Sabrina Hahn: How to kill garden rats without harmful baits and what to do if you spot citrus gall wasp

Each week Sabrina Hahn rolls up her sleeves to answer West Australian gardeners’ most burning questions. This week, she’s breaking down exactly how to deal with citrus gall wasp, diagnosing a haggard hedge, and sharing a reader’s ingenious idea for banishing rats without the use of harmful baits. To submit your own question to the Green With Envy column, published inside Saturday’s The West Australian, write to Ask Sabrina, GPO Box D162, Perth 6001 or email home@wanews.com.au. Please include your full name and suburb. Due to the volume of questions, not all of them will be answered. Rat race Q I saw your article on rat poison (Daily Coffee Break, March 20). I learnt of an alternative to poisons from my uncle via my mother. Red kidney beans — the hard ones, before they’re cooked, will kill rodents. The way I’ve used them is to put them in a blender until they’re turned into a powder. I then keep it in an air tight container. To make the bait station, I use the lid off a glass jar. Drop of super glue to stick it to the fence capping where the “rat run” is, then mix some of the powdered kidney beans with some peanut butter (coarse mix) and put it in the lid. I then top it up as it’s eaten. The trick is to wear latex gloves when you’re handling any part of the process so that you don’t transfer your scent as rats are very wary. It works! Apparently, they only need one per cent of it in their diet for it to kill them. Google it for the scientific explanation — it messes with their red or white blood cells. This may be an alternative to poisons for some people to use and isn’t that much trouble to prepare. Especially if it’s saving wildlife. Andrew Meechin, Ocean Reef A That is the best red hot tip we have ever had, and I will certainly trial it at my own place. What a great and safe way to deal with rats without the use of any rat bait. It’s simple, cheap, accessible, and something we can all do at home. When gardeners share information it helps us all, and proves gardeners are always looking for better ways of solving problems. Hedges on edge Q The hedges surrounding our apartment block keep having sudden plant deaths when nearby healthy plants thrive. It is not a lack of water! Do you have any suggestions as to why this is happening? Teresa McManus, Carine A My guess is that it’s fungal or a problem below with the root system below soil level. Over the past three years the same problem has occurred in my viburnum hedge, where some died and others beside it thrived. They do get hit with spider mite in summer, but that’s not the cause. The plants I dug up to investigate didn’t show any symptoms of root knot nematode, bacterial rot or anything eating the root system. Another cause could be genetics; some plants are more susceptible to heat stress than others after 10 years. When I’ve removed the dead plants and replanted, the new plantings are thriving. Wasp worries Q I read your column every week in the Saturday paper — it’s a ripper! The citrus gall wasps have well and truly arrived here in Perth at the moment (mainly on the lemon trees). I know to either remove the galls entirely or to scrape them with a sharp blade to expose the larvae to the wider world, but I wonder how commercial citrus growers deal with this pest over a significant number of trees? And is this available to gardeners? And further, what would happen if no action were to be taken — the infestation would obviously get worse but how would it affect the tree and the crop yield in the future? Cheers and many thanks in advance. Love your work! Craig M. Gumley, Shenton Park A I definitely wouldn’t recommend leaving the galls, as it will only spread throughout the tree and your neighbours’ trees. The most important time to remove galls entirely is from April to June. Slicing the tops off the galls is only effective in mid to late winter. The commercial growers may have pesticides not available to the home gardener but they also use parasitic wasps for control. Most orchards are large so they can control the gall wasp with careful monitoring. They don’t fly very far so if you have cut out all the galls by the end of June they should be under control. Check your trees thoroughly in spring for any fresh attacks.