Orchardists and Nurserymen: Beware of Nematodes

Orchardists and Nurserymen: Beware of Nematodes

A Hoarding at a busy crossing in Rajahmundry (Andhra Pradesh)

K. Poornima and R.K. Walia

Project Coordinating Cell All India Coordinated Research Project on Nematodes in Cropping Systems LBS Building, ICAR-IARI, New Delhi-110 012

Trilingual video documentary on root-knot nematode management in guava and pomegranate

Orchardists and Nurserymen: Beware of Nematodes

K. Poornima Professor, Department of Nematology Tamil Nadu Agricultural University, Coimbatore

R.K. Walia Project Coordinator, AICRP on Nematodes in Cropping Systems ICAR, New Delhi

Project Coordinating Cell All India Coordinated Research Project on Nematodes in Cropping Systems Lal Bahadur Shastri Building, ICAR-IARI, New Delhi-110 012 25

Citation Poornima, K. and Walia, R.K. 2017. Orchardists and Nurserymen: Beware of Nematodes. All India Coordinated Research Project on Nematodes in Cropping Systems, ICARIARI, New Delhi-110 012, 24 pp.

Authors

K. Poornima R.K. Walia

Project Coordinating Cell All India Coordinated Research Project on Nematodes in Cropping Systems Lal Bahadur Shastri Building, ICAR-Indian Agricultural Research Institute New Delhi-110 012 Ph.: 011-25846400, Email: [email protected]

Printed at Venus Printers and Publishers, B-62/8, Naraina Industrial Area, Phase-II, New Delhi-110028 Ph.: 45576780 M.: 9810089097, E-mail: [email protected]

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भारतीय कृ�ष अनुसध ं ान प�रषद Indian Council of Agricultural Resear

Foreword कृ�ष

भवन, डॉ. राजे�� �साद रोड, नई �द�ल�-110 Krishi Bhavan, Dr Rajendra Prasad Road, New Delh

Dr. P. K. Chakrabarty Dr. P.K. Chakrabarty, PhD., FMASc AdjunctProtection Professor, UF& Biosafety) Assistant Director General (Plant Assistant Director General Indian Council of Agricultural Research (Plant Protection & Biosafety) Krishi Bhawan, New Delhi – 110 001

Da

Pollination of crops by honeybees is one of the most practical and most promising m

Plant parasitic nematodes are posingcrop a production. major threat the successful cultivation Honeyin bees exhibit flower fidelity and possessofpotential for long w can be managed in sufficient numbers for deployment whenever and wherever require horticultural crops. Nematode dissemination through planting materials has been and nectar, substantial amount of which is dispensable for use by the mankind wit known since long, but it has attained menacing proportions due to increased commercial consequence to bee health, whereas the other insects collect for their individual need activities associated with horticultural some dreaded foodcrops. securityRecent demand ininterceptions the country, cropof pollination medicated enhancement of c paramount significance. Food production (fruits and seeds) for human depends, to nematode pests along with planting materials and their spread to new areas is an eyesymbiosis between species to be pollinated and the pollinator. The reduction and/or lo opener. We need to educate our nurserymen, both in private and public sector, and the survival of both. Two third of the world's 3000 species of agricultural crops dep train our horticulture/quarantine officers in field jobs,organisms on the provide need to sanitizeservices for more th animalsengaged for pollination. Various pollination crops and for of all the a flowering plants of the world. About 70% of the wo planting materials in the nurseries. We intend to90% undertake series of training courses pollinator to produce fruits/ seeds of which 35% are crop species. on these aspects through our specialists under “All India Coordinated Research Project The values of pollination services contributing to yields in cross pollinated c on Nematodes in Cropping System”.

times the value of honey produced during the process. It is a matter of pleasure that A Research Projectthis on Honey Bees and Pollinators (ICAR)laymen, is organizing a Biennial Gro This booklet is specifically designed to serve purpose i.e., sensitizing Parmar University of Horticulture and Forestry Nauni, Solan, Himachal Pradesh from nurserymen, horticulturists, extension workers, and quarantine officers about This will provide a forum for scientists to interact with each other, analyze the status o nematodes, the nature of their damage to cropsactivities and associated symptoms, how and developmental in order to enhance scientific knowledge in the country abstracts of apicultural research being brought out on occasion of Biennial Group M nematodes are disseminated through nursery materials and how to raise nematodebe useful for updating the knowledge of the stakeholders on the various aspect free planting materials. pollinators. I take this opportunity to congratulate Dr. R. K. Thakur, Project Coordina bees and pollinators and his team for compiling and updating the abstracts of research I congratulate Drs. Poornima and Walia, who have made strenuous efforts to of All India Coordinated Research Project on Honey bees and Pollinators.

highlight this problem at the national level. I am sure this pictorial booklet, sumptuously enriched with illustrations, hand drawings and cartoonist depictions will serve its intended purpose with the readership.

