Domain:        Eukaryota

Kingdom:      Animalia

Phylum:        Arthropoda

Class:            Insecta

Order:            Hemiptera

Suborder:     Sternorrhyncha

Family:          Pseudococcidae

Genus:           Brevennia

Species:         B. rehi

Binomial Name: Brevennia rehi (Lindinger)

Tamil Nadu, Andhra Pradesh, Karnataka, Orissa, Madhya Pradesh, West Bengal and Kerala in India, Bangladesh, Thailand.

Host Range: Rice, Graminaceous weeds

Mealybug bodies are distinctly segmented and usually covered with wax. Older individuals may have wax filaments around their body margins. In some species the filaments are longer in the rear and can be used to help distinguish between different species. While adult females are wingless and similar in shape to nymphs, adult male mealybugs, which are rarely seen, are tiny two-winged insects with two long tail filaments.

Egg: The female lays numerous yellowish-white eggs/ simply deposits nymphs in outer leaf sheaths. The elongated or oval eggs are hyaline to yellowish to pinkish. They are 0.3 by means of 0.5 mm. They are lined with wax. The eggs turn grayish red when about to hatch.

Nymph: The newly hatched nymphs remain crowded within the waxy filaments for 6-10 hours before they disperse to various parts of the same plant. The pale yellowish nymph is active and crawls about the plant for a while, settles itself on the stem and turns dark yellow after a day. The body gets covered with waxy material on the second day. The first instar nymphs or crawlers measure 0.1-0.2 mm wide and 0.3-0.5 mm lengthy. Mature crawlers are 3-4 mm long.

Adult: Nymphs and adults being wingless look alike. Females are reddish, oval, soft-bodied, and living in colonies inside the leaf sheath. Males are small, slender, pale-yellow, having a single pair of wings and a style like process at the end of the abdomen but lack mouthparts. Males are seldom found in the colonies, so reproduction is mainly through parthenogenesis. The light yellowish male adults have an unmarried pair of wings and a waxy style-like procedure on the end of the stomach. The first and heart legs of the male are approximately equivalent, while the last or 3rd legs are longer. The body is 0.7-0.9 mm long. Adult women folk are rectangular and wingless. They are reddish-white and soft-bodied. Their body is covered with a definite waxy or powdery coating. They measure about 1.2- 3.0 mm long and 0.5-1.5 mm large. They resemble woodlice in shape.

Stunting is a harmful symptom led to by means of different insect pests like root grubs and rice root aphids. However, the presence of rice mealy worms confirms its harm to the rice plant. To confirm the cause of damage, check for the presence of insects: hyaline to yellowish to pinkish eggs. crawlers or nymphs, unwinged pink female adults, and winged pale-yellow males removing plant sap. Both adult and nymph mealybugs remove plant sap by sucking.

The rice mealybug is found in upland and rainfed environments. It is not common in irrigated rice. It occurs in great numbers all over the rainy season. The insect feeds on rice all over the tillering and stem elongation phases. Mealybugs are usually found feeding in colonies in somewhat protected areas such as between two touching fruits, in the crown of a plant, in branch crotches, on stems near the soil, or between the stem and touching leaves. A few mealybug species feed on roots. Dry periods and the presence of grassy weeds that harbor this insect pest favor the population buildup of the rice mealybug. Likewise, well-drained soils are also suitable for insect pests. The nymphs are active until they molt. They first stay under the body of the adult female and later crawl from plant to plant. They are also dispersed by wind. After dispersal, they stay between the leaf sheath and stem to feed and complete their entire larval development. After molting, the female attaches itself to the plant for life and grows in size. The adult females remain stationery and feed while the winged adult male flies off. The insect is abundant from April to early July. Two generations are completed during this period.

The mealybug is a small reddish-white, soft-bodied, wingless insect covered with filamentous materials. It lays 126-139 eggs in the leaf sheath and reproduces parthenogenetically. The egg period is 1-2 days; the nymphal period is 17-34 days; nymphs remain within the leaf sheath and suck the plant sap.

Life cycles vary somewhat by species. Adult females of most mealybugs lay 100-200 or more eggs in cottony egg sacs over a 10- to 20-day period. Egg sacs may be attached to crowns, leaves, bark, fruit, or twigs. An exception is the long-tailed mealybug, which produces eggs that remain within the female until they hatch.

Newly hatched mealybug nymphs (called crawlers) are yellow to orangish or pink, lack wax, and are quite mobile, but they begin to secrete a waxy covering soon after settling down to feed. Although older nymphs and adults have legs and can move, they don’t move very far or very rapidly. Nymphs molt through several instars before becoming adults.

Depending on species and environment, mealybugs may have two to six generations a year. Where climates are warm or plants are growing indoors, all stages may be present throughout the year. On deciduous plants such as grapevines, mealybugs may overwinter on or under bark as eggs (within egg sacs) or as first-stage nymphs.

