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Chrysanthemum is one of the important commercial loose flower crops in India, valued for its wide range of flower forms, colours, sizes and long-lasting florets. It is extensively used for religious offerings, garlands, Veni, bouquets and ornamental purposes. The chapter describes its origin, distribution, genetics, botanical characteristics and important annual and perennial types. It provides information on suitable varieties, climate, soil, propagation and field establishment. Production practices including nutrient management, irrigation, pinching and other cultural operations are explained systematically. The chapter also discusses important pests and diseases, harvesting, postharvest management and yield, providing a practical foundation for commercial chrysanthemum cultivation and floriculture teaching.

Insects, belonging to the phyllum-arthropoda, have an open circulatory system. An open circulatory system is that in which blood bathes the organs rather internal organs directly in the haemocoel, the coelom of the insects, which actually is not a true coelom. Almost entire haemocoel of insects is formed from the epineural sinus. The haemocoel is divided into the perineural sinus and perivisceral sinus by the dorsal and ventral diaphragm respectively. The characteristic of insects is the presence of dorsal vessel, which comprises of anterior aorta and a posterior heart and is the only conducting tube present in insects. The blood of insects mostly does not perform gaseous exchange, therefore it does not contain haemoglobin, and blood in insects is called the haemolymph, which is red-coloured. So in order to study the circulatory system of insects, the major focus must be on the dorsal vessel, which has been described as follows, along with its accessory structures.

1. Gummosis.
Diagnosic Symptoms
• First symptoms are dark staining of bark which progresses into the wood.
• Bark at the base is destroyed resulting in girdling and finally death of the tree.
• Bark in such parts dries, shrinks and cracks and shreds in lengthwise vertical strips.
• Later profuse exudation of gum from the bark of the trunk (characteristic symptom).
• The infection spreads both upward to the leaves and even fruits and downward to the roots causing fibrous root rot.
• The fibrous root rot destroys a major portion of the root system.
• However, the trunck and root infections may usually result in ultimate drying of the tree (Fig-1).
Etiology
Scientific Classification
Kingdom : Fungi
Division : Eumycota

Citrus crop includes lime, lemon, sweet orange, mandarin orange, Kamala orange, grapefruit, malta and pomelo etc. The disease which attacks one species of citrus mostly attacks other species also.

Subtropical and Tropical Fruits

Most of the area of India experience subtropical and tropical climate. Subtropical and tropical fruits contribute maximum to the overall fruit production. Major fruit crops cultivated in subtropical and tropical region are citrus, mango, litchi, guava, sapota, pomegranate, banana, ber, sapota, grapevine, papaya etc. Various pests affect the fruit production by infesting at various stages of the tree growth quantitatively as well as qualitatively. The pests of these crops are described fruit wise.

Citrus

Most of the area of our country is tropical and subtropical, where the citrus, Citrus spp. cultivation is practiced and main citrus growing areas are in Maharashtra, Andhra Pradesh, Punjab, Karnataka, Uttarakhand, Bihar, Orissa, Assam and Gujarat. As for as the ranking in the world

History on Classification of Herbicides

Copper sulphate (CuSO₄) was the earliest inorganic salt used as selective herbicide for controlling dicot weeds in cereal crops during 1896 in France, Germany, and USA. Sulphuric acid (H₂SO₄) was used as herbicide in cereals during 1909. In selective killing action depends on the fact that it runs off the leaves of the cereals and scorches rough surfaces of certain seeds. Sodium chlorate (NaClO₃) under the name mort-herbs is used in France for killing deep rooted perennials. Another non-selective herbicide, ammonium sulphamate (NH₄SO₃NH₂) was introduced in 1945 as ammate for the control of woody plants. Organic herbicides are more effective and selective.

Classification of Herbicides

Classification of herbicides is modified periodically as and when new herbicides are developed. Herbicides are classiûed based on their method of use (soil and foliage applied), mode of action (systemic or translocated and non-systemic or contact herbicide) and chemical key structure (aliphatic-aromatic, dinitrophenal, etc. Some herbicide molecules contain more than one classifying key structure and they are put into the group most likely to be contributing activity.