(P

Dated: 21st June, 2017



(P. K. Chakrabarty)

Telefax: 91-11-23384414 Mobile: 91-9540029275 Email: [email protected]

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FOREWORD Dr. K. Ramasamy, Ph.D. Vice Chancellor Tamil Nadu Agricultural University Coimbatore-641 003

Nematodes have gained increase in momentum due to several factors such as changes in cropping systems, irrigation systems, cropping patterns, climate change and introduction of new varieties and cultivars of crops from other countries. Nematodes have their own niches and their pattern of behavior varies when the soil rhizosphere is disrupted, thus becoming a major challenge for nematologists across the country to address the trigger in nematode population. Nowadays, nematode genera previously viewed as benign or non-damaging, are becoming pests due to these facts. Fruit nurseries are facing the challenge of producing nematode-free planting materials as these microscopic entities present in the unsterilized contaminated soil used in nurseries, infest the vegetative propagules and rootstocks. There is an urgent need to find out ways to prduce safe materials free from nematodes and to strengthen and enforce domestic quarantine mechanism to suspend spread of these nematodes through propagating materials from place to place and state to state. The booklet on ‘Orchardists and nurserymen-Beware of nematodes’ authored by Dr. K. Poornima, Prof (Nem), TNAU, Coimabtore and Dr. R.K.Walia, Project Coordinator, AICRP (Nematodes), ICAR, New Delhi is very timely as it will enable extension officials and nursery people to know clearly about nematodes, their behavior and entry modes into roots and help in learning techniques to prevent their entry into nursery propagating materials. I congratulate the authors for this effort and in laying out the booklet in a pictorial way so as to make it palatable for the starter of an orchard, laymen and also for extension and quarantine officials who may be new to the science of nematodes.

Date: 22nd June, 2017

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Preface The dissemination of plant parasitic nematodes through planting materials is not new; it has been going on unimpeded and unknowingly since ages. However, the diversification towards horticulture in the recent times has led to movement of planting material, particularly of fruit crops, in a big way. The Horticulture Officers, Quarantine Officers, Nurserymen and Orchardists are all untrained and unaware about nematode infestations associated with planting materials. In the last couple of years, a number of cases have come to our notice wherein the orchardists purchased plants of elite cultivars of fruit crops from reputed nurseries at exorbitant costs, established new orchards in another part of the country, and the plants started dying after some time. We could establish the link between origin, spread and cause of such failures in most of these cases. As a sequel to these developments, AICRP on Nematodes decided to embark upon the issue and sensitize all concerned. An action plan has been developed and submitted to Govt. of India on educating the State Govt. officials, as well as nurserymen and orchardists. This campaign was started at Kadiyam nursery (Rajahmundry, Andhra Pradesh) during April, 2017, and it is our endeavor to take it to all parts of the country. This pictorial booklet is an outcome of this development. It includes - introduction to plant parasitic nematodes, their kinds, mode of parasitism; major plant parasitic nematodes associated with fruit crops and their symptoms of damage; sources of nematode infection in fruit nurseries; cleaning nurseries of nematode infection; precautionary measures before establishing a new orchard; and managing nematode problems in established orchards. We have tried to make it a simple, light and illustrated reading material, yet deliver the message effectively. Hope it will serve the intended purpose.

K. Poornima R.K. Walia

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About Nematodes Nematodes, also known as threadworms, roundworms or eelworms, are the most numerous multicellular invertebrate animals on earth. Soil dwelling nematodes are microscopic, but they do not qualify to be called as micro-organisms, because they have all the systems that higher animals possess, except the skeleton. They inhabit any conceivable habitat on this earth – the oceans, the rivers, the lakes, and soil (cultivated or barren lands). Basically nematodes are aquatic; even in soil they live in soil water, not soil air. A handful of soil anywhere from this earth harbours hundreds, if not thousands, of nematodes. If all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable…..we would find its mountains, hills, valleys, rivers, lakes and oceans represented by a film of nematodes........................ Nathan Augustus Cobb

Soil Environment and Nematodes Imagine a cubic meter piece of fertile field soil with its millions of soil particles, big and small, enclosing between themselves a network of labyrinthine pores and spaces filled with air and moisture. Imagine this physical structure coming to life with teeming millions of micro-organisms – protozoans (~ 5x108 units, biomass 39 g), bacteria (~ 3x1014 cells, biomass 300 g), fungi (biomass 400 g), viruses, and a few macroorganisms like insects, mites etc. Perceive the growth of plant roots within this system – displacing soil particles as they proliferate, respiring, secreting and exuding gases and chemicals. Interspersed in this piece of soil are millions of nematodes (~ 1x107, biomass 12 g) of different kinds – the free-living, the predators, and a few thousands of them plant parasites. This is the nematode ecosystem.

