Evergreen, perennial shrubs or trees with thick, sword-shaped leaves, the many species of yucca plant are susceptible to infestation by a variety of bugs. These insects range from selfish intruders that kill the plant when it is stressed, to a moth that does its best to provide the plant with new life.
Mealybugs feast on the lower surface of leaves and on the roots of the yucca, looking like a collection of white cotton. They leave behind their waste product -- honeydew -- from which springs the disorder known as sooty mould: dark, sticky globs that cling to the plant. The feeding stunts the growth of the yucca and severe infestation by the mealybug can potentially kill the plant. Application of insecticide is effective in controlling the pest.
Scales and Thrips
Scales are round or oval, brown insects camouflaged well by the yucca and may be difficult to view. They feed on the leaves and stems of the yucca and are managed efficiently my chemical methods. Thrips are tiny insects with a fringe of hairs around the edges of both wings. The colour of the thrip varies according to the species and the leaves they feed on become curled and distorted with the damaged areas taking on a silver or grey look.
The yucca weevil (Scyphophrus acupunctatus) is a black, snout-nosed weevil that produces white larvae that tunnel beneath both the bark and the tip of the plant. They also feed on the leaves, leaving behind a collection of holes. Approximately 1/2 inch long, the yucca weevil infests only the yucca. A severe attack is capable of killing the plant. No control measures are known; a yucca rarely recovers after being inhabited by this pest.
The yucca moth (Tegeticula) is the exclusive pollinator of the yucca moth. A symbiotic relationship that has carried on for 40 million years, the moth carries pollen from one yucca to another and deposits eggs in the plants it pollinates. Those eggs turn into larvae that feed on the seeds of the yucca until they burrow into the ground, spin cocoons and wait to be transformed into the adult moth. The hungry larvae are initially white before turning pink or red with maturity.
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