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Item Improving weed control options for ryegrass/clover pastures that contain plantain (Plantago lanceolata) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Plant Science at Massey University, Manawatū, New Zealand(Massey University, 2023) Shrivastav, NidhiThe inclusion of narrow-leaved plantain (Plantago lanceolata) in the traditional pasture system of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) is preferred by many New Zealand farmers nowadays to assist with nitrogen loss mitigation and to improve summer production. Control of weeds using selective herbicides becomes more difficult after adding extra species to a grass/clover sward. The work in this thesis investigated weed control options for ryegrass/clover pastures in New Zealand that contain plantain. This included determining the tolerance of plantain to different herbicides and identifying the herbicide options most effective for weeds. There has been some breeding of phenoxy herbicide tolerance into the Agritonic cultivar of plantain in New Zealand. In this thesis, the level of tolerance in Agritonic plantain was compared with Tonic plantain to MCPB, MCPA, MCPB/MCPA mix, 2,4-D and 2,4-DB in two glasshouse experiments. The tolerance generally appeared to be 1.3 to 3.4-fold, so not large but potentially useful. The thesis also investigated the tolerance of plantain, white clover and perennial ryegrass to a range of herbicides applied to a mixed sward of these species at an early stage of establishment in spring. The effectiveness of the herbicides was also assessed for controlling weeds that established within the swards using two field trials. Half of the recommended rate of MCPB was less damaging to both cultivars of plantain than the recommended rates of MCPB and MCPB/MCPA, but could not control most of the weeds present. The recommended rate of MCPB/MCPA had very little detrimental effect on young clover or Agritonic plantain and gave good weed control. Flumetsulam was fairly safe to use in the plantain-based pasture though it suppressed plantain initially, which recovered after 3-6 months in each trial. Bentazone was safe for the plantain, ryegrass and clover and suppressed most of the weeds, but only if there was no rainfall in the hours after herbicide application. Mowing after each harvest controlled redroot, black nightshade and fathen and also suppressed docks temporarily. The most effective weed control strategy that was also selective involved a combination of bentazone + half rates of MCPB/MCPA followed by mowing which gave useful control of weeds including docks for many months. The mechanism of tolerance of Agritonic plantain to 2,4-D was investigated using radiolabeled herbicide (¹⁴C-2,4-D) in two experiments. Absorption/translocation and metabolism of the herbicide was studied in both this cultivar and Tonic plantain for comparison. The tolerance to 2,4-D in Agritonic plantain appeared to involve reduced translocation of the herbicide, though reduced absorption may have also contributed. Two glasshouse experiments were conducted to test the tolerance of mature plantain plants (both Agritonic and Tonic) to application of some herbicides suitable for use in weed wipers (glyphosate, clopyralid, aminopyralid, dicamba, picloram and triclopyr) to the seed-heads, simulating potential contact during wiper application to pasture weeds. Aminopyralid and a low rate of glyphosate were found to be the least damaging treatments and should be safe to use for weed wiping within swards containing plantain. A high rate of glyphosate and a glyphosate/metsulfuron mix caused the most damage to plantain, and this damage was greater following simulated rainfall after application.Item A study of the susceptibility to Dalapon of four common pasture grasses : a thesis presented at Massey Agricultural College in part fulfilment of the requirements for the degree of Master of Agricultural Science in the University of New Zealand(Massey Agricultural College, 1959) Lawson, H. M.One of the more important developments of recent years in New Zealand agricuture has been the introduction of herbicides selective against grass species. Originally intended for the control of grass weeds in arable crops these herbicides have proved capable of being utilized in many other aspects of farming practice, the most spectacular of which is 'chemical ploughing'. This popular name has been coined to describe the process whereby pastures may be improved with the aid of herbicides on land which cannot succesfully be cultivated by conventional means. Extension of this technique to land which is only accessible to the aeroplane is being investigated by Blackmre (1958) and the preliminary reports suggest that 'chemical ploughing' may be a useful aid to aerial top-dressing and oversowing. Every new development, however striking, must satisfactorily blend with or replace existing practice before it becomes generally accepted. Many problems of practical application require solution before recommenbdations can be made to farmers and there are at present under investigation in field trials throughout the country. At the same time a thorough knowledge of the properties of the herbicides and the factors affecting their efficiency under a wide range of field conditions is essential. Where herbicides are applied to a mixed population of plants, as in a pasture, it is desirable to know, within fairly narrow limits, the tolerance of each constituent species. The experiments reported in this thesis were undertaken to investigate the susceptibility of some common pasture species to dalapon, the most important of the selective grass-killing herbicides involved in 'chemical ploughing' and associated techniques.Item Chemical control of Poa trivialis on New Zealand racetracks : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science at Massey