Examination of common ragweed's (Ambrosia artemisiifolia L.) allelopathic effect on some weed species.

In the last decades the importance of some weed species increased in Hungary. The common ragweed (Ambrosia artemisiifolia L.) also belongs to this group. The allelopathic effect of watery extract made from different plant parts of common ragweed (air dried leafy shoots, seeds) were studied on the germination and growth of some weed species. The extracts were prepared with tap water, chopped dry plant materials were added to water and 24 hours later the material was filtered. The germination took place in a Binder KBW type thermostat in dark. 25 seeds were put into one Petri-dish, adding 15 ml plant extract to each in four repeats. The timing of germination was checked in every two days and the rate of growth was estimated after a week, by counting the numbers of germinated seeds and measuring the length of the radicle and plumula. The measured data were statistically analysed and the effect of extracts on germinating ratio and seedling length were evaluated.

Study on the development of yellow nutsedge (Cyperus esculentus L.) with growth analysis.

Yellow nutsedge (Cyperus esculentus) is a cosmopolitan, tropical, subtropical plant. Nowadays, the Working Committee of Invasive Plants of the EPPO considers it as a highly damaging internationally important weed. During our work the development of the yellow nutsedge grown was examined until the end of flowering. The 5 repetition pot experiment has been started April 19 2007. Large-sized pots were filled with a mixture of mould and sandy loam in a ratio of 1:1, and planted in each pot 25 yellow nutsedge tuberlets. Weekly one plant and its progeny were harvested from each pot to measure their fresh and dry shoot and underground part (root, tuber and rhizome) weights and leaf area. Samplings were made at 16 occasions between 2007 26 of April and 24 of August. Results were considered by growth analysis. We studied RGR (relative growth rate), LAR (leaf area ratio), RLGR (relative leaf growth rate). Summarised it can be stated, that the beginning of the dynamic growing is 6 week after germination. The dry weight of the shoots is over the dry weight of the underground parts in the examined period. The RGR shows just a minimal change. The LAR was the highest between 17 May and 8 June.

Spreading and germination of yellow nutsedge (Cyperus esculentus L.) in Hungary.

Yellow nutsedge (Cyperus esculentus) is a cosmopolitan, tropical, subtropical plant. On the basis of Ujvarosi life-form it is a G2 perennial plant, overwintering with tubers in the soil. It occurs in all continents: along Eastern and Western coastlines of Africa and even in South-Africa, North and South America, Japan, India, Near-Eastern countries, Western, Southern and Eastern Europe. It has been spread since the 70's in Europe, but its remarkable occurrence was between 1980 and 1995 years. Nowadays it occurs in Germany, the Netherlands, Belgium, France, Portugal, Austria, Croatia, Switzerland, Italy and Hungary among the European countries. The first occurrence of C. esculentus was observed in Hungary in 1993, at the surroundings of Keszthely and H&viz towns in a maize-ecosystem (Dancza 1994). It can be presumed, that its import happened with Gladiolus tubers and seed-grain of maize. At present C. esculentus occurs in four regions and surroundings of 20 habitations of Hungary. Somogy county is the most infected area, where it occurs on 10,000 hectares. C. esculentus took the 16th place in the important order of weeds of the world in the 70's. On the basis of EPPO IAS Panel at present this weed specics is considered as one of the most harmful invasive species of the world, due to its severe economic injury. Most harmful effect of C. esculentus is expressed in spring-sown hoed cultures, mainly in maize. Beside this it also occurs in sunflower, potato and sugarbeet cultures. C. esculentus has a good competitive ability by reducing crop quality and quantity. Vegetative reproduction is dominant in spreading but its propagation by seeds is also presumed in Hungary. Cool, rainy weather favours for the vegetative reproduction, while warm, dry one for the flowering. It has a 1-1.5 mm long fruit with one seed. One clustering can contain 600 seeds. According to Lapham (1985) there are areas in Zimbabwe where one can find 100 million C. esculentus seeds in a hectare. At a 1-2% germination rate it means 1-2 millions seedlings for a hectare, therefore its generative reproduction may be also considerable. The aim of our study was to examine germination characteristics and the possibility of generative spreading of C. esculentus. Germination tests were carried out in petri dishes under laboratory conditions with different thousand grain weight seeds. Average thousand grain weight and germination percentage was 0.154 and 60%, respectively. Experiments were repeated with lower thousand grain weight seeds (0.069) on sandy soil, where lower germination rate (2%) was obtained. On the basis of these results generative propagation and spreading of C. esculentus can be easily presumed.

