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FOZ DO IGUASSU - BRAZIL - June 6 to ll 200QJ i «*»..,,.-^
Third International Weed Science Congress -IWSC
ABSTRACTS^
Third International Weed Science Congress Foz do Iguassu—2000
Poir., and Stellaria media (L.) Vill. The assessment caiTied out at the end of stem elongation showed that the dry biomass and weed density in band-planting were similar and lower (23%), respectively, than those recorded in traditional-planting plots. The weed control with herbicides in traditional-planting plots was similar to that of the plots carried out in bands but was more effective (84%) than that with harrow (36%). The herbicide application was very effective against V. persica and S. media but was very weak against P. rhoeas. The mechanical intervention provided a good control against S. media but was ineffective against V. persica and P. rhoeas. The wheat yield, obtained in band-planting treatments subjected to chemical and mechanical weed control, was not statistically different from that of the corresponding traditional-planting treatments (8.89 t ha-1, on average). The height of the crop, number of spikes nr2, harvest index, and the weight of 1000 seeds were not statistically different for the treatments where weeds were controlled either with herbicides or harrow. The band-planting system, with the herbicide application on the band and the mechanical intervention on the inter-band area, was as effective against weeds as broadcast herbicide weed control in traditional row spacing. This integrated weed management allowed a 37.5% reduction of herbicide spraying.
Weed control in Vigna unguiculata L. Walp bean, under agronomic and ecological conditions of the Maracaibo plain, Venezuela (117) WERNER GUTIERREZ Agronomy Faculty Zulia University. P.O Box 15205 Maracaibo. Zulia 4005. Venezuela;
[email protected] Maracaibo plain, a region with a surface of 540 000 hectares shows agronomic and ecological conditions appropriate to bean production, this crop possesses special nutritional characteristics that gives it a very promising potential. However, the specific characteristics of these soils besides a deficient handling have been occasioning the loss of its capacity for the agricultural production. Since 1994, several studies have been carried out in relation to the bean production without damaging the soil besides to assuring a significative reduction of production costs. Nevertheless, to obtain a success through this novel technology is essential to control weeds in an effective way. This work summarizes the results of several researches in which were evaluated different methods for its control, from its identification and description. Thus, it was determined the effect of technology on the environment and the structure of the production costs. The results confirm the viability of the direct seeding for the bean production in the plain conditions. Between the differents treatments evaluated set off the application of glyphosate or ghyphosate trimesio 960 g a.i. ha '. There is the possibility of reducing the application dose of these herbicides until a 30% through the use of coadjuvants.
A weed flora of Mazandaran, Iran (118) M.T. BARARPOUR, A. M. MANSOOJI University of Mazandaran, Sari, Iran;
[email protected] More than one-third of the pesticides used in Iran are used in the Mazandaran province. Studies were conducted from 1996 through 1999 to: 1) identify the weed flora of Mazandaran; 2) study biology and ecology of dominant species; and 3) determine best control of these species. Dominant weed species included Abutilon theophrasti, Echinochloa crus-galli, Cyperus spp., Avena fatua, Phalaris minor, Chenopodium album, Amaranthus spp., Sorghum halepense, Brassica kaber, and Xanthium strumarium. The focus of this report is on A. theophrasti, one of the most troublesome species in soybean (Glycine max) and cotton (Gossypium hirsutuin) in Mazandaran. Field studies were conducted at the Main Agricultural Experiment Station, Sari, Mazandaran to evaluate the effect of various A. theophrasti densities on cotton growth and yield; and to determine the effect of tillage and split applications of bentazon on A. theophrasti population, seed production, and control. In cotton study, the experiment was initiated as a randomized complete block design with four replications. One A. theophrasti plant nr' of cotton row caused 23, 28, 32 54
