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 7630 IREC Farmers' Newsletter No. 195 ­ – Rice R&D 2016 that the impact of aquatic earthworms declined as well. Whilst the best option for minimising aquatic earthworm populations is to precede rice with a dryland (or minimally irrigated) winter cereal crop, repeat cropping is also likely to keep populations at manageable levels. Where possible, drill sowing provides excellent protection against aquatic earthworm damage. Snails Snail problems are closely linked to repeat cropping. When ‘new’ ground is flooded for rice production, snail infestations develop very slowly, as snails (main photo, page 29) and their egg masses enter the bays gradually and generally in quite low numbers through the supply channels. By the time significant populations develop the plants are past the establishment phase and no longer susceptible to damage, and there are also alternative food sources available, such as algae and broadleaf weeds at the crop margins. As the water level falls after irrigation ceases prior to harvest, snails tend to accumulate in the toe-furrows and near the water stops. While some of these snails die, a large number burrow into the soil and enter dormancy. Studies at Yanco indicate that 40–50% of these snails will still be alive if a repeat crop is sown in the following spring, and will emerge from dormancy to start feeding and reproducing immediately when the ground is flooded. The result? Large mixed populations of adult and immature snails at a time when the young plants are vulnerable to attack, and when there are few alternative food sources available. Breaking the cycle of repeat cropping generally solves the problem — at least temporarily — because dormant rice snails can’t survive in the soil for more than 12 months at most. Increased repeat cropping has led to a much greater emphasis on the chemical control of snails and the use of copper sulphate (bluestone), the only currently registered treatment for snails, is known to be problematic. Soils with high levels of organic carbon compounds dramatically reduce efficacy, and copper has no impact on snail eggs. Work on niclosamide during the RIRDC-funded project Improving pest and disease biosecurity in the Australian rice industry resulted in an application to the APVMA for a commercial trial permit (limited area) for this chemical, which will hopefully be granted in time for the 2016–17 rice season. Niclosamide is effective against both snails and their eggs at a low application rate, does not produce persistent soil or water residues, is safe to the crop and is unlikely to be significantly affected by soil chemistry. Armyworms Until around five years ago, armyworms were a fairly sporadic problem in rice, with l Figure 1. Rice bloodworms (approximately 18 mm) partially cleared to make their head capsules easier to see. Aquatic earthworms are generally much longer and do not have head capsules. l Figure 3. The adult common armyworm moth (wingspan approximately 35 mm) l Figure 2. Aquatic earthworms (approximately 60 mm) l Figure 4. Pupae of a parasitic wasp developing inside a dead armyworm caterpillar