eChapters

Aphids: Myzus persicae : Aleyrodidae

Aphids are considered as the most serious pest of carnation. Both adults and nymphs suck sap from the leaves and debilitate the plants. They transmit carnation ring spot and carnation mosaic virus disease. They are thus more important as vectors. Regular monitoring for the incidence of the aphid and spot spray-ings of contact insecticides on the shoot tips can easily manage the pest.

Chrysomelid beetle : Aulacophora foveicollis : Chrysomelidae

Adults cut tender shoots and feed on leaves resulting in holes and loss of leaf. Grubs feed on roots and underground stems leading to yellowing,wilting and drying of attacked plants.

Chrysomelid beetle : Aulacophora foveicollis : ChrysomelidaeAphids : Macrosiphoniella  sanborni; Myzus  persicae; Brachicaudus  helichrysi; Aphis  gossypi; Aphis fabae; Aulocorthum circumflexum: Aphid

Chrysanthemum   is infested by different species of aphids. Aphids are small, soft bodied insects and their colour varies with species. Both nymphs and adults cluster on the growing stem tips and under surface of leaves. As a result, the plants show loss of vigor, distortion of leaves and flowers, yellowing, premature leaf fall and stunted growth. The damaged plants bear only undersized buds and they remain unopened. Peak damage period is November-December. Secretion of honeydew by the aphids favor development of sooty mould which hinders photosynthesis and the plants become stunted. They are also vectors of virus diseases.

Spikeborer : Helicoverpa armigera : Noctuidae

Larvae of this polyphagous moth feed on the spikelets, flowers and developing seeds. The young larvae bite holes into the spikelets and the grown up ones attack the mature spikes

Thrips : Taeniothrips simplex : Thripidae

Yellow coloured nymphs and black adults damage leaves and spikes by rasping tissues and sucking the sap.  Affected leaves and spikes develop silver streaks, turn brown, get deformed and dry when attack is severe.  Corms in storage are also attacked. Infested corms are sticky, get shriveled and produce weak plants.

Bud-worm : Hendecasis duplifascialis : Pyraustidae

This pest is serious on J.sambac. The larvae are dark green with black head which bores into immature buds.  They make a hole on the buds, and feed inside, leaving behind faecal pellets entangled in few silk strands. Webbing is seen in severe infestation and pupation takes place in soil.

Bud caterpillars : Helicoverpa armigera : Noctuidae

Eggs are laid singly on young buds.  Larvae feed on developing flowers by damaging florets. They can also eat the leaves.

Leaf webber : Phycita sp. : Phycitidae

Larvae of Phycita sp. feed on heads of buds and flowers.

Biosduval Scale/Orchid scale : Diaspis boisduvalii : Diaspididae

These scales are round flat and yellow in colour. Only the first instar crawlers move. The others are sedentary. The young and mature scales suck the juice from the leaves, petioles and shoots and also inject toxins into the plant. Affected plants turn yellow in patches, lose vigour and get stunted.

Hard Red scale: Aonidiella aurantii :Diaspididae

Both adults and young scales suck the sap from the stem and cause spot yellowing and loss of vigour of the plant. Infested shoots bear reddish brown encrustations of the scale and in case of severe damage the shoots dry up.

Thrips: Thrips tabaci : Tuberose thrips Franklinella schultzei: Thripidae

These minute insects, preferring hot humid weather, rasp and suck the cell sap, causing bronzing, withering and drying up of leaves and flowers. This is the most serious pest on tuberose. Damage to young plants results in stunted growth.

Spindle bug: Carvalhoia arecae :Miridae

Spindle bug is a serious pest multiplying rapidly with the close of monsoon. The adults are red and black and nymphs are greenish in colour with reddish brown patches. Both these stages colonize the top-most leaf axils at the base of the spindle. Adults and nymphs suck the sap from emerging spindle, tender leaves and other tender parts. For feeding they move out and later return to the axils again. At the site of feeding a longitudinal narrow, decolourised zone develops rapidly on either side of the puncture, along the length of the leaf blade. The decolourised patch gradually turns yellowish, then brownish, become stunted, twisted and malformed in a few days and dries up. In this way the tissues may break away and drop off in the wind leaving shot holes on the leaves. In cases of severe infestation the leaves get shred, stand erect and the palms become stunted.

The Tea mosquito bug : Helopeltis antonii : Miridae

The host range of this bug also includes tea, neem, moringa and guava. The attack can cause inflorescence blight, terminal drying of young shoots and heavy yield loss. The adult is a reddish brown bug with black head, red thorax, and black and white abdomen. The easiest identifying character for this pest is a pin like process on the scutellum mid dorsally on the thorax. It is reddish brown, erect and knobbed, and would seem as a pin inserted into the scutellum.