Diversity of Soil Nematode Fauna The soil nematode fauna can be broadly classified into two groups – the free-living (including predators) and plant parasitic nematodes. While free-living nematodes inhabit all types of soils, being most abundant in organic soils; the plant parasites dominate in soils having vegetation. Free-living nematodes mostly devour microorganisms or feed on dead organic matter. Some of the free-living nematodes play role in organic matter recycling. 1

Typically, the plant parasitic nematodes (PPNs) are vermiform, thread-like without any appendages (arms, legs, wings, antennae etc.); majority of them range between 0.5 to 2.0 mm in length. They are characterized by the possession of a hollow needle-like protractible structure (stylet) in their snout that is used to pierce the plant tissues and ingest the plant cell cytoplasm (the food of nematode) by the pumping action of their oesophagus (pharynx). This is very much akin to drawing blood from our blood vessels by using a hypodermal needle (= stylet of PPN) and a syringe (= oesophagus of PPN) for testing in a pathological lab. PPNs can survive only on plant cell cytoplasm and nothing else, and are therefore, obligate parasites. They are associated with any kind of vegetation and do not discriminate between grasses and trees, crops or natural flora. They dwell in all types of climatic conditions, from temperate to tropical; wherever vegetation can thrive, the nematodes are prevalent. Usually a mixture of 4-5 species of PPNs may be associated with any plant. Some of them are ectoparasites; they do not enter the plant tissues, instead remain in soil and feed on roots and other underground plant parts from outside. Others enter the plant roots, either partially (semi-endoparasites) or completely (endoparasites). Between them, there is a category in which nematodes are capable of moving within the plant tissues (migratory endoparasites), while others become fixed in the roots after penetration and do not move (sedentary endoparasites). The latter category is considered most harmful because they have the capability to modify the conducting vessels (xylem and phloem cells) of plant tissues and direct the flow of water and nutrients for their own feeding; thus partially blocking the flow of nutrition to plant system. Sedentary endoparasites usually assume varying shapes (kidney to spherical) after infecting the plant roots. There is yet another category of PPNs that specializes in infecting above-ground plant parts (stem, leaves, inflorescence, seeds). Such nematodes are very few, thrive under high humid conditions and have special survival mechanisms to overcome water stress conditions; they become temporarily inactive (quiescent) but revive whenever moisture is available again.

Nature of Damage by PPNs and Associated Symptoms Basically PPNs live in soil and feed on plant roots and other underground plant parts (bulbs, tubers, rhizomes, suckers etc.) ectoparasitically or endoparasitically. Imagine hundreds of PPNs in the rhizospheric soil feeding intermittently on finer roots, withdrawing plant cell cytoplasm and in turn causing plant cell mortality. Mostly the feeder roots (fine branches) are destroyed by the nematodes, while the main roots are spared. This is a continuous process that impacts the growth and development of roots leading to undersized “bare root system” devoid of fine rootlets. Consequently, the absorption of water and nutrients by the roots from soil and their translocation to shoots is adversely affected. Being obligate parasites, PPNs rarely kill their host 2

A typical plant parasitic nematode

Ectoparasite

Semi-endoparasite

3

Endoparasite

plants in order to ensure their own survival; instead the plants are rendered weak, stunted, and give a pale appearance due to poor supply of nutrients. In nutshell, the damage to plants by nematodes is slow, debilitating, cancerous, and does not appear in epidemic form which is usually the case with other fungal and bacterial diseases. The damage symptoms are more akin to undernourished plants, and in most cases go undiagnosed. Q. How do most people (including farmers and extension workers) judge the occurrence of diseases from plant symptoms? A. By looking at symptoms on above ground plant parts. Q. And what is their inference if the plant gives a sick (pale/stunted) appearance? A. Deficiency of nutrition or water stress. Yes, that is true, but this situation has been created by the nematodes due to their damage to the roots, even if abundant nutrients and moisture are available in soil the roots are not able to translocate these to the shoots. Q. But how many people uproot the plants to diagnose symptoms on the roots? A. Rarely. There lies the key to nematode damage symptoms. If only we uproot the sick plants and study the damage to roots, at least some important nematode diseases can be diagnosed. So, the general above-ground symptoms of nematode damage are – stunted plant growth in patches, yellowing of foliage, wilting, poor tillering in field/ annual crops; and dieback (poor seasonal flushes), defoliation type of symptoms in perennial crops. All these above-ground symptoms are a manifestation of root damage and malfunctioning of roots, ultimately leading to qualitative and quantitative loss in crop yields. Another important issue related to damage by nematodes is their densities. Plantnematode relationship is quantitative: means the extent of damage is correlated with their soil densities. In most cases it is possible to forecast the likely reduction in crop yield if we can assess the nematode population at the time of sowing/planting of the crop.

