Many gardeners are misidentifying the white insects on plant stems. In most cases it is planthoppers rather than mealybugs. The planthoppers are very destructive and jump away when touched. Mealybugs stay put. A water blast is all that’s needed for the planthoppers. For mealybugs, I would probably try the EcoSMART insect control product. The line is in quite a few of the retail stores now. Another option is to spray the Mound Drench mixture. It has worked for me in the past. Mix equal parts orange oil, compost tea and liquid molasses. Use 4 oz per gallon of water for the spray formula. It can also be made by adding 2 oz of orange oil to the Garrett Juice formula. This method gives the plants foliar feeding as well as insect control.
There's a lady beetle that can also help. Cryptolaemus or mealybug destroyer larvae don't have the loose white residue and and move about a little more freely. Mealybugs will sometimes have several long tails and usually are seen in clusters rather than alone like the beneficial. The mealybug destroyer's white growth looks very much like dreadlocks. This beneficial is primarily used in greenhouses but is good to know about.
It's also important to know that mealybugs are on your plants because they are in stress. No matter what method is used for control, the pest will return if the cause of the stress isn't eliminated. Stress that attracts harmful insects like the mealybugs can be caused by too much or too little water, too much or the wrong kind of fertilizer, soil compaction or contamination or improper planting heights. The most common cause of mealybug attack is the use of toxic herbicides around the trees.
This beneficial is primarily used in greenhouses but is good to know about.
Common name: Mealybug
Scientific name: Order Homoptera, family Pseudococcidae, several species
Identification: Female adults have soft, oval, segmented pink bodies covered by white waxy material. The rarely seen males have two wings and look like tiny flies.
Biology and life cycle: Female adults lay eggs in a cottony white mass that hatches in ten days. Active yellow nymphs called crawlers feed for one or two months or more. Several generations a year. Some mealybugs bear live young. Females molt twice; males form a thin cocoon before becoming adults. Winter is passed in all stages.
Habitat: Most fruit trees, grape, potatoes, and many ornamental and indoor foliage plants. They especially like citrus, grapes, and tropical plants. Common pest on interior plants and outdoor landscaping plants that are in stress.
Feeding habits: Female adults and nymphs suck juice from primarily the new growth of plants. Leaves turn yellow, and fruit drops prematurely. Honeydew from these insects supports growth of sooty mold and other diseases. Males don't have mouth parts (all they do is mate).
Economic importance: Can damage plant foliage and reduce fruit production.
Natural control: Birds and lizards. Healthy, stress-free plants are immune to this pest.
Organic control: Attract and release parasitic wasps. Release mealybug destroyer Cryptolaemus montrouzieri (indoors only), lady beetles, lacewings. Strong water spray, seaweed, and garlic tea or garlic/pepper tea.
Insight: This is one of the most common insect pests on indoor plants, but it will attack landscape and garden plants as well. It is quick to show up on stressed plants.