Cacao Mealy Bug : Planococcus lilacinus : Pseudococcidae

The adult female mealy bug is 3.9 mm in length and 2.25 mm in width. Eggs are laid on the plant parts within a mass of tangled waxy strands, a female laying 50 to 300 eggs. The eggs hatch in less than 6 hours and the nymphs feeding on the plant juice become full-grown in 20-25 days with a mean of 23 days in the case of females and 17 to 20 days for the males. The male nymph assumes a pupal period which lasts for 4 to 6 days and the adult male is winged. They live for 2-3 days while the adult female has longevity of 12 -16 days. The females dominate the population, 67.6 per cent of the crawlers developing into female mealy bugs.

Though the coconut palm is subjected to attack by a number of insect and non insect pests although only 8-10 species of insect pests are considered to be important. Others assume importance, once in a while at isolated locations.

Major pests

The major pests of coconut include the rhinoceros beetle, red palm weevil, black headed caterpillar, root grub and the perianth mite.

Coffee is an important cash and export crop for small-scale farmers. The crop suffers heavy yield losses due to damage caused by a wide range of insect pests
 
White stem-borer : Xylotrechus quadripes : Cerambycidae

This is one of the important and serious pests of arabica coffee. Other types are also attacked to a slightly lesser extent. The adult is a dark-brown longicorn beetle having several white markings on the elytra and thorax.

Spindle bug: Carvalhoia arecae :Miridae

Nymphs and adult bugs suck the plant sap from spindle leaf and tender leaves.  Feeding marks are seen as necrotic lesions in the spindle and fully opened leaves.  The pest is seen in the nursery plants round the year but incidence is high during rainy season.

Tea tortrix/flushworm: Homona coffearia:Tortricidae

The tortrix is  an important pest of tea leaves. The larvae make leaf nests by webbing the leaves using silken threads and feed from inside. A single caterpillar makes several cases. Young larvae prefer tender leaves, while the older larvae are seen in mature leaves. The economic produce being the leaves, and since chemical control is not advised, especially during the picking phase, the pest becomes a management problem.

Scale insect: Lepidosaphes sp.: Diaspididae

The mature scale is elongated and oval in shape and dark grey in colour. They infest the stems, leaves and petioles, causing shriveled leaves due to sucking of the sap. The affected parts wither and dry up. In severe infestation leaves dry up and give sticky look and gradually the vine wilts.

Cardamom thrips: Sciothrips cardamomi: Thripidae

Thysanoptera

This thrips attacks other crops like amomum,  tea, colocasia, grapevine, castor, cotton, ginger and turmeric also. The thrips are minute greyish brown insects with fringed wings. They breed on unopened leaves, spindles, leaf sheath, flower bracts and floral tubes .

Cinnamon butterfly: Chilasa clytia clytia : Papilionidae

Larvae defoliate plants. The larvae are pests on many crop plants and weeds and are common in the plains. The larvae are jet black at hatching. They develop a series of broad white patches. The adult is a common butterfly rich velvety brown, and spotted with white dots. The hind wings have arrow shaped streaks and crescent shaped spots.

Stem-borer: Sahyadrassus malabaricus: Hepialidae

Presence of the pest is understood when chewed tissue is seen at at the col­lar region. The mouth of the tunnel in which the borer feeds show pieces of bark, wood and frass particles held together by silk. The saplings break off at the point of injury. When the main stem is attacked, there is mat-like frass at basal region of stem. Larvae girdle main stem and bores downward killing the tree.

Adult moth is peculiar and hangs vertically down by the support of two pairs of legs. Egg period is for 7-10 days, and larvae live for about 10 months inside the larval tunnels. They pupate for 3-5 weeks.

Coriander aphid: Hyadaphis coriandri: Aphididae

Coriander aphids are yellow-green in color, dusted with grayish wax. They have short, dusky, slightly swollen, siphunculi (or cornicles). The Aphids form dense, damaging colonies on leaves, heads, and stems of their host plants.

In its native land, Florida, USA, the life cycle of the coriander aphid is similar to that of other host-alternating aphids. Overwintering eggs occur on other hosts.  A fundatrix (or stem mother) hatches from the egg in the spring. Her offspring are parthenogenetic, and the winged-females are spring migrants. They colonize summer host plants in the family Umbelliferae.

Shoot borer: Conogethes punctiferalis: Pyraustidae

The main damage done by the caterpillar of this pest is to bore holes in the pseudostem and to plug it with excreta, causing dead hearts. Larva is pale greenish with pinkish tinge and dark head and has fine hairs on the body with a pro thoracic shield. Adult is a medium sized moth, pale yellowish with small black spots on the fore and hind wings.

