*2.3.4.3.1 Predators*

The mealybug destroyer *Cryptolaemus montrouzieri* Mulsant (Coleoptera: Coccinellidae) from Australia was introduced into California in 1982, which effectively controlled the CMB infestation in field. This coccinellid predator provides the effective control by reducing the eggs masses, nymphs, and adult population of CMB [152, 153] but Hattingh and Tate [154] found that *C. montrouzieri* is sensitive to IGR, pyriproxyfen, which is used for control of red scales in citrus orchards. It is recommended to release about 500 *C. montrouzieri* beetles per acre in the citrus orchard for effective control [155]. The other most common predators of CMB include *Scymnus syriacus* (Mars.) (Coleoptera: Coccinellidae) and the chrysopid predator, *Chrysoperla carnea* (Stephens) (Neuroptera: Chrysopidae) [156]. Efforts should be made to conserve and enhance the effectiveness of these predators in the orchards by relying less on chemical control.

### *2.3.4.3.2 Parasitoids*

The hymenopteran wasps are most abundant biological control agent for CMB in various regions of the world. The two parasitoids *Leptomastix dactylopii* Howard and *Leptomastidea abnormis* (Girault) (Hymenoptera: Encyrtidae) are used as bio-control insects against CMB [157–159]. However, Mani [160] reported that the indigenous, *Coccidoxenoides peregrines* (Timberlank) (Hymenoptera: Encyrtidae) is more abundant and having parasitism rate of about 10 to 30%. Krishnamoorthy and Singh [161] reported the successful example of release of *L. dactylopii* in India in 1983 on mandarins. Within two month of release, it provided 100% parasitism rate by feeding on all stages of CMB. In South Africa, *C. peregrines* are reared at commercial level and provide good control against CMB [147].

#### *2.3.4.3.3 Pheromone*

A synthetic pheromone [(1R-cis)- 2, 2-dimethyl 3-(1-methylethenyl) cyclobutyl methyl acetate] of CMB elicits a positive response against male adults and half-life of this pheromone is about 2 weeks in field and maximum males are caught at the dose of 400–700 mg [162].

#### *2.3.4.3.4 Entomopathogenic nematodes*

The entomopathogenic nematodes (EPN) have ability to control the wide range of insect pests including CMB and can be applied as bio-control agent. Once they penetrate inside the host haemocoel and release symbiotic bacteria, the host is killed within 24–48 h. EPN have no negative effect on environment, human, and other vertebrates. The six indigenous species have been used to access the susceptibility of CMB. Three heterorhabditids species (*H. zealandica*, *H. safricana*, and *H. bacteriophora*) and three

steinernematids (*S. yirgalemense*, *S. khoisanae*, and *S. citrae*) were evaluated. *The S. yirgalemense* and *H. zealandica* caused highest mortality of about 97 and 91%, respectively, as compared to the other four tested species of nematodes [125], therefore these two species should be incorporated in the biological control program of CMB.

#### *2.3.4.4 Chemical control*

The management strategies for control of CMB have been mainly based upon biocontrol agents. However, the control with chemical method is most common and widely used strategy because of poor adaptation of natural enemies in varying climatic conditions [10]. The control of CMB by using chemicals can be difficult and effectiveness of chemicals depends on correct application at time when needed. However, acceptable control of CMB may not be achieved with single treatment; the follow-up application of chemicals is necessary. The effective control can be achieved if application is started at the time of initial infestation of pest population [163]. To preserve the natural enemies, it is mandatory to use selective insecticides for control of CMB [164]. Kütük et al. [124] conducted a study to evaluate the effect of biological and chemical control against CMB. They found that summer oil and spirotetramat are compatible with natural enemies, for example, *C. montrouzieri* and *L. dactylopii*, while these natural enemies showed incompatibility with chlorpyrifos-ethyl, due to its side effect on these bio-control agents. Due to cryptic nature and protection with waxy material of CMB, it is necessary to use the chemicals with high vapor pressure. The major insecticides recommended for the control of CMB are from organophosphate (e.g., chlorpyrifos, malathion, dimethoate, azinfos-methyl, dichlorvos parathion, diazinon, and pirimiphos-methyl) and carbamate group (e.g., methomyl, thiodicarb, and carbaryl). These insecticides are applied individually or are mixed with mineral oils [141, 165]. The excessive use of these insecticides for the control of CMB might lead to development of insecticide resistance; therefore, some alternative insecticides such as dinotefuran, acetamiprid, imidacloprid, and thiamethoxam from neonicotinoid group can be employed in the management program of CMB [141].