University(Massey University, 1996) Fleming, Philip BrianPoa trivialis is a perennial grass weed commonly found in perennial ryegrass (Lolium perenne) racetrack swards throughout New Zealand. Its presence is undesirable as it does not tolerate high wear and is susceptible to dying out over the summer. Two pot trials at Massey University and one field trial carried out at the Awapuni racecourse were conducted during winter and spring 1995 to test the relative susceptibility of Poa trivialis and perennial ryegrass to a wide range of herbicides. A bioassay was also conducted to determine whether herbicide residues from the field trial could affect the germination of perennial ryegrass seed sown soon after treatment. Results showed that none of the chemicals at their chosen respective rates could completely remove Poa trivialis from a racetrack sward in the spring without some damage being caused to perennial ryegrass. Propyzamide and fenoxaprop at rates of 0.2 and 0.15 kg/ha respectively showed the most potential of the chemicals, severely damaging Poa trivialis (causing 50 to 75% reductions) with no adverse effect on perennial ryegrass 8 weeks after spraying. Propyzamide can also provide some control of Poa annua. Fenoxaprop was not improved by increasing the application rate or adding an oil. The performance of fenoxaprop was substantially reduced when applied with either MCPA or a picloram/triclopyr mix. Dalapon and asulam showed good potential to control Poa trivialis but at the high rates tested caused variable or harmful effects to perennial ryegrass. Ethofumesate and chlorpropham applied at rates of 2.0 and 2.5 kg/ha respectively gave inadequate control of Poa trivialis. None of the above herbicides, when used in the field trial resulted in residues which reduced the germination of perennial ryegrass seed sown 3 weeks after spraying. Herbicides tested in the pot trials which showed poor control of Poa trivialis were atrazine, dicamba, isoproturon/diflufenican, linuron, mecoprop, methabenzthiazuron, metsulfuron, pendimethalin, prometryne, thifensulfuron-methyl, triclopyr, and trinexapac-ethyl. Diuron applied at 2.6 kg/ha provided good control of Poa trivialis but caused significant damage to perennial ryegrass. It is concluded that an integrated management approach that incorporates both cultural and chemical techniques will be required to control Poa trivialis on New Zealand racetracks. Future trial work should be carried out on propyzamide applied at rates of 0.2-0.3 kg/ha in autumn to establish the most appropriate time of year to apply this herbicide.Item Weed control practices in New Zealand pipfruit orchards: a thesis presented in partial fulfilment of the requirement for the degree of Master of Horticultural Science at Massey University(Massey University, 1992) Berry, Simon BlairA survey of 77 growers, mainly in Hawkes Bay and Nelson, was undertaken during the summer of 1989/90. Personal interviews were conducted on each property. All growers were found to use herbicides for weed control, and all but one established herbicide strips with mown grass between. The major herbicide application period was spring. Three-quarters of growers relied on four herbicide formulations, amitrole, glyphosate, simazine and terbuthylazine/terbumeton. Of the residual herbicides used, 70% were triazines. Grower knowledge about herbicides was found to be lacking. Grass species from the sub-family Paniceae were found to be the most problematic weeds, along with mallows, black nightshade, Californian thistle, tall willow herb and docks. These weeds were not adequately controlled by current weed control practices. Off-label use and herbicide damage to crop trees was noted. Growers were found to be applying herbicides through a wide array of equipment, through fan and off-centre nozzles with one to four nozzles on each boom. Only 37% of sprayers were calibrated at least annually. During the survey 41 sprayers were calibrated, with only 17% being correct within ± 5% of intended application rate. Of those sprayers with errors over ±5% two-thirds were underapplying at mean error of 37%, and one-third were overapplying at a mean error of 18.1%. Spray distribution patterns were found to be unacceptably uneven across the herbicide strip in most cases. Over 40% of growers were not able to relate the actual amount of herbicide used to a target application rate per hectare. A lack of training in both chemical use for weed control and sprayer calibration was apparent, and 80% of growers saw a need for a field manual. ADDITIONAL KEYWORDS New Zealand; pipfruit; weed control practices; herbicide use; sprayer calibration; accuracy of application; portable spray patternator.Item Ground cover plants for weed control in amenity horticulture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Palmerston North, New Zealand(Massey University, 2012) Foo, Chin LuiAspects of the establishment and use of ground cover plants for urban weed control were investigated. Established ground cover populations of different taxa were monitored over 1 year at 14 sites for their ability to block light from the soil and prevent weeds from establishing. Field trials compared 12 ground cover species of widely differing growth form for rate of establishment and ability to block light and suppress weeds. Another field trial compared various types of mulch with selective herbicides and hand weeding as techniques for establishing ground cover species. No single growth form was superior to others, and it was the density of the foliage that was key to suppressing weeds. Ground cover plants should be selected for having persistently dense canopies throughout the year, such as Coprosma acerosa ‘Taiko’ and Juniperus procumbens. Deciduous species like Persicaria capitata, evergreen species which become sparser in winter like Pimelea prostrata, and plant canopies which open up during flowering like