*3.1.1 Distribution*

The CLM is a most destructive pest of citrus nurseries, top grafting trees, and also citrus growing in plastic greenhouses in various parts of the world [220]. This pest is native to eastern and southern Asia occurring in China, India, Thailand, Japan, and Vietnam [221, 222]. It was reported in southern Florida in 1993 [223, 224], most of Caribbean region and Southern part of USA [225, 226]. It has also been reported in Northern part of South America, Uruguay, and Mediterranean coast of Europe [227], in the Middle East [228], Reunion Island [229], and North Africa [227]. In 1999, its damage was reported from Arizona [230].

#### *3.1.2 Eco-biology*

The number of eggs laid per female is about 30–75. The eggs are translucent, white, and appear similar to tiny water droplets. Usually female lays eggs underside of leaves and along the leaf mid-vein toward leaf petiole. Eggs hatch in 2–10 days according to the environmental conditions. CLM has four larval stages and having total developmental time of about 5 to 20 days. Upon hatching, larvae immediately begin mining beneath the epidermal cells. The 1st instar larvae are green in color, translucent, and difficult to detect. The 2nd and 3rd instar larvae are also translucent and yellow-green in color. The 4th instar larvae are clearly visible and form silken cocoon within mines. 4th instar larva curls the leaf edge as silk dries over the cocoon and forming a protective shell called pupa. In initial stage, pupa is yellow-brown in color but at later stage it becomes darker. About 6–22 days are required to complete the pupal duration. The adult is white and has silvery scales on the dorsal surface of forewings and distinctive black spots on the tip (**Figure 4**). The moth is small and of the size of mosquito and active during early morning and evening. The entire life cycle of CLM is completed in 14–50 days depending on temperature of the environment [230].

#### *3.1.3 Damage*

The CLM damages the trees by forming mines especially underside of young leaves and the fruit is rarely mined (**Figure 5**). The leaf mining by CLM results in partial chlorosis, necrosis, leaf deformation, and ultimately causes defoliation, which reduces the photosynthetic activity of plants. The mining in spring flush causes more damages as it is responsible for fruit development than that of fall flush. Besides this, mining also facilitates the entry point for number of plant pathogens such as bacterial citrus canker. The bacterium *Xanthomonas citri* (Hasse) is the cause of an important disease in citrus plant called Asian citrus canker [231]. The canker-infected tree produces lesions on leaves, stems, and fruits, which results in defoliation, fruit drop, blemishing on fruit, twig dieback, and general tree decline [232–234].

#### *3.1.4 Management*

#### *3.1.4.1 Chemical control*

Many farmers apply insecticides to mitigate the effect of CLM as they see visual impact of foliar damage on trees. This control measure is expensive and often ineffective because none of product provides long-term control than just for two week [235, 236]. To control the CLM, the chemical control is often inappropriate strategy because of high cost to manage the pest, risk of development of resistance in pest population, accumulation of pesticides residues in food and also in ground water, effect on natural control agents, harmful effect on field workers, and also to environment [237]. Tan and Huang [238] also reported development of resistance to pesticides in CLM.

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

#### **Figure 4.**

*Adult stage of* Phyllocnistis citrella *with distinct black spots at the dorsal surface of both forewing and hindwing. Photograph by Jack Kelly Clark, University of California, Statewide IPM program.*

#### **Figure 5.**

*A newly developed leaf of Kinnow mandarin is under the infestation of three larvae of* Phyllocnistis citrella. *Feeding of larvae upon leaf tissues results in the development of prominent mines, which is one of the diagnostic damage patterns of* P. citrella*. Photograph was taken by Dr. Muhammad Babar Shahzad Afzal at citrus nursery of Citrus Research Institute, Sargodha, Punjab, Pakistan on August 29, 2017.*

#### *3.1.4.2 Monitoring using traps*

Pheromones traps should be used to determine pest population abundance in field. However, control decision is based on sampling of active larvae. Usually, monitoring should be done in February through May and September–October, at that time 50% of trees are actively flushing. Randomly ten leaves are selected and live larvae are observed with hand lens. The young trees should be treated when 30% of leaves have active mines with live larvae, while older trees are treated unless severely damaged.

#### *3.1.4.3 Cultural practices*

In the irrigated areas of citrus production, CLM population might be suppressed by modifying the trees to produce alternate flushing by managing the irrigation

and fertilizer application but it is not possible in areas where summer rainfall is too high such as Florida's subtropical climatic conditions. Other management options such as development of host plant resistance also do not provide long-term control and there is no clear evidence that varieties are resistant to attack of CLM. The water sprouts usually develop on branches and above grafting on tree trunk and rapidly produce the new flushes for long period of time. Removal of such water sprouts is crucial because it provides sites for oviposition. Besides this, the water sprouts below root stock should also be removed as they do not produce desirable fruits [239].
