First Hand Experiences in Managing Different ... - Weeds Australia

! Asparagus declinatus^! Asparagus asparagoidesCase study siteNo Reported Occurrencerequires detailed understanding of plant life cycles,soil types and climatic conditions.In the Adelaide Hills and Fleurieu Peninsularegions, many native annuals such as orchids, liliesand ferns withdraw into their rootstock for a periodof summer dormancy with the onset of hotter, drierconditions in mid to late spring. The asparagusweeds, with their larger tuber and rhizome systems,persist a few weeks longer on the surface. Duringthis time they can be sprayed without impacting thedormant native plants.Spraying with a strong solution at this stage oftheir cycle has proven particularly effective, asthe herbicide is drawn down into the rootstock.However, younger seedlings fade earlier in theseason and are likely to be missed. It is importantto revisit the site during the same window ofopportunity the following year to manage seedlings.‘If the project runs for three to four years, you’vegot a good chance of picking up all the weeds.’Refining the techniqueKnapsack foliar spraying using metsulfuron-methylat 5–7 g per 100 L is the preferred application.A surfactant is added, which makes the herbicidego further and helps penetrate the waxy asparagusfoliage. Fine spray nozzles are used on the veryfine foliage of A. declinatus which enables theoperator to apply small hits onto little patches andavoid overspray. Dye is used to keep careful trackof applications.‘Metsulfuron-methyl is very effective on A.declinatus and A. asparagoides. Glyphosate willwork but it is less selective and can do a lot of offtargetdamage.’Instead, glyphosate is used to treat watsonia(Watsonia meriana var. bulbillifera) and Africancornflag (Chasmanthe floribunda (Salisb.) N.E.Br.)using similar principles to those for asparagusweeds.Reading the sites – timing is keyThere is a lot of variation from site to site, soeach must be assessed individually and itsconditions understood. During the brief window ofopportunity, usually in October to early November,the work is intensive. As rainfall and temperaturevary from year to year, so does the timing. Thismakes it difficult to forward plan and covermultiple, dispersed sites. For example, plants willdry off earlier at sites with a northerly aspect or onexposed heights and will linger longer at sites witha southerly aspect or in sheltered valleys where it iscooler and wetter.Soil type and weather conditions affect how longmetsulfuron-methyl has a residual activity in thesoil. When to control must be carefully plannedaround predicted weather conditions to limitdamage to off-target plants. Typically, there is atwo-week dry spell after spring rain events, givingsufficient time for the herbicide to become inert.98