Plant Protection Department, National Research Centre, Dokki Cairo, U.A.R.

The Ecological Approach to the Management of the Citrus Rust Mite Phyllocoptrrcta oleivortls (Ashin.)

By ALY H. RASMY, M. A. ZAHER' and M. E. EL-BAGOURY

With 2 Figures

Abstract

Ecological studies on the citrus rust mite P. oleivorus infesting citrus orchards a t the north- ern coast of the Mediterranean Sea in the U.A.R. and its management were carried out for two years. Population behaviour of the pest was influenced by the prevailing climatic con- ditions and host preference, while the rBle of the predacious mites was not considerable there. One acaricide application was sufficient to suppress the mite outbreak below the economic level for the entire year if it was applid when mite population started to increase.

Introduction

The eriophyid mite Phyllocoptruta oleivorus (Ashm.) is one of the most important citrus pests. MOHAMED (1953) and RASMY (1966) reported that the infestation of this pest is confined to citrus orchards of the northern coast of the Mediterranean Sea in the U.A.R. where weather conditions are in favour of its reproduction. The pest was formerly of minor importance in the U.A.R., apparently having been held in check by natural enemies,. yet with the increase use of organic phosphorus pesticides, it becomes a noxious pest. RIPPER (1956) in his review on the effects of pesticides on pest popula- tions balance cited many instances of resurgence in mites following the in- crease use of pesticides. LORD et al. (1956), PUTMAN and HERN (1959), RASMY (1969) and many other workers have shown that if pesticides could be eliminated or greatly reduced, orchard mites would not be a problem.

The present research is a step towards establishing a successful manage- ment to control the citrus rust mite.

Materials and Methods

Population studies of mites were carried out in two successive years of 1967 and 1968 on five years old Navel orange, Valencia orange, mandarine, Addalia lemon and Baladi lemon

Professor of Plant Protection, Faculty of Agriculture, Cairo University.

2. ang. Enr. 70 (1972), 68-71 @ 1972 Verlag Paul Parey, Hamburg und Berlin

Citrus Rust Mite Phyllocoptruta oleivorus 6 9

orchards at Alexandria. Samples of 25 leaves were collected, at random every other week. Mite populations were estimated by examining both leaf surfaces. Acaricide rreatmcnts were carried out in Navel orange orchard when mite population started to increase. The orchard was devided into six plots of 25 trees each. An additional plot was sprayed with plain irrigation water to evaluate its effect on mite population. The acaricides used were dicofol 0.12 "/o, zineb 0.15 "/a, galecron 0.1 "/o, phosalone 0.15 "/a and Rodocidez 0.15 "1'0.

Mite determinations were carried out after one, seven, 14 days and every other week till ten weeks from application.

Results and Discussion

The results revealed that the citrus rust mite P. oleivorus prefers infesting Navel orange, Valencia orange and mandarine respectively (Fig. 1). Its population was high during summer and fall on Navel orange and Valencia

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Fig. 1. Population trend of P. oleiworrs on different citrus varieties

orange, while it reached its minimum level during spring and winter. Sam- ples of mandarine were free from infestation during 1967 season, while slight infestation was noticed in the next season. The accumulated average of the mite during the two year-study was 12, 8.6 and 0.2 individuals per leaf on Navel orange, Valencia orange and mandarine respectively. No infestation was noted on either Addalia or Baladi lemon except some few fruits of Addalia. The findings of MOHAMED (1964) may clarify the preference of the pest to citrus varieties. He suggested that thickness of citrus leaf cuticle, oil glands, tannin and PH value might be responsible for the preference of mite

* bis 0,O.. dimethyl dithicphosphoryl) methane.

70 A!y H . Rasmy, M. A . Zaher and M . E . El-Bagowy

to citrus varieties. In Florida, MUMA (1955) noted that heaviest population of P. oleivorus occurred in winter, spring and summer on citrus. In 1958 he noted that the peak population occurred almost durin, 0 summer.

Statistical analysis proved that temperature had a positive significant correlation with mite population on Valencia orange, while a non significant

negative correlation was noted with relative humi- dity.

