Ground Cover Supplement : GC Supplement - Foliar fungal diseases
Ground covEr FoliAr FunGAl disEAsEs 16 FungiCides For adequate control of barley leaf rust, fungicide application should occur before disease levels become extreme. in general, timing of foliar application should target the stem-extension stage prior to flag leaf emergence, protecting the important flag-1 and flag-2 leaves. choice of fungicide product and rate for leaf- rust control will depend on the yield potential as well as the rainfall zone (higher rainfall zones usually have greater disease pressure). the justification for a second application of fungicide depends on the disease pressure for both leaf rust and other foliar diseases. a second application is more likely to be justified with high disease pressure where the first spray has been applied early, in longer- season environments and where a range of diseases are present in the crop. although foliar sprays prove the most valuable for controlling barley leaf rust, seeding fungicide treatments have a proven history of reducing losses associated with barley powdery mildew, a disease that predominates in Wa due to the extensive use of susceptible varieties. Foliar fungicide application is highly effective in reducing powdery mildew infection and well-timed sprays with registered fungicides result in significant yield and quality benefits. Similarly, in trials in southern and central Wa foliar fungicide applications have been shown to maintain green leaf area and reduce yield and quality losses associated with infections of both spot-type and net-type net blotch. Practical management information for barley diseases in Wa is available in a new DaFWa Farmnote, ‘managing Barley Disease’, which will be released in autumn 2008. grdC research Codes daW00106, paa more information: dr Kith Jayasena, plant pathologist, dAFwA, 08 9892 8477, email@example.com; Quenten Knight, agronomist, Precision Agronomics Australia, 0427 720 004, firstname.lastname@example.org cost-EFFEctivE FunGicidE trEAtmEnts hiGh lEvEls oF disEAsE control AchiEvEd with Full rAtEs ArE not AlwAys thE most cost-EFFEctivE oPtion by nick PoolE the intrODUctiOn OF strobilurin fungicides to australia has provided new chemistry to help control foliar fungal diseases. these fungicides can attack the pathogens at an earlier stage in spore germination and have a longer active period. however, this chemistry comes at a higher cost than the traditional ‘azole’-based Dmi fungicides. Fungicide trials to assess the implications of fungicide choice, application timing and rates to control stripe rust in wheat and leaf rust and powdery mildew in barley, found that the rate of return from fungicide use could range from 3:1 to 17:1, even when disease pressure was relatively low. note: three rates were used in these fungicide research trials: n half the minimum label rate n the minimum label rate n the full label rate. only rates listed on product labels are registered for use and are recommended. the following information is based on the 2006 trial results for barley grown at munglinup and wheat grown at Scaddan in southern Wa. in the trials – part of a GrDc-funded project – fungicide treatments improved green leaf retention of the crop canopy during grain fill, increasing yield and margin compared with untreated crops. For example, in the barley trial foliar fungicide application increased yield by between 0.36 and 1.75 tonnes a hectare, taking the untreated yield from 2.79t/ha to a maximum of 4.54t/ha. barley three fungicides and rates were compared on the cultivar Baudin A . the principal diseases were leaf rust (caused by Puccinia hordei) and powdery mildew (caused by Blumeria graminis) and the treatments were: tilt® Xtra* (cyproconazole and propiconazole) 125, 250 and 500ml/ha, Opus® * (epoxiconazole) 125, 250 and 500ml/ha and the strobilurin/triazole-based fungicide amistar® Xtra* (cyproconazole and azoxystrobin) 200, 400, 800ml/ha. each product rate combination was applied as a single spray at GS33 (third node – flag leaf minus 1 emergence) and as a two-spray program at GS30 (start of stem elongation) and GS49 (first awns emerging), essentially doubling the amount of active ingredient applied. Despite impact® 400ml/ha (flutriafol) in-furrow being used in all treatments at sowing, leaf rust and mildew were evident on the older leaves at the GS30 application, though infection on newer leaves, flag minus 3 (F-3) and flag minus 4 (F-4) levels was less than 1.5 per cent. Disease levels in the untreated plots continued to build up through stem elongation, mildew being dominant trials are indicating that foliar, rather than in- furrow or seed-applied, fungicides provide better control of barley leaf rust. * Rates applied are less than the minimum label rate. Only rates listed on the product label are registered for use and recommended.
GC Supplement - Integrated pest management
GC Supplement - Partners in grain