Weed control in sunflower (helianthus annuus L.) with post-emergent herbicides.

Sunflower is the most important oil crop in Hungary, is the base of the production of cooking oil and moreover takes an important part in production of margarine too. Extracted sunflower groats as a secondary product origining from the mentioned procedure can be used in forage successfully. The amount of harvested sunflower reaches the 20-25% of the EU's yield. The sowing area approaches 500 thousand hectares. The essential condition of successful crop production is the perfect weed control. Sowing areas are infected with monocotyledon and dicotyledonous weeds too. Annual dicotyledonous weeds are the most troublesome. The worst species is the Ambrosia artemisiifolia L. Many other weed species as Abutilon theophrasti MEDIC., Datura stramonium L. and Xanthium strumarium L. can cause serious damages. In our model experiments we examined the herbicide sensibility of two commercial sunflower cultivars as "Iregi szürke csikos", "Marica II" and a sulfonylurea-urea tolerant new hybrid "PR63E82". The experiment was set up under greenhouse conditions with the use of four important weed and different post-emergent herbicide as Modown 4F (bifenox), Pledge 50 WP (flumioxazin) and Granstar 75 DF (tribenuron-methyl). We applied normal and double doses too. Sunflower was cultivated to 4-6 leaf stage. Post-emergent herbicides were sprayed out when weeds were in 2, 2-4 and 4-6 leaf stage. Weed killer and phytotoxic effects of post-emergent herbicides were examined. We declared that development of weeds had significally effect on the effectiveness of different herbicides.

Vegetative reproduction and chemical control with post-emergent herbicides of field bindweed (Convolvulus arvensis L.).

It is clearly seen from data that roots of Convolvulus arvensis L. have more and less intensive regenerative period during growing season. The more intensive period is in autumn, because in that time roots culminate nutrients, carbohydrate as starch and sugar. The less intensive regenerative or shoot-growing period is in spring, called "late spring bud dormancy". Experiments were conducted to get more information and further details about the regenerative capacity of roots close to and far from the collar of Convolvulus arvensis L. Root segments closer to collar have an intensive regenerative capacity than those ones further to collar. By data of Bakke et al. (1939) is well known, roots exhumed from deep soil layers are able to create shoots with low intensity. So finally we can exclaim that regenerative capacity is decreasing further to collar. Using mechanical weed control it is sufficient to till the upper layer of soil, but many times. Chemical treatments are most effective in the integrated weed control. It is clearly seen that auxin-type herbicide such as 2,4-D, fluroxipir, MCPA. dicamba give the best result. They gave 95% weed control effect used them separately or in combination with other herbicides. Combination of Banvel 480 S (dicamba) and Logran 75 WG (triasulfuron) introduced 95% weed control effect. Only one time got absolutely 100% weed control effect, in the case of Glyphosate active substance. Caused total plant destruction. Excellent result was given with the application of Pledge 50WP (flumioxazin). Herbicides mentioned above are absolutely allowed to take an important and significant part in chemical plant protection against Convolvulus arvensis L. Other herbicides like Granstar 75DF (tribenuron-methyl), Basis 75DF (rimsulfuron + tifensulfuron-methyl) and Huszár (jodosulfuron-methyl-sodium + mefenpir-diethyl) are not so effective against Convolvulus arvensis L., as compared to the previous ones.

Susceptibility of some weed species to Pepino mosaic virus (PepMV).