Grevillea lanigera, all allow weeds to germinate while the ground is exposed. Ground cover plants appear to deter weeds mainly by keeping weed seeds dormant through preventing red light from reaching weed seeds and triggering a phytochrome response leading to germination. Keeping the ratio of red to far-red light below 0.3 appeared to give best inhibition of weed seed germination. Presence of mulch and spot application of selective herbicides can help prevent weeds causing problems should gaps appear within ground covers, and these may be preferable to hand weeding. Little herbicide tolerance information exists for ornamental ground cover plants, so herbicide tolerance trials were conducted on eight ground cover plant species. This work showed that herbicides can aid in ground cover plant establishment and subsequent maintenance to selectively spot-treat weeds that appear. Ground cover species were assessed which grow low enough to be mowed but which seldom need mowing, to replace grass turf in situations where mowing is inconvenient such as under trees, on slopes, or roadsides. Dichondra micrantha and Soleirolia soleirolii showed the most potential, forming dense low growing swards that tolerated a wide range of herbicides.Item Interaction of population processes in ragwort (Senecio jacobaea L.) and ragwort flea beetle (Longitarsus jacobaeae Waterhouse) : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University(Massey University, 2000) Aung, Kyi; Aung, KyiThe primary goal of this study was to improve understanding of biological control of weeds by investigating how population processes in ragwort and herbivorous insect interact. Specific aims were to measure the consumption rates of the three larval instars of ragwort flea beetle (Longitarsus jacobaeae), to investigate how the process of herbivory by ragwort flea beetle affects the population density of ragwort, and to investigate how soil moisture influences the population densities of ragwort flea beetle and ragwort. An extraction apparatus was constructed to obtain L. jacobaeae larvae from ragwort roots and root crowns. This apparatus was 84% efficient . A preliminary survey of ragwort flea beetle numbers included ragwort plants from B allantrae, Turakina, and Pahiatua (Southern North Island, New Zealand). The larval population was highest at Ballantrae but the adul t population was highest at Turakina. Data were collected from Ballantrae from 1996 to 1998 to develop the interaction model between L. jacobaeae and ragwort. The interaction depended on the effect that soil water content had on the populations of both L. jacobaeae and ragwort, the effect that larval density has on larval mortality, and the effect of ragwort density on the population of L. jacobaeae larvae. Soil water content was positively correlated with the increase in numbers of L. jacobaeae. L. jacobaeae larval mortality was dependent on larval density. High numbers of larvae per plant resulted in a reduction in the number of larvae over time ( 1 3 .6 larvae/plant on November 1 997 to 1 .8 larvae/plant in December 1997). The average number of larvae extracted at Ballantrae was lower in October and November 1996 (4.4 and 4.6 larvae/plant) than in October and November 1 997 ( 1 3.4 and 1 3. 6 larvae/plant). However, the average numbers of rosettes was higher in October and November 1 996 (7.6 and 5 .78m -2) than in October and November 1 997 (2.8 and 2 .7 m -\ There was a significant inverse correlation between the numbers of L. jacobaeae larvae and ragwort rosettes (-0.4608). When 0.8983 in 1 5 day old larvae, 0.926 1 in 30 day old larvae, and 0.9454 in 45 day old larvae. The lowest percentage survival (0.9067 in 15 day old larvae) was found at the highest larval density (40 larvae per plant). Finally, the same experiment was tested in a field and the data from this was used to construct an interaction model for L. jacobaeae and its food, ragwort. This model was based on the correlation between soil water and populations of L. jacobaeae and ragwort; the effect of larval density on the mortality of larvae and on the weight loss o f ragwort; and on the effect that ragwort density has on the mortality of L. jacobaeae larvae. Mean soil water was 1 2 ± 0.29 to 7 6 ± l.8 1 % over the first 1 5 days, then 3 6 ± 1 . 1 0 to 8 2 ± 0.99% up to 30 days, and 35 ± 0.76 to 65 ± 1 .78% up to 45 days of larval life. These were the soil water contents that occurred during the field experiment. The model showed that the highest larval survival again occurred when few larvae were introduced to ragwort plants ( 1 7.5% survival from 0- 1 5 days, 1 4.33% from 1 6-30 days, and 1 8 .5% from 3 1 -45 days). High larval densities also produced the lowest survival (8.4% survival over 0- 15 days, 5 .87% over 1 6-30 days, and 6.7% over 3 1 -45 days). The effect of plant density on larval survival was also tested in the field. The highest larval survival (10.76%) occurred when there were on 1 6 plants m-2, and the larvae were 0 to IS -days old. The lowest larval survival (6. 6 1 %) occurred with 1 6-30 day old larvae on plants at a density of 4 plantsm-2. A cohort life-table was constructed for predicting population fluctuations of L. jacobaeae. Values from this life table were used to model populations of L. jacobaeae, ragwort and the interactions between these species using "STELLA" software. Data for the ragwort model was obtained from published papers. Additional data from the experimental determination of feeding rates of L. jacobaeae larvae were used when both the L. jacobaeae and ragwort models were combined to examine the interactions between these species. This latter model was used to estimate population fluctuations of L. jacobaeae and its food over two years. It indicated that L. jacobaeae is a very effective control agent for ragwort, and that it can cause ragwort populations to decline to extinction within two years.