Temperature With reference to the Humidity - 0.08 predacious mites, their

numbers were too small 1 Significant at 5 "/o level of probability.

for plotting on a graph. Members of the families

Phytoseiidae, Tydeaidae and Stigmaeidae were commonly noticed although their role in checking mite population was not considerable. O n the other hand, mites of families Stigmaeidae, Eupalopsellidae, Cheyletidae, Cu- naxidae and Bdellidae were rarely observed. However, the following pre- dacious mites were recorded associated with citrus trees at Alexandria: T y - phlodromus pyri Scheuten, Amblyseius swerskii (Athias-Henriot), Procto- laelaps bickleyi (Bram), P . hypudaei (Oud.), Tydeus kochi (Oud.), Prone- matus ubiquitus (McG.), Paralorryia mali (Oud.), Paracbeyletia bakeri (Ehara), Cheletogenes ornatus (Canestrini and Fanzago), Agistemus exrertus Gonzalez, Eupalopsis aegyptiaca Zaher and Soliman, Stigmaeus h e n s (Sum-

Factors Correlation coefficient values

I

? 5 1

Rodocide 0 Water 0 Check

30 45

I Zenib H Dicofol Ill Galecron LiiJ Phosalone

60

DAYS AFTER APP Fig. 2. Number of P. oleivorus on the treated navel orange

75

I

Citrus Rust Mi te Phyllocoptruta oleivorus 71

mers), Saniosulus nudus Summers, Eupodes sp., Neophyllobius citri Zaher and Soliman and N . aegyptium Zaher and Soliman.

The effects of dicofol, zineb, diethion, phosalone, galecron and Rodocide on P . oleivorus population are presented in Fig. 2. Results indicated that dicofol, zineb, Rodocide and phosalone caused more than 98 O/o reduction in mite population, while galecron decreased 75.7 O / o during the sampling pe- riods. Spraying with plain irrigation water was in favour of P. oleivorus population as it allowed for a 6-fold increase in population than the check. The acaricides used were generally effective for 90 day-post application but exerted a leathal effect on the predacious mites. The early increase of P . olei- V O Y U S population in the following season on treated trees may be due to the effect of the acaricides used on the host contents which might rendered them to be more favourable for mite feeding as suggested by RODRIGUEZ (1960) and RASMY and ALI (1 970).

On the basis of such ecological studies, the suitable timing of acaricide application to suppress the out-break of the citrus rust mite P. oleivorus can be approached. The study reveals that the predacious mites associated with citrus orchards of the northern coast of the Mediterranean sea are ineffective to check the high population of the pest under the economic injury level. One acaricide application is sufficient to control this pest for the entire year if it is practiced when the mite population starts to increase.

Zusammenfassung

Zur Ukologie und Bekampfung der Citrusmilbe Phyllocoptruta oleivorus (Ashrn.) Es wurden 2jahrige Untersuchungen uber die Ukologie und Bekampfung von P. oleivorus: einem Schadling der Zitrus-Kulturen, in den nordlichen Kiistengebieten des Mittelmeeres der U.A.R. durchgefuhrt. Die Populationsdichte wurde hauptsachlich von den klimatischen Be- dingungen sowie dem Wirtsangebot bestimmt, wahrend die Rolle rauberischer Milben nicht erheblich war. Es geniigt eine Behandlung im Jahr mit Insektiziden, um die Milbe in einer wirtschafilich vertretbaren Dichte zu halten, sofern die Anwendung mit dem Beginn der Massenvermehrung des Schadlings zusammenfallt.

References

LORD, F. T., HERBERT, H. J., and MACPHEE, A. W., 1958: The natural control of phyto- phagous mites on apple trees in Nova Scotia. Proc. 10th (1956) Int. Cong. Ent. 4,

MOHAMED, I. I., 1953: The biology of Phyllocoptruta oleivows (Ashm.) and its distribution in Egypt. M. Sc. Thesis, Fac. Agr. Cairo Univ., pp. 92. - 1964: Host preference of the citrus brown mite Eutetranychrs banksi (McG.). Bull. SOC. ent. Egypte, L 48, 163-170.

MUMA, M. H., 1955: Factors contributing to the natural control of citrus insects and mites in Florida. J. econ. Ent. 48, 432-438. - 1958: Predators and parasites of citrus mites in Florida. Proc. 10th Int. Congr. Ent. 4,

PUTMAN, W. L., and HERN, D. H., 1959: Gross effects of some pesticides on population of phytophagous mites in Ontario pea& orchards and their economic implications. Can. Ent. 91, 567-579.

RASMY, ALY H., 1966: Integrated control of citrus mites - Ph. D. Thesis, Fac. Agr. Cairo Univ., pp. 128. - and ALI, A. M., 1970: Effects of acaricides on citrus contents and resulting effect on mite population. 2. ang. Ent. 65, 156-159.

RODRIGUEZ, J. G., DONALD, E. M., and SWITH, W. T., 1960: Effect of soil insecticides and absorbents on plant sugars and resulting effect on mite nutrition. J. econ. Ent. 53, 491-495.

617-622.

633-647.