Management involves spraying dimethoate or malathion 1.5 ml/lit or phosphamidon 0.75 ml/lit of water. This is mainly intended to manage the adults flying in the crop canopy and the first instar caterpillars that are seen on the outside of the plants and before thsy enter the pseudostem. The spray has to be given at the very first spotting of dead haearts.

Grasshoppers: Mecopoda elongata :Tettigonidae; Oxya velox: Acrididae

These pests occur both in nurseries and plantations. Both adults and nymphs feed on leaves by scrapping and eating outer tissues and margins. The emerging leaves are nibbled and the spot holes appear when the leaf unfurls. In severe conditions the entire leaf is eaten leaving behind only the midrib.

Scale insects:Pseudaulacaspis cockerelli, Parasaisettia nigra:Coccidae

Attack Adults and nymphs feed on plant sap and cause wilting and drying of seedlings and young plants.
 
Brown soft scale: Lecanium sp. (=Coccus) hesperidum : Coccidae

Thrips: Thrips tabaci: Thripidae

The nymphs and adults of the thrips desap from the narrow spaces between the inner leaf axils. Leaves are faded, with curled tips and shining silver streaks or brown spots.  Many minute yellow or white insects are seen moving, generally near the base or middle of leaves and they suck the sap from the plants.  Plants are faded and the yield is reduced.

Pollu beetle: Longitarsus nigripennis:Chrysomelidae

This pest is monophagous to pepper and no alternate host has been reported so far.

Nature of Damage

Adult is a shining blue flea beetle with yellow head and thorax and has thick enlarged femur and tibia. The adult beetle is only the size of a pin head.  The infested berries dry up and turn dark in colour. Berries become hollow and crumble when pressed and such hollow berries are called “Pollu” meaning empty. The eggs are laid on the berries @ 1-2 eggs in each hole. Eggs hatch in 5-8 days. The grub period extends for 30-32 days. The emerging grubs feed on the berries of pepper and consume the internal contents.

Aphids: Aphis gossypii :Aphididae

The aphids congregate on growing points and suck the sap. Honey dew secreted by the aphids can cause sooty mould in severe infestation. Attack leads to yellowish speckling and curling of leaves.
 
Thrips: Caliothrips indicus: Thripidae

Characteristic silvery white specks with black dots which are mostly faecal pellets, develop on leaves. Consequently, the leaves dry up.

Cassava scale : Aonidomytilus albus: Diaspididae

White elongated scales appear in colonies on stems. Plants die in the field and under storage.  Stem becomes weak and dry, causing side branching to give bushy appearance.  Viability of planting material is reduced, resulting in poor establishment.

Leaf-and shoot folders: Hymenia recurvalis : Pyraustidae

Pycnarmon cribrata;Phostria piasusalis

Aphids: Myzus persicae, Lipaphis erysimi and Brevicoryne brassicae Aphididae
 
Aphids suck the sap from potato foliage, causing wrinkling, cupping and downward curling of young leaves. The older leaves will become yellow, wilt and fall off.  They also excrete honeydew on which sooty mould develops covering affected parts with a thin superficial black coating that hinders photosynthetic activity of leaves resulting in stunted growth of plants. In addition, they also act as vectors, for transmitting potato leaf roll virus. Major damage by M.persicae and A. gossypii is through transmission of potato leaf roll virus.

Sweet potato weevil: Cylas formicarius: Apionidae

It is a specific pest of sweet potato and the most important one. Adult weevils are ant-like, slender bodied having elongated snout-like bluish-brown head with geniculate antenna, bright red thorax and leg tips and bluish-brown elytra. Females make small cavities on the tubers or stems and lay eggs singly. Each female lays 180-200 eggs. Grubs are elongate, legless, pale-yellowish white in colour with smaller brown head. Pupation takes place in larval tunnels in the tuber. Incubation, grub and pupal stages last for 5 to 8, 14 to 17 and 4 to 5 days respectively. Life cycle is completed in 4-5 weeks and adults live for 95-110 days. The grubs bore into stems, tunnel inside and feed on soft tissues. Grubs and adults bore into tubers both in field and storage godowns. Affected tubers develop dark patches, which later start rotting. Feeding holes and adult emergence holes can be seen on vines and tubers.  In severe infestation the collar region of the plants shows unusual thickening due to proliferation and hypertrophy of tissues causing a characteristic terpenoid odour.  Even the slightly damaged tubers are unsuitable for cooking and consumption.  Hence yield loss in practice may come to 100% in many cases.

