Domain: Eukaryota

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Diptera

Family: Cecidomyiidae

Genus: Orselolia

Species: O. oryzae Binomial

Name: Orselolia oryzae (Wood Mason)

It is a major insect pest of rice in Southern and Southeast Asia. The pest is distributed in various regions of Bangladesh, Bhutan, Cambodia, China, India, Indonesia, Lao PDR, Myanmar, Nepal, New Guinea, Pakistan, Sri Lanka, Thailand, and Vietnam. It is also found in rice-growing regions of Africa.

Host Range
 Mainly Rice and corn. Oryza sativa, Cynodon dactylon, and Isachne aristatum.

• Egg: Eggs are elongate and tubular. The newly laid eggs vary from white to pink, red, and yellow colors. The eggs turn like shining-ambers before hatching. They are laid either singly or in groups of 3-4 at either on the base of the plant, the ligule, the leaf blade, or on the leaf sheath. The egg development lasts for 3-4 days.
• Larva: The larva is maggot-like, about 1 mm long, and is grayish-white in color. It situates itself at the growing point of the apical or side buds of a node in order to feed. One larva occupies a single tiller. The larval feeding damage causes the formation of a tubular gall at the base of the tiller and inhibits growth of the leaves and the panicle. The gall enlarges at the base of the tiller as a result of the larva’s continuous feeding. There are 3-4 larval stages, which last for 15-20 days.
• Pupa: The pupa is light-pink with abdominal spines and it turns red before emergence. It is 2-2.5 mm long and 0.6-0.8 mm wide. Pupation is 2-8 days. Both the larval and the pupal developments are completed inside the gall.
• Adult: The adult looks similar to a mosquito. The female midge has a bright red abdomen while the male has a yellow-brown body. The male is generally smaller than the female. It has a wing expanse of 3.0-3.5 mm. Both adults have bead-like antennae with more than 10 segments. The adults are nocturnal. They are easily collected using light traps. They mate soon after emergence. A female midge mates only once. It can lay as many as 100-200 eggs in its lifespan of 4 days. The male midge lives only 12 to 18 hours.

Most of the time confusion is created with yellow stem borer.

The Asian rice gall midge is found in irrigated or rainfed wetland environments during the tillering stage of the rice crop. It is also common in upland and deep-water rice. The adults are nocturnal and can easily be collected using light traps. During the dry season, the insect remains dormant in the pupal stage.

The adults are mainly nocturnal and hide during the day. The females lay small batches of eggs (two to six) on the undersides of rice leaves, totalling 100-400 in a lifespan. The eggs are red at first, but by the time they hatch, two to four days later, they are chocolate-brown. The tiny larvae crawl down the leaf sheath till they reach the leaf axil where they bore their way into the stem. After feeding for about ten days and forming a gall, they pupate inside. Four to seven days later they use spines on the tip of the abdomen to make a hole in the gall near its tip. Here the adult insects emerge. They live for three or four days, and there may be as many as eight generations of midge in the year. The lifecycle of Asian rice gall midge (Orseolia oryzae) consists of the following four distinct stages: Egg stage: The lifecycle begins with tiny red-brown eggs, measuring upto 0.44 mm in length and 0.25 mm in width, deposited singly or in groups on various parts of the host plant. These eggs hatch within 3-4 days under favorable conditions (24-35°C). Larval stage: Upon hatching, the newly emerged larvae are spindle-shaped and embark on a downward journey, reaching the central shoot of the apical or side buds within a day. These larvae equipped with a pair of antennae and kidney-shaped eye spots, progress through three distinct instars. The first instar larvae, measuring 0.50 × 0.127 mm, are characterized by a brown spot on the head region, spines on the penultimate and last segments, and one pair of open spiracles on the eighth abdominal segment. The second instar larvae, measuring 1.5 × 0.4 mm, shed the spines on the penultimate segment and retain only three pairs of short spines on the last segment. The spot on the head region divides into two comma-shaped sections. The third instar larvae, measuring 3.2 × 0.8 mm, exhibit nine pairs of spiracles and a heavily chitinized Y-shaped sternal spatula. These larvae, the largest of the three instars, play a crucial role in inducing gall formation. Pupal stage: The mature larvae transition into the pupal stage as soon as the tubular gall takes shape. This transition is preceded by a short prepupal period of about a day. The pupal stage, lasting 4-5 days at 24-35°C, is characterized by heavily chitinized cephalic horns and two similarly chitinized horns below the compound eyes. The male pupa can be distinguished from the female pupa by the shorter abdomen and visible claspers. Adult stage: Following the pupal stage, the adult Asian rice gall midge emerges as a tiny, winged insect. These adults, with females outnumbering males, exhibit a lifespan of 1-5 days. They mate readily, with females laying 200-285 eggs during their lifetime. The life cycle, from egg to adult emergence, is completed in 14-21 days under optimal conditions (26-30°C and 82%-88% RH). The Asian rice gall midge is a fly about the size of a mosquito. The females are about 3.5 mm (0.14 in) long, bright red, with broad abdomens and dense short hair, while the males are slightly smaller, yellowish-brown, and more slender. O. oryzae and O. oryzivora are morphologically, and even microscopically, indistinguishable, and so DNA differentiation methods have been developed.

