Mealybug: Kill! Kill! But How?

Species 473: Solenopsis mealybug, Phenacoccus solenopsis on peanut

Question: “Hi Jerry, This year I have had the worst infestation of mealybug ever. My garden has never had them in the past, but this year everything including established Gordonia’s five metres high are white with them. I have lost quite a few hibiscus to them. Is this a bad year? Do you have one of your amazing remedies? Regards”, Mal.

Answer: Dear Mal, we’ve had a drought year. In drought, ants farm sap-sucking pests for honeydew to boost their food supply.

My Brisbane garden has had its first outbreak of Solenopsis mealybug (Phenacoccus solenopsis). This is a recently introduced and destructive pest which is rapidly spreading. Juvenile mealybug are mobile, travelling from garden to garden, eventually settling down to attack root systems, tubers and new growth.

* Trees, shrubs, bamboo, palms and cycads can be sprayed with white oil. See how to make white oil here.

* You can spot spray small outbreaks with pyrethrum. See how to spot spray with pyrethrum here.

* You can dab methylated spirits on them where they infest tubers used for propagation.

* I got Solenopsis mealybug off my harvested peanuts (so I could roast the peanuts) by dipping them in scalding soapy water.

* Before you spray, learn to identify beneficial species of ladybird and their larvae.

Australia has several common ladybird species which attack mealybug, scale and aphid. The most famous is the Mealybug destroyer (Cryptolaemus montrouzieri) which saved the nascent Californian citrus industry about a century ago. These biocontrols are very effective, controlling pests in hard to spray locations.

For mealybug infestations on trees or shrubs with single (or few) stems, you can apply a horticultural glue as a band around each stem. This prevents ants from spreading sap sucking pests. Prune back side shoots touching fences or neighbouring plants to restrict access by ants. In some cases, glue plus biocontrols have saved me from spot spraying. See how to apply horticultural glue here.

Just for fun, I’ve added a picture of the Mealybug palm (Dypsis mananjarensis), a rarity from Madagascar, a feather palm grown by collectors for its unusually patterned stems.