Amaranthus stem weevil: Hypolixus truncatulus :Curculionidae
 
It is an important pest of amaranthus and is widely distributed in India. It attacks both wild and cultivated amaranthus, especially the leafy varieties with large leaves. Hence, management involves destruction of unwanted, weedy wild amaranthus plants, to reduce the breeding place for the weevil. Adults are ash-grey in colour, with elbowed antennae and brown elytra. Females lay eggs singly in holes made on the stem, branches, petioles or midribs. Eggs are smooth, oval and pale yellow in colour. Incubation period is 3 to 8 days.

Shoot and fruit borer: Earias vitella (=E.fabia), E. insulana: Noctuidae

This is a pest on cotton, bhendi, hibiscus, holly hock and other malvaceous vegetables. The damage is due to the larva that bores into tender terminal shoots in the vegetative stage and flower buds;  flowers and young fruits in the fruit formation stage.  The damaged shoot drops, wither and dry up.  The infested fruits have bore holes, are deformed and become unfit for consumption.  Bore holes are plugged with excreta.

Shoot and fruit borer: Leucinodes orbonalis: Pyraustidae

The pest is active throughout year, but more during monsoon period. Heavy losses up to 60% can occur.

The adult is a greyish brown medium sized moth with white and hyaline wings, having triangular brown and red markings on forewing. A crescent shaped mark facing outside at the apical margin is typical for the species. About 150-250 creamy white eggs are laid singly on leaves, tender shoots, flowers and developing fruits. Egg period is 3-5 days and the hatched larva completes its life in 15 days with 5 instars.

Diamond back moth: Plutella xylostella: Plutellidae
 
The adults of this moth are small, greyish brown having pale whitish narrow wings and with inner margins yellow. There are three pale whitish triangular markings on hind margins of each forewing. At rest, when both forewings come together, they form a dorsal median patch of three diamond shaped yellowish white spots that give them their name diamond back moth. Hind wings have a fringe of long hairs.

Chilli thrips: Scirtothrips dorsalis, Thrips palmi: Thripidae

The adults of this insect are small brownish black with fringed wings. The nymphs are slender and yellowish straw coloured, later acquiring more brownish hue. They lacerate the tissues and feed on the exuding sap. Leaves become crinkled, curled upward and shed. The attack can be confused with chilli mosaic symptom.  In capsicum and chilli, they also feed beneath calyx of flowers and fruits causing flower/fruit drop and reduction in yield and market value of capsicum. Buds become brittle and drop down. Plants get stunted and bronzed. The fruits if at all formed are crinkled and small.

The cowpea aphid: Aphis craccivora: Aphididae

Hosts
 
Groundnut, red gram, peas, beans, safflower, lab-lab niger

Symptoms of damage
 
Both nymphs and adults cause the damage by sucking the plant sap from shoot tips, pods and leaves.  Infested pods become malformed and withered.  Severe infestation may result in complete drying of affected pods.  They also act as vector of virus diseases in pea. 

Fruit flies: Bactrocera cucurbitae:Tephritidae

This pest is more serious in bitter gourd, snake gourd and to a certain extent on ridge gourd. Other cucurbits are attacked to a lesser level. Damage by this pest causes losing the fruit quality, rotting and fruit drop. The adults lay many eggs inside the fruit sing their big ovipositor that hatch out into worm like apodous maggots. Feeding by the maggots on the pulp of fruits result in rotting, yellowing and fruit drop. The dropped fruits allow pupation by the maggots in the soil from where they emerge out as adults and start egg laying on fresh frits.

Sciarid(mushroom flies): Bradysia paupera, Lycoriella auripila: Sciaridae

The larvae feed on the mycelial attachments and restrict the growth of the spawn. The maggots also feed on the developing mushrooms or pinheads and thus cause loss in yield. They also bore the developing mushrooms and render them hollow.

Fruit borer: Helicoverpa armigera: Noctuidae

This is a medium sized moth yellowish brown in colour with a wing

span of about 3 cm and a body length up to 1.4 cm. There is a dark speck and a dark area on the outer margin of each forewing. The forewings also have greyish wavy lines and black spots of different sizes on the upper side.

Reducing insecticide application to the lowest level is the motto of IPM in vegetables. Monitoring for the initial build up and timely mechanical removal of the first population is a must in vegetables. Always remove the first affected plants, by diseases like mosaic, and destroy them by burying or burning. Remove insect eggs, insect affected plant parts and adults and immature stages of insects, and destroy them every day. Do not throw them in the field. They will either come back, or pupate and attack later. During nursery stage, use wood ash, cow dung solution, and plant extracts to deter all pests. Use only low residual insecticides like Dichlorvos 1ml/l, Malathion 2ml/l, Endosulfan 2ml/l or Quinalphos 2ml/l, in spots, at the beginning of attack itself.

