Mealybugs are common sap-feeding pests that infest a wide range of houseplants and greenhouse plants. Mealybugs are insects in the family Pseudococcidae, unarmored scale insects found in moist, warm climates. Mealybugs occur in all parts of the world. There are about 275 species of Mealybugs known to occur in the continental United States. Mealybugs are common insect pests that tend to live together in clusters in protected parts of plants, such as leaf axils, leaf sheaths, between twining stems and under loose bark. They suck sap from plants and then excrete the excess sugars as a substance called honeydew. This lands on the leaves and stems where it is often colonized by sooty moulds, giving the surfaces a blackened appearance. Mealybugs are active all year round on houseplants and in greenhouses.
Since mealybugs are insects, they do not undergo complete metamorphosis in the true sense of the word, i.e. there are no clear larval, pupal and adult stages, and the wings do not develop internally. However, male mealybugs do exhibit a radical change during their life cycle, changing from wingless, ovoid nymphs to wasp -like flying adults. Mealybug females feed on plant sap, normally in roots or other crevices, and in a few cases the bottoms of stored fruit. They attach themselves to the plant and secrete a powdery waxlayer used for protection while they suck the plant juices. The males on the other hand are short-lived as they do not feed at all as adults and only live to fertilize the females.
They are considered pests as they feed on plant juices of greenhouse plants, house plants and subtropical trees and also act as a vector for several plant diseases. Mealybugs are found mainly on greenhouse plants and houseplants, especially cacti and succulents, African violets, bougainvillea, citrus plants, fushcia, grapevines, hoya, orchids,oleander, passion flower, peach and tomato. Some other mealybug species can attack outdoor plants, such as , laburnum, New Zealand flax.
Mealybugs tend to be serious pests in the presence of ants because the ants protect them from predators and parasites. Mealybugs also infest some species of carnivorous plants such as(pitcher plants; in such cases it is difficult to eradicate them. Small infestations may not inflict significant damage. In larger amounts though, they can induce leaf drop. Infestations are usually first noticed as a fluffy white wax produced in the leaf axils or other sheltered places on the plant. The insects or their orange-pink eggs can be found underneath this substance
Heavy infestations may result in an accumulation of honeydew. This makes plants sticky and encourages the growth of sooty moulds, giving the leaf and stem surfaces a blackened appearance. Damage is caused by mealybugs feeding on host tissues and injecting toxins or plant pathogens into host plants. In addition, mealybugs secrete a waste product, honeydew, which is a syrupy, sugary liquid that falls on the leaves, coating them with a shiny, sticky film. Honeydew serves as a medium for the growth of sooty mold fungus that reduces the plant’s photosynthetic abilities and ruins the plant’s appearance. Feeding by mealybugs can cause premature leaf drop, dieback, and may even kill plants if left unchecked. Severe infestations will reduce plant vigor and stunt growth. Heavy infestations may cause premature leaf fall.
Mealybugs can be found on all plant parts, but especially roots, rhizomes, pseudobulbs, and the underside of leaves. They are adept at hiding on roots and rhizomes deep in the potting media, in crevices and under sheaths. Unlike scales, mealybugs wander in search of feeding places and will leave plants, and hide under rims of pots and trays, in bench crevices, and even drop from overhead plants. Spread of crawlers can occur both indoors and outdoors by floating on breezes or air currents produced by circulating and heater fans. The occurrence of infestation hotspots may be due to crawlers settling on plants where the air currents are the weakest. Similar effects are found with aphids, scales, and spider mites.
There are different kinds of Mealybugs that affect different crops like bamboo mealybug, citrus mealybug, and cotton mealybug. There have been numerous instances of crop damage owing to mealybug all over the world. The most prominent amongst them is the incident reported widely about Bt. Cotton getting affected in India due to mealybugs. The article is as follows:
Bt cotton not pest resistant
Gur Kirpal Singh Ashk, TNN Aug 24, 2007, 02.39am IST
PATIALA: The attack of the mealy bug on the Bt cotton crop in Punjab has stripped it of its aura and destroyed the illusion that it is resistant to all pests. Two years back the Punjab government had described the introduction of Bt cotton as a great achievement. However, this season, the third year after its introduction, thousands of acres in the Malwa region are facing attack by the pest.
Desperate farmers, gripped by panic, are resorting to intensive pesticide sprays and some of them have started ploughing their fields. The state directorate of agriculture has put out advertisements in vernacular daily papers prescribing a list of pesticides for spray to control the bug.
Now agricultural experts have also started saying Bt cotton is not totally free from attacks by pests. Punjab agricultural director BS Sidhu said he or his department had never claimed that Bt Cotton was pest free. “Rather, we had told cotton growers that, except for the bollworm group, other pests could attack Bt cotton like any other cotton crop. Two years back the Punjab government had described the introduction of Bt cotton as a great achievement.