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Dried twig

Nematode Rhizosphere

Normal absorption & translocation of nutrients & water

Partial absorption & translocation of nutrients & water

Nematodes feeding on roots and blocking supply of nutrients

There is yet another mechanism by which nematodes inflict indirect damage to the plants, and this in fact is much more prevalent in nature. Just reconsider the figures cited above on the biomass and populations of fungal, bacterial, protozoan propagules present in a fertile field. The mechanical (injuries inflicted by stylet on roots) and systemic (physiological changes in plant system due to nematode enzymes) alterations in the plants by nematodes pave the way for dormant fungal, bacterial propagules to invade the roots and cause diseases. Some of the PPNs carry such propagules on their surface externally (fungal/bacterial) or even internally (viruses) while penetrating and feeding on the plant tissues. Such situations lead to “disease complexes” that are

Propagules are everywhere; the environment select Fungi

Nematodes

Bacteria

Fungi Viruses

Disease complexes

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much more rampart in nature, and nematodes play the role of “facilitators”. The necrotic (dead)/diseased tissues rendered by nematode feeding are usually more prone to secondary infection by saprophytic organisms in soil, causing root rots.

Major Plant Parasitic Nematodes Associated with Fruit Crops Root-knot nematodes (Meloidogyne spp.): This is a group of several species, but the most common ones world-wide are – M. incognita and M. javanica which attack more than 2000 plant species including horticultural crops. M. hapla is restricted to temperate climate areas only. Guava root-knot nematode, M. enterolobii has attained menacing proportions in the recent years in India and some South-Asian countries. The root-knot nematode is soil-borne; only the vermiform juveniles are present in soil that invade the roots and modify the vascular tissues (xylem and phloem cells) into “giant cells” that nurse the developing juveniles. Soon after invasion and establishing the “feeding relationship” with its plant host, the nematode becomes sedentary and assumes swollen shape. Most of the invaded juveniles become sac-like females, while some of them become vermiform males. The adult males leave the roots and emerge into soil. The females draw nutrition flowing through the conducting vessels via giant cells and start laying eggs (200-400 eggs per female) on the root surface nested in masses. Sometimes, the egg masses are formed inside the roots. The total life cycle takes about a month under optimum conditions; temperature plays a major role in regulating the nematode life cycle duration, usually 25-30º C is most optimum. Reinfection takes place once the eggs hatch and several generations are completed in a cropping cycle. In perennial crops host crop is available Life cycle of root-knot nematode continuously. 6

Besides formation of giant cells, the damage to roots also manifests in the form of root galls or knots – hence the name of the nematode. Initially the galls are very minute and hardly visible, but these become prominent consequent to secondary infection. The intensity and size of galls varies with host crops. Nematode induced galls are often confused with rhizobium nodules formed in leguminous plants. The rhizobium nodules are beneficial, side-appendages and can easily be detached from roots with slight disturbance; while the nematode galls are swellings of roots themselves and cannot be removed from roots.

Heavy (left), Medium (centre) and Light (right) galling

Root with (nematode) galls

Root with (bacterial) nodules

The above-ground symptoms of root-knot infection are not diagnostic; yellowing of leaves, stunted plant growth in patches, wilting, dieback in case of trees are commonly observed. However, the roots bearing galls or knots are most diagnostic and almost confirmatory symptoms in field situations. In some cases, particularly in perennial plants, some ectoparasitic nematodes may also form similar swellings on roots that may resemble galls induced by root-knot nematodes. Root-knot nematodes are considered most important among the PPNs world over and they cause approximately 5% crop losses on a global basis. Fruit crops, particularly pomegranate, guava, papaya, grapes etc. are most severely attacked by 7

root-knot nematodes. The average annual losses due to nematodes in 20 horticultural crops have been estimated up to 14%; while in India avoidable losses estimated in individual fields in various high value horticultural crops varies from 10-69% in fruits, 13-99% in vegetables, 13.8-70% in ornamentals, 24-64% in medicinal plants, 18.6-76% in spices and condiments, and 35-100% in mushrooms (Walia and Poornima, 2017). Reniform nematode (Rotylenchulus reniformis): Reniform nematode is also fairly wide spread in tropical and subtropical regions, but prefers heavy to medium textured soils. This is also soil-borne, the vermiform immature females infect the roots, while the males are non-parasitic and remain in soil. Within 7-10 days after infection, the immature females become swollen, kidney-shaped (hence the name “reniform”, renal means kidney); their anterior portion is embedded deep inside the stelar region while the posterior portion remains outside the roots. The adult females deposit eggs (40-80 per female) in masses around their bodies on the root surface. Reniform nematode also completes one generation in about 25-30 days. This sedentary semi-endoparasite of roots can attack a wide range of plants and draws its nutrition from transformed (syncytial) phloem cells, hence it is considered as highly pathogenic. The incidence of this nematode often goes unnoticed for want of clear symptoms on shoots and roots as well. The roots show malformation and necrosis. The nematode is potentially equally damaging as root-knot nematode, many times occurring concomitantly with root-knot nematode in nursery plants. Reniform nematode is more important on grapes and papaya among fruit crops.

