MEALYBUGS-BIOLOGY AND CONTROL

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Nairobi, December 6’17. With research implicating mealybug as a cause of 30% loss in plant produce, a solution to cub this menace is definitely a good medicine to stressful farmers.

Mealybugs are small insect pest. They are elliptical in shape, white in color and have a protrusion extending from the body. A female mealybug is wingless and is longer than a male mealybug. They undergo asexual reproduction (lay eggs) and have a life cycle lasting 25 – 60 days consisting of five growth stages (egg, three nymph and adult) however for males,the stages are six which includes two pupal stages.

The important mealybug species are citrus mealybug, longtailed mealybug, madeira, pink hibiscus mealybug and various root mealybug. These are hosted by various plants ranging from: harbaceous annuals or perennual, fruits, folliage plants, vegetables, herbs and ornamentals

Mealybugs are active in warm and humid condition with adult female being capable to produce up to 600 eggs but die after depositing eggs. Adult males mate with females but die after2-3 days.

The spread of mealybug is due to wind or air currents, workers activities during scouting, pruning and harvesting, by watering especially drip irrigation can spread root mealybugs, and by introduction of infested materials.

The damage caused by mealybug infestation is severe. Most feed on stem and leaves sap while other species feed on roots of plant. Direct signs of infestation to look out for include stunted growth, wilting, yellowing of leaves, leaf drop, fewer new shoot growth and plant death. Indirectly, mealybug also excrete large amount of sticky honeydew which hosts black sooty mould which interferes with photosynthetic process of the plant.

Control of mealybug infestation involves physical/insecticidal strategies like spraying of high pressure water twice per week, use of insecticidal soap sprays, oil sprays and silicone based wetters; biological strategies like use of parasitic wasps, ladybird beetles, hover flies and lacewings and cultural management strategies which involves removal of infested plant parts, limiting use of nitrogen based fertilizers and ensuring balanced soil fertility.

Even though farmers inject lots of resources in implementing these control strategies, they are usually faced with challenges. Some of which involve the tendency of mealybugs to hide in concealed sites of the plants where sprays do not reach, overlapping generations with all life stages hence affecting spray program, hydrophobic waxy body covering on adult body and eggs that repels hydrophilic insecticides, pesticide resistance and also insecticides use tend to kill bio-agents.

Scouting for mealybugs is key to ensure successful management. Plant materials should be inspected thoroughly before they are are introduced into growing areas, plant tissues-stems and leaves-should be checked for white cotton like substances, shiny and sticky areas of honeydews,

For successful management of mealybug, there is need to establish sustainable solutions. Growers should ensure selective use of insecticides and conservation of natural enemies, they should focus on management rather than control and they should shift emphasis from curative to preventive control programs.

By.James Kiboi

Contact: kjwahome@gmail.com

 

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