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1 Acarologia A quarterly journal of acarology, since 1959 Publishing on all aspects of the Acari All information: acarologia@supagro.inra.fr Acarologia is proudly non-profit, with no page charges and free open access Please help us maintain this system by encouraging your institutes to subscribe to the print version of the journal and by sending us your high quality research on the Acari. Subscriptions: Year 2018 (Volume 58): Previous volumes ( ): 250 / year (4 issues) Acarologia, CBGP, CS 30016, MONTFERRIER-sur-LEZ Cedex, France The digitalization of Acarologia papers prior to 2000 was supported by Agropolis Fondation under the reference ID through the «Investissements d avenir» programme (Labex Agro: ANR-10-LABX ) Acarologia is under free license and distributed under the terms of the Creative Commons-BY-NC-ND which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original author and source are credited.

2 EFFECT OF INFESTATION OF ACALITUS HIBISCI (ERIOPHYOIDEA : ERIOPHYIDAE), A GALL FORMING MITE ON AGE AND HAIRS OF LEAVES OF HIBISCUS VITIFOLIUS BY Saswati CHAKRABARTI 1, Sibani CHAKRABARTI 2 and Samiran CHAKRABARTI 1, 3 (Accepted July 2000) ERIOPHYID, ACALITUS HIBISCI, HIBISCUS VITIFOLIUS, INOCULUM, INCUBATION PERIOD, GALLS, LEAF HAIRS, LEAF AGE. ERIOPHYIDES, ACAL/TUS HIBISCI, HIBISCUS VIT/FOL/US, INOCULUM, PERIODE D'INCUBATION, GALLES,PILOSITE FOLIAIRE, AGE DES FEUILLES. SUMMARY : Acalitus hibisci, a pouch gall forming mite on leaves of Hibiscus vitifolius was studied to find out optimum inoculum size for the initiation of gall. Size of mites was correlated with size of space in between leaf hairs. Susceptibility of the host was correlated with leaf age. Total number of mites per gall increased with the size of gall significantly. Gall of 7 mm diameter was found as the most optimum size to be used as inoculum for gall initiation with minimum incubation period (6.6 days). First leaves on the branch (5 days old), were the most susceptible and produced galls in 6.6 days after inoculation. RESUME: Acalitus hibisci, parasite des feuilles d' Hibiscus vitifolius a ete etudie en vue de determiner!'inoculum optimal pour la formation de galles. La taille des acariens est correlee a l'espace entre les poils foliaires, et la susceptibilite de l'h6te avec l'age de la feuille. Le nombre total d'acarien par galle augmente significativement avec la taille de celle-ci. Les galles de 7mm de diametre sont les plus favorables en vue de leur utilisation comme inoculum avec une periode d'incubation de 6,6 jours. Les premieres feuilles des branches (age 5 jours) sont les plus receptives et produisent des galles apres 6,6 jours d'incubation. INTRODUCTION The eriophyid mite, Acalitus hibisci produces pouch galls on the lower surface of the leaves of Hibiscus vitifolius, a very common shrub in the locality (MONDAL & CHAKRABARTI, 1982). Anatomy of the gall was studied by GHOSH (1983). But no information on the host-mite interaction for this mite is available. Size of inoculum is important for successful infection by bacteria and other microbes. In case of different groups of insects (i.e. thrips) ANANTHAKRIS HNAN (1981) reported that population size has an impact on the size, shape and morphological complexities of galls. Very little information is available for gall mites particularly eriophyid mites about the impact of inoculum size for gall initiation. In 1982, CuLLEN et al. reported that by putting a complete gall (4-5 mm in diameter) of A ceria chondrillae at the stem apex of Chondrilla juncea it was possible to produce galls on the stem. 0LDFIELD & PERRING (1996) indicated that when compared to other plant feeding arthropods, eriophyids present special problems with respect to rearing. Hence, it seems that for successful rearing, inoculum size may play an important role for I. Biosystematics Research Unit, Department of Zoology, University of Kalyani, Kalyani , West Bengal. 2. Department of Botany, B.K.C. College, I I 1/2 B.T.Road, Calcutta Author for correspondance.

