PflKrankh. 3/05 Environmental management and biological aspects of two eriophyid olive mites in Egypt: 287 Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz Journal of Plant Diseases and Protection 112 (3), 287–303, 2005, ISSN 0340-8159 © Eugen Ulmer GmbH & Co., Stuttgart Environmental management and biological aspects of two eriophyid olive mites in Egypt: Aceria oleae and Tegolophus hassani Umweltmanagement und biologische Aspekte von zwei eriophyiden Olivenmilben in Ägypten: Aceria oleae und Tegolophus hassani B. A. A-A1 *, A. M. M 2 , M. M. A-A2 Plant Protection Department, National Research Centre, 12622 Dokki, Cairo, Egypt 2 Department of Agricultural Zoology and Nematology, Faculty of Agriculture, Al-Azhar University, Cairo * Corresponding author, e-mail: badawi_abou_awad@hotmail.com 1 Received 7 January 2004; accepted 3 May 2004 Summary Mites from an abandoned olive nursery in Egypt were observed for two years, during which species diversity, seasonal fluctuations and biological aspects of specific eriophyid species were studied. T wo eriophyid species – the olive bud mite Aceria oleae Nalepa and the olive rust mite Tegolophus hassani (Keifer), representing a basic trophic level – were fed upon by two predacious mites – Neoseiulus cydnodactylon (Shehata and Zaher) and Agistemus olivi Romeih. Population abundance of the eriophyid mites was affected by climatic conditions, predation, shady and sunny zones, leaf age and vertical distribution. About 12, 5, 15 and 4 generations were recorded for both eriophyid species during the two successive years, respectively. A control measure of one spring pesticide (abamectin) seemed to be the most successful against the harmful mites. Life table parameters showed that the population of T. hassani multiplied 9.92 times in a generation time of 14.42 days at 31 °C and 80 % r. H., while the A. oleae population increased 16.70 times in a generation time of 13.50 days at the same conditions. Field and laboratory studies indicated that the olive bud mite is considered to be a disastrous mite on shrub and young olive trees. Key words: ecology; biology; Aceria oleae; Tegolophus hassani; Eriophyidae; Neoseiulus cydnodactylon; Phytoseiidae; Agistemus olivi; Stigmaidae; Acari; phytophagous and predacious mites Zusammenfassung Milben in aufgegebenen Olivenanlagen in Ägypten wurden zwei Jahre lang beobachtet, während der die Untersuchung der Artendiversität, der jahreszeitlichen Fluktuationen und der biologischen Aspekte spezifischer eriophyider Arten erfolge. Zwei solche Arten – die Olivenknospenmilbe Aceria oleae Nalepa und die Olivenrostmilbe Tegolophuy hassani (Keifer), die ein Grundnahrungsniveau repräsentieren – dienten zwei Raubmilben – Neoseiulus cydnodactylon (Shehata & Zaher) und Agistemus olivi Romeih – als Beute. Die Populationsdichte der Milben wurde durch klimatische Faktoren, Beutegewinnung, schattige und sonnige Zonen, Blattalter und vertikale Verteilung beeinflusst. Ungefähr 12 und 5 bzw. 15 und 4 Generationen konnten für die beiden Milbenarten während der beiden Jahre beobachtet werden. Eine Bekämpfungsmaßnahme mit Abamectin im Frühjahr schien am erfolgreichsten gegen die schädlichen Milben zu sein. Die Parameter der Lebenstafel zeigten, dass sich die Population von T. hassani um das 9,92-fache vermehrte bei einer Generationsdauer von 14,42 T agen bei 31 °C und 80 % rel. Luftfeuchtigkeit. Unter diesen Bedingungen nahm die Population von A. oleae 288 Abou-Awad/Metwally/Al-Azzazy 3/05 PflKrankh. um das 16,7-fache zu bei einer Generationsdauer von 13,5 T agen. Freiland- und Laboratoriumsversuche deuten darauf hin, dass die Olivenknospenmilbe als ein verheerender Schädling an jungen Olivenbäumen betrachtet werden muss. Stichwörter: Ökologie; Biologie; Aceria oleae; Tegolophus hassani; Eriophyidae; Neoseiulus cydnodactylon; Phytoseiidae; Agistemus olivi; Stigmaidae; Acari; Raubmilben 1 Introduction T he olive bud mite Aceria oleae Nalepa and olive rust mite Tegolophus hassani (Keifer) are host-specific and occur whenever olive trees are cultivated. A. oleae is the main acarine pest of all varieties of olive in the mediterranean area, especially the young trees. It prefers warm areas, and, when feeding on and around growing points, makes developing leaves twisted and stunted and may even kill shoots. T. hassani also sucks the plant sap causing yellowish