What are Mealybugs?

Mealybugs are small, oval, soft-bodied insects, often pinkish, and are characterized by their white-waxy coating, which gives them a fluffy and cottony appearance.

This insect belongs to the Family Pseudococcidae and the Order Hemiptera.

Image credit: Antropocene.it

Mealybug Biology

The adult male is winged and small. The female is wingless and bigger. Females can be identified by their flat shape, covered with white flocculent wax. Males are short-lived, have no mouthparts, and don’t feed, and their only function is to mate. The attack of the mealybug is found to be more under dry weather climates, and very often the heavy incidence occurs following periods of prolonged drought. Activity is most common from July to October.

Lifecycle of Mealybug

Mealybug undergoes incomplete metamorphosis (egg, nymph, and adult stages). In many species, the female crawl down tree in month of april-may and enter in cracks, in soil for laying eggs in huge numbers encased in white cottony waxy filamentous ovisac; whereas in some species egg laying is done on plant in ovisac; made of cottony and sticky wax; attached to the end of female mealybug adult female lays 300-600 eggs in clumps of 5 to 20 inside egg sac (ovisac). The average egg laying capacity per female is 450 eggs; The mealybug undergoes three nymphal instars in females and four nymphal instars in male. Some species are active and mobile during their entire life span.

Mode of spread

Mealybugs are not very fast crawlers, and adult female mealybugs cannot fly.

• Crawling: Juvenile mealybugs, or “crawlers,” can crawl from an infested plant to a healthy one, especially if plants are close together.
• Wind: Small crawlers can be carried by wind to nearby plants, particularly in open areas.
• Water: Mealybugs can be transported by irrigation water or rain.
• Human Activity: Infested plants or plant material can be moved from one location to another, spreading mealybugs.
• Ants: Ants, attracted to the honeydew that mealybugs secrete, can inadvertently carry mealybugs from plant to plant.
• Long-distance dispersal: Long-distance movement is most likely through the transport of infested planting material, fruits, and vegetables.
• Natural Carriers: Mealybugs can also spread through natural carriers such as raw cotton, linted cotton seeds, wind, water, rain, birds, human beings, ants, and farm animals.

Nature of Damage

Damaging stage –Both nymphs and adult females. Mealybugs feed on the sap of various plant parts, particularly the tender and young growth. The feeding causes several forms of damage:

Direct Damage from Feeding:

• Leaf Deformation: Mealybugs feed on the underside of leaves and stems, injecting a feeding fluid that causes the leaf tissue to distort. This leads to yellowing (chlorosis), curling, and sometimes the complete necrosis of the affected areas.
• Stunted Growth: As mealybugs continue to feed on the plant’s phloem, they disrupt the plant’s nutrient flow, leading to poor development of leaves, stems, and branches. This results in reduced growth and weak plants more susceptible to other stress factors.
• Honeydew Secretion: As mealybugs feed, they excrete a sticky substance known as honeydew, which can accumulate on leaves and branches. This sugary substance becomes a breeding ground for sooty mold, a fungal growth that further interferes with photosynthesis and reduces the plant’s overall health.
• General Decline: Heavy infestations can lead to an overall decline in plant health. Reduced photosynthetic capacity, weakened root systems, and nutrient deficiencies caused by mealybug feeding contribute to poor plant vitality, leading to reduced fruit-bearing capacity and increased susceptibility to other pests and diseases.

Indirect Damage (Disease Transmission):

• Viral Infections: Mealybugs are vectors for several plant viruses, including pomegranate fruit stain virus. By feeding on infected plants and then moving to healthy plants, mealybugs can spread these viruses, which can result in fruit discoloration and poor fruit development.

Damage to Pomegranate Flowers:

Mealybugs also target pomegranate flowers, which are vital for fruit set and yield. Feeding on Flower Buds and Blossoms: Mealybugs can feed on tender flower buds, flowers, and newly formed inflorescences that lead to bud drop, poor pollination, and aborted flowers, which affects fruit set. When mealybugs attack flowers, they extract the plant’s sap, weakening the flower’s reproductive structures and reducing the overall flowering capacity.

