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Biological Control of Mealybugs

Mealybugs can be very difficult to control, so if only a few plants are heavily infested, it is best to destroy the infested plants to minimize further spread.    Some of the more common species found in greenhouses and interiorscapes are the citrus mealybug (Planococcus citris) and the longtailed mealybug (Pseudococcus longispines).    Other species include the Mexican mealybug (Phenacoccus gossypii), the Maderia mealybug (Phenacoccus maderiensis) and root feeding mealybugs (Rhizoecus spp). For more information see Managing Mealybugs in the Greenhouse  on the UConn IPM website and references listed at the end of this fact sheet.

Figure 1: Adult citrus mealybug and egg mass. Photo by L. Pundt

Figure 2: Longtailed mealybug adult. Photo by L. Pundt

 

Biology and Life Cycle

Mealybugs are soft-bodied, segmented oval- shaped insects.  Adult females are from 1/20 to 1/5 of an inch long and covered with white, powdery, waxy secretions.  Their life cycle consists of an egg stage (except for the longtailed mealybug that gives birth to live young), immature stages that can move ("crawlers") and adults.  Crawlers mature in about 6 to 9 weeks.  Eggs hatch in 5 to 10 days, with mature females dying after egg laying.   The small winged adult males do not resemble the females and their primary role is to fertilize the female mealybugs.

Scouting

Early detection of mealybugs can be difficult due to their tendency to hide in protected locations.  Look for white flecks or cottony residues along the leaf midribs, on leaf or stem axils, on the underside of leaves and near the base of plants.   Focus on those plants that are prone to mealybug infestations such as begonia, citrus, coleus, croton, gardenia, palms, and many foliage plants.   Mealybugs may also be found on the inside of containers, or in container drainage holes.   Adult females may crawl off plants moving to crevices under benches where they lay eggs. Honeydew, sooty mold and the presence of ants may also be an indication of a mealybug infestation.

Cultural Controls

Biological Controls

Host specific parasitic wasps and generalist predators are commercially available.   It is important to identify the specific mealybugs species present in order to select the most appropriate natural enemy.  

 

Parasitic Wasps

Anagyrus pseudococci

The parasitic wasp, Anagyrus pseudococci,   parasitizes citrus mealybug larvae.  The parastitized pupa swells becoming a hard yellow brown mummy.   After 1 to 5 days (depending upon temperature), the adult parasitic wasp emerges from a hole at the posterior end of the mummy. The first mummies can be seen about two to three weeks after the first release (depending upon temperatures).   Optimum temperature is 76˚ F with a minimum temperature of 51˚ F.  Anagyrus pseudococcus is commercially available as mummies containing the parasitic wasp pupae mixed in inert material. Consult with supplier on recommended release rates. 

Tips for using Anagyrus pseudococci

 

Predators

Cryptolamus montrouzieri

An Australian ladybird beetle, commonly known as the mealybug destroyer (Cryptolamus montrouzieri) is commercially available for use against the citrus mealybug.  Cryptolamus can also feed on soft scales and aphids but prefers mealybugs.  The mealybug destroyer only reproduces on mealybugs with egg masses so is not as effective against the longtailed mealybugs.    Mealybug destroyer adults and larvae are predacious, seizing and consuming prey.  

Adults are shiny black beetles with a reddish head and thorax.   Larvae resemble mealybugs.  But, the mealybug destroyer larvae are longer, and more mobile than mealybugs with longer wax threads than mealybug larvae.  

Figure 3: Adult Mealybug destroyer. Photo by L. Pundt

 

Figure 4:  Mealybug destroyer larvae. Photo by L. Pundt

Optimum conditions are temperatures between 72 and 77° F and a relative humidity of 70 to 80 %.   Mealybug destroyer eggs are deposited within the egg sac of mealybugs.   They are most active during sunny conditions and are less active during short winter days.   Cryptolamus are most effective when mealybug density is high and can fly off in search of new prey.   Cryptolamus montrouzieri are commercially available as adults packed in plastic tubes with a carrier. They have recently become commercially available as larvae that can be released among infected foliage in the evening individually on the leaves or placed in a distribution box.  It is helpful to release both larvae and adults, according to Sarah Jandricic, Greenhouse Floriculture IPM Specialist OMAFRA.  Larvae attack all mealybug life stages so are effective in hot spots but do not disperse very far.  Adult beetles only eat mealybug egg masses, but can disperse through the crop to lay their eggs which will hatch into mealybug destroyer larvae.

