Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 7629 IREC Farmers' Newsletter No. 195 ­ – Rice R&D 2016 Mark Stevens and Andrew Watson NSW Department of Primary Industries, Yanco Agricultural Institute U SING the residual water in the soil profile after rice can reduce the water needed at fill-up for a subsequent rice crop and overall crop water consumption by up to 10%. However repeat cropping does come at a cost in terms of the risk posed by some common rice pests and at least one rice disease. Bloodworms and aquatic earthworms Bloodworms (Figure 1) are the larvae of midges, which fly in from surrounding areas and lay their eggs just below the water surface. The midges often arise from larvae that have developed in non-rice environments such as dams, channels and roadside puddles, and can disperse over long distances. The density of bloodworm infestations in rice seems to depend most strongly on the number of adult midges present in the area (which is linked to habitat availability), and to some extent the prevailing weather conditions. Wet winters followed by calm and mild crop establishment periods favour bloodworm colonisation of rice crops, however crop rotation status (‘new’ rice versus repeat rice) has little if any impact on bloodworm populations. Aquatic earthworms (Figure 2) were a major problem when growers with dispersive clay soils, particularly in the Murray Valley, followed irrigated clover pastures with an aerial sown rice crop. Irrigated clover pastures are essentially ‘worm factories’, and when their use in rotations declined many growers found Repeat cropping, where rice is grown on the same paddock for two or more consecutive seasons, is becoming increasingly common as growers try to minimise water consumption. QUICK TAKE l  Repeat rice crops pose particular challenges for pest and disease management. l  Some pests like bloodworms will be unaffected — they will be no more or less abundant in repeat crops than in rice crops on ‘new’ ground. l  Aquatic earthworms are a declining problem now that growers who aerial sow rarely plant rice immediately after irrigated pastures. l  Snails and the disease stem rot become increased risks in repeat crops. l  While armyworms are unaffected by repeat cropping, other water-saving measures such as delayed permanent water in drill sown crops and mid-season drainage may increase armyworm problems. l The rice snail Isidorella newcombi (shell height approximately 10 mm) REPEAT RICE – WHAT IT MEANS FOR PESTS AND DISEASES