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The mealybug destroyer, Cryptolaemus montrouzieri, is probably the most successful natural enemy of mealybugs.

shorter days of winter seem to reduce their activity, although the mealybugs will continue to increase under these conditions. Beetles are available from several commercial insectaries.

Other lady beetles. Many coccinellid beetles are important predators of mealybugs in other cropping systems, but few have been investigated for biological control of mealybugs in greenhouses. Diomus flavifrons is native to southern Australia where it commonly feeds on the longtailed mealybug.The beetle was introduced into Texas for control of citrus mealybug on citrus.The small black adults consume about 800 mealybug eggs over a 70-day period. Scymnus (=Nephus) reunioni and S. bipunctatus are two other coccinellids available commercially for mealybug control in other countries.

Green lacewing larvae. Chrysopa and Chrysoperla larvae will feed on young mealybugs but will also feed on other natural enemies that are present.

The larva of the mealybug destroyer resembles a mealybug.

Possibilities for effective biological control

Biological control of citrus mealybug is a promising alternative to chemical pest control on commercial greenhouse crops. Mealybug species other than citrus mealybug are more difficult to control biologically because parasitoids are not as widely available.The natural enemies of citrus mealybug tend to be specific, and several effective ones are available from commercial suppliers.

The mealybug destroyer has been successfully used against citrus mealybug on various ornamentals, such as gardenia and chrysanthemum, when temperatures remain above 70°F. Plants grown in large numbers or with dense bushy growth are better suited to mealybug control with the mealybug destroyer. Because the beetle needs to oviposit among mealybug egg masses, it may be less effective against long-tailed mealybug, which produces live young. It is ineffective against mealybug infestations on roots.To enhance control, avoid using residual pesticides in the month prior to beetle release and control any ants in the area by using a boric acid bait. Otherwise, the ants will protect the mealybugs from predators and parasites.To favor the mealybug destroyer, adjust temperatures to 72°-77°F and relative humidity to 70-80% so that maximum control may be achieved.The pest population does not need to be reduced to a lower level before introducing the predator.

Adult mealybug destroyers should be released as soon as the shipment arrives, although they can be stored in a refrigerator for a short time. Release beetles in early morning or late evening onto plants at various infestation sites. Vents and windows should be screened to prevent the beetles from escaping, and during distribution workers should avoid wearing white clothing, which will attract the beetles. Optimal release rates will vary depending on the crop, but two to five beetles per 10 ft2 is a good general guideline. Researchers have achieved control with one beetle per plant on gardenia and one beetle per two plants on chrysanthemum. Mealybug destroyers should control the mealybug population in about 10 weeks. Periodic releases may be necessary if other natural enemies are not being used.

Citrus mealybug can be effectively controlled within 3 months using the parasitic wasp Leptomastix dactylopii.For best results, reduce heavy mealybug populations first either by releasing mealybug destroyers or by hosing off dense accumulations and then spraying with insecticidal soap (if no other natural enemies are present) or kino-prene. Also, adjust the greenhouse temperatures to 75°-81°F. No other residual pesticides should be used for a month prior to wasp release. Adult wasps should be released at several sites throughout the infested area at a rate of five wasps per 10 ft2.Place the wasps as close to the mealybug infestations as possible. Periodic releases may be necessary to maintain control.

The best biological control of citrus mealybug has been achieved using a combination of natural enemies, especially supplementing the mealybug destroyer with parasitic wasps. However, experimental results have been quite variable, depending on the plant species, the greenhouse temperature, and the greenhouse size.When used together in French greenhouses, the mealybug destroyer and L.dactylopii completely controlled citrus mealybug on clivia (Kaffir lily) and crotons, and provided reasonable control on geraniums, African violets, cattleya orchids, and Pilea.The wasp Leptomastidea abnormis, the mealybug destroyer, and three other natural enemies were used to reduce high citrus mealybug infestations to less than 1% in gardenia within 3 months in a California commercial greenhouse.

Releases of 19,300 L. dactylopii and 600 mealybug destroyers over a 4-month period reduced citrus mealybug infestation on commercially grown Stephanotis from 66% to zero in a small California greenhouse maintained at 70°F and above.The mealybug destroyers were able to maintain a small population in the greenhouse after the disappearance of citrus mealybug by using hemispherical scale as an alternate food source. Even after an accidental re-introduction of citrus mealybug into the greenhouse several months later,the mealybug population remained well below economically damaging levels.

Mealybugs

Researchers in the Netherlands used two wasps (L. dactylopii and L. abnormis) and two beetles, mealybug destroyer, and Scymnus (=Nephus) reunioni, against citrus mealybug on 50,000 Stephanotis plants grown for cuttings in a commercial greenhouse.They released over 1300 adult beetle predators in areas with heavy mealybug infestation, and released 13,330 L.dactylopii and 15,520 L. abnormis approximately every other week from May through October. Citrus mealybug was controlled during the summer months, but not during the winter, when temperatures were 55°-63°F and the parasites were inactive.

The predatory beetle Scymnus (=Nephus) reunioni, has been used with some success in greenhouses in France, but no published research on this predator has been conducted in the United States. In combination with L. dactylopii, it achieved excellent control of citrus mealybug on bromeliads. Similar control on a wide range of ornamentals was noted in the United Kingdom.

Mealybugs

Enemies

egg

-nymph- adult

Anagyrus pseudococci

Letpomastidea abnormis

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