No description available.

3 pp. / “Summer slump” is a decline in growth of alfalfa usually beginning in July in areas where maximum daily temperature exceeds 100 °F, such as the low elevation deserts of Southwestern U.S (Fig. 1). In more temperate regions, there is a gradual decrease in alfalfa yield in successive harvests throughout the year, but the yield decline in the summer is not as sharp as in hot summer regions. The term summer slump has also been applied to reduction in growth of perennial cool season grasses such as tall fescue during the summer.

Six pathogenic fungal species were isolated from naturally-infected Echinochloa species and evaluated as biological control agents for E. crus-galli, E. colona, and E. glabrescens in rice. Bipolaris sacchari, Curvularia geniculata, and Exserohilum monoceras were non-pathogenic to rice and caused high mortality of Echinochloa species. E. monoceras was selected for further study. Under regulated greenhouse conditions, an inoculum dose of 2.5 $ times$ 10$ sp7$ conidia/m$ sp2$ killed E. crus-galli and E. glabrescens seedlings while 5.0 $ times$ 10$ sp7$ conidia/m$ sp2$ caused 100% mortality of E. colona seedlings. The 1.5-leaf stage was the most susceptible growth stage for all three Echinochloa species. E. glabrescens was most susceptible to E. monoceras infection, E. crus-galli had an intermediate susceptibility, and E. colona was least susceptible. The optimum temperature for 100% mortality was between 20 and 30 C for all Echinochloa species, whereas the minimum dew period for 100% mortality was 16 h for E. colona, 12 h for E. crus-galli, and 8 h for E. glabrescens. Under screenhouse conditions and in the absence of an artificial dew period, over 90% of Echinochloa seedlings were killed when inoculum was sprayed in an oil emulsion or when applied as a dry powder to the water surface of a simulated paddy field. Maximum conidia production occurred on V-8 juice agar or centrifuged V-8 juice agar, at 28 C in the dark. No conidia were produced in liquid media. Of various agricultural products tested as solid substrates, the highest sporulation (1.81 $ times$ 10$ sp6$ conidia/g dry weight) occurred on corn leaves. Host range tests on 54 plant species in 43 genera and 19 families showed that Rottboellia cochinchinensis, was also highly susceptible to this fungus. Of the crops tested, only corn seedlings were lightly infected under optimum greenhouse conditions but no disease occurred on corn under field conditions. Bipolaris sacchari, Exserohilum monoceras, and E. oryzae

A culture system was established for mass rearing of the Russian knapweed nematode, Subanguina picridis (Kirjanova) Brzeski. This system consisted of two parts; a shoot culture system used as the host plant source for the nematode culture, and a monoxenic nematode culture system. The nematode developed and reproduced in this system. Galls were induced on the leaves, stems, and shoot tips of cultured Russian knapweed (Acroptilon repens (L.) DC.) shoots. After 3 months in culture, the nematode number per petri dish increased from the initial 50 inoculated to 7,000-10,000, a 140 to 200 fold increase. This study represents the first time that an above-ground gall forming nematode has been propagated in vitro. It also represents a unique monoxenic nematode culture system to mass rear above-ground endoparasitic plant nematodes. / Various factors, including tissue type, tissue age, medium, and temperature, which affect the formation and development of galls, were examined. The nematode failed to reproduce in callus tissues, and it could not develop beyond the 4th stage in excised root cultures. The optimum incubation conditions determined were: 60-80 $ mu$molm$ sp{-2}$s$ sp{-1}$ light intensity, 20 C temperature, and 4-8 mm for shoot length. / The virulence of cultured nematodes was tested in the greenhouse on Russian knapweed seedlings and vegetative shoots from root segments. The results demonstrated the feasibility and application of this novel mass production system. Nematodes produced in this system were virulent and the growth rate of infested Russian knapweed were reduced.

An automated prototype variable rate (VR) sprayer was developed for control of eight individual nozzles on a 6.1 m sprayer boom for spot-application (SA) of agrochemicals in wild blueberry fields. The VR control system consisted of eight ultrasonic sensors and four cameras mounted on a separate boom in front of the ATV, flow controller, VR controller, ruggedized computer, flow valve and solenoid valves. Custom software was capable of processing the images to detect weeds or plants in real-time and automatically send a signal to the VR controller for SA at the correct target. The performance of VR sprayer for SA on weeds (herbicide) and foliage (fungicide) was evaluated in commercial wild blueberry fields. Based on the results of this study, the VR sprayer was reliable, efficient and accurate enough for SA of agrochemicals. The average volume of chemical saved with SA was 70 % herbicide and 30 % fungicide.