spots on the upper leaf surface, the scales on the lower surface turn apart and more water is lost. At heavy infestations, individuals of each mite species twist and deform leaves, causing misshaped fruits and seriously reduce the amount and quality of olives available for pickling. T he pesticides used in olive nurseries destroy the predacious mites, which are most important in controlling the eriophyid species (A-A and E -B  1986; E -L 1999; A-A 2002). Chemical control has been used to achieve a fast effective management, but this method rarely produced more than a temporary reduction of the pest population. T he number of species and the relative abundance of the prevailing predacious mites can be integrated with a pesticide to reach a successful pest management. T his study is an ecological investigation approach to develop a method for controlling eriophyid populations infesting olive nurseries. T he different biological aspects of the life history of the olive bud mite and the olive rust mite were also studied. Special attention was paid to the effect of the average of different temperatures and relative humidities, which were dominant throughout the year, on the life table parameters. 2 Materials and methods 2.1 Locality and materials Ecological studies of the olive bud mite Aceria oleae Nalepa and the olive rust mite Tegolophus hassani (Keifer), as well as their predators ( Agistemus olivi Romeih, Neoseiulus cydnodactylon (Shehata & Zaher)) were carried out in an abandoned olive nursery, six months old, in Giza nursery at the farm of Agriculture, Cairo University, during two years (2000–2002). Sixty-five young olive trees (Olea europeae L., cv. ‘Eigezy’) of the same size, vigor and shape were selected. Young trees, which were 90 cm tall at the beginning of the experiment, reached a height of nearly 200 cm when the observations were completed after two years. Samples of 25 leaves were chosen every week at random. Phytophagous and predacious mite populations were estimated by examining leaf surfaces. Eriophyid occurrence was also observed by examining a sample of 25 leaves of the sunny terminal parts of the shrub branches from all directions and another one from the shady central core of the same shrubs, as well as 25 of each old and succulent young leaves collected regularly every other week during summer months. T o study the comparative abundance of leaf surfaces and vertical distribution of eriophyid mite species, 270 leaves were collected randomly from the top, bottom and middle of olive young trees. Observations were made for a period of 12 months, from April 2000 to March 2001 at Giza nursery. Samplings were carried out on the 15 th of every month. In the present investigation, leaves of the young trees from the upper 10–15 cm of the bushes, were considered “top-level leaves” and those present on the bushes of the young trees up to a height of 40–50 cm above ground level, were treated as “bottomlevel leaves”. T he foliage present in between the top and the bottom level were regarded as “middlelevel leaves”. PflKrankh. 2.2 3/05 Environmental management and biological aspects of two eriophyid olive mites in Egypt: 289 Treatment An area of the same abandoned olive young trees in Giza nursery, with a history of eriophyid mite infestations was selected. Abamectin (Vertimec E. C. 1.8 % at the rate of 27 oz., 764 g / ha), was used. T reatments were carried out when mite populations started to increase. T hey were replicated four times with a replicate of seven young trees (cv. ‘Eigezy’). T reated and untreated replicates were represented each by 40 leaves. Pre-spray counts were made for all treatments and replicates to determine the initial distribution and density of the mites. Observations were made one, three days and eight weeks post treatments. Reduction percentage was calculated according to the formula of H  and T  (1955). Spray was applied with a conventional high pressure spray motor and hand spray gun. Adult stages of the predacious mites were mounted in Hoyer’s solution, as modified by S and P (1963), for identification. Records for the daily rate of temperature and relative humidity, prevailing at the locality and corresponding to sample periods, were taken from the Central Meteorological Department, Ministry of Scientific Research. Under vertical distribution, central shady and sunny terminal zones, as well old and succulent young leaves, f-test and t-test were used for comparison. 