BIOLOGICAL CONTROL OF PLANT PARASITIC NEMATODES BY PREDATORY SOIL NEMATODES. M. PHIb. DISSERTATION

Transcription

1 BIOLOGICAL CONTROL OF PLANT PARASITIC NEMATODES BY PREDATORY SOIL NEMATODES M. PHIb. DISSERTATION (NEMATbLOGY) BY ZakauUah Khan AGRICULTURE CENTRE ALIGARH MUSLIM UNIVERSITY ALIGARH (INDIA) December, 1989

2 DS2d65

3 DEPARTMENT OF ZOOLOGY ALIGARH MUSLIM UNIVERSITY ALIGARH , U.P. (INDIA) Phones: [^"ir^^v-jl^ LPublic ; 5646 Seetlota : 1. ENTOMOLOGY Ref. No. 2. PARASITOLOGY 3. ICHTHYOLOGY & FISHERIES 4. AGRICULTURAL NEMATOLOGY B. GENETICS Date //. /. / ^^Q Supervisor: This is to certify that the entire research work which is being presented in the dissertation entitled, "Biological control of plant-parasitic nematodes by predatory soil nematodes" by Mr, Zakaullah Khan is original and was carried out under my supervision, I have allowed Mr, Khan to submit it to Aligarh Muslim University in fulfilment of the requirements for the degree of Master of Philosophy in Agriculture. (Hematology). 'ay^^^^yi^^^^^y^^^^ (M, Shamim Jairajpuri) Ph,D., D.SC.,PZSI,PLS,FIBiol Professor of Zoology.

4 ACKNOWLEDGEMENT I am deeply Indebted to Professor M, shamlm Jairajpuri for his continuous encouragement and guidance during the present work and also for critically going through the manuscript. Thanks are also due to Professor Khalid Mahmood Co-ordinator, Agriculture Oentre«Aligarh Muslim University, Aligarh for providing necessary facilities. sincere thanks to Drs. Irfan Ahmad, Masim Ahmad and A.L. Bilgrami for their valuable suggestions. Thanks are also extended to Or. Samina shafqat. Dr. Qudsia Tahseen, Mr. P. Pazal Rahman and other colleagues of Nematology Research Laboratory for their help and co-operation. The financial assistance provided by Indian Council of Agriculture Research, New Delhi is gratefully acknowledged, Zakaullah Khan

5 C O N T E N T S Page INTRODUCTION - «1-4 MATERIALS AND METHODS 5-8 PREDATORY BEHAVIOUR OF APQRCELAIMELLUS NIVALIS 9-14 RESULTS DISCUSSION REFERENCES FIGURES (1-4)

6 INTRODUCTION Hematology, the science of plant parasitic and soil nematodes^ is a young and an important discipline of Agricultural and biological sciences. Nematodes constitute one of the most diverse and numerous groups of the animal kingdom. They are found in both terrestrial and aquatic environments. Nematodes have very different modes of feeding and can be broadly categorized on the basi? of their feeding habits viz., plant-parasitic, predator^/, microphagous or saprophagus. For the control of plant-parasitic nematodes different strategies are adopted, such as chemical, physical, cultural and biological control methods. Besides the high cost involved in chemical control, the chemicals also kill the beneficial micro-organisms indiscreetly, leave residual effect and thus pose a potential threat to human and animal health. Many nematicides which are considered safe and highly promising have proved to be highly toxic and their use has already been banned in many countries. hence Keeping in view the harmful effects of nematicides and in disturbing ecological balance the use of biological control of plantparasitic nematodes has received greater attention in the recent years. Biological control of plant-parasitic nematodes enjoys advantages over the conventional rr;ethods like the

7 -2- physical and chemical controls in being inexpensive and ecologically non-pollutant in nature. This has been an area of research, extensively pursued during the recent years. However, a thorough knowledge of predators and their prey is required to practise such an inexpensive and pollution-free control method. It will be essential to understand the biology, ecology, fecundity, mortality and longivity of predators, their prey-range, predation ability, the degree of susceptibility and resistance of prey species to predation by different predators. Most of the predatory nematodes belong to Orders Mononchida, Dorylaimida, Diplogasterida and Aphelenchida. Many dorylaim and nygolaim nematodes are predacious, but a large number of them are considered to be only suspected predators. It is therefore, proposed to carry out extensive research on dorylaim predators, to evaluate their predatory abilities and to assess their role in the biological control of plant parasitic nematodes. Many genera of soil nematodes are known to predate upon other nematodes. On the basis of their feeding habit the predatory nematodes have been Categorized into three types. The first ones are the predators which swallow their prey and have plain oesophagus without any differentiated region. stoma is usually unarmed and the lumen of stoma is capable of pronounced dilation, e.g., Tripla spp, Cobb, The second type