3 these mites. The present study was aimed to investigate this problem. Another important factor for successful infestation is the susceptibility of the host plant. Loruo (1986) proposed that susceptibility of plants bears a relationship with host-physiology and developmental phases. In plant pathology age of leaves plays an important role in resistance. BURRATTI et al. (1988) found that age of leaf plays a definite role in case of sawfly attacking pine needles. Presence of some antifeedant chemicals in very young leaves allowed the larvae to feed only on mature or one year old foliage. But in case of eriophyid mites so far studied no such data is available. The present study was aimed to determine optimum size of inoculum and total number of mites per inoculum which was a single gall, separated from infested leaf. WEBSTER (1975) noted that plant hairs are associated with resistance to insects in at least 18 plant genera. Wheat leaf pubescence was related to resistance to cereal leaf beetle, Oulema melanopus (GAL LUN, 1966) and Hessian fly, Mayetiola destructor (Say) (ROBERTS et. al., 1979). HARVEY & MARTIN (1980) studied the effect of infestation by Eriophyes tulipae (Keifer) on wheat pubescence. Present study was undertaken to correlate the size of mites with the size of gap between two bunches of stellate hairs on leaf, the space occupied by mites covered with muslin bags. Incubation period i.e. time of appearance of gall was noted in each case. Effect of leaf hair density and size on mite infestation : The total number of hairs/mm of normal and galled leaf, length and width of hair, the distance between two bunches of hairs and distance between two branches of a bunch were measured under stereobinocular microscope with x 60 magnification. The length and width of different stages of life of the mite were also studied. Behaviour of the mite viz., location of egg laying, movement of the mite in between leaf hairs etc. were observed under stereo binocular microscope with x 60 magnification. Statistical analysis : The usual Analysis of Variance technique was followed to test the significance of differences in the inoculum sizes and leaf ages and their interaction (SNEDECOR & COCHRAN, 1967). RESULTS AND DISCUSSION Total number of mites/gall : The total number of mites including all growth stages from egg to adult increased with the increase in size of galls as it is evident from TABLE 1. TABLE I. Total number of mites per gall. MATERIAL AND METHODS Collection of sample : The mite was reared in its natural habitat on leaves of Hibiscus vitifolius. Galls of different sizes, as well as healthy leaves were collected in polythene bags and brought to the laboratory for study. Determination of number of mites/gall: the total number of mites including all stages from egg to adult in each gall was counted under stereo binocular microscope with x 60 magnification. Determination of optimum size of inoculum : Different sizes of galls were attached to healthy leaves and each leaf with its attached gall was then covered with a muslin bag. At 24 hrs. interval random samples from each treatment were collected and observed through stereo binocular microscope with x 60 magnification. Effect of leaf age on incubation period : The galls with optimum size (7mm diameter) were tagged to 1st, 2nd, 3rd, 4th and 5th leaves (5, 8,10, 12 and 15 days respectively) and Size of gall Number of mites S.D. ± (diameter/mm) *All results are mean of 5 random samples. Optimum size of inoculum and leaf age for gall initiation: No gall was found to be produced when the size of the inoculum (i.e., gall cut from leaves and attached to healthy leaves) was below 7 mm. Above 7.5 mm, the inoculum also shows a sharp increase in incubation period, i.e., gall initiation due to inoculation was delayed and slow. From the TABLE 2, the C.D. value indicates that the effect of difference

4 TABLE 2. Effect of leaf age and inoculum size on gall production by eriophyid mites on Hibiscus vitifolius. Leaf age (A) (days old) Incubation period(in days)** Inoculum size( diameter of Gall) 7 mm*(b) 7.5 mm(c) 1st leaf (5) nd leaf (8) rd leaf (10) th leaf (12) th leaf (15) *No gall is produced below inoculum size of 7 mm; above 7.Smm total incubation period shows a sharp increase. ** Results shown in the table are mean values of 5 random samples. C. D. value at 5% level : Interactions : B x C = 4.17; A x B = ; A X c = between the two inoculum sizes, 7 mm and 7.5 mm sizes of galls respectively, is not significant. Analyzing the results, it may be stated that gall of 7 mm diameter is the optimum size for its use as inoculum TABLE 2 also shows that the effect of leaf age on mite infestation is highly significant. The younger leaves are more susceptible and the first leaf (5 days old) is the most. These leaves present a high level of photosynthates for growth. As there is continuous supply of food, young leaves are favourable to successful mite attack. The results of the present study supports the hypothesis proposed by MOONEY et al. (1983). They proposed that a genetically determined time