However, this season, the third year of its cultivation, thousands of acres in the Malwa region are facing attack by the pest. Desperate farmers, gripped by panic, are resorting to intensive pesticide sprays and some of them have started ploughing their fields.
The state directorate of agriculture has put out advertisements in vernacular daily papers prescribing a list of pesticides for spray to control the bug.
Umendra Dutt, executive director of the Kheti Virasat Mission (KVM), Punjab, put a question before them that if Bt cotton was safe from only one pest then why was the hype about Bt cotton’s invincibility created. He said earlier cotton seeds were available for Rs 20 to 30 per kg and the farmers were then lured to purchase the Bt cotton seed for Rs 3,600 per kg.
The previous Congress government had put out official advertisements that made tall claims about the advantages of Bt cotton, among them an increase in yield by 25% to 28% per hectare, net increase in income by Rs 10-15,000 per hectare and savings on agrochemicals up to Rs 1,000 per hectare.
Talking to TOI, Dutt claimed within a span of two months Rs 500 crore worth of pesticides to control the mealy bug were sold and, if the trend continues, the total sum may surpass Rs 800 crore.
Apart from pesticides farmers had also applied chemical fertilizers like DAP and urea. “Not only causing huge losses to the already distressed farmers, the mealy bug has destroyed the illusion of Bt cotton’s infallibility.
“As the mealy bug is destroying the cotton crop in Punjab’s Malwa region, in desperation the farmers are intensively spraying pesticides that are toxic and costly on their crop.”
There have been various other reports pertaining to damages caused by mealybugs in the agricultural sector in countries like Thailand, etc. Early in 2008, organic farmer Ram Kalaspurkar of Yavatmal, Maharashtra in India had vivid photographic evidence of mealy bug infestations on demonstration plots of different seed companies in Vidarbha, all bearing the Bollgard label. He was convinced that the mealy bug entered Vidarbha cotton fields through Bt cotton seeds imported from the US.
Kalaspurkar described how, when the cotton plants died at the end of the season, the mealy bug moved to nearby plants such as the Congress weed. By mid-June when farmers were ready to plant the new cotton crop or another crop, the bug had multiplied enormously.
A year later, scientists at the Central Institute for Cotton Research (CICR) in Nagpur, India, corroborated Kalaspurkar’s findings, reporting widespread infestation of an exotic mealy bug species on Indian cotton. The scientists conducted a survey at 47 locations in the nine cotton-growing states, and found two mealybug species infesting the cotton plants from all nine states: the solenopsis mealy bug, Penacoccus solenopsis, and the pink hibiscus mealy bug, Maconellicoccus hirsutus. However, P. solenopsis was the predominant species, comprising 95 percent of the samples examined. Furthermore, the scientists confirmed that P. solenopsis is a new exotic species to India originating in the US, where it was reported to damage cotton and other crops in 14 plant families.
During 2006, the mealy bug caused economic damage, reducing yields by up to 40-50 percent in infested fields in several parts of Gujarat. At around the same time, mealy bug infestations were found in all the nine cotton-growing states: Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh, Maharashtra, Tamil Nadu, Andhra Pradesh and Karnataka. Severe economic damage was reported in 2007 in four districts of Punjab, two districts of Haryana, and low to moderate damage in parts of Maharashtra, Tamil Nadu and Andhra Pradesh. Nearly 2 000 acres of cotton crop were destroyed by the mealy bug by mid-July 2006, and over 100 acres of bug-infested Bt cotton was uprooted in Arike-Kalan village in Bathinda. A report published by the Centre for Agro-Informatics Research in Pakistan in 2006 also stated that the exotic mealybug P. solenopsis had destroyed 0.2 million bales and 50 000 acres of cotton area across Pakistan, especially in Punjab and Sindh provinces. It warned that the pest was still increasing, and could result in an epidemic in the cotton-growing areas if unchecked.
Thus is the unstemmed devastation caused by this tiny bug. Methods hitherto used to combat this menace include the use of toxic pesticides, which come with their own set of cons. A effective and green solution needs to be devised to counter this destruction. Termirepel™, a product by C Tech Corporation aims to do just that. Termirepel™ is a non-toxic, non-hazardous insect and pest repellant. It can be best described as a termite aversive. It is effective against a multitude of other insects and pests like weevils, beetles, thirps, bugs, etc. It works on the mechanism of repellence and therefore does not kill the target as well as non-target species. Being non-toxic, it does not harm the soil and environment. Termirepel™ can be added to a thin agricultural film to protect cotton and other crops. It can also be incorporated in irrigation pipes to ward of pests.