom die kompetisievermoë van dieselfde ses onkruidspesies te bepaal as dit saam met koring groei en om te besluit wanneer onkruidbeheer koste effektief sal wees. 'n Additiewe reeks eksperiment wat uit vier herhalings bestaan het, is in plastiekpotte in 'n glashuis uitgevoer. Die invloed van die onkruidspesies op koring planthoogte, halmgetal by verskillende groeistadiums, droë massa en graanmassa is bepaal deur onkruiddigthede te gebruik. Onkruide het koring opbrengs verlaag deur die vermindering van halmgetal en hierdie kompeterende effek kon verminder word deur 'n toename in die plantestand van koring. Verskillende onkruiddigthede het 'n betekenisvolle invloed op koring planthoogte, halmgetal, droë massa en graanmassa gehad. Die resultate het getoon dat spesies 'n betekenisvolle effek (p< 0.05) op koring planthoogte, stem verlenging en aarverskyning gehad het. Die totale bogrondse droë massa van koring is betekenisvol (p< 0.05) verminder deur 'n verhoging in onkruiddigtheid.

2 pp. / Camelthorn is an invasive weed classified as a noxious weed in Arizona. The weed has the potential to cause serious damage for private landowners and their property. This fact sheet provides the means for landowners to identify and take steps to control and eliminate this weed.

No description available.

No description available.

Little Malva (Malva porviflora L.) is an important weed that is resistant to herbicides that will selectively control most other broadleaf weeds in alfalfa. Oxyfluorfen (Goal) has been placed under an Experimental Use Permit for alfalfa. In 1987, this herbicide was evaluated for the selective control of malva in alfalfa in the Avra Valley west of Tucson. Oxyfluorfen stunted both the malva and the alfalfa. However, the alfalfa was stunted to a lesser degree, and had begun to recover three weeks after the application of oxyfluorfen. The malva did not recover, and the alfalfa was relieved from weed competition three weeks after treatment.

Two formulations of Velpar® (DF, L) were evaluated over multiple alfalfa varieties to compare the potential phytotoxic effects this product. Treatments were made April 15, with yield and stem data collected on May 10. Both Velpar® formulations resulted in yellowed alfalfa within three days of application, with symptoms disappearing by 21 days post treatment. Yield data indicated increased yields from alfalfa treated with Velpar®, due to increased numbers of stems. The reason for the stem increase associated with Velpar® usage is unknown.

No description available.

Lauko eksperimentas buvo vykdomas nuo 1999 metų pagal šią schemą: A veiksnys: Šiaudų įterpimas: šiaudai pašalinti (-Š), šiaudai susmulkinti ir paskleisti (+Š). B veiksnys: Žemės dirbimo sistemos. Eksperimentas buvo atliktas Lietuvos žemės ūkio universiteto bandymų stotyje. Eksperimentas vykdytas 2010 metais. Atlikus tyrimus nustatyta, kad šiaudų įterpimas ir žemės dirbimo sistemos neturėjo esminės įtakos piktžolių daigų skaičiui. Daugiausiai daugiamečių piktžolių daigų rasta sekliai purentuose variantuose, o mažiausiai – tiesiogiai sėjant į neįdirbtą dirvą. Trumpaamžių piktžolių daigų kiekiui esminės įtakos turėjo šiaudų paskleidimas (+Š). Trumpaamžių piktžolių daigų skaičius buvo 43 procentais mažesnis nei dirvoje, kur šiaudai buvo pašalinti (-Š). Nustatyta, kad šiaudų paskleidimas neturėjo esminės įtakos vasarinių rapsų piktžolėtumui, nustatytam prieš derliaus nuėmimą. Esminių skirtumų buvo rasta skirtingose žemės dirbimo sistemose, sekliai purentuose laukeliuose. Palyginus seklųjį purenimą kultivatoriumi plokščiapjūviais noragėliais ir lėkštiniais padargais (KL) bei seklųjį purenimą rotoriniu kultivatoriumi (RK) su giliu arimu (kontrolė) (GA), piktžolių kiekis padidėjo 1,5 ir 1,6 karto. Daugiamečių piktžolių esmingai padidėjo laukeliuose, kur buvo sekliai arta (SA). Šiaudų paskleidimas turėjo esminės įtakos trumpaamžių piktžolių kiekiui. Dirvoje su šiaudais, palyginus su laukeliais be šiaudų, trumpaamžių piktžolių sumažėjo 1,3 karto. Esmingai trumpaamžių piktžolių kiekis... [toliau žr. visą tekstą] / Field experiment was carried out since 1999, as follows: Factor A: Insert a straw: straw removal (-S), straw, shredded and spread (+S). Factor B: tillage systems. The experiment was carried out in Lithuanian University of Agriculture Experimental Station. The experiment was conducted in 2010. It was determined that straw incorporation and tillage system had no significant effect on the number of weed seedlings. Most perennial weed seedlings found in shallow scratch in the treatments, while at least - when sown directly into uncultivated soil. Short-lived weed seedlings had a substantial impact on the quantity of straw spreading (+S). Short-lived weed seedling density was 43 percent lower than in the soil, where straw was removed (-S). It was found that the spreading of straw had no significant effect on weed control in spring rape, before the harvest. Significant differences were found in different tillage systems, shallow scratch boxes. Compared shallow scarification autum cultivator tines and implements Disc (KL) and a rotary cultivator shallow scarification (RK) with deep plowing (control) (GA), weeds grew 1.5 and 1.6 times. Perennial weeds has increased substantially in the fields, where it was shallow plowing (SA). Spreading straw had a substantial impact on short amount of weed. The soil with straw, as compared with the boxes without straw, weeds, fallen short 1.3 times. Substantially short amount of weeds growing through tillage systems. Studies have shown that both... [to full text]

