**1. Introduction**

Citrus is one of the largest grown fruit crops in various tropical and subtropical regions of the world, including Brazil, China, USA, India, Pakistan, Italy, Spain, Australia, and Argentina. The genus *Citrus* includes various species of oranges, mandarins, grapefruits, limes, and lemons, which belong to Rutaceae [1, 2]. The production of citrus is limited by biotic (insect pests and pathogens) and abiotic factors (temperature, humidity, soil conditions, and availability of water). Within biotic factors, insects are major constraints in the optimum production of citrus [3–5]. About 250 species have been reported to cause damage to citrus plants but only few pests become a regular problem and cause heavy damage [6]. Overall, the yield losses due to activity of citrus insect pests may reach to 50% without timely diagnosis and management. Citrus insect pests are categorized into sucking and chewing. The ecobiology, damage pattern, and management strategies for each of these citrus pests are discussed in detail in this chapter (summary of citrus insect pests is also given in **Table 1**). Proper pest identification and understanding the eco-biology and damage patterns of citrus insect pests can help to devise and implement suitable pest management program, which can be cost-effective and environmentally friendly and ultimately help to enhance the yield potential of citrus crop.

## **2. Sucking insects**

These insects deprive the citrus plants from essential nutrients by feeding on sap of tender plant parts such as leaves, fruit buds and green stems, and branches using piercing-sucking or rasping-sucking mouthparts. Detail of important sucking insect pests of citrus is given below:

#### **2.1 Asian citrus psyllid**

It is also known as citrus psylla. The biological name of this insect is *Diaphorina citri* Kuwayama. It belongs to order Hemiptera and family Liviidae.

### *2.1.1 Distribution*

*Diaphorina citri* is a serious insect pest of citrus groves in different regions of the world. It was first reported in Taiwan [14] from where it invaded to many citrusgrowing regions of the world, including Brazil [15], India [16, 17], Pakistan [18], Southern California [19], Texas [20], Florida [21], Australia [22], Colombia [23], Caribbean [24], Mexico [25], Indonesia [26], Iran [27], Kenya [28], Japan [29], Oman [30], Ethiopia [31], Malaysia [32], and Bangladesh [33].

#### *2.1.2 Eco-biology*

*Diaphorina citri* is mainly a pest of tropical and subtropical climate. New foliage growth (flush) regulates the dynamics of *D. citri* requiring soft tissues for oviposition and development [34]. The peak period of psyllid is coinciding with new flush and pest becomes active at the end of February (late winter) and population reaches at maximum level in March and April (spring season). The adults become active in May (early summer) and June and new colonies develop in July (mid-summer). The population begins to decline in October (autumn) and only fraction of population is observed at the end of December and January (winter season) [35]. Reproduction of *D. citri* is totally dependent on availability of young shoots containing feather stage to recently expanded tender leaves. Adult females feed on tender shoots to mature their eggs and prefer opening buds and emerging shoots for oviposition. During the following 2–3 weeks, shoot and leaf tissues are still tender and are utilized by nymphs and adults to complete development and mature eggs, respectively [34, 36]. Adults can also feed and survive on the fully developed leaves for several months. Temperatures between 24°C and 30°C are most favorable for both adult survival and reproduction, as adults survive for 30–50 days and females lay about 500–800 eggs at these temperatures [37, 38]. The damage caused by *D. citri* is most severe in autumn than in


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

#### **Table 1.**

*Summary of citrus insect pests.*

summer. The order of severity varies due to type of host plant, age, abundance of flush, variation in flush phenology, and management practices [39].

*D. citri* has three developmental stages of life, for example, egg, nymph, and adult. Bindra [40] observed almond-shaped eggs that are yellow in color and are laid during day time either isolated or in masses of double or triple lines embedded into leaf tissue with short stalk. *D. citri* has five nymphal instars that are orange to yellow in color,

with rounded flattened body (**Figure 1**) [35]. Pande [41] studied the biology of *D. citri*, finding that mating onset just after adult emergence.

The egg laying capacity per female is about 180–520. The incubation period ranges from 4 to 18 days according to environmental conditions. Nymphs have five instars, which take 10–30 days to adult molt. The adults survive longer and take 14–48 days to complete their life cycle. *D. citri* has 10 overlapping generations per year [41].