Females surrounded by eggmass

Juveniles in soil

Immature females and males in soil

Reniform nematode – Females attached to roots (above) and covered with eggmasses (below)

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Life cycle of reniform nematode

Citrus nematode (Tylenchulus semipenetrans): As the name suggests, this nematode attacks mainly citrus; all citrus types throughout the world. The nematode juveniles are soil-borne and penetrate the feeder roots. But unlike root-knot and reniform nematodes, the citrus nematode modifies only the cortical parenchyma cells to “nurse” itself. The nematode grows to adult in about 3-4 weeks, the adult females are swollen, the posterior part hangs outside, while the neck portion remains inside the roots. This is sedentary semi-endoparasite. The females lay eggs (40-80 per female) in a gelatinous substance forming egg masses on root surface. No symptoms are visible in first 5-7 years, until then the nematode attains damaging population levels. After that, the trees start showing slow decline symptoms that intensify year after year, the seasonal flushes are weak, the yields decline and the trees become uneconomical within next few years. The roots, however, show diagnostic symptoms; the infected feeder roots appear dirty brown, while the uninfected roots retain creamish colour. Under heavy infection, the root cortex can easily be sloughed off.

Healthy (left) and infected (right) roots

Females with eggmasses

Juveniles in soil

Life cycle of citrus nematode

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Lesion nematodes (Pratylenchus spp.): Most species of lesion nematodes are polyphagous and attack several fruit crops without any specificity. All stages are vermiform and can cause infection; initial infection commences from soil. Being a migratory endoparasite, the juveniles and adults cause extensive damage to the cortical parenchyma tissues while migrating, besides feeding. They deposit eggs in plant tissues, scattered as they keep on moving. The nematodes can leave the roots and come out into the soil at the end of crop season, to infect the new crop. Symptoms on roots initiate as discrete elliptical water-soaked lesions that intensify as the crop grows. The lesions merge and necrotic tissues girdle the roots, eventually the cortical tissues slough off. They are commonly seen in nursery plants of fruit crops just as root-knot nematodes.

Root girdling

Nematodes in soil and root

Life cycle of lesion nematode and symptoms on roots

Ectoparasites: Several ectoparasitic nematodes are associated with fruit crops – the major ones include, spiral nematode (Helicotylenchus spp.), stunt nematode (Tylenchorhynchus spp.), lance nematode (Hoplolaimus spp.), ring nematodes (Criconema and Criconemella spp.), pin nematode (Paratylenchus spp.), dagger nematode (Xiphinema spp.), and needle nematode (Longidorus spp.). These nematodes do not enter the roots and feed on the outer layers of cortical tissues. Dagger and needle nematodes in particular feed on root tips with their very long stylets, causing typical fish-hook symptoms and microscopic bulges like galls. When they occur in huge numbers, they pave way for the entry of other disease causing microorganisms like fungi and bacteria, resulting in rotting and drying of roots and ultimate wilting of plants. 10

Lance nematode

Stunt nematode

Ring nematode

Pin nematode

Needle nematode

Spiral nematode

Fruit Nurseries – the Major Source of Nematode Infection and Dissemination Dissemination of nematodes through nursery planting material has been going on unimpeded since long. However, promotion of horticulture in general by the respective governments due to self sufficiency in food grains, diversification of agriculture, profitability of horticultural produce, and incentivization of horticulture have led to shift towards horticulture in the recent times. More and more farmers are taking up horticulture in a big way; consequently, there is an increase in the movement of planting materials not only at national level, but internationally as well. Well-to-do farmers make all out efforts to procure elite cultivars of fruits at exorbitant costs to establish new orchards. 11

Although certification of nursery planting material is in place, but scant attention is paid towards pests and disease incidences. Lack of knowledge both at the level of nurserymen as well as farming community is the main factor contributing towards dissemination of nematodes. During the recent couple of years, we have intercepted several cases of nematodeinfected planting material of fruit crops, particularly guava, procured from renowned private as well as government nurseries for establishment of new orchards at distant places. Such plants start showing symptoms of withering soon after planting and within a period of six months to one year, most of the plants succumb, inflicting heavy monitory losses to the farmers. A peep into the preparation of planting materials at nurseries: Most of fruit plants are propagated vegetatively. The choice of rootstock is immaterial, but the daughter plants are prepared by various methods like – ground layering, air-layering, grafting, cloning etc. Sphagnum (moss) and root promoting growth regulators (like IBA) form essential constituents of these techniques. Upon initiation of rooting, the cuttings are established in “native soil” in polybags for hardening. All these operations are usually done within the premises of established orchards. This “native soil” which is already contaminated with nematodes results in infected seedlings, and is the “root-cause” for this problem. Ground layered cuttings are more often found prone to root-knot