8 -3- Includes mononchs and diplogasterids having feeding apparatus which is armed with one or more large puncturing tooth or grasping denticles jr both. The mononchs may swallo'. a nematode whole or puncture iti. cuticle to suck its body contents/ e.g. species of Hpnonchus, Mvlonchulus, lotonchus, Parahadronchus. whereas the diplognsterid predator feed by puncturing the cuticle of prey e.g. Mononchoides sp, Butlerlus sp. The predators of the thini group are styletbearing nematodes. These predators puncturetheir prey with the help of stylet (Dorylaims: Dorvlaimus, Labronema. Discolalmus, Sectonerna), Mural tooth (nygolaims: AQuatldes, ivyqolaimus) or spear (aphelenchs: Seinura). Many genera and species of the Order Dorylairr.ida are known to predate on other soil micro-organisms (fungi, <^gae etc.) Thome & Swanger il936). Thorne (1930, 1939) had suggested that species of many dorylaims and nygolaims may be predatory in habit. Later several species of Dorvlaimus. Dlscolaimus and Actinolaimus have been reported to be predacious on nematode species (Linforrj i Oliveira, 1937). Esser (1963) found that the species of Dorvlaimus. Labronetna, DiscoJ,aimus and Carcharolaimus are predatory in habit. The dorylaim predators are also omnivorous deriving their food from algae (Mollis, 19 57; Wood, 19 73) and fungi (Mollis, 1957; Ferris, 1968). Labronema ferox feeds on ^ifnall nematodes like Rhabditis sp. and Cephalobids and also

9 -4- on their eggs (Ferris, 1968). Wyss & Grootaert (19 77) were the first to study the feeding mechanism of a dorylaim predator, Labronema vulvapapillatum, in detail. Small & Grootaert (1983) also evaluated predation ability of I^, valvapapjllatum and some other predators. Very recently Bilgrami gt a^. (1985), Shafqat, et al.. (1987) have made detailed observations on the predatory behaviour of a nygolaim predator, Aquatides thornei and Dorvlaimus staqnalis respectively and concluded that predation by ^. thornei and D, staqnalis was greatly dependent on activity of prey and predators. Esser (1987) has given a long list of dorylaim predators and their prey. In the present study detailed observations were made on the predatory behaviour of APorcelaimelius nivalis (Altherr, 1952) Heyns, The studies include prey catching and feeding mechanisms, prey-preference, attraction towards prey, prey selection in different prey combination, effect of various factors on rate of feeding such as prey density, agar concentrations, temperatures, starvation of predators, predation by adult and juvenile stages, feeding pattern over a period of 8 days.

10 -5- MATBRIAL AND M2TH0DS Sample Collection: Soil samples containing predaceous and other soil nematodes were collected from around palm tree near Victoria gate, Aligarh district. These were taken from a depth of 10 inches usually. The soil samples were collected in polythene bags, brought to the laboratory and stored at 10*C and processed either ImmGdiately or within 3-4 days. Proceaaina of soil samplest About 500 gm soil was taken in a bucket and mixed thoroughly with a small amount of water. Large pebbles and plant debris were removed and lumps were broken, if present, with finger tips. The bucket was then refilled with water to about 2/3 of its volume and the suspension was stirred gently by hand to make a homogeneous suspension. The bucket containing the suspension was left undisturbed for about seconds to allow the heavy particles to settle down at the bottom of the bucket. The muddy suspension was poured into another bucket through a coarse sieve of 2 mm pore size. Large pebbles and debris like leaves, roots etc., retained on the coarse sieve were thrown away. The suspension in the. second bucket was then poured through a 300 mesh sieve (pore size 53 /im). The