schedule of resource allocation for growth and differentiation is operating in plants and this result to open "Windows" of susceptibility towards herbivores. Infestation by pests changes the normal schedule and normal metabolic pathways are disturbed resulting malformation. Effect of mite infestation on leaf hairs and its relation to the size of mites and their behaviour: The leaf hair of Hibiscus vitifoliusis of stellatetype. From TABLE3, it is found that number of leaf hairs/sq.mm increased almost twice in galls although there is no significant difference in their length. The distance between two branches of a bunch as well as the distance between two bunches decreased more than 50%. TABLE 3. Effect of mite infestation on leaf hairs of Hibiscus vitifoilus. Hairs Normalleaf(A) Number/mm leaf area(i) Length from base to apex (mm) (ii) Diameter of the bunch at the middle (mm) (iii) Distance between two bunches (mm) (iv) Distance between two branches of a bunch (mm) (v) S.D. ± Galled leaf(b) S.D. ± * All results are mean of 5 random samples. * Interaction between A & B. C. D. values at 5% level : (i) , (ii) , (iii) 9.572, (iv) , (v) TABLE 4 shows the size of mites at different ages. It was found that females lay eggs in space between two bunches of hairs, but not in the space between the branches. Because round eggs of J.lm diameter could be accommodated only in between two bunches (space J.lm in normal leaf and J.lm in galls) but not between two branches of a bunch (space J.lm in normal leaf and 8.13 J.lm in galls). As mites gradually become mature passing through protonymph and deutonymph stages, their size also increases. Using stereobinocular microscope (x 60 magnification), it was noted that as space diminished,

5 -316- TABLE 4. Size of mites at different stages of life cycle. Stages of growth Length ()lm) S.D. ± Width ()lm) S.D. ± Egg Protonymph Deutonymph Adult *All results are mean of 10 random samples the mites oriented their bodies almost vertically (length ~-tm, width ~-tm for adults while space between two bunches ~-tm in galls). Adult mites were found to crawl to the tip of hairs and sometimes remained clinging to it and swinging. KRANTZ (1973) noted that some eriophyid species were air borne at wind velocities less than 4-5 rn!s. Swinging of mites at the tip of hairs may add momentum and thrust which help in their dispersal even through low wind velocities. ACKNOWLEDGEMENTS The first author thanks the University of Kalyani for granting a research fellowship and the Head, Department of Zoology, University of Kalyani, for providing laboratory facilities for this work. The second author thanks the University Grant's commission, New Delhi for Financial assistance. REFERENCES ANANTHAKRISHNAN( T. N.), Thrips-plant gall association with special reference to patterns of gall diversity in relation to varying thrips population. - Proc. Indian Natn. Sci. Acad. B 47: BURATTI (L.) ALLAIS ( J. P.) & Barbier (M.), The role of Resin acids in the relationship between Scots pine and the Saw fly, Diprion pini (Hymenoptera : Diprionidae). I. Resin acids in the Needles. -In Mechanism of woody plant defenses against insects : Search for Pattern (W. J. MATTSON, J. LEAVIEUX & C. BERNARD DAGAN, Eds.). Springer-Verlag, N. Y CULLEN(J. M.) GROVES (R. H.) & Alex (J. F.), The influence of A ceria clwndrillae on the growth and repro- ductive capacity of Chondrillajuncea.- J Appl. Ecol., 19: GALLUN (R. L.) RUPPEL (R.) & EVERSON (E.H.), Resistance of small grains to the cereal leaf beetle.- J Econ. Entomol., 59 : GHOSH (BASUDEV), Taxonomy of eriophyid mites (Acarina : Eriophyoidea) of Bankura and Hooghly districts of West Bengal and Morphology of some eriophyid galls.- Ph.D. Thesis, University of Kalyani, India. HARVEY (T.L.) & MARTIN (T.J.), Effects of wheat pubescence on infestation of Wheat Curl Mite and incidence of Wheat Streak Mosaic.-J Econ. Entomol., 73 : KRANTZ (G.W.), Observations on the morphology and behaviour of the filbert rust mite Aculus comatus (Prostigmata : Eriophyoidea) in Oregon. - Ann. entomol. Soc. Am., 66: LORIO (P. L. JR.), Growth differentiation balance: a basis for understanding southern pine beetle tree interactions. - Forest Ecol. Manage., 14: MONDAL (S.) & CHAKRABARTI (S.), Studies on the eriophyid mites (Acarina : Eriophyoidea) of India. XI. Descriptions of three new species from West Bengal. - Entomon., 7 (3): MOONEY (H.A.) GULMON (S.L.) & JOHNSON (N.D.), Physiological constraints on plant chemical defenses. In "Plant resistance to insects" (P.A. HEDLIN, Ed.). - Ame1: Clzem. Soc., Washington DC LDFIELD (G. N.) & PERRING (T. M.), Rearing Techniques. In Eriophyid mites-their biology, Natural enemies and control (E. E. LINDQUIST, M. W. SABELIS & J. BRUIN, Ed.). Elsevier Science B. V ROBERTS (J.J.) GALLUN (R.L.) PATTERSON (F.L.) & FoSTER (J.E.), Effect of wheat leaf pubescence on Hessian fly.- J Econ. Entomol., 72: SNEDECOR (G.W.) & COCHRAN (W.G.), Statistical methods, 6th ed. Iowa State University Press. I. A., USA. WEBSTER (J.A.), Association of plant hairs and insect resistance.- USDA Mise. Pub.I 1297: 1-18.