Scrubbing Cycads with a Toilet Bowl Brush

It seems my efforts as a volunteer in the greenhouse often involve cleaning plants that have been infested by damaging insects. I know I've not been singled out for this task. It takes non-stop team effort from everyone on the staff of the University of Minnesota Conservatory to help control pests from overwhelming the plant collections.

The greenhouse staff rightly favors the use of biologic pest control over the use of toxic chemicals. The biologic controls are usually in the form of predatory critters. But the beneficial predators alone are not enough to keep plants healthy indoors. Along with "beneficials," a multi-prong approach is needed. It includes the use of physical removal of pests from the plants - usually scrubbing with soap and water. Another prong is the use of essential oils which are noxious to the pests, the oils are sprayed onto the leaves to deter the pests from spreading. A solution of peppermint and clove oil are commonly used.

My tasks today began by collecting paper sachet bags that had been hung on the branches of plants. These bags contain beneficial mites which slowly exit the sachets to prey on the thrips and other mites that feed on plant leaves and stems. The sachets are hung on the plants throughout the greenhouse at regular intervals, usually every 4 weeks. But before a new batch is distributed, the old batch must be collected and discarded.

Sachet of beneficial predator mites hanging on an oak branch showing autumn color

The next task was to reduce the population of mealybugs and scale insects from the leaves and trunks of cycad trees. These ancient plants predate the dinosaurs, and were included in their diet. To defend against being eaten, cycads evolved tough, spikey leaves with sharp edges. Endangered in the wild due to habitat loss, they grow well in the greenhouse. However, like any other plant, they may suffer from sap-sucking bugs despite their tough constitution.

Small white fluffy mealybugs sucking sap from the leaves, to the left of the cycad cone.

I've found that scrubbing a cycad is like bathing a cat - it is all claws. But, from experience, I've learned to use stiff, elbow-length rubber gloves and a long-handled toilet bowl brush to scrub the leaves with soap and water. The brush is able to dislodge most of the pests. A tall ladder helps to reach the very highest leaves, which appears to be the favored location for mealybugs.

A tall ladder helps to reach the very highest cycad leaves, which appears to be the favored location for mealybugs.

Following the bath, the trees are spritzed with a solution of peppermint and clove oil to deter the sap-sucker from returning. The oils are repellent to the pests. This is a third form of biologic control in addition to the sachets and physical removal.

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