Lauko eksperimentas atliktas 2010 m. Lietuvos žemės ūkio universiteto bandymų stotyje. Eksperimento lauko dirvožemis yra sekliai glėjiško karbonatingo išplautžemio LVg-p-w-cc(sc)-Calc(ar)i- Epihypogleyic Luvisol dulkiškas priemolis. Eksperimento tikslas buvo nustatyti sąveiką tarp kukurūzų, tarpinių augalų ir piktžolių bei jos įtaką kukurūzų pasėlio produktyvumui. Į kukurūzų tarpueilius buvo įsėti vasarinių rapsų (Brassica napus L.), baltųjų garstyčių (Sinapis alba L.), vasarinių miežių (Hordeum vulgare L.), vienmečių svidrių (Lolium multiflorum Lam.), apyninių liucernų (Medicago lupulina L.), persikinių dobilų (Trifolium resupinatum L.), ankstyvųjų raudonųju dobilų (Trifolium pratense L.) įsėliai, kaip tarpiniai augalai. Kaip ir buvo tikėtasi, į kukurūzus įsėti įsėliai stelbė piktžoles, tačiau konkuravo su pačiais kukurūzais bei mažino jų produktyvumą. Didžiausią neigiamą įtaką kukurūzų produktyvumui turėjo persikinių dobilų įsėlis. Mažiausią neigiamą įtaką turėjo vasarinių rapsų įsėlis. / Field experiment accomplished in 2010 in the Experimental Station of Lithuanian University of Agriculture. Field experiment soil is shallow calcareous soil luvisols (Calc(ar)i-Epihypogleyic Luvisol) silty loam. The aim of experiment was to establish the interaction between maize and living mulch and its influence on maize crop weediness and productivity. Maize crop inter-rows were sown with spring oilseed rape (Brassica napus L.), white mustard (Sinapis alba L.), spring barley (Hordeum vulgare L.), Italian ryegrass (Lolium multiflorum Lam.), black medic (Medicago lupulina L.), Persian clover (Trifolium resupinatum L.) and red clover (Trifolium pratense L.) undercrop as catch crops. As expected, the undercrop of maize drown weeds, but they competed with corn and reduced their productivity. The biggest negative impact on productivity of maize was persian clover undercrop. The minimum negative impact on productivity of maize was spring oilseed rape undercrop.

Conflicting opinions about the effectiveness of H. pakistanae as a biological control agent for hydrilla prompt researchers to find a method for assessing the fly's success. Developing a physiological age-grading system for the fly using ovarian morphology to detect changes in reproductive activity is useful for evaluating reproductive status of the fly in field populations. Changes in the appearance of follicular relics in ovaries with oviposition provide a reliable method to estimate fecundity. Characteristics of follicular relics were used to develop a system with eight physiological age classes, three nulliparous and five parous. Changes that occur in the fat body were used to assist in classification of nulliparous females or those with low egg counts.