Remove any excess soil and compost piles from the growing area to prevent an alternative infestation site. Destroy heavily infested greenhouse plants as they will be difficult, if not impossible, and very costly to clean up. All new plant material should be inspected upon arrival and any infested plants should be returned to the supplier. Non-Chemical: The best mealybug management is avoidance. Check for white cottony masses around drainage holes to determine whether a closer inspection of the roots is necessary. This is particularly common in African violets. Yellowed or wilted foliage may indicate an underground mealybug infestation. Examine any white mass carefully to determine whether it is a mealybug, a mealybug egg mass, or the larval stage of the beneficial mealybug destroyer (see below). Long-tailed mealybugs can often be found in whorls. Scouting Suggestions: Visually inspect the leaf whorls of susceptible plants. One generation develops every one to three months depending on temperature. Adult males are tiny and winged, but rarely seen, and only live a few days. Immature males (nymphs) settle and spin a white, waxy cocoon. Young female mealybugs go through three instars (stages) and are mobile their entire lives. After laying eggs over a period of five to 10 days, the female dies. Long-tailed mealybugs don’t lay eggs, but bear live young in a manner similar to aphids. Egg-laying is temperature dependent with fewer eggs laid at high temperatures. Life Cycle: Mealybugs lay up to 600 small, yellow eggs in a protective cottony mass. Citrus mealybugs cause additional problems by injecting a toxin as they feed. Honeydew is sticky and can support the growth of sooty mold fungi, which are not harmful to the plant, but if present in high enough concentrations, can impair photosynthesis in the leaves. Because mealybugs feed on sugary plant juices (photosynthates), their waste contains a high sugar content and is referred to as honeydew. Symptoms of mealybug feeding include stunting, chlorosis, defoliation, and wilting. Long-tailed mealybugs prefer dracaena over other species. The citrus mealybug is more common on tropical foliage plants or soft-stemmed, succulent plants such as coleus, fuchsia, and cactus. Symptoms and Effects: Mealybugs feed at stem tips, and where the leaf meets the stem. Unlike their close relatives the scales, mealybugs retain their legs throughout their life. Because of their appearance, mealybugs may be confused for cottony cushion scale or wooly aphids. They are covered with a white or grey cottony wax. They are somewhat elongated and segmented and have waxy filaments extending from their hind end, giving the appearance of a tail. The citrus mealybug ( Planococcus citri) is the most common greenhouse species and is the most damaging.Īppearance: Mealybugs are pink, soft-bodied insects that range in size from 1/20 to 1/5 of an inch. They can infest all plant parts including the roots. They are tropical insects that are typically only found on perennial foliage plants, and rarely on flowering or bedding plants. Mealybugs are slow-moving, small, oval insects that are covered with a white, cottony wax. Karen Delahaut, formerly UW-Madison Fresh Market Vegetable Program
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