Any approved herbicide is known by three names: common name, chemical name and trade name. Common name of herbicide is a technically accepted abbreviation of its chemical name. Chemical name reads out its full molecular structure. Trade names refer to their formulations offered by the chemical companies for the consumers.

According to G.C. Ainsworth (1973) the fungus is free-living, parasitic or mutualistic, saprotrophs, necrotrophs or biotrophs and devoid of chlorophyll. Cell wall composition very variable, majority contain chitin and glucans, reserve materials glycogen, oil and mannitol, characteristic disaccharide and trehalose. Some yeast-like but majority with thread-like filaments, hyphae, branched profusely to form the vegetative mycelium on which spores are produced, asexually or sexually, free on hyphae or enclosed in complex reproductive structures. Separated mainly on morphology of the latter.

2.1 Divisions: Myxomycota

These are wall-less and quite unusual organisms only included in the fungi as mostly studied by mycologists. Possess either a plasmodium, a mass of naked, multinucleate protoplasm, which feeds any ingesting particulate matter and moves by amoeboid cells. Both of slimy consistencies hence slime molds. Four classes:

2.1.1 Class: Acrasiomycetes (Cellular slime molds)

Assimilative phase, free living amoebae which aggregate to form a pseudoplasmodium before reproduction.

There are number of diseases which attacks crop plants. Therefore It is mandatory to classify plant disease into more manageable and more specific group based on several criteria for easy and better understanding. Let us discuss one by one.

1. On the basis of type of infection

On the basis of type of infection disease can be classified into two types

Introduction
Plant diseases pose significant challenges in agriculture, affecting crop yields, quality, and overall plant health. To manage these diseases effectively, it is essential to classify them systematically. Accurate classification helps researchers and farmers understand the nature of the diseases, identify the causal agents, and implement appropriate control measures. This chapter explores various ways to classify plant diseases based on different criteria, such as the causal organism, symptoms, host range, type of crops infected, and whether the diseases are infectious or non-infectious.
Basis of Classification
On the basis of various criteria, plant diseases can be classified into the following categories:
1. Causal Organism
2. Symptoms
3. Host Range
4. Crop Plants Infected
5. Infectious vs. Non-infectious Diseases

There are thousands of diseases, which attack crop plants. Classification can be made based on several criteria. The various ways of classifying diseases of plants are given below.

A. Based on Type of Infection

1. Localized disease- affecting only a part of the plant; leaf spots and anthracnoses caused by different fungi.

2. Systemic disease- affecting the entire plant.

B. Based on Symptoms

Rusts, smuts, wilts, blights, cankers, mildews, rots, damping-off, die-back, scab etc.

There are thousands of diseases, which attack crop plants. Classification can be made based on several criteria. The various ways of classifying diseases of plants are given below.
A. Based on type of infection
1. Localized disease: Affecting only a part of the plant; leaf spots and anthracnoses caused by different fungi.
2. Systemic disease: affecting the entire plant.
B. Based on symptoms: Rusts smuts, wilts, blights, cankers, mildews, rots, damping-off, die-back, scab etc.
C. Based on the host plant
1. On the basis of host e.g. Diseases of apple, diseases of wheat, diseases of rose, diseases of coconut, diseases of coffee, diseases of cotton.
2. On the basis of host group- e.g. cereal crop disease, pulse crop diseases, oilseed crop diseases, root crop disease, forage crop disease, plantation crop disease etc.

The nematode feeding on plant can be divided into above ground feeders and below ground feeders.

Classification of Living Organisms

The classification of living organisms has passed through several changes and has reached the present stage with the gradual assimilation of more and more knowledge about them. The classification is mainly based on the morphology, anatomy, life style, habits, habitats, metamorphosis and such other characteristics. Though the concept of classification of living organisms was perhaps started by Aristotle between 384 - 322 BC, it was the Swedish Scientist Carl Linnaeus (1788), who presented the classification, which was acceptable to most of the Taxonomists. He propounded the binomial nomenclature of naming each and every organism of animal and plant origin with a genetic and species name. In his classification he was consistent in using Latin names for all the organisms.