Ants protect mealybugs from Cryptolamus so should be controlled before releasing these generalist predators. Consult with supplier on recommended release rates. 

Tips for using Cryptolamus montrouzieri

Lacewings

Green lacewings (Chrysoperla sp),  are better known as a aphid predator, hence their common name,” aphid lion, “ but they can also feed upon mealybugs , whiteflies, spider mites and thrips.   Lacewings are not relied upon exclusively for control, but they may help suppress mealybugs.  Only the larval stage is predacious, adults feed upon pollen, honeydew or nectar.   Repeated releases are often needed, but do not release the small larvae when the larger larvae are on the plants, as the larvae are cannibalistic. 

Green lacewings are commercially available as eggs glued onto cards, or loose in an inert mixture of rice hulls or as larvae in small individual cells so they don’t eat each other or as adults in a cardboard tube that is screened at both ends.  They are active during a wide range of temperatures (54 to 95˚ F).  Consult with supplier on recommended release rates. 

Figure 5: Lacewing larvae. Photo by L. Pundt

 

Figure 6: Lacewing adults. Photo by L. Pundt

Tips for using Chrysoperla sp.

 

Ants will protect mealybugs from natural enemies, in order to feed upon honeydew, so identify the type of ant species so you can determine the best type of bait to use.

In summary, parasitic wasps, mealybug destroyers and lacewings can help suppress mealybug populations.  It may be necessary to spot treat with a compatible pesticide to manage mealybugs.

By Leanne Pundt, Extension Educator, University of Connecticut, 2014. Revised 2015.

 

References

Cloyd, R.  2011. Mealybug Management in Greenhouses and Interiorscapes.  Kansas State University Agricultural Experiment Station and Cooperative Extension Service. Factsheet MF3001. http://www.ksre.ksu.edu/bookstore/pubs/MF3001.pdf

Gilrein, D. 2013.  The usual suspects.  Greenhouse Management.  May 2013. http://www.greenhousemag.com/gm0513-mealybug-control.aspx

Heinz, K.M., R.G. Van Driesche, and M.P. Parella (Ed). 2004. Bio Control in Protected Culture. Ball Publishing, Batavia, Ill. 522 pp

Jandricic, S. 2015.  Floriculture IPM for Mealybug.  Post on onfloriculture blog. https://onfloriculture.wordpress.com/2015/07/31/floriculture-ipm-for-mealybug/

Lamb, E. and B. Eshenaur. 2014. Greenhouse Biocontrol Workbook.  NYS Integrated Pest Management Program. Cornell University Cooperative Extension.  84 pp. http://www.nysipm.cornell.edu/ 

Malais, M.H. and W. J. Ravensberg. 2003. Knowing and recognizing: The biology of glasshouse pests and their natural enemies. Koppert Biological Systems and Reed Business Information. The Netherlands.  288 pp.

Osburne, L. 2010.  University of Florida.   IFAS Mid- Florida Research and Education Center Mealybugs  http://mrec.ifas.ufl.edu/lso/mealybugs.htm

Smith, T. and L. Pundt. 2014. Greenhouse Pest Guide web App.  http://tiny.cc/greenhousepestguide.

Stack, Lois Berg. (Ed). 2015-2016. New England Greenhouse Floriculture Guide. A Management Guide for Insects, Diseases, Weeds and Growth Regulators. New England Floriculture Inc and the New England State Universities.

Thomas, C. 2005. Greenhouse IPM with an Emphasis on Biocontrol. Publication No. AGRS-96. 89 pp. Pennsylvania Integrated Pest Management Program.

http://extension.psu.edu/pests/ipm/agriculture/copy_of_greenhouse/greenhouse-manual

 

 

 

Disclaimer for Fact Sheets:

The information in this document is for educational purposes only.  The recommendations contained are based on the best available knowledge at the time of publication.  Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended.  UConn Extension does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.  The University of Connecticut, UConn Extension, College of Agriculture, Health and Natural Resources is an equal opportunity program provider and employer.



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