• Flower Drop: Prolonged mealybug feeding on the flowers can lead to premature flower drop, especially if infestation is heavy. This reduces the number of flowers available for pollination, ultimately leading to lower fruit yields.
• Honeydew and Mold Growth: As with leaves, mealybugs excrete honeydew on the flowers, encouraging the growth of sooty mold. The presence of mold can interfere with pollination and reduce the attractiveness of flowers to pollinators like bees. This may lead to poor pollination and fruit setting.

Damage to Pomegranate Fruits

The damage caused by mealybugs to pomegranate fruits is one of the most significant concerns for growers, as it directly impacts the marketability and yield of the crop.

• Feeding on Developing Fruits: Mealybugs typically feed on the tender, developing fruits. This causes localized feeding scars and soft, sunken lesions on the fruit surface. Infected fruits may appear deformed, with scabby, darkened patches where the mealybugs have fed. These feeding wounds provide an entry point for secondary infections, including fungal and bacterial diseases.
• Honeydew and Sooty Mold: As mealybugs feed on the fruit, they excrete honeydew, which accumulates on the fruit’s surface, leading to poor quality and smaller fruit size. This sticky substance serves as a medium for sooty mold growth, which can cover the entire surface of the fruit. Sooty mold creates a black, unattractive coating that makes the fruit unappealing to consumers and reduces its market value.
• Fruit Drop and Reduced Yield: Severe mealybug infestations on fruits can result in premature fruit drop. The damaged fruits are often weak and unable to mature properly, reducing the overall yield and quality of the harvest. It can cause the fruit to become misshapen or discolored, with reduced shelf life. This deformed fruit is typically unfit for sale in the market, leading to significant economic losses.

Key Factors Influencing Mealybug Infestation:

• Climate: Mealybugs thrive in warm, dry, and humid conditions. The monsoon season, followed by post-monsoon warm weather, creates an ideal environment for their proliferation. However, mealybugs can also infest pomegranates during dry seasons when irrigation is used, providing them with ample moisture.
• Plant Growth Cycle: Pomegranate plants are typically more vulnerable to mealybug infestations during certain periods of growth. The following are important stages when mealybugs are more likely to infest.
• Pre-flowering (Late Spring to Early Summer): This is a critical period for mealybug infestations, as the plant is actively growing and tender new shoots and leaves are more susceptible to pest attacks. Mealybugs feed on these new shoots, which can stunt growth and affect the overall health of the plant.
• Post-monsoon (Late Summer to Early Autumn): After the monsoon rains, the humidity levels remain high, which provides favorable conditions for mealybug reproduction. During this time, mealybug populations may multiply rapidly on young fruit, flowers, and growing shoots. This is when growers often observe a noticeable increase in mealybug activity.
• Fruit Maturation (Late Autumn to Early Winter): Mealybugs can also infest the developing fruits if not controlled during the flowering stage.

Seasonal Patterns of Mealybug Infestation

In India, the following seasonal pattern of mealybug infestation is typically observed:

• Pre-Monsoon (March to June): As temperatures rise and pomegranate trees are actively growing, mealybugs may begin to infest tender plant parts such as leaves and young shoots. Infestation is generally low but can increase under irrigated conditions or in regions with high ambient temperatures.
• Monsoon Season (June to September): During monsoon, mealybugs tend to multiply rapidly due to high humidity and ample moisture. However, heavy rainfall may also disrupt their spread and activity, especially if waterlogging occurs. Despite the rains, mealybug populations often remain significant, particularly in orchards with poor drainage or those located in areas with intermittent dry spells followed by wet periods.
• Post-Monsoon (October to November): The period following the monsoon is when mealybug infestations are usually at their peak. The combination of warm temperatures, high humidity, and new growth in pomegranate trees provides an optimal environment for mealybugs to multiply and spread. This is the most critical time for pomegranate growers to monitor and manage mealybug populations, as this period also coincides with the fruit setting and maturation stages.
• Winter (December to February): The cold weather during winter months (December to February) typically reduces the activity of mealybugs, especially in cooler regions. However, in warmer regions of India, such as parts of Gujarat, Maharashtra, Tamil Nadu, or Andhra Pradesh, mealybugs may remain active in sheltered areas of the plant, particularly if the temperature remains relatively mild. Infestation may still occur, particularly if the orchard management practices are inadequate.