2.3 Life history study Many unsuccessful trials were performed in rearing eriophyid olive mites on lower and upper surfaces of different succulent young, intermedium or old leaves. T hese trials were mostly based on known methods used for several other species of eriophyoid mites (A-A 1979, 1981; E  1979; AA et al. 2000). Plastic cages were also used for the same purpose (A-A 2002). However, all these mentioned trials were unsatisfactory and only the method described below was adequate. A medium consisted of: Agar 8.0 g, Murashige and Skoog 1.1 g, rose bengal 1.0, indole acetic acid 1.0 ml, solved in distilled water 1000 ml. Agar was transferred to a vial and was melted using a boiling water-bath, then a vial was removed. Murashige and Skoog was agitated in the melted agar till dissolved. T he obtained mixture was then sterilized by adding rose bengal which was dissolved by agitation. T hereafter, indole acetic acid was added to the dissolved mixture. Soft lateral olive branches were washed and divided into sections of 15–20 cm length. All attached leaves were removed, except one leaf was left for each part of the divided branches to rear the eriophyid species. Cuttings were dipped, for 2 s, into indole acetic acid to encourage developing roots, before inserting into tubes containing the above-cited prepared medium. Fifty newly mated females of the olive bud mites A. oleae or the olive rust mite T. hassani were obtained from heavily infested olive leaves, and placed singly on the leaves of cuttings by mean of a human eyebrow, fastened to a hanndle. Each female was allowed to deposit one to two eggs, then it was removed. According to ecological study, treated cuttings were placed in the incubator at different temperatures and relative humidities (20 ± 1 °C and 50 % r. H.; 25 ± 1 °C and 70 % r. H., 31 ± 1 °C and 80 % r. H.). Mite development was observed twice daily. After the last moult of either sex and to insure insemination by spermatophores produced by males, each newly emerged female was transferred, for 24 h, to a leaf previously inhabited by an adult male, then females and males were transferred back to their original leaves. K’s (1954) three-step recipes for fixation and embedding were used. Life table parameters were calculated according to H  et al. (1990). 3 Results and discussion 3.1 Seasonal variations T he population dynamics of the eriophyid mites and their predators for a 2-yr study on the young olive trees along with the weather data for the corresponding period, are given in Figure 1. 3.1.1 Eriophyid mites T wo species of eriophyid mites were commonly found on young olive trees: T he olive bud mite A. oleae and the olive rust mite T. hassani. 290 Abou-Awad/Metwally/Al-Azzazy 3/05 PflKrankh. Fig. 1. Population trends of eriophyid olive mites and their predators on abandoned young olive trees in Giza nursery during two successive years. PflKrankh. 3/05 Environmental management and biological aspects of two eriophyid olive mites in Egypt: 291 A. oleae was the most prominent on leaves, while T. hassani came second in the order of abundance on the same leaves. T he highest A. oleae population occurred in mid July 2000 with 53.92 individuals per leaf, when temperature and relative humidity averaged 29 °C and 71 %, respectively. T he population then decreased till it reached 1.3 individuals per leaf in January 2001, when temperature and relative humidity averaged 18 °C and 59 %, respectively. T he most suitable months for population growth were from April to early October 2000. T he numbers of this mite varied greatly during fall and winter seasons. T he reverse was observed in the second year, young trees, which were 90 cm tall at the beginning of the experiment, reached a height of nearly 200 cm when the observations were completed after end of March of the second year (2001–2002). It had been noted that the population of A. oleae suddenly declined and tailed off throughout the second year, except the period from late April to the beginning of July, being 3.64 individuals per leaf in mid of June. T his sharp decline of the population density is possibly due to the prevailing predatory phytoseiid and stigmaeid mites as well as to the increasing unsuitability of the new young trees