Mealybugs are sometimes confused with other pests that produce waxy coatings, honeydew, and black sooty mold, including the cottony cushion scale, woolly aphids, and even some soft scales and whiteflies. Be sure to carefully examine the insect beneath the wax to identify it properly.

Mealybugs suck sap from plant phloem, reducing plant vigor, and they excrete sticky honeydew and wax, which reduces plant and fruit quality, especially when black sooty mold grows on the honeydew. Large accumulations of mealybugs, their egg sacs, and wax can be unattractive. High populations feeding on foliage or stems can slow plant growth and cause leaf drop; however, healthy plants can tolerate low populations without significant damage. Ground mealybugs, which are not very common in landscapes and gardens, feed on roots and can cause plant decline but are generally not seen until plants are dug up and roots are exposed.

1. Presence of hyaline to yellowish to pinkish eggs

2. Crawlers or nymphs, unwinged purple female adults and winged light yellow males disposing of plant sap

3. Appearance of wax overlaying the eggs, nymphs, and adults that stick at the stem or leaf

4. Not uniform development of wear and tear.

1. Large number of insects remain in leaf sheath and suck the sap, affecting plants in circular patches.

2. Plants become weak, yellowish, and very much stunted.

3. Presence of white waxy fluff in leaf sheaths. The infestation is referred to as ‘Soorai’ or ‘Chakdhora’ disease.

4. Wilting of plants

When conditions are favorable to the insect, high population of the pest can cause yellowing and stunting of the crop. Rice mealybug causes heavy losses to crops in Bangladesh, India, and Thailand. High pest density (>100 mealybugs/hill) can cause plants to wilt and die.

Mealybugs are very difficult to manage with insecticides. Fortunately, most species have natural enemies that keep their populations below damaging levels in outdoor systems such as landscapes and gardens. The best approach to managing mealybugs is to choose plants known to be less prone to problems, inspect plants for mealybugs before bringing them onto your property, and rely on biological control and cultural practices to keep mealybug numbers in check.

Mealybugs are often introduced into landscapes (and especially into indoor areas) on new plants or on tools or pots. Because adult females can’t fly and mealybugs can’t crawl very fast, they don’t rapidly disperse in the garden on their own. Inspect any new plants thoroughly for mealybugs before installing them. If you can’t remove all the mealybugs present, discard and destroy the plant or, if possible, take it back to the source.

Regularly inspect mealybug-prone plant species in your landscape or indoor plantings for mealybugs. If you find an infestation, physically remove the insects by handpicking or prune them out. Toss out older “grandmother” plants that may be a source of infestation for new plants. Check pots, stakes, and other materials for mealybugs and their egg sacs and dispose of any infested items.

If mealybugs are somewhat exposed, it may be possible to reduce populations on sturdy plants with a high-pressure or forcible spray of water. Repeat applications at several-day intervals may be necessary.

Avoid unnecessary applications of nitrogen fertilizer on plants with mealybugs. High rates of nitrogen coupled with regular irrigation may stimulate tender new plant growth as well as mealybug egg production.

If your landscape or interiorscape has a history of serious mealybug problems, consider using only plant species that are not prone to mealybugs for at least a year or two to reduce mealybug density and harborage potential.

Ground mealybugs are even more difficult to control than those that feed aboveground. Prevent the introduction of ground mealybugs and quickly dispose of infested plants before the pests can move onto clean plants.

Some physical controls are like:

• Early transplanting to reduce mealybug pressure.

• Remove grassy weeds which can harbor this insect.

• Application of raw coir pith, raw sugarcane trash and farmyard manure to reduce infestations.

• Destroy ant colonies as ants are commonly found with mealybugs.

• Ponding of irrigation water at 5 cm depth throughout the growing period.

• Monitor crops on a weekly basis during growing period.

• Continuous monitoring in upland rice and rainfed cultivation.

• Consider direct control actions as soon as pests are found.

• Removal and destruction of affected plants.

Many natural enemies feed on and kill mealybugs on fruit trees and woody ornamental plants in the landscape. These beneficial insects generally can be relied upon to keep numbers at tolerable levels. Natural enemies include a number of species of parasitic wasps that lay their eggs in or on developing mealybugs. Common parasites (or “parasitoids”) include species in the genera Coccophagus, Leptomastix, Allotropa, Pseudaphycus, and Acerophagus. Look for parasite pupae within mealybug colonies or emergence holes in mummified mealybugs. Leptomastix dactylopii is sold commercially for release in greenhouses, citrus groves, and interiorscapes, but it kills only the citrus mealybug. Some other biological control agents are small encyrtid wasps, spiders, chloropid fly, drosophilid, and lady beetles.

