- Adult stage by the white, yellowish-white, whitish-grey, or pale pink to pale blue in colour coating. The body is oval and the sides of the body have short waxy filaments and there may be 2-4 short to long filaments on the posterior end of the body.
- Mealybugs can be found on all plant parts, but especially roots, rhizomes, pseudobulbs, and the underside of leaves.
- Unlike scales, mealybugs wander in search of feeding places and will leave plants, be sure to check for them in cracks and in joints on benches, under lips of pots and trays, and other hiding places.
- Mealybugs have a three-stage life history: egg, larva (nymph or crawler), and adult.
- The eggs hatch after about a 10 days into the mobile nymphs, the crawlers, that appear as diminutive adults. The crawlers are the most active stage that can move between plants.
- In a warm greenhouse or indoors there may be upwards of 8 overlapping generations per year.
- Indoors, mealybug management is difficult because of their propensity to move into the potting medium and feed on roots.
- Repeated application of any treatment is required to kill the immatures, and treatments are at their greatest effectiveness against the small crawlers.
- Hand removal is effective only for the obvious adults and larger nymphs.
- When possible, immediately isolate infested plants from others to prevent the mealybugs from moving amongst them.
- Check the lips and cracks of pots, trays, and benches because females will wander and leave the plant to find hiding places
- Because the life cycle of mealybugs can be so short combined with the overlapping of generations, you will need to do a treatment every 10-14 days
- Probably the most popular home remedy against mealybugs is to swab and daub plants with a cotton-tipped swab or ball of cotton dipped in isopropyl (rubbing) alcohol.
- On hard-leaved plants, gentle rubbing with the fingers, a cotton ball, cotton-tipped swab, or a soft infants toothbrush is effective. Remove all mealybugs, large and small. Afterwards, you will still need to repeat the alcohol treatment to remove the tiny yellowish spots which are the recently hatched crawlers. Pay particular attention to the folds, crotches, branch bases, midrib areas, and roots.
- These insects like to move into the potting media and feed on roots, or move off of the plant to find hiding places to lay eggs.
- Unless the roots are checked and the media changed, removal of mealybugs from only the upper plant portions is not a guarantee of success.
Oils and Soaps
- Horticultural oil, neem oil, mineral oil, and insecticidal soaps are effective for mealybug suppression.
- None provide absolute control over mealybugs, but frequent use during the presence of crawlers can serve to reduce their populations dramatically.
- Some orchids are sensitive to neem oil, such as species of Miltonia and Masdevallia.
- Persistent populations of mealybugs or infestation in many plants may demand the need for use of synthetic insecticides.
- Never use any insecticide that is not specifically labelled for ornamental plants.
- There are many parasitic wasps and various predatory insects that feed on mealybugs outdoors, but these species are rarely of value in a small greenhouse or in the home.
- Heavy infestations of mealybugs, especially on many plants, may require severe control methods using insecticides.
- On the extreme side if you have a plant showing signs of decline from infestation you may have to seriously consider destroying that plant, as the low likelihood of rejuvenating that plant may not justify the expense and effort of continued treatments.
- The destruction of a sick plant can be used to justify the purchase of a new and healthier plant!
Adapted from Dr Paul J. Johnson South Dakota State University To view the entire article go to this website Click Here