growth as a feeding medium for the mites, and the new growth also looses its succulence as the season progresses. T he data obtained are in agreement with those reported by S-M  (1981), who found almost the same behaviour for the pear bud mite Eriophyes pyri (Pagen). T he population was positively correlated with the prevailing temperatures for two successive seasons, while no significant correlation was noted with the relative humidity in the second season (T able 1). It may be concluded that during certain periods, the effect of other environmental conditions on the olive bud mite’s population may become more predominant so as to overshadow other factors. T he distribution of the olive rust mite T. hassani differed from that of A. oleae. It was found that its density gradually increased from the beginning of April to a remarkable rate during summer months in the first season (2000–2001) with a peak reached in mid of July being of 36.76 individuals per leaf, when temperature and relative humidity averaged 27.6 °C and 64.6 %, respectively. In late January, the population suddenly decreased till it reached its lowest rate. T he population was positively correlated with prevailing temperatures and relative humidities recorded throughout the first year, but in the season year (2001–2002), the population seriously declined and tailed off throughout the season (similar to A. oleae), except the period from late April to beginning of July, being 5.52 individuals per leaf in mid of May (Fig. 1). T he behavioural findings are in general agreement with those obtained by C  and P-S (1982) for the vagrant eriophyid mite, Aculus olearius Castagnoli. It infests olive trees during the flowering period between May till July. Its population density differed greatly during three years of study with cv. ‘Leccino’, but was less fluctuating with cv. ‘Carolea’. Individual behaviour could be due to the varieties and the microclimate prevailing in the investigated area. T o determine the number of annual generations passed by the olive bud mite A. oleae and the olive rust mite T. hassani under the local environmental conditions, the percentage of immature stages in weekly mean populations was estimated. T he time at which the highest percentage of the immature stages occurs represents a new generation. About twelve and five and fifteen and four generations were recorded for both eriophyid species during the two successive years, respectively. T he longest generation for both mites is that, which passes throughout the fall and winter seasons and lasts for about four to five weeks, while the shortest generation occurs in spring and summer and lasts for about one week interval during the two successive years (Figs. 2 and 3). T able 1. Correlation coefficient between temperature, relative humidity and eriophyid mite populations in an abandoned olive nursery during two successive seasons (2000–2002) Eriophyid mites Correlation coefficient values 2000–2001 season A. oleae T. hassani * Significant at 5 % level. 2001–2002 season T emperature Humidity T emperature Humidity 0.629** 0.733** 0.186 0.265 0.338* 0.217* –0.531 –0.441 ** Significant at 1 % level. 292 Abou-Awad/Metwally/Al-Azzazy 3/05 PflKrankh. Fig. 2. Percentage of the immature stages in the total population of the olive bud mite Aceria oleae in abandoned olive nursery in Giza. PflKrankh. 3/05 Environmental management and biological aspects of two eriophyid olive mites in Egypt: 293 Fig. 3. Percentage of the immature stages in the total population of the olive rust mite Tegolophus hassani in abandoned olive nursery in Giza. 294 Abou-Awad/Metwally/Al-Azzazy 3/05 PflKrankh. A great difference is observed between eggs and motile stages of A. oleae and T. hassani populations on leaves for both sunny and shady zones of the young olive trees during summer season 2000. T he central cores always tend to harbour a higher significant mite population of both previous species than the sunny terminal zones during May, June, July and August, being 19.44 & 6.58 and 6.86 & 4.63 individuals per leaf, respectively. Positive relationships were also detected between the eriophyid species and their predators of prevailing phytoseiid and stigmaeid mites, being 0.92 and 0.22 predators per leaf for both shady and sunny zones, respectively (T able 2). T his phenomenon could be due to the preference