Grafting

Air layering

Ground layering

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nematode infestation than air layered cuttings, as the former has direct contact with soil while the latter does not. Concealed in the black polythene bags are the roots of plants that are already infected with endoparasitic nematodes, and the balled soil contains the ectoparasitic nematodes. Such plants are never inspected for nematode infection and are transported to far flung areas, thus nematodes also get introduced into newer places inadvertently. Symptoms of nematode infestations in nurseries: Root galling due to Meloidogyne spp. at nursery stage is generally inconspicuous and can easily escape the notice; these are primary galls and very minute. Fruit nurseries such as pomegranate, guava etc. show bronzing of leaves at nursery stage, defoliation is common, growth is stagnant. Roots of layers, clones and rooted cuttings do not show any visible galls as they are often microscopic. Galls in grafts and rootstocks are quite conspicuous and can be seen with naked eyes. Dagger and needle nematodes also produce small swellings that can be mistaken for root-knot nematode galls. The prospective buyers of planting material are advised to take a careful look at the roots by opening the polythene bags randomly. Alternatively, they can seek the help of specialists from State Agricultural Universities or ICAR Institutes located in their region. The root symptoms due to reniform nematode are difficult to diagnose in field; dirty root appearance is an indication of reniform/lesion nematode infection.

Nematode infected guava rootstock with visible galls

Nematode infected guava graft

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Nematode infected guava clone with minute galls

Nematode infected guava ground layer with minute galls

Pomegranate infected roots emerging out of polybag

Opened polybag shows profuse galling on roots of pomegranate

Profuse galling on guava planting material purchased from a private nursery

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Raising Nematode-free Planting Material Nematode-resistant rootstocks: One of the best methods is to raise planting material using nematode resistant root-stocks, but unfortunately, there are no rootstocks available in case of guava and pomegranate till date that are resistant to nematodes, especially root-knot nematodes. Locally available wild seedlings can be used as rootstocks for grafting as they would often have resistance against nematodes. Tissue culture plants: Tissue cultured (TC) plants offer the guaranteed material that is free from all pests and diseases. But TC plants are available in select few cases only, e.g., pomegranate, banana and citrus whereas it is not so in case of guava. Using soil-less medium: Coir pith or vermiculite can be used for hardening of rooted planting material. Air layering: Wherever air layering is possible, it would be a safe method of vegetative propagation, since the rooting media used is soil-less and can even be bio-fortified so as to ensure protection and can be shifted to sterilized media for hardening and for further growth of plants. Using nematode-free soil for hardening: Under the present circumstances, there seems to be no better option than getting soil free from plant parasitic nematodes. The bulk soil to be used as hardening medium can be alleviated of plant parasitic nematodes by several methods, each having its own advantages and disadvantages. u

Use of chemicals such as formaldehyde, Hydrogen peroxide

u

Solarization of soil in open. For soil Solarization, use of thin transparent polythene sheets for about 2-3 months during peak summer has been found to be very effective and may be used as a routine good horticultural practice.

u

Solarization of soil/polythene bags filled with soil by covering with polythene sheets

u

Use of virgin soil

Soil to be used for filling nursery bags being solarized in a heap using polythene sheet for 2-3 months based on atmospheric temperature

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Nursery bags filled with solarized soil being re-solarized using polythene sheet

Farmers’ practices: Some nurserymen have devised their own novel methods for obtaining nematode-free soil that may be useful for the readers. These are reproduced below. u

Use of soil from virgin lands or dried up ponds to fill their nursery polybags. Rooted cuttings are made in sand medium under mist chambers and then changed into bigger polybags filled with sterilized soil medium using formaldehyde.

u

Soil sterilization using either formaldehyde or hydrogen peroxide (100 ml in oneliter water), soak it overnight followed by solarization using polythene sheets for 12-15 days before filling polybags.

u

Use of soil-less media such as coir pith and vermiculite which are also drenched in either formaldehyde or hydrogen peroxide followed by solarization for few weeks to ensure nematode-free medium for filling nursery bags.

u

Some farmers procure soil from paddy fields for filling polybags, solarize it for two to three months, fill it in polybags and again solarize the bags by covering them with polythene sheets for a month, to ensure that no nematode population survives.

Use of plant growth-promoting rhizobacteria (PGPR): PGPR colonize the roots of plants following inoculation onto seed before planting and enhance plant growth and/ or reduce disease, nematode or insect damage e.g., Pseudomonas spp. and Bacillus spp. PGPR could be fortified in the rooting media and in potting media in nurseries so that they give protection to the roots by producing compounds lethal to nematodes, inhibitory to nematode movement or development and repellent to nematodes on roots. 16

Use of bio-agents: Commercial formulations of nematode egg parasitic fungi, Purpureocillium lilacinum, Pochonia chlamydosporia are now available. Additionally, broad spectrum bio-agents like Trichoderma viride, T. harzianum, Pseudomonas fluorescens can be multiplied in organic material, like FYM and incorporated in the potting media used for filling nursery bags.