11 -6- nematodes and fine soil particles were retained on the sieve. This residue was washed repeatedly and collected finally into a 250 ml beaker. The process was repeated thrice for the remaining soil in the bucket for better recovery of nematodes. Isolation of nematodes: The suspension collected in the beaker was poured on a small coarse sieve lined with tissue paper. This was then placed on a 3aermann's funnel filled with water just touching the bottom of the sieve. During the placement of sieve special care was taken to avoid air bubbles in between the bottom of sieve anci water level. The stem of the funnel was fitted with a irubber tubing provided with a stopper. The active nematodes migrated into the water and settled down at the bottom of the funnel. After about 24 hr a small amount of water was taken from the funnel through rubber tubing in a cavity block for the examination of nematodes. Culturinot The predaceous dorylaim nematodes and free-living prey nematodes were cultured in 5.5 cm diameter petri-dishes containing water-agar. For preparing culture to media and^study the feeding behaviour of predaceous nematodes, 1 gm agar was mixed with 100 ml water in a beaker and boiled for a few minutes over an electric heater. suspension was then poured in clean The hot oetridishes and left undisturbed for about an hour of so to allow it to cool down and solidify. Both sexes of predatory nematodes alongwith

12 -7- the prey nematodes were inoculated into these petridishes with the help of a picking needle (bomboo splinter) or a few drops of thoroughly stirred nematode suspension. A very small amount of lactogen milk powder was spread over the surface of the agar to encourage the bacterial growth which served as food for the free-living prey nematodes. These petridishes were examined every day under the binocular microscope. When agar layer of culture dishes became dry or loose, then the nematodes were transferred to fresh petridishes containing the agar mediurr, of same concentration. Free-living nematodes like Rhabditis sp, Plectus sp# and Acrobeloides sp were used as prey, reared in separate petridhshes. The species of plant-parasitic nematodes viz., Hoplolaimus indicus^ Tylenchorhynchus mashhoodi. Helicotvlenchus indicus,hirschmanniello orvzae and HemlcvclioDhora sp that were used as prey in different experiments were isolated fresh from the soil from different localities. The second stage juveniles of Heterodera mothi and Meloidoovne incognita were collected from the cysts and egg masses respectively. Handling of nematodes; The nematodes, when required in small numbers, were picked up from the culture dishes or the water suspension. Whenever large numbers were required nematodes were obtained from the cultures by modified Baermann's funnel method in which pieces of agar

13 -8- were cut from the petridishes and were then placed on a small coarse sieve lined with moist tissue paper. Most of the active nematodes migrated from these agar pieces into the clean water of the funnel within 24 hr. Observation Chamber: The feeding behaviour of APor<;elaimellus nivalis at higher magnifications, was observed in observation chamber as designed by Ahmad & Jairajpuri (1979). A plastic ring of 1 cm diameter and 2-3 mm thickness was fixed to a metallic slide. A coverslip was fixed on one side of the ring and then a small piece of water-agar was placed on the top of the coverslip. The whole chamber was then covered by another coverslip.

14 PREDhTORY BEHAVIOUR OF APORCELAIMELLUS NIVALIS -9- Prev Catching and feeding mechanism; Prey catching and feeding mechanism of A. nivalis were studied under stereoscopic binocular microscope by Inverting the petrl-dishes containing p^. nivalis end prey nematodes in 1% water-agar. To study the feeding mechanism in detail i.e. at 400 X or higher magnificationjten adults of A. nivalis were placed separately in observation chamber containing VA water-agar with 100 specimens of Rhabdites sp, an H, orvzae as prey. It was then covere^^ with a coverslip. The nematodes were allowed accllmitization for 20 mlr. before observations/we're recorded. Attraction of ^. nivalis towards prey: Attraction of ^. nivalis towards prey nematodes was tested in petridishes of 7 cm diameter, containing 1'/^ wateragar (agar layer 0.5 mm thick). Petridishes were divided into seven sectors. Each sector of 1 cm width, was marked by straight line parallel to each other at the bottom of the petridishes. These sectors were numbered serially as 1/2,3...,7 (Azml & Jalrajpurl, 1977). A piece of straw pipe 5 mm In height and 5 mm in diameter was taken. end of the strawplpe was sealed with a small piece of One filter paper and placed vertically in the first sector in such a way that the closed end of the strawpipe remained inside

15 -10- the agar touching the surface of the dish. 40 prey nematodes, viz, second stage juveniles of M. incognita and H. orvzae were placed in straw pipes in separate dishes. These petridishes were kept in the incubator for 24 hr at 2 5'C. After incubation twenty five predators were released at different spots in the central sector of petridishes, i.e./ sector 4, The distribution of predators was recorded after 4 and 8 hr under the binocular microscope. Separate experiments were conducted to test the attraction of predators towards live and excised (cut into two part) prey nematodes. While the control experiments were run without prey. Each experiment was replicated ten times. Feeding rate of adults and juveniles: To find out the difference in the rate of feeding oi males, females and juveniles of ^. nivalis^ five specimens of each stage were placed in small cavity-blocks containing 1% water-agar along with twenty five prey nematodes, Predation of each stage was tested separately on plant parasitic nematodes, viz., juveniles of M. incognita and H, oryzae separately. The inoculated cavity-blocks were placed in an incubator at *0. The number of prey killed or ingested was recorded after 24 hr.