The aim of our investigations was to study the susceptibility of 22 weed species to Pepino mosaic virus (PepMV). Seven plants of each species were mechanically inoculated at 4-6 leaf stage with PepMV in a vector free virological glasshouse. Inoculated plants were tested on the basis of symptoms, by DAS ELISA serological method and back inoculation. Among the 22 weed species, only some Solanum ones (S. aethiopicum, S. dulcamara, S. luteum, S. nigrum) were susceptible to PepMV infection. All of them--except S. aethiopicum--belong to Hungarian weed flora, therefore these weeds--occurring mainly in tomato ecosystems--may play important role in the epidemiology of PepMV. Other 18 weed species seemed to be resistant to PepMV, and on the basis of back inoculation not even latent infection has been observed.

Experimental and natural weed host-virus relations.

Weeds, as alternative hosts of plant viruses and nutrient plants of virus vectors play important role in virus ecology and epidemiology. The aim of our study was to discover new weed-virus relations. Therefore some weed species were mechanically inoculated with 28 viruses (strains or isolates) maintained in our glasshouse. Different weed species with and without visible symptoms were collected from agro-, water ecosystems and wastelands of Hungary between 1997 and 2003. Virus infections were evaluated by biotests, DAS ELISA serological methods, electronmicroscopy and immunosorbent electronmicroscopy (ISEM). Under glasshouse conditions Ambrosia artemisifolia was considered as a virophob species, showing resistance to all viruses listed above. A series of new artificial (Chenopodium album--SoMV (LH+SH)*, AMV (LH+SH); C. berlandieri--PVY(NTN) (LH), AMV (LH+SH), CMV (LH), SoMV (LH+SH), ObPV (LH+SH), ZYMV-10 (LH): C. ugandae--ObPV (LH), SoMV (L); C. glaucum--ObPV (LH), SoMV (L); Echinocystis lobata--PVX (L), ZYMV (LH+SH); Solanum nigrum--MYFV (LH+SH), PVY(N) (L), PVY(NTN) (LH+SH), SoMV (LH), TMV (SH), CMV (SH); S. dulcamara--CMV-U/246 (SH), PVY(NTN) (LH), SoMV-H (L), TMV-O (L); S. luteum--PVY(N) (SH), PVY(NTN) (LH+L), TMV(SH).) and natural (Asclepias syriaca--TMV, AMV, TSWV; Alisma plantago-aquatica--PVY, SoMV; Ambrosia artemisiifolia--CMV; Chenopodium album--CMV, PVS, PLRV; C. hybridum--CMV; Cirsium canum--CMV, PVM; Carex vulpina--CMV; Comium maculatum--PVY; Datura stramonium--PVA, PVX, PVS, PVM, CMV, TMV; Lysimachia vulgaris--ArMV, BNYVV, CMV, TMV; Lythrum salicaria--ArMV; Malva neglecta--CMV; Mercurialis annua--SoMV; Solanum nigrum--CMV, PVY, PVY(N); Solidago gigantea--CMV, RpRSV, BNYVV; Stenactis annua--PVM, PVA) weed--virus relations were detected. The epidemiological role of perennial hosts (A. syriaca, A. planlago aquatica, C. canurm, L. vulgaris, L. salicaria, S. gigantea) is especially high, because they can serve as infection sources as well as overwintering hosts of different plant viruses.

Changes in nutrient content of Cirsium arvense (L.) Scop. during the vegetation period.

Cirsium arvense /L/ Scop. nowadays is popular in all territory of Hungary, it can be found almost on every soil types. Cirsium arvense is one of the most difficulty eradicated weed of the fields, the ruderals, and also the roadsides. On the base of IV. Hungarian Weed Survey 1996-1997, it takes the fifth place in the dominance sequence of the weeds, with 1.8% average covering. In the interest of effective weed control we can know the biological characteristics of the weeds in detail. In our experiments we followed the nutrient uptake and its changing in Cirsium arvense plants. Nitrogen concentration of shoots altered between 1.5-3.6%. We established that plants can uptake potassium in a great quantity. Roots and shoots contained potassium in high concentration between 2.2-5.9%. The maximum of shoot production from the adventitious buds of the roots was in October and the minimum was in April and May.