Sabrina Hahn: African lawn beetles may not be harming your lawn, instead it may be your soil or sprinklers

Many Facebook gardening groups incorrectly attribute patchy and brown lawns to the African lawn beetle (Heteronychus arator). While this insect is often blamed as a primary cause of lawn issues, there are actually many other factors that can contribute to the problem. Concerned lawn enthusiasts often share pictures of beetles, and those eager to help quickly identify them as African lawn beetles. However in many cases, this identification is incorrect, as the beetles shown can be completely harmless. The real issues affecting lawns often stem from factors such as nutrient-poor soil, hydrophobic areas, inadequate irrigation coverage, soil compaction, fungal diseases, and high pH levels in the soil. African black beetles lay eggs in spring, and the larvae appear in 2-5 weeks. They then pupate and emerge as adults about two weeks later. Adult beetles hibernate in winter. The most effective time to spray for them is during the early larval stage in spring because it’s only the larvae that do the damage. Beetles are vitally important to our ecosystem and the worldwide food chain. Australia has around 23,000 described species but the total species number is estimated to closer to 80,000 to 100,000. Insecticides used to control lawn beetle do not discriminate solely against the African black lawn beetle alone. The most commonly applied insecticide used by lawn lovers is Acelepryn with Chlorantraniliprole as the active constituent. This chemical can also affect ladybirds, scarab beetles and larvae of moths, butterflies and sawflies. There is nothing published about the effect this chemical has on birds such as magpies when they eat the grubs that have ingested the chemical. Chlorantraniliprole is highly toxic to aquatic invertebrates and should never be used near water courses or where run-off can reach the surface. It is also persistent in the soil and can accumulate over successive years when used repeatedly. The African lawn beetle is around 12-15mm long, has glossy black wings and an oval shape, and spiny legs. The larvae or grub are creamy coloured with yellow/brown heads and black jaws. They curl in a U-shape and grow from 5-25mm in length. Kids dig beetles, and I vividly remember my childhood in New South Wales when Christmas beetles would arrive each summer. It was always exciting to find jewel beetles and fiddler beetles. Unfortunately, our native beetle populations have drastically declined due to habitat loss and the overuse of insecticides. This issue doesn’t only affect the beetles; there are also repercussions for other insects and birds that suffer from secondary poisoning or are considered non-target species. Tip of the week Always send pictures to MyPestGuide Reporter (an app designed to report pests across Australia) to have insects correctly identified before reaching for insecticides. In many cases the insect will be beneficial and harmless in your garden. Three jobs to do now 1. Look for cicadas hanging on the bark of trees. You will hear them starting to sing late afternoon. 2. Check your garden around 6pm to see if any male native bees are clinging to the stalks of flowers or on fencelines. They like to cluster together at night. 3. Apply a wetting agent, kelp and liquid fish fertiliser to lawns to keep them healthy over summer. Do you have a question for Sabrina? To submit a question to Green With Envy, 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.