Third International Weed Science Congress Foz do Iguassu—2000
and 76% reduction in height, number of nodes, canopy width, and dry weight as compared to the cotton alone, respectively. Cotton boll number reductions were 71, 80, 84, 87 and 88% for 1, 2, 3, 6, and 12 A. theophrasti plants or1 in the cotton row, respectively. Control treatment produced 2629 kg ha-1 seedcotton yield while plots infested with 1, 2, 3, and 6 A. theophrasti plants nr1 produced 456, 149, 65 and 0 kg ha-'. In bentazon study, the experiment was a split plot with four replications. Tillage (no tillage and conventional tillage) was the main plot. Subplots were bentazon at 1.44 kg ha-' (recommended rate) applied once at 1- to Meaf stage of A. theophrasti; 0.71 kg ha~ ! applied at the 1- to 3-leaf stage and repeated 10 days later; and 0.45 kg ha-' applied three times, 1- to 3-leaf stage and repeated 10 days after the first and second application. The no-tillage system reduced Abutilon theophrasti population, dry weight, and seed production T90% compared to conventional tillage. In tillage plots, population was reduced 81, 97, and 99%; dry weight was reduced 53, 87, and 95%; and seed production was reduced 26, 87, and 94% for 1.44, 0.71, and 0.45 kg ha 1 compared to untreated plots. The first application at 1.44, 0.71, and 0.45 kg ha 1 controlled Abutilon theophrasti 87, 79, and 69%, respectively, 9 days after application. Abutilon theophrasti control was 83, 90, and 84% (at 1.44, 0.71, and 0.45 kg ha'1), 10 days after the second application timing. Control after the third timing was 78, 85, and 84% for 1.44, 0.71, and 0.45 kg ha-' of bentazon, respectively.
Weed control in Florida citrus (119) STEPHEN H. FUTCH Citrus Research & Education Center, 700 Experiment Station Road, Lake Alfred, FL United State of America, 33850;
[email protected] Citrus is one of the most important agricultural crops in Florida, comprising 845,260 acres with an on-tree value of 1.15 billion for the 1998-99 crop year. Control of weeds is a major economic cost, estimated at $172.8 million or 25% of annual production budget. Florida's favorable climate allows for weed germination and year-round growth. Weeds compete with citrus trees for nutrients, water, light and harbor insects and rodents that attack citrus trees. Additionally, weeds increase cold damage from radiation freezes, increase the incidence of Phytophthora foot rot, impede harvesting of citrus crops, interfere with low volume irrigation systems and intercept soil-applied chemicals. Thus, the objective of today's citrus weed management program is the suppression of weed populations to a level that minimizes economic losses. Herbicides used in groves are divided into two groups: soil-applied preemergence, and foliar-applied postemergence. The postemergence herbicides can be further divided into systemic or contact. Postemergence herbicides include non selective paraquat and glyphosate, and selective grass control herbicides are fluazifop-p-butyl, and sethoxydim. Commonly used preemergence herbicides for the control of grasses include: bromacil, norflurazon, oryzalin, and thiazopyr. Preemergence herbicides for the control of broadleaf weeds include: diuron, oxyfluorfen, and simazine. Soon to be released azafenidin controls both broadleaf and grass weeds. Control of specific weeds are product and rate dependent. For the effective control of all weed species combinations of products may be necessary.
Interactions between narrow row spacing and low dosages of atrazine on weed control in grain sorghum (Sorghum bicolor) in La Pampa, Argentina (120) FERNANDO D. GARCIA, MIGUEL A. FERNANDEZ, DANIEL R. ALI, MARTA I. BRUSCO Facultad de Agronomia. Universidad Nacional de La Pampa, Argentina, CC 300, L6300 Santa Rosa, La Pampa, Argentina; garcia@agro. unlpam.edu.ar Interactions between row spacing (0.35; 0.52 and 0.70 m) and low dosages of atrazine applied at preemergence (0, 250, 500 and 750 g a.i. ha-') on grain sorghum (Sorghum bicolor) yield under conventional tillage and weed control have been evaluated during 1996/97; 97/98 and 98/99. These treatments have been compared with hand weeded plots. Chenopodium album, Digitaria sanguinalis, Panicum capillare and Hirschfeldia incana were the major weeds during the three years of research. Low herbicide dosages (250 g 55