16 -11- Feedlng pattern of A, nivalis: Experiment was conducted to test the feeding pattern of A. nivalis over a period of eight days. Five specimens of ^, nivalis and twenty five prey nematodes were placed together in small cavity blocks containing 1% wateragar. The cavity-blocks were kept in an incubator at 25 ± 1*C and were observed 24 hr after inoculation. Each day/ after observations, the predators were transferred to another cavity block containing same amount of fresh wateragar and number of prey. The second stage Juveniles of M, incognita and H. orvzae were used as prey separately. To determine prey selection by ^. nivalis the second stage juveniles of M, incognita and Heterodera mothi, adults of H. orvzae, Tvlenchorhvnchus ma^hhoodi, HoDlolaimus indicus. Hell cot vlenchus indicus and Hemicvcliophora sp. were used as prey. Five individuals of A. nival^is and twenty five individuals of each type of prey were placed in separate cavity blocks containing small amount of water-agar. These cavity blocks were kept in incubator at 25 +! C. Number of prey killed or consumed by predators was recorded 24 h, after the inoculation of prey and predators.

17 -12- Prev selection In combination! To determine the prey selection by ^, nivalis of plant-parasitic nematodes, different prey combination were used (25 Ji, incoonitf^ juveniles + 25 H, orvzae. 25 M. incognita + 25 T. mashhoodi, 25 M, incognita juveniles + 25 H. tnothi juveniles and 25 H. oryzae ^ 25 T, mashhoodi). Each combination of prey nematodes was placed together with five ^, nivalis in separate, small-sized cavity blocks containing small amount of 1% water-agar. These cavity blocks were left at C, Number of prey killed or consumed by predators was recorded after 24 hr. Sach experiment was replicated five times. Effect of prev densitvt To determine the effect of prey numbers on the rate of predation five individuals of A, niva^^ together with 25, 50, 75, 100, 125, 150, 175 and 200 individuals of prey nematode were placed in separate cavity-blocks containing a small amount of 1% water-agar. Second stage juveniles of M. 4,ncoqrtf.ta and H. oryzae served as prey. Number of prey killed or devoured by predators was. counted after 24 hr. ^ach experiment was replicated five times.

18 -13- Effect of starvation; To study the effect of starvation of predators on the predation of ^. nivalis fresh specimens of ^. nivalis isolated from the soil were kept in cavity blocks containing water without prey. Five specimens of ^. nivalis were pi'cked from the cavity blocks everyday and placed in small cavity blocks containing a little amount of 1% water-agar together with twenty five prey nematodes. The process was continued up to the 10th day. Juveniles of M. incognj^ta and adults of H. orvzae were used as prey separately. The number of prey killed or fed by predators was counted after 2 4 h. Effect of temceratufe: To study the influence of temperature on the feeding rate of ^. nivalis, five specimens of A. nivalis were placed in cavity-blocks containing 1% water-agar together with twenty five prey nematodes. The cavity blocks were kept in an incubator at different temperatures ranging from 5-40'C (with intervals of 5*C). Juveniles of M. incognita and H. orvzae were used as prey separately. The number of prey killed or fed Was counted 24 hr after incubation. Each experiment was replicated five times.

19 -14- Effect of agar concentration! To find out the effect of agar concentrations, on the rate of predation by A, nivalis, five predators were placed in cavity blocks containing 0,5, 1,0, 1,5, 2,0, 2,5, 3,0, 3.5, 4.0, 4,5, 5.0, 5,5, and 6,0 percent water-agar together with twenty five juveniles of M, incognita and H, orvzae separately. The whole set of cavity-blocks was placed in an incubator at C and observations were made after 24 h of inoculation. The experiment was replicated five times.