Magistrantūros baigiamasis darbas atliktas 2011–2013 m. Aleksandro Stulginskio universiteto Bandymų stotyje ir Agroekosistemų ir dirvožemio mokslų instituto laboratorijoje. Tyrimų objektas – žieminis rapsas (Brassica napus L.) ir jo atskirų morfologinių dalių liekanos dirvoje. Taip pat, piktžolės: baltoji balanda, dirvinė pienė, kibusis lipikas. Tyrimų tikslas – nustatyti ir įvertinti atskirų žieminių rapsų morfologinių dalių liekanų – kūlenų, ražienojų ir šaknų (po derliaus nuėmimo, dirvoje irusių tris, septynis ir keturiolika mėnesių) – vandeninių ištraukų alelopatinę įtaką piktžolių (baltosios balandos, dirvinės pienės ir kibiojo lipiko) dygimui ir augimui. Tyrimų schema – A veiksnys – rapsų liekanos: 1) žieminių rapsų kūlenos; 2) žieminių rapsų ražienojai; 3) žieminių rapsų šaknys; B veiksnys – vandeninių ištraukų koncentracijos: 1) distiliuotas vanduo; 2) 1:6250 (rapsų liekanų ir vandens santykis); 3) 1:1250; 4) 1:250; 5) 1:50; 6) 1:10. Darbo rezultatai. Vertinant žieminių rapsų liekanų morfologinių dalių ir skaidymosi trukmės įtaką piktžolių sudygimui nustatyta, kad po derliaus nuėmimo labiausiai variavo dirvinės pienės sudygimo duomenys. Skirtingose žieminių rapsų šaknų ištraukose sudygo 94–100 % mažiau dirvinės pienės sėklų, nei distiliuotame vandenyje. Po trijų mėnesių skaidymosi geriausias sudygimo procentas (76,0 %) buvo kibiojo lipiko sėklų. Visos, septynis mėnesius skaidytos, žieminių rapsų liekanų ištraukos 46–82 % slopino dirvinės pienės sudygimą lyginant su... [toliau žr. visą tekstą] / The master wokr were conducted at Experimental Station and Laboratory of Agroecosystems and Soil Science Institute of the Aleksandras Stulginskis University in 2011–2013. Research object - winter oilseed rape (Brassica napus L.) and its various morphological parts of the residues in the soil. Also, weeds: Chenopodium album L., Galium aparine L., Sonchus arvensis L. The aim of investigations was to evaluate the allelopathic effect of aqueous extracts of winter oilseed rape residues (threshing remains, stubble and roots) on Chenopodium album L., Galium aparine L., Sonchus arvensis L. germination and early growth. Treatments of the investigations: Factor A – winter oilseed rape residues: 1) threshing remains, 2) stubble, 3) roots; Factor B – concentrations of aqueous extracts: 1) distilled water, 2) 1:6250 (ratio of oilseed rape residues and water), 3) 1:1250, 4) 1:250, 5) 1:50, 6) 1:10. The results of work. Evaluation of winter oilseed rape residues morphological parts and decomposition duration on weed emergence showed that after harvesting the most variavo Sonchus arvensis L germination data. Winter oilseed rape roots extracts germinated 94-100% units less Sonchus arvensis L seeds than in distilled water. All seven months biodegradable, winter oilseed rape residues extracts 46–82% units suppressed Sonchus arvensis L germination compared with distilled water. And after fourteen months of division all winter oilseed rape residues extracts stimulated (6,5 to 43%) Sonchus... [to full text]

There has been little documentation of the success of introduced agents for classical weed biological control. Field evaluation of an insect's establishment, spread and early host impact within its new environment must be performed before agent success can either be doucmented or predicted. Population attributes of the ednophagous biological control agent, Mecinus janthinus Germar (Coleoptera: Curculionidae), and interactions with its target weed, Dalmation toadflax, (Linaria dalmatica (L.) Mill.) (Scrophulariaceae), were explored across variable levels of resource availability and insect abundance. Patterns of population growth and impact of this biocontrol agent were very consistent throughout this study. Within four years of release, populations of M. janthinus achieved outbreak population levels and virtually eliminated the seed producing shoots from toadflax stands. There is a tight but flexible relationship between oviposition site selection and offspring performance in this endophagous herbivore, maximizing offspring survival even under moderate to high M. janthinus densities. These attributes allow M.janthinus to be an effective biocontrol agent under changing levels of resource availability. / ix, 134 leaves : ill. ; 28 cm.