1.1 Definition of Statistics

Statistics has been defined differently by different ‘Statisticians’ from time to time. These definitions emphasize precisely the meaning, scope and limitations of the subject.  The reasons for such a variety definitions may be stated as follows:

    i.    The field of utility of statistics has been increasing steadily and
    ii.    The word statistics has been used to give different meanings in singular (the science of statistical methods) and plural (numerical set of data) senses.

In order to have a clear grasp of the subject, we give below some selected definitions of statistics which are grouped under two main heads: ‘Statistics as numerical data’ and ‘Statistics as Methods’.  The former one is in plural sense and the latter singular sense.

2.1 Quantitative Classification

It the data are classified on the basis of phenomenon which is capable of quantitative measurement like age, height, weight, prices, production, income expenditure, sales, profits, etc., it is termed as quantitative classification. The quantitative phenomenon under study is known as variable.  For example the daily incomes of different retail shops in a town may be classified as under.

3.1 Introduction

One of the most important objectives of statistical analysis is to summaries the information contained in the data which may be considered either as a population or as a sample (or sub-population). If the set of data consists of all conceivably possible (or hypothetically possible) observations of a certain phenomenon or a variable, we call it as population. If a set of data contains only a part of these observations, that is selected values of a variable, we call it as sample. Frequency distribution and graphical representation summarize to some extent.  They reduce a mass of data to a more understandable form but not to a single value. The aim of this lesson is to determine descriptive measures or statistical constants which will describe the nature of the data.

4.1 Introduction and Measuring

A measure of central tendency exhibits only one of the important characteristics of distribution, namely they typical representative figure to the whole set of its values. This measure alone will not adequately describe a set of observation unless all the observations are alike. Moreover one cannot understand completely about the data set with a measure of central tendency.  Because in real practical situation there may exits a number of sets of observations (or different distributions) whose measures of central tendency are same but they may differ individually from each other in a number of ways.  In particular two sets of values have the same mean but whilst one set of data is grouped close to the mean the other one is more spread out.  The following examples will illustrate this view point clearly.

In day-to-day life, one comes across many statements which create doubt about certain happenings and one may want to determine the chance of occurrence of a particular happening, e.g., if one desires to know the chance of rain based on some metrological observations.  In the case of coin tossing, one wants to know what will be the chance of winning if a person always stakes for head in a fixed number of tossing. There can be innumerable such queries which one would like to make and meanwhile evaluate mathematically the chance of the occurrence of such possibilities.  This invoked the need of probability theory. The theory of probability came in existence when problems of games were referred to mathematicians like Karl Pearson, Laplace and others. Complicated applications involving advanced theory of probability and axionmatic approach of probability are not dealt within this book.

It has been a general notion that if an experiment is conducted under identical conditions, values so obtained would be similar. But the experiences of people have dispelled this belief. Observations are always taken about a factor or character under study, which can take different values, and the factor or character is termed as variable.
Hence, we have a set of outcomes (sample points) of a random experiment. A rule that assigns a real number to each outcome (sample points) is called random variable. The rule is nothing about a function of the variable, say, X, that assigns a unique value to each sample point of the sample space.

7.1 Meaning of Sampling
    
Before we consider sampling theory, we first define the terms population and sample.
 
The word ‘population’ or ‘universe’ in statistics is used to refer to any collection of individuals or of their attributes or of results of operations which can be numerically specified. For example the assemblage of heights of all the individuals in the population is called a population of heights.  Similarly we may consider the population of weights, wages, yields of grain; prices of wheat, mileages of automobile tyres, etc. a population containing a finite number of individuals or members is called a finite population.  For instance the population f ages of the workers in a factory constitute a finite population of ages. A population with infinite number of members is known as infinite population.  For example the population of pressures of temperatures at various points in the atmosphere is an infinite population. 

8.1 Statistical Hypotheses

in attempting to reach decisions about the populations, it is useful to make assumptions or guesses about the populations involved. When the assumption or statement about a phenomenon occurring under certain conditions is formulated as proposition it is called a scientific hypotesis. We can construct criteria by which a scientific hypothesis may be ‘the  yield of a new paddy variety will be 3500 kg per hectare’. In statistical language it may be stated as ‘the random variable (yield of paddy) is distributed normally with mean 3500 kg/ha’. Such a statement or proposition about the probability distribution of a random variable is called the statistical hypothesis.