20 RESULT3 Prev catching and feeding mechanismx -15- A» nivalis and prey nematodes moved randomly in agar medium. During random movement the predators contacted prey as a matter of chance. ^ niva3,is attacked its prey only when it made lip contact with any pairt of the prey body. No preference was shown for any particular region of the body. Prior to attack ^. nivalis probed the body surface of the prey over a short distance by moving its lip. During probing a few weak oesophageal pulsations were seen in the predator. After probing A, nivalis began to thrust its spear repeatedly against body cuticle of prey in order to puncture the cuticle. Peneteration of spear through the cuticle was completed in about 7-12 spear thrusts. During observations it was seen that the predators thrusted their stylet repeatedly at the body of prey so as to puncture its cuticle. However, all attacks did not result in the injury or death of the prey. Some times the prey escaped from the grip of the predator by making strong undulations. This happens to be more frequently in cases where the prey is more active. A. nivalis inserted its spear into the body of prey, and rendered it immobile by disorganizing the body organs with the help of stylet. To ingest the body contents, thrusting and sideways movements of spear commenced. The

21 -16- predators sucked the body contents of prey through spear aperture and supported the contraction of oesophagus. The predator retained its spear inside the prey body throughout the ingestion period. During ingestion the body contents of prey were visible passing through the lumen of spear and oesophagus. The ingestion was intermittant. The predators punctured prey cuticle at more than one place to suck all the body contents. Only body cuticle of the prey left at feeding site when feeding was over. The whole feeding pirocess of ^. nivalis on a single adult Rhabditis sp. requited minutes and minutes on H. orvzae. The duration of feeding varied with different prey and depended on the size and type of prey. At many instances it was seen that two or more predators were aggregated around a single prey which was earlier wounded by a predator, ^. nivalis also fed upon the eggs of Rhabditis sp, but did not attack their own eggs. Attraction towards orev (Fig, 1 & 2): From the data obtained it is evident that, ^. nivalis were not attracted either towards live or excised prey. The number of predators present in each sector, (in the presence of live and excised prey) slightly differed from the control (P> 0.05). The distribution of predators in different zones was also not different after 8 h (P>0.05). Similarly,

22 -17- in petridishes containing excised prey, there was no difference in the behaviour of predators after 4 and 8 hrs (P>0.05). Rate of predation of adult and juveniles (Fig. 3A) All stages except first stage juveniles of ^. nivalis were observed to feed on prey nematodes. All predatory stages including adults (male and female) killed more juveniles of M. incognita than H. orvzae. There was no significant difference between the number of prey killed by the males and females of ^. nivalis. The number of prey nematodes killed by fourth, third and second stage juveniles of ^. nivalis was markedly less (P<0.05) than those killed by their adults. Feeding pattern (Fig, 3B) A' nivalis showed little variation in the rate of predation when tested over a period of eight days. The difference between the number of prey killed by ^, nivalis after first and eight day was insignificant (P>0,05). Prev preference (Fig. 3C} Data obtained from the experiments revealed preference in A. nivalis. The second stage juveniles of M, incognita and H, mothi were killed in greater numbers

23 -leas compared to any other nematodes used as prey. H. orvz^e was preferred moderately. The number of H. oryzae killed by predators was significantly higher than T. mashhoodi (P<0,05) which v/as preferred least. r.'o specimen of Hoploj.aimus indicus. Helicotvlenchus indicug and Hemicvcliophora sp was injured or killed by ^. nivalis. Prev selection in combination (Fig. 3D ) ^, nivalis fed selectively, when placed in various combinations of prey, viz., juveniles of H. incognita, ii» mot hi and adults of H, orvzae and T. mashhoodi. Juveniles of M, incognita and H, mpthi were killed and consujied by the predators in greater numbers than other prey nematodes in various combinationa T, mashhoodi was killed the least. The predators preferred jj, orvzae moderately. Effect of prev density (Fig. 4A): The rate of predation by A. nivalis was influenced by the number of prey, Predation increased with the increase in prey numbers. Maximum predation occured in a population of 150 or more specimens of prey. ^. nivalis killed minimum number of individuals when subjected to predation with 25 prey (P<0.05).