Mealybug Management

Management of the mealybug is a very herculean task due to its polyphagous nature, high fecundity (fast multiplication), and relatively waterproof ovisac (protecting eggs) because of enmeshed waxy fluff. Insect has a waxy layer on their bodies, therefore, even direct application of insecticides doesn’t work. Hence, Integrated approaches are essential, and among them, Biological control is the most effective and long-term solution for the management of mealybug.

Here are some tactics to overcome the mealybug:

Avoid Excessive use of fertilizers: Excessive, Injudicious/Overuse of nitrogenous fertilizers reduces a crop’s resistance/tolerance to pest attack; due to it, plant tissues become more succulent and easy to digest. Therefore, fertilizers should be applied only as per the recommended dose. Excessive use of Phosphatic fertilizers fixes the other elements in soil, such as calcium, magnesium, and iron, and it is highly immobile, which hampers the complete protein development and other enzymatic activities to fight against insect attack.

Cultural Practices such as – Weeding, Sanitation, Pruning, Flooding, Raking of soil

Weeding – The Field should be free from weeds (all unwanted plants) because it provides an alternate host for mealybugs and ants, both

Sanitation – Collection and destruction of all infested plant parts such as leaves, peduncles, twigs, and fruit. Destroy ant nests during land preparation. Because ants help mealybugs move from one place to another

Pruning – Pruning of branches attached to the ground because that helps crawlers to climb up and spread easily.

Flooding – Flooding of orchards with water in winter to kill the eggs (in many species, eggs and crawlers are the hibernating stages)

Physical Barrier – Banding of the stem bottom (or tree trunk) with a polythene sheet (30 cm wide) pasted with grease would be effective to prevent nymphs (crawlers) from ascending up on tree.

Racking of Soil – Racking of soil around the tree region during flowering to destroy eggs present in the soil by sun exposure and natural enemies.

Importance of Brix in pest management

For effective mealybug control in pomegranate, aim for a Brix value of at least 12° Brix. Plants in this range will be more resistant to mealybug infestations and overall healthier. Regular monitoring, proper plant care, and soil management practices are key to achieving high Brix levels, which help reduce the risk of pest problems and ensure good fruit quality. If Brix levels fall below 8°, pomegranates are more vulnerable to mealybugs and will require more aggressive pest management strategies.

Huntin’s Recommendation to Control Mealybugs in Your Pomegranate Crop:

Soil Application of Nok-Out: Soil application of Nok-Out 250 ml/ acre through irrigation to destroy egg mass. Repeat every month to reduce the colonies

Spray of this combination of products-  Nok-out + Nanosulf + Nanoreach gives almost 100% control of mealybug.

For Prevention: Spray Nok-out @ 1 ml/L water + Nanosulf @ 2 ml/L water + Nanoreach @ 1 ml/L water. Repeat this spray every 15 to 20 days to keep mealybug under check on plant

For Cure: Nok-out @ 2 ml/L water + Nanosulf @ 2 ml/L water + Nanoreach @ 1 ml/L water 

After 7 days spray –  All Rounder @ 2.5 ml/L water + Nanosulf @ 2 ml/L water + Nanoreach @ 1 ml/L water. Repeat this alternate spray every 7-10 days to keep mealybugs under check and to prevent population build-up from July to November (until it disappears) &for 100% control of mealybugs in field conditions.

Note: These products are safe for beneficial insect populations, including predatory beetles, ladybird beetles, lacewing larvae and parasitoid wasps