Naturally occurring predators of mealybugs include lady beetles, green and brown lacewings, spiders, minute pirate bugs, and larvae of predaceous midges. The mealybug destroyer lady beetle, Cryptolaemus montrouzieri, is the most important of these predators in many areas. It does not tolerate cold winters, so it is more common in southern California and in coastal areas. The mealybug destroyer can be purchased for augmentative release and is often released in greenhouses and interiorscapes or in citrus orchards after a cold winter has killed off native populations. Adult beetles are bicolored with reddish-brown heads and hind ends and black in the middle; older mealybug destroyer larvae are covered with white wax, which makes them look somewhat like large mealybugs. When releasing mealybug destroyers, focus on periods when there are many mealybug egg sacs, because the lady beetles require mealybug eggs as food to stimulate their own reproduction. There is little point in releasing them when mealybug numbers are low or when they are not reproducing.

Operators of greenhouses or interiorscapes with regular mealybug problems can establish their own mealybug destroyer colonies for self-release. The lady beetle can be reared in wide-mouth jars on mealybugs grown on sprouted potatoes or other hosts. A ring of petroleum or other sticky material smeared inside jars around the top will prevent the flightless mealybugs from crawling out but allows the lady beetles to fly out into the greenhouse.

Preserve naturally occurring biological control agents by avoiding use of broad-spectrum insecticides for any pests in the area. Also keep ants out of mealybug-infested areas and plants because ants protect mealybugs from their natural enemies.

Non Chemical methods usually provide sufficient control for outdoor plantings in gardens and landscapes. Home and garden insecticides are not very effective for mealybugs, especially on larger plants. The mealybugs’ waxy coating repels most contact insecticides, and their habit of aggregating in hidden locations makes them hard to reach.

• Spraying of 1% Azadiractin at a rate of 400 ml per acre.

• Spraying of fish oil resin soap (25 g per litre).

• Spraying of Buprofezin 25% SC (e.g., trade name: Applaud, Flotis, Blunt) at a rate of 300 ml/acre. [WHO Class III (slightly hazardous)].

• Spraying of Thiamethoxam 25% WG (e.g., trade name: Tafgor, Rogor, Rogorin) at a rate of 50 g/acre. [WHO Class II (moderately hazardous)].

• Spraying of Dimethoate (30 EC) 400 ml/ ac

For houseplants, greenhouses, and interiorscapes where it is not physically possible to remove mealybugs and where biological control may not be feasible, spot treatment may be used to suppress populations of aboveground feeding mealybugs.

Spot Treatment with Isopropyl Alcohol

On small infestations on houseplants, a 70% or less solution of isopropyl (rubbing) alcohol in water may be dabbed directly on mealybugs with a cotton swab to kill them or remove them. Test the solution out on a small part of the plant 1 to 2 days beforehand to make sure it does not cause leaf burn (phytotoxicity). In some cases, a much more diluted solution may be advisable. Where infestations are extensive, a 10-25% solution of isopropyl alcohol can be applied with a spray bottle. You will need to repeat this procedure every week until the infestation is gone [1]

Insecticides

Insecticidal soaps, horticultural oil, or neem oil insecticides applied directly on mealybugs can provide some suppression, especially against younger nymphs that have less wax accumulation. Be sure to test for phytotoxicity of these materials prior to treatment as well.

Products containing the systemic insecticide dinotefuran may reduce mealybug numbers on some landscape plants, and plant spikes or granules containing the related insecticide imidacloprid may reduce mealybug crawler numbers on houseplants. These neonicotinoid products are less reliable against mealybugs than against other piercing-sucking insects in many situations. Their use should be avoided, when possible, especially on flowering plants, because of potential negative impacts on natural enemies and pollinators.

Other insecticides, including pyrethroids, are also labeled for some situations but may not be much more effective than soaps and oils and can be devastating to natural enemies. Be aware that none of the available insecticides will likely provide complete control of all individuals, and that you will need to monitor and treat again as needed. When infestations become severe, consider discarding houseplants rather than repeatedly treating them with insecticides. On outdoor plants, cultural practices and biological control should be adequate for suppressing mealybugs in most situations. [1]

• Avoid resurgence pesticides.

• Always wear protective clothing when handling chemicals, follow product label instructions.

No information found

No information found

1. https://ipm.ucanr.edu/PMG/PESTNOTES/pn74174.html

2. https://en.wikipedia.org/wiki/Brevennia_rehi

3. https://agritech.tnau.ac.in/crop_protection/rice/crop_prot_crop_insectpest%20_cereals_paddy_m14.html

4. http://www.eagri.org/eagri50/ENTO331/lecture01/006.html

5. https://plantwiseplusknowledgebank.org/doi/10.1079/pwkb.20207800533

6. https://agrinfobank.com.pk/rice-mealy-bug/

WARNING ON THE USE OF PESTICIDES