24 -19- Effect of atarvrttlon (Fig. 4B): Prom the data it Is evident that the period of starvation did not effect the rate of predation of ^. nivalis. The number of prey killed from first to tenth day of starvation remained constant. Effect of temperature (Fig. 4c): Feeding rate of A. nivalis was affected by temperature on both species of prey nematodes, viz., juveniles of M, incognita and adults of H. orvzae. It was observed that the temperature between 25 and 30"G was most suitable for A* nivalis at which maximum number of prey were killed. The temperatures below 25"C and higher than 30'C reduced the rate of predation (P<0,05). The number of prey killed at 20*C and 35*C was moderate. Effect o:^ agar concentrations (Fig. 4D): The predation of ^. nivalis was influenced by different agar concentrations. killed in 1 to 2% water-agar. Maximum number of prey were Concentrations more than 2X water-agar reduced the feeding rate of ^. nivalis,though \ the difference between the number of prey killed in 1% and 2% i water-agar was insignificant (P>0.05). Agar concentrations above 2% and below 1%, retarded rate.of predation (P<0,05),

25 -20- No prey was killed in 5.5ji water-agar because the activities of prey and predators were ceased.

26 -21- DISCUSSION The present observations on the predatory behaviour of A* nivalis revealed that they are predaceous in nature. The predation depended on chance encounter with the prey nematodes. Similar observations were also made by Nelmes 11974), Grootaert & Maertens (1976) Wyss & Grootaert (1977). Bilgrand jgt ajl, (1985) and Shafqat t^ a^. (1987) on different nematode species. A. nivalis was not attracted towards their prey when placed with live and excised prey nematodes separately. Wyss & Grootaert (1977) recorded similar observations on I.abrnnema vulvaoapi 1 latum. This was also supported by the studies of Bilgrami t al. (1985), shafqat ot a^. (1987) on AQuatides thoynei and Dyrvlaimus staqnal,!^ respectively. Ssser (1963) suggested that several dorylaim predators were attracted from a short distance towards a live prey which were cut into two halves. Bilgrami & Jairajpuri (1988) also reported that Mononchoides lonqicaudatus and >l. fortjdens were positively attracted towards the live and excised prey nematodes. This was not observed during present experim'bnt s. However, aggregation of A. nivalis around a prey which was injured or killed earlier by predator suggest soj^e kind of attraction as was also suggested by 2sser, (1963) Bilgrami t ^. (1985), Shafqat ^t ^. (1987).

27 -22- Similaf" to ^. thprnel and D. gtaorialis. i^. nivalis also exhibited affinity towards its own eggs (Bilgrami ^ ajl., 1985, Shafqat et al., 1987), However, when in contact with the eggs of prey, A. nivalis probed, attacked and fed on them. This indicated that ^. nivalis is able to recognize its own members and eggs. The food catching and feeding mechanism of ^. nivalis was similar to those reported by Wyss & Grootaert (1977) and Shafqat gt ai., (1987) for Labronema vulvapaoillatan and D_. staqnalls respectively. selnura spp. paralysed its prey by injecting salivary secretion into the body of prey through spear aperture (Linford & Oliveira, 1937; Hechler, 19&3). ^, nivalis also paralysed its prey by disorganising the internal body organs with its stylet similar to other dorylaim predators (Mollis, 1957; Wyss & Grootaert, 1977; Shafqat ^ a^., 1987), Observations on predation by ^. nivalis shov/ed that they have no consistent predatory pattern on different prey nematodes. Some of the prey nematodes, viz., second stage juveniles of M, incognita and H, mothi were killed and devoured in greater numbers than other prey by ^. nivalis. Bilgrami ^ al_. (1933), Bilgrami & Jairajpuri (1989) and Shafqat ^^ ^. (1937) PISO found differences in the rate of predation by Mononchus aquaticus, Mononchoides lonaicaudatus. M.fortidens and D, staonalis respectively on different types of prey. They have attributed the size and type of prey as the most likely

28 -23- cause of the difference. Small & Grootaert (1983) observed that several species of predators preferred some kind of prey over the others and found Panaqrellus redlvivus to be more susceptible to attack than the other species of prey used. During the present observations the differential rate of predation by A, nivalis may be related to size, activity and behaviour of prey. Besides, the thickness and texture of prey cuticle might have also affected the predation. Esser (1963, 1987) reported that species of Hoplolaimus and Helicotvlenchus can resist predation because of the thick cuticle and secretions of toxic substances respectively. Bllgrami & Jairajpuri (1989) reported similar mechanism in Hoplolaimug and Helicotvlenchus beside Hemlcyiconerooides manqjfera which resisted predation because of ^nnulation on the body. The predatory activities of j^. nivalfis was enhanced when the population of prey was increased as was also observed in predation by Dlplentron potohikus {Yeates, I969); Prionchulus punctatus (Nelmes, 1974), ^. thornei (Bilgrami ^t al., 1985). However, M. aouatiqus (Bilgrami ^t a^,, 1984) did not show any significant difference in predation when placed with different prey populations. These differences in the rate of predation reflects the predatory capabilities of predators. Temperature and agar concentrations also influenced the rate of predation by ^. nivalis as the number of prey