Parasitoids are important natural enemies that regulate insect-pest populations and reduce dependence on chemical pesticides. They lay eggs in or on host insects, and their developing offspring eventually kill the hosts. Rising temperatures, altered rainfall, elevated carbon dioxide and extreme weather can affect parasitoid survival, development, reproduction, host-searching ability, distribution and seasonal activity. Climate change may also disturb synchronization between parasitoids and their hosts, thereby reducing the effectiveness of natural biological control. This chapter examines how changing climatic conditions influence parasitoid diversity, abundance and pest-suppression services. It also highlights management approaches for conserving and strengthening parasitoid populations in agricultural ecosystems.

Entomopathogens are microorganisms that infect and kill insects, mites and other arthropods and are widely employed in biological control and integrated pest management. They include bacteria, fungi, viruses and entomopathogenic nematodes. Their effectiveness depends greatly on temperature, humidity, solar radiation, rainfall and interactions among the host, pathogen and environment. Climate change can alter pest populations as well as pathogen survival, infectivity, multiplication and field persistence. These effects may enhance some microbial-control agents while reducing the effectiveness of others. This chapter introduces major groups of entomopathogens and examines their performance under present and projected climatic conditions, emphasizing their importance in environmentally responsible pest management.

Climate and weather strongly influence annual fluctuations in agricultural insect-pest populations. As ectothermic organisms, insects respond rapidly to variations in temperature, humidity, rainfall and wind. Climate change can modify their development, survival, reproduction, adaptation and geographical distribution. It may increase the number of generations, improve overwintering survival, alter host synchronization, encourage invasive species and reduce the effectiveness of natural enemies and existing control methods. Indirect effects also occur through changes in host-plant growth, resistance and nutritional quality. This chapter examines the responses of important agricultural insect pests to changing climatic conditions and discusses their implications for crop productivity and sustainable pest management.

Forests support diverse insect communities that contribute to pollination, decomposition, nutrient cycling and other ecological processes. Certain insects, however, become destructive pests when environmental changes weaken natural regulation and favour population outbreaks. Increasing temperature, altered precipitation, drought and land-use change can affect insect development, reproduction, survival and geographical range. Climate change may also disrupt synchronization between forest trees and associated insects, intensify native-pest outbreaks and facilitate the establishment of invasive species. Such changes can reduce tree growth, increase mortality and transform forest landscapes. This chapter examines climate-related forest-pest dynamics, ecological consequences and mitigation strategies for strengthening forest health and resilience.

Climate change affects horticultural crops through rising temperatures, irregular rainfall, extreme weather, altered carbon dioxide levels and changes in seasonal patterns. These conditions influence plant growth, flowering, fruit development, nutritional quality and geographical suitability. They also alter the development, survival, reproduction and distribution of horticultural insect pests. Warmer conditions may accelerate insect life cycles, increase the number of generations and intensify crop infestations. Changes in rainfall can either suppress pest activity or create favourable conditions for outbreaks. This chapter examines interactions among climate, horticultural crops and insect pests and highlights the need for proactive monitoring and climate-adaptive pest-management strategies to safeguard horticultural production.

Insect pollinators are essential for the reproduction of most flowering plants and contribute substantially to global crop production and food security. Bees, butterflies, moths, flies, beetles and other insects transfer pollen and support fruit and seed formation. Climate change can influence their physiology, development, activity, foraging, migration, distribution and seasonal emergence. It may also create mismatches between flowering periods and pollinator activity, reducing pollination efficiency. Drought, extreme heat, habitat loss and changes in floral resources further threaten pollinator diversity and abundance. This chapter examines the direct and indirect effects of climate change on insect pollinators and discusses conservation and management measures