Ground Cover North : Ground Cover 089 November-December 2010 - North
2 Remove any spilled grain, weeds, rocks and other rubbish from the storage area. 3 Pressure test the silos in the morning within an hour of sunrise or on a cool, overcast day when ambient temperature is stable and the sun is not heating the silo. Silo security needs to be a storage Biosecurity NOVEMBER -- DECEMBER 2010 GROUND COVER 22 By Nicole Baxter n As another harvest begins, grain storage expert Chris Newman is urging growers everywhere to put hygiene in and around silos at the top of their priority list to cut the level of insect pest infestations that occur in on-farm grain storage facilities. Mr Newman, a grains storage specialist with the Department of Agriculture and Food, Western Australia (DAFWA), says it is imperative that farm storage is better managed to preserve grain quality and slow down the development of phosphine resistance among grain storage pests. Yet he worries that many growers are still not taking storage hygiene seriously. "There's far too much grain left lying around silos and as a result most farms have a problem with stored grain insect pests," he says. The Perth-based extension officer says one factor contributing to the rise of pesticide resistance is a lack of pressure testing to check for gas-tightness before fumigating sealable silos. "When phosphine is put in an unsealed storage facility you get an illusion that the fumigation has been a success because most adult insects may die," he says. "But it's the next generation -- the eggs and the pupae -- that develop tolerance and then emerge as a problem in subsequent years." One part of his GRDC-supported extension program is running on-farm workshops to facilitate better knowledge of silo hygiene, pressure testing and seal replacement. Another is working with silo manufacturers to improve factory sealing of grain silos. "Although most silos are sealed when purchased from the factory, some are difficult to reseal on-farm," he says. But with the introduction of the new Australian Standard (AS2628) for gas-tight sealable silos, Mr Newman says a benchmark is now in place that buyers can refer to when buying new silos. Before making a decision, Mr Newman suggests asking manufacturers to perform a five-minute, half-life pressure test to demonstrate that the silo can be sealed on-farm. "It's like buying a new car: you want a demo drive to check the features operate as claimed," he says. "It's the same when buying a silo." A pressure test involves filling a silo with air until it creates a 25-millimetre difference in an oil pressure relief valve or a simple manometer made from clear plastic tubing, and watching the oil level over time as the pressure in the silo reduces. In gas-tight silos, oil levels will fall slowly, but should remain at least 12.5mm apart at five minutes or longer. Mr Newman says this means the silo is sufficiently gas tight to hold phosphine for long enough to eliminate all insect pests at all growth stages. For older silos, he says three minutes is acceptable. The other factor worth confirming is how easily silos are resealed. "Check if the silo has easy-to-reseal lockdown lids and a lock-on plate at the base." To those who want to increase their on-farm storage, Mr Newman suggests starting small and increasing the capacity over time. Grain storage specialists are urging growers to make a concerted effort this harvest to lift hygiene standards to help the industry keep on top of insect infestation KEY POINTS n Pressure test sealable silos yearly n Clean away spilled grain n Replace rubber seals regularly Chris Newman says removing residual grain from the base of silos is the starting point for preventing an unwanted insect pest incursion. "Hygiene is the first line of defence so cleaning up grain spills and grass from around silos will remove food and shelter for insects," he says. "However, the silo itself also warrants a yearly check to make sure it is gas-tight." Mr Newman warns against using phosphine in silo facilities with seals that have not been replaced for many years or those that have not been pressure tested. "Using phosphine without conducting a pressure test is the path towards higher levels of pesticide resistance," he says. 1 Clean out any residual grain from the silos before harvest. Small silos allow for better segregation of grain, blending and insect control. For old and unsealed silos, he advocates fitting aeration fans to keep the grain cool, which maintains the quality and has the added benefit of reducing insect populations. "Insects are exothermic, which means they cannot regulate their own body temperature and rely on the atmospheric temperature to develop. At temperatures of less than 20ºC insects breed slowly and at 15ºC they stop breeding," he says. To register interest in the 2011 line-up of on-farm quality grain storage workshops contact Chris Newman (WA), Philip Burrill (Queensland and northern NSW) or Peter Botta (southern NSW, Victoria, Tasmania and South Australia) or go to www.storedgrain.com.au. □ GRDC Research Code DAQ00158 More information: Chris Newman, 08 9366 2309, 0428 934 509, firstname.lastname@example.org; Philip Burrill, 07 4660 3620, email@example.com; Peter Botta, 0417 501 890, firstname.lastname@example.org; visit www.grdc.com.au/factsheets to download a new series of grain storage factsheets; www.grdc.com.au/DAQ00158 SIMPLE STEPS FOR KEEPING GRAIN PEST-FREE 5 Using an air compressor, pressurise the silo through a tubeless tyre valve until there is a difference of 25mm in the two chambers of the pressure relief valve. When the difference has been reached, remove the air compressor from the silo and note the time taken for the oil level to fall to half of the original level. For an adequate seal, the time taken is five minutes or longer for newer silos or three minutes or longer for older silos. 6 For a faster result use a blower-vac gun fitted to the end of an air hose, pushed on to a poly vinyl chloride (PVC) fitting in the wall or a seal plate. The PVC fitting can be drilled into the inspection opening cap of the pressure relief valve used on some silos. 7 If a silo does not remain pressurised for at least five minutes, repressurise it and spray soapy water on the lid and base plate to find leaks. 8 Bubbles indicate the seals are faulty and need replacing. 9 Inspect the quality of the rubber seals at the top and bottom of the silos. An effective rubber seal will appear free from damage and display a 'good memory' by springing back when compressed. Photos by Peter Maloney, DAFWA, unless otherwise specified. Photos 1, 2 and 3 by Chris Warrick, Kondinin Group. 1 2 3 4 6 5 7 8 9 PHOTO: NICOLE BAXTER 4 Ensure there is sufficient light hydraulic oil in the pressure relief valve.
Ground Cover 090 January-February 2011 - North
Ground Cover 088 September-October 2010 - North