29 -24- killed at different temperatures and agar concentrations was different. This is probably because of the inhibited activity of the predators and prey at higher temperature and concentration Bilgrami ^ a^,, (1983); Shafqat et al., (1987). During.the present experiment on A, nivalis it was observed that the adults, fourth, third and second stage juveniles killed and fed on prey nematodes. The first stage juveniles did not kill or injure any prey. The differential rate of predation of adult and different juvenile stages reflected their predatory potential. The adults were more efficient than their juvenile stages in predation. The rate of feeding of ^, nivalis on its prey remained more or less same over a period lasting for eight days. Bilgrami _ t al. (1934, 1985) while working on M, aguaticus --and ^. thornei also found a consistent predatory pattern.

30 -25- RSFSRSKGES ALTHSRR, S, (1952), 'Les nematodes du park National Suisse, 2", Srqebn. Wiss. Unters. Schweiz. ijat. Parks. n.s. 1 (26), A2MI, M.I. & JAIRAJPURI, M.S. (1977). Attraction of plant parasitic nematodes to host roots. Nematologica 23., BILGRA^'II, A.L.; AHMAD, I; & JAIRAJPURI, M.S. (1983). Some factors influencing predation by Hononchus aauaticus. Revug. Nematol., BILGRAMI, A.L.; AHMAD, I & JAIRAJPURI, H.3. (1984). Observations on the predatory behaviour of Hononchus aguatlcus, Nematol. Medit, 12, BILGRAMI, A.L,, AHMAD^ I & JAIRAJPURI, M.S. (1935). Pr'^datory behaviour of AQuatides thornel (Nygolaimina: Nematoda), Nematologica. 3g, (1984), BILGRAMI, A.L., JAIRAJPURI, M.S. (1988). Attraction of Mononchoides lonqicaudatus and M. fortidens (Nematoda:Diplogasterida) towards prey and factors influencing attraction. Revue Nematol. 11, BILGRAMI, A.L. & JAIRAJPURI, M.S. (1989). Resistance of prey to predation and strike rate of the predators, Mononchoides longicaudatus and M. fortidens (Nematoda:Diplogasterida) Revue Nematol.. 12,

31 -26- COBB, N.A. (I9I8), Nematodes of the slow sand and filter bed of American cities. Contribution to the science of NematoloQV VII, pp SSSSR, R. P. (1963), Nematode interactions in plates of nonsterile water-agar, Proc. soil crop, sci. goc. Fl^. 2^, ESSER, R. P, (1987). Biological control of plant parasitic nematodes by nematodes. 1/ Dorylaims (Nematoda; Dorylaimida). Nematoloqv circular No pp FERRIS/ V.R, (I968), Bioinetric analysis in the genus Labronema (Nematodaj Dorylaimida), with a description of li, thornei n.sp. Nem^.tologica GROOTAERT, R. & MASRTEN3, D. (1975). Cultivation and life cycle of Mononchus aguaticus Nematoloqica lSl. HECHLER, H.C, (1963). Description, developmental biology and feeding habits of Seinura tenulcaudatus (de Man). J.3. Goodey, i960 (Nematodaj Aphelenchida), a nematode predator. Proc. he],minth. -goc. W^sh. _3Q, IS HEYNS, J. (I965). On the morphology and taxono^ny of tb--? Aporcelaimidae, a nev; family of dorylaimoid nerr.atodes. Sntomol. M^^n., 3. Africa i, H0LLI3, J. P. (1957). Cultural studies with :Joryl,^irnus ettersberqensis. Phytopathology 47, -^69-473,