Powdering of FYM

Mixing bio-agents in FYM

Moistening of bio mixed FYM

Keep in shade for multiplication of bio-agents in FYM

Steps involved in preparation of bio-agents multiplied in FYM

Structure of a tap root (found in grafts and root stocks) and a fibrous root (found in air and ground layers)

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Nursery certification: The certification of nursery planting material must be enforced strictly by Govt. agencies to ensure movement of nematode-free planting material. The infected material must be discarded and destroyed. Myths of nurserymen about nematodes and their behaviour S. No.

The Belief

The Fact

1.

Paddy nematodes will not Root-knot nematode infesting paddy does not infest fruit nurseries. infect nursery plants especially fruits, vegetables or ornamentals.

2.

Soil taken from fields where previous crops were vegetables, there is possibility of infestation in nursery plants.

Nematodes infesting vegetables such as rootknot nematode and reniform nematode that infest vegetables can also become a problem in nursery plants such as fruit, vegetable and ornamentals.

3.

Nematodes occur in top 1015 cm soil depth and hence it is preferred to dig out soil from deeper depths for filling nursery bags.

Though most of the plant parasitic nematodes are found in the top 20 cms, but endoparasitic nematodes can penetrate deeper into soil along with roots. Many of the dorylaimid nematodes prefer deeper soil depths due to their preference for root tips for feeding.

4.

Grafts escape nematode infestation better than layers and soft wood cuttings in fruit crops especially guava.

Grafts are better in escaping nematode infestation compared to layers and cuttings as the rootstocks possess tap root system which can grow deeper into the soil thereby escaping nematodes. However, grafts also succumb to nematodes whenever the irrigation is by drip rather than conventional where the infestation is less.

5.

Guava cv. Lucknow 49 is a Lucknow 49 is highly susceptible to guava root-knot resistant/tolerant rootstock nematode, Meloidogyne enterolobii. for guava against guava rootknot nematode.

6.

Guava clones and cuttings Clones and rooted cuttings also succumb to rooted in mist chamber nematodes if the medium used to harden them are are free of guava root-knot not sterilized or not from virgin land. nematode.

7.

Denematisation of the nursery saplings can be done by dipping in chemical insecticides before taking up planting.

There is little possibility that the chemicals can knock out the juveniles or prevent eggs from hatching. Nevertheless, eradication of nematodes by chemicals is impossible.

Establishing a New Orchard – Pre-requisites for Nematode Management Care should be taken that the site selected for establishing a new orchard should not have a history of vegetables, turmeric or banana as previous crop as they may leave an inoculum of root-knot nematode, reniform nematode and lesion nematode. 18

Collection of soil samples for nematode assay from proposed site a. Remove 2-3 cm upper layer of the soil with the help of a hand hoe (khurpi/spade) b. Collect about 50 grams (a handful) soil up to a depth of 15-20 cm (subsample). c. Draw 10-20 such subsamples from one-hectare area in a zig-zag manner (Fig. 1) covering the whole field area. d. Put all the subsamples in the same polythene bag (composite sample); the total weight should not be less than half kg and tie it with a rubber band. Keep the sample in another polythene bag. e. Write the sample details on a paper and keep it in between inner and outer polythene bag. f. Seal the outer bag; it is ready for dispatch to a nearest nematology lab for assay.

Fig. 1. Sampling from proposed site for establishing a new orchard (about 1-hectare area)

Based on the soil sample assay report for nematodes, further field preparation can be taken up. u

No detection of any serious plant parasitic nematode: Go ahead as per other recommended Good Horticultural Practices.

u

Detection of serious plant parasitic nematodes: De-nematisation of the soil must be taken up before transplanting plants by following methods.



l



l



l

Deep summer ploughing Keeping the land free from any plants, including weeds



Repeat sampling after 2-3 months for nematode assay till the site is free from major plant parasitic nematodes 19

Managing Nematodes in Established Orchards/Vineyards Sampling for detection of nematodes problems: Care should be taken to take samples only from infested trees that are not completely dead and are still having some fresh roots, as totally dead trees and plants harbour other saprophytic nematodes and fungi that feed on dead decaying matter, making it difficult for an accurate nematode assay.

Sampling from a single Tree a. Collect five subsamples each, from around the main stem and drip line of the tree (Fig. 2) by the method described above. b. The depth of sampling will vary with the kind and age of the tree, but it should include feeder roots. c. Put all the subsamples in the same polythene bag and label it.