#### **2.4 Citrus thrips**

Citrus thrips is piercing-sucking insect, which belongs to order Thysanoptera and family Thripidae. Various species of phytophagous thrips have been reported upon citrus in the world such as *Scirtothrips citri* (Moulton), *S. aurantii* Faure, *S. dorsalis* (Hood), *S. inermis* Priesner, *Pezothrips kellyanus* Bagnall, *Megalurothrips kellyanus* (Bagnall), western flower thrips *Frankliniella occidentalis* (Pergande), *F. bispinosa* (Morgan),*Thrips major* Uzel,*T. hawaiiensins* Morgan,*T. meridionalis* (Priesner),*T. angusticeps* Uzel,*T. obscuratus* (Crawford),*T. tabaci* Lindeman, *Heliothrips haemorrhoidalis* Bouché, *Chaetanaphothrips signipennis* (Bagnall), and *C. orchidii* Moulton [166–175].

#### *2.4.1 Distribution*

Different species of thrips reported on citrus have worldwide distribution. Among all the species, *S. citri* commonly known as citrus thrips or California citrus thrips is of great economic importance in USA and Asia. In USA, it is infesting citrus particularly oranges (Navel oranges), grapefruit, and lemons in California, Arizona, northwestern Mexico, Florida, Washington, and Georgia [174, 176–179]. In Asia, *S. citri* has been

*Ecology, Biology, Damage, and Management of Sucking and Chewing Insect Pests of Citrus DOI: http://dx.doi.org/10.5772/intechopen.109846*

recorded in India, China, Iran, and Thailand [179, 180]. Another thrips of economic importance on all type of citrus plantations (lemons, oranges, and grapefruits) is *P. kellyanus*, commonly known as Kelly's citrus thrips (KCT). *P. kellyanus* is Mediterranean in its origin and has been distributed in various geographical regions around the world in Australia [170, 181], New Zealand [182], Southern France [183], Cyprus [171], Italy [184, 185], Spain [186], Turkey, and Greece [187, 188], Portugal [189], Chile [190], Morocco [191], and Tunisia [175].

#### *2.4.2 Eco-biology*

Citrus thrips complete their life cycle from egg to adult stage in two to three weeks. The duration of each stage varies with the host species attacked, as well as temperature and humidity of the environment [192]. Citrus thrips is hemimetabolous insect and has following stages: eggs, 1st and 2nd instars or larvae (active feeding immature stages), 1st and 2nd stage pupae (non-feeding instars known as pre-pupa and pupa), and adult or imago (equipped with fringed wings) [176]. The adult female prefers to lay eggs deeply inside the soft and young tissues of leaves, stems, and floral buds with the help of saw-like ovipositor; the egg laying-puncture is completely closed after egg laying. On an average 25–35 eggs are laid per female with maximum of 250 during its life time. Fertilized eggs mostly develop into females and seldom to males. However, only male offspring is developed from unfertilized adult females. Eggs hatch in 5–8 days depending upon the temperature. First and second instars are active feeders and complete their development in 4–14 days by feeding upon soft leaves and under the sepals of tiny fruits. The third and fourth instars known as pre-pupa and pupa, respectively, are passive stages and do not feed, and they spend their time on the ground, tree crevices or inside the curled leaves. Development period from egg to adult formation varies according to temperature such as it requires 16 and 13 days at 25°C and 31°C, respectively. The adult female lives for 26–30 days at 31°C. The number of generations of citrus thrips ranges from 8 to 12 in various agro-climatic conditions. The activity of thrips commence usually in spring and at the beginning of summer at the temperature range of 20–25°C as it coincides with the flowering period and formation of young fruits on trees. The rise in temperature above 30°C and absence of flowers and young fruits result in decrease in thrips population density [175, 177, 193–196].

#### *2.4.3 Damage*

Citrus thrips attack usually commence during the flowering stage mostly at petal fall or new fruit formation. Thrips nymphs (1st and 2nd instars) and adults with the help of their asymmetrical piercing-sucking stylet inflict damage to citrus leaves, flowers, buds, and young fruits by extracting the cell contents. Feeding activity upon newly developed citrus flush often results in curling of leaves, along with the appearance of silvery or grayish scars upon the leaves. The damage also results in poor development and growth of infested plant [197–199]. Fruit scarring is the diagnostic damage pattern of citrus thrips, which usually starts when fruit is developing (≤2.5 cm diameter) (**Figure 3**).

Due to thigmotactic nature of citrus nymphs, they prefer to feed under the calyx of young fruit, which results in the development of ring-shaped scar around the calyx or fruit peduncle. In some citrus cultivars such as Navel oranges, thrips activity develops the scaring marks at the styler end of the fruit surface. "Russetymarking" and "tear staining" upon the peel or ring of citrus fruits such as in oranges is also sign of thrips induced damage. Scarring marks are mostly observed upon fruits, which lie outside the canopy. Thrips herbivory upon developing citrus fruits also causes abortion, irregular development or deformity, discoloration, and necrosis of the fruit [200]. Blemishes and scar patterns (cosmetic losses) due to feeding of citrus thrips enormously reduce the market value of citrus fruits leading to export and monetary losses to citrus growers and exporters [184, 201, 202]. Abrasion and scarring of citrus fruits by citrus thrips negatively affects the physiochemical qualities of fruits such as higher percentage of TSS and sugar/ acid ratios, lower titratable acidity, increase in water loss, and more rapid weight loss [203].