The infested rice plant has a hollow cavity or a tubular gall at the base of a tiller which does not bear panicle. Its feeding damage also causes elongation of leaf sheaths called ‘Onion leaf or Silvershoot’. The gall is a silvery-white hollow tube which has a size of 1 cm wide and 10-30 cm long.

The larvae of the Asian rice gall midge irritate the tissues of the rice plant which forms a gall commonly known as a “silver shoot” or “onion shoot”. This is a pale cylindrical, hollow tube with a green tip replacing the normal culm (stem). The gall is formed from the walls of the leaf sheath growing together, after which the culm stops developing. The stem is stunted and the seed-head does not develop. When the adult insects emerge, the gall withers away and the shoot dies. The plant may respond by producing more tillers, but these usually become infected in their turn. The disease may be localized and patchy or widespread throughout the crop.

The most obvious symptom caused by O. oryzae is the development of ‘onion shoot’ galls in growing crops. These galls are easily seen, especially as they often have a light-colored silvery appearance (‘silver shoots’) and are quite unlike the symptoms produced by other pests or diseases. There is a superficial resemblance to ‘dead heart’ symptoms produced by lepidopterous stem borers, but the midge galls are easily distinguished as they are hollow, elongated cylinders, not dead rolled leaves. When midge infestations are at a low level there will not be any obvious effect on the incidence of ear-head formation, but severe infestations will stunt plants, suppress heading, and enhance tillering. In a nutshell:

1. Plants/Growing point/dwarfing; stunting
2. Plants/Leaves/abnormal colours
3. Plants/Leaves/abnormal forms
4. Plants/Leaves/abnormal forms
5. Plants/Leaves/internal feeding

Rice gall midge forms a tubular gall at the base of tillers, producing elongated silver leaf sheaths called onion leaf or silver shoot (about 1 cm wide and 10-30 cm long). The affected tiller inhibits the growth of leaves and fails to produce panicles. Plant stunting and leaf deformity, wilting and rolling are also symptoms caused by drought, potassium deficiency, salinity, and by rice thirps. To confirm the cause of the problem, check for the presence of insects. Particularly, elongated – tubular eggs and maggot-like larva Feeding inside developing buds.

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. 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.

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

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1. https://en.wikipedia.org/wiki/Brevennia_rehi
2. https://agritech.tnau.ac.in/crop_protection/rice/crop_prot_crop_insectpest%20_cereals_paddy_m14.html
3. http://www.eagri.org/eagri50/ENTO331/lecture01/006.html
4. https://plantwiseplusknowledgebank.org/doi/10.1079/pwkb.20207800533
5. https://agrinfobank.com.pk/rice-mealy-bug/
6. https://ipm.ucanr.edu/PMG/PESTNOTES/pn74174.html
7. WARNING ON THE USE OF PESTICIDES