No description available.

In order to determine if weed control as practised during the establishment phase of tree growth had a beneficial and long term (over a six to eight year rotation) impact on tree performance, a Eucalyptus hybrid clone (GC304) was planted in a field trial in 1990. The trial was situated in the coastal Zululand region near the KwaZulu-Natal town of Mtunzini. Nine different vegetation management treatments were imposed from establishment. These included a weedy control, a manually weeded treatment, a chemically weeded treatment, a 1.2 m row and 1.2 m inter-row weeding, a 0.5 m radius ring weeding, a complete weeding except for a 0.5 m radius ring around the tree, and the use of two legume cover-crops, Mucuna puriens (cowpea) and Vigna sinensis (velvet bean). Initial improvements in tree performance from these competition control treatments were detected from 60 days after planting, and were maintained over seven growing seasons. This occurred despite the absence of competitive vegetation after the first growing season due to reduced light, following crown canopy closure. There were strong indications that initial competition was mainly for moisture and possibly also for nutrients, rather than competition for light. Initially those trees that had weeds within their immediate vicinity were most affected (weedy control, inter-row weeding and the complete weeding except for a 0.5 m radius around the tree). With time, tree performance was more closely related to an increase in the percentage of the area kept free of weeds. The best performing treatment at felling, the manually weeded control, produced 17.1 % and 38.5 % more merchantable timber than the 1.2 m row weeding and the weedy control, at an increased profit of 8 % and 27 %, respectively. Two forms of competition (interspecific and intraspecific competition) were evident in the weedy control at different stages of tree development in contrast to the one (intraspecific competition) in the manually weeded treatment. Interspecific competition resulted in greater variability between the trees in the weedy control by the time canopy closure had occurred. This differentiation in tree size was further enhanced by asymmetric intraspecific competition once the trees had become established. The onset of intraspecific competition was first detected 995 days after planting for the manually weeded treatment and 1641 days after planting for the weedy control. Of the various competition indices that were tested in order to try and explain this differential growth in terms of individual tree performance, none was able to do so to complete satisfaction. The growth rates of different tree size classes were therefore compared for the weedy control and manually weeded treatment. The diverging slopes of the different stem area classes indicated that the larger trees were growing at the expense of the smaller trees. This type of competition is known as asymmetric intraspecific competition. In addition, a comparison was made between the slopes for the weedy and weedfree treatments for similar stem area classes. No significant difference was detected, indicating that similar size classes in these two treatments grew at similar rates. Trees from three treatments were selected (manually weeded treatment, 1.2 m row weeding treatment and the weedy control) and tested for the wood and pulping properties of density, active alkali consumption, extractable content, screened pulp yield, pulp yield per hectare and fibre length and coarseness. The use of Canonical Variate Analysis to determine if there were differences between the three treatments for the variates measured, indicated that they were significantly different. There was a significantly positive trend of an increase in density, extractable content and active alkali consumption with increased weed control. A possible explanation for this could be that the larger trees of the manually weeded treatment were under more stress (from increased intraspecific competition) during the latter phase of their growth. This was demonstrated by comparing the growth rates for these three treatments. The smaller trees of the 1.2 m row weeding treatment and the weedy control exhibited a lower rate of decline. As no significant difference was detected for screened pulp yield between the treatments, any differences in the pulp yield per hectare values could be attributed to differences in the merchantable volume. There was a 22.6 % and 40.8 % increase in the pulp yield per hectare for the manually weeded treatment in comparison to the 1.2 m row weeding treatment and the weedy control. The planting of cover-crops, although beneficial in terms of weed suppression, caused significant tree suppression. This occurred despite the fact that their initial biomass accumulation was slower than that of the natural weed population. Of the two cover-crops, the use of the velvet bean was not considered suitable due to its vigorous vining habit which affected the growth form of the trees. Subsequent work suggests that if the beneficial qualities of cowpeas are to be realised (that of weed suppression, erosion control and nitrogen fixation), a delay in their planting by three months after establishment of the trees should alleviate any negative impacts on tree growth. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1999.

No abstract available. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.