32 -27- LINFORD, M.B. & CLIVBIRA, J.M. (1937). The feeding of hollow spear nematodes on other nematodes. Science 85, NSLMBS, A.J. (1974). Evaluation of the feeding behaviour of Prionchulus Punctatus. (Cobb.) a nematode Predator. jj. Anlm Ecol. ^, SHAPQAT, S; BILGRAMI, A.L.,&JAIRAJPURI, M.S. (198 7). ^valuation of the predatory behaviour of Dorvlaimus staqnalis Dujardin, 1845 (Nematoda: Dorylaimida). Revue Nematol! (4); SMALL, R. W.,a GROOTAERT,P.(1983). Observations on the predation abilities of some soil dwelling predatory nematodes. Nematolooica 22, THORNE, G, (1930). Predaceous ne.nas of the genus Mygolaimus and a new genus sectonema. J. Aoric. Reg THORNE, G. (1939). A monograph of the ne:natodes of the super family Dorylaimoidea. Capita. Zool., 3, THORNS, G. & SWANGER, H.H. (1936). A monograph of the nematode genera Dorvlaimus. Aporcelaimus. n, g., Dorvlaimoides n.g, and Punoentus n.g. Capita Zpol. 6, WOOD, F.H. (1973). Feeding relationship of soil dv/elling nematodes. Soil. Biol. Bloch.^^^^_^593-6oi. -> "^^^gs^^.^^^^^

33 -28- HYSS, U & GROOTAERT, P, (19 77). Feeding mechanism of Labronema vu1vapapi 1latum. Med. Fac. Landbouww Riiks. Univ., Gent., Belgium, 4^, YEATES, G.W. (1969). Predation by Mononchoide^ pptphikus (Nematoda : Diplogasterida) in Laboratory culture, Nematoloaica. 15, 1-9.

34 -29- Pig. 1 Attraction of A. nivalis towards prey 4 h after inoculation A. Meloidoqyne incognita juvenile (live), B. Heloidoqyne incognita juvenile (excised), C. Without prey, D. Hirschmanniella gryz^g (live), E. Hirschmanniella oryzae (excised).

35 8n A B 6. S 4 I 6-4. o z 2. I Zones 8-, 1 2 i (, Zon«s I i * Zones 8-, D 8- E a o z 6_ M O 5 4- a. o ^ Zones zones l^i g 1

36 PIG. 2 Attraction of A, nivalis towards prey inoculation 8 h after A, Heloidogyne incognita juvenile (live), B, Meloidoqyne incognita juvenile (excised), C, Without prey, D, Hirschmanniella oryzae (live), E, Hi rschmanni ella oryzae (excised).

37 0 A B 6 _ ^ 6-4 S "- 2 _ Zone* Zon»s c I 5 i Zones 8n 6, D 6. 4_ 2_ 3 4 Zorifs zones Fig 2

38 FIG. 3 A, Feeding rate of adults and juvenile stages of A, nivalis A. Males, B. Females, C. Fourth stage juveniles, D. Third stage juveniles, E. Second stage juveniles, B, Predatory pattern of A, nivalis over eight days, C, Prey preference by A. nivalis, A, Meloidoqyne incognita juvenile, B, Heterodera mothi juvenile, C, Hirschmanniella oryzae, D, Tvlenchortiynchus mashhoodi, E, Helicotvlenchus in^icua, E, Hoplolaimus indicus> G. Hemicvcliophora sp. D, Prey selection by A, nivalis in combination, A. 25 M. incognita juveniles + 25 H. orvzae^ B. 25 M, incognita juveniles + 25 T, maahhoodi. C. 25 M. incognita juvenile 25 H. tnothi juvenile, D. 25 H. oryzae 25 T. mashhoodi.

39 12. 12_ B M.incoqnilo J y a, o "A H.o'Yzqe. 8- a. c ^- b 2: 2. I 1 I A B C D E F Feeding rale of adult & juveniles o ' M.incoqnitaij O HQiyzae "I ' ^ No 01 days 12_ _ RiMcognitaJy I 8-1 r o ^8H a. "o T-aMs^ooi. ^^ H-mc^ii A B C D E F G Type of prey 2_ I B C Prey combination Fig 3

40 -32- FIG. 4 A. Effect of prey density on the rate of predation of A, nivalis B, Effect of starvation on the rate of predation of A. nivalis C, Effect of temperature on the rate of predation of A, nivalis D. Effect of agar concentrations on feeding rate of A, nivalis

41 12-, \ 22-. \,/* 10_, _, 8 8-»8H /X X^ X X X X X X jr^'^x^'^./ ^ M M / ^ Mincognita X H. QfyzQe J2 2J NO Of pr»y Starvation p«riod (days) 12_ D 10. i(m H 8-^ - «J o / X X X \. \ \ o 2-J 2-^ \ X \ X ' I's ' 2-5 ' 3^ ^ i*mp»r«lur* C "> 7,. ' I I I I I -1 I I» ' SO 6.0 Agar concfntmtion /, Fig 4