Sampling from an Orchard a. Take two subsamples from one tree up to a depth of 30-60 cm (feeder root zone) depending upon the age of the tree. b. Collect subsamples from 10 trees randomly from one-hectare area (Fig. 3). c. Pool all the subsamples in the same polythene bag (composite sample) and label it. Drip line

Main stem

Fig. 2. Sampling from a Tree

Fig. 3. Sampling from an Orchard

Recommendations for Nematode Management in Fruits Based on the nematode assay reports, the package of practices (POPs) recommended by TNAU should be followed for Tamil Nadu. For other states, the POPs of the respective State Agricultural University should be followed. 20

Banana (TNAU Coimbatore POP): Pre-treat each sucker with 40 g carbofuran 3G. If pre-treatment is not done, apply 40 g carbofuran around each plant one month after planting or pare and dip the corm into 0.75% monocrotophos solution; shade dry and plant. Grow sunhemp after 45th day and incorporate one month later. Apply press mud @ 15 t per ha and neem cake @ 1.5 t per ha one month after planting to manage rootknot nematode, Meloidogyne incognita, lesion nematode, Pratylenchus coffeae, burrowing nematode, Radopholus similis and spiral nematode, Helicotylenchus multicinctus. Grapes (TNAU Coimbatore POP): Apply 60 g carbofuran 3G or 20 g phorate 10G per vine a week before pruning and irrigate the plots profusely. The soil should not be disturbed for at least 15 days. Thereafter normal manuring may be done. Application of neem cake @ 200 g/vine also controls root-knot nematode, Meloidogyne incognita. Alternatively, apply Pseudomonas fluorescens @ 100 g per vine in talc formulation (15 x 108 colony forming units/g), 30 cm away from base of the vine at 15 cm depth at the time of pruning. Papaya (TNAU Coimbatore POP): Apply carbofuran 3G @ 1g/polythene bag after germination at nursery stage against reniform nematode, Rotylenchulus reniformis. Citrus (CCS HAU Hisar POP): Apply carbofuran 3G @ 13 g/m2 (about 9 m2 around a plant) just before flowering; pulverize the soil in the basin area and mix the chemical thoroughly followed by flood irrigation. Alternatively, apply carbofuran 3G @ 7 g/m2 + 1 kg neem cake in a similar manner. Pomegranate (MPKV Rahuri POP): Soil application of Pseudomonas fluorescens or Trichoderma viride (cfu 2x106/g) @ 20 kg/ha through 100 kg FYM at Bahar (Blossom). Pomegranate (AAU Anand POP): Apply Purpureocillium lilacinum (= Paecilomyces lilacinus) (cfu 2x106 spores/g) @ 20 kg/ha + castor cake @ 2 tonnes/ha in root zone, 1218 inch away from tree trunk approximately 9-inch deep in soil at 6-month intervals. Guava: The problem of root-knot nematode, Meloidogyne enterolobii has emerged recently and is spreading fast throughout the country through infected planting material. Intensive research is going on to develop management technologies for this problem. However, until then, several pre-emptive measures can be taken up. u

Propagation through healthy planting material

u

Ensuring root-knot nematode free planting site for new orchards

u

Addition of bio-agents such as P. lilacinum at planting sites as well as to established plants at three months’ interval

u

Addition of mycorrhizae in the rhizospheric zone

u

Growing Tagetes (Marigold) around the basin area 21

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Role of Drip Irrigation Nematodes live in soil water, and availability of optimum moisture in soil accentuates their damage potential. In conventional irrigation systems, irrigation is done at specific time intervals, usually there is a gap of 15-20 days depending upon season. This results in wide fluctuations in the soil moisture levels, which is not always conducive for nematode activities. Drip system of irrigation ensures continuous availability of moisture in the upper layer of soil, thus facilitating nematode infection. Moreover, nematodes are also able to maintain their biological activities at the near optimum levels. However, drip irrigation systems are indispensable now-a-days, and we have to find ways to combat nematodes using drip irrigation systems.

Healthy Roots for Nematode Management “What we see above is dependent on what grows below”. The plant system is healthy only when the root system is healthy. Healthy roots manage to keep away the risks of falling prey to invading pathogens, pests and nematodes. Root health can be prompted either by means of chemical boosters or bio-fertilizers which enhance the growth of roots by induction of new flushes that are essential for uptake of water and nutrients from soil. Organic soil amendments stimulate the activities of microorganisms which are in turn antagonistic to plant parasitic nematodes. Further, organic amendments (humus)

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such as bio-compost, organic cakes, farm yard manure and vermicompost when added in optimal quantities alter the microflora in soil rhizosphere, loosens the soil pores creating more aeration and space for root growth. It also changes the soil structure increasing the water holding capacity. Soil amendments both inorganic and organic can be added to increase the fertility of soil thereby improving root growth and health. Increased growth of roots and newer flushes are essential for a plant to attain tolerance if not resistance to invading nematodes.

I have to learn to live with nematodes

How? Read Further Walia, R.K. and Poornima, K. 2017. Nematode management in horticultural crops for improving productivity. In: “Doubling Farmers Income through Horticulture” (Ed. K.L. Chadha et al.), The Horticultural Society of India, New Delhi, Daya Publishing House, pp. 429-439. 24

Trilingual video documentary on root-knot nematode management in guava and pomegranate

Orchardists and Nurserymen: Beware of Nematodes

A Hoarding at a busy crossing in Rajahmundry (Andhra Pradesh)

K. Poornima and R.K. Walia

Project Coordinating Cell All India Coordinated Research Project on Nematodes in Cropping Systems LBS Building, ICAR-IARI, New Delhi-110 012