of both mite species and associated predators to the shady zones seeking shelter from heat during the summer season. T he degree of infestation with eriophyid olive mites was positively correlated with leaf age. Individuals of A. oleae and T. hassani preferred the immature leaves to mature ones (T able 3). Mite populations averaged 13.04 & 7.44 and 5.89 and 4.13 individuals per young and old leaf during summer months, respectively. Young leaves were also preferred for depositing eggs than old ones during summer season. A-A et al. (2000) indicated that the fig bud mites Aceria ficus (Cotte) preferred the immature leaves instead of mature ones, while the latter were preferred for oviposition throughout the season. Significant correlation was also noted in mite predator population on both young and old leaves (T able 3). T he numerical changes in vertical distribution of the olive rust mite T. hassani and the olive bud mite A. oleae on young trees from April 2000 to March 2001, along with temperature and relative humidities for the corresponding period are given in Figures 4 and 5. T racing up the population trend, it was found that its density exhibited a gradual increase from April, reached its peak in June–July and started declining from August onwards. Mean number of both mites per leaf was high on leaves at the top and on middle leaves of olive bushes and harbouring almost equal numbers of the two species. At the bottom level, leaves had relatively less numbers of species in comparison to the top and middle levels (T able 4). Percentage distribution of the two eriophyid species on surfaces of olive leaves at the vertical levels of bushes demonstrated that the distribution of A. oleae differed greatly from that of T. hassani. T he first was the highest on the leaves at three levels, whilst the latter was the lowest (T able 5). On the other T able 2. Population of eriophyid and predatory mites on olive leaves of sunny and shady zones in an abandoned nursery during the 2000 season Data of sampling No. of mite stages/25 leaves Terminal zone (sunny) T. hassani May 10 25 Jun. 10 25 Jul. 10 25 Aug. 10 25 T otal mean A. oleae Central core (shady) Predators T. hassani A. oleae Predators E. M. E. M. N. cydnodactylon A. olivi E. M. E. M. N. cydnodactylon A. olivi 12 07 06 13 10 09 17 14 100 067 063 106 081 064 192 054 00.0 00.0 00.0 00.0 15.0 00.0 05.0 08.0 0299 0063 0106 0184 0059 0160 0291 0209 01.0 00.0 02.0 03.0 02.0 04.0 03.0 00.0 05.0 03.0 03.0 03.0 04.0 05.0 05.0 00.0 037 034 016 025 082 018 033 082 0225 0188 0111 0094 0078 0168 0208 0243 00.0 00.0 00.0 00.0 15.0 00.0 07.0 20.0 0457 0415 0121 0307 0661 0168 0980 0779 04 04 05 04 04 07 05 04 008 010 025 016 019 026 017 026 88 11.0b 727 90.9b 28.0 9.3b 1371 171.4b 15.0 2.5b 28.0 4.0b 327 40.9a 1315 164.4a 42.0 14.0a 3888 486.0a 37 4.6a 147 18.4a E. = Eggs, M. = Moving stages. Different letters in horizontal column denote significant difference ( P < 0.01, t-test). PflKrankh. T able 3. 3/05 Environmental management and biological aspects of two eriophyid olive mites in Egypt: Population of eriophyid and predatory mites on both old and young olive leaves of abandoned nursery during the 2000 season Data of sampling No. of mite stages/25 leaves T. hassani Old May 10 25 Jun. 10 25 Jul. 10 25 Aug. 10 25 T otal mean 295 Predators A. oleae Young Old Young Old Young E. M. E. M. E. M. E. M. N. cydnodactylon A. oleae N. cydnodactylon A. oleae 011 026 026 034 017 043 032 027 121 091 067 092 142 061 075 176 067 030 050 040 034 045 055 051 0233 0193 0138 0231 0193 0129 0178 0193 00.0 00.0 00.0 00.0 00.0 026.0 021.0 015.0 0085 0113 0083 0121 0152 0157 0175 0292 00.0 00.0 00.0 00.0 00.0 032.0 055.0 026.0 0346 0362 0271 0218 0134 0207 0511 0558 03 04 01 04 03 01 01 03 09 07 02 05 04 09 05 03 19 08 06 05 04 01 08 08 021 022 019 017 010 010 023 015 216 27.0b 825 103.0b 372 46.5a 1488 186.0a 62.0 20.7b 1178 147.3b 113.0 37.7a 2607 325.9a 20 2.5b 44 5.5b 59 7.4a 137 17.0a E. = Eggs, M. = Moving stages. Different letters in horizontal column denote significant difference ( P < 0.01, t-test). hand, individuals of A. oleae were frequently found on the lower surface of leaves, while T. hassani preferred the upper surfaces. About 78.60, 87.30 and 80.70 % as well as 70.31, 74.80 and 56.30 % of the total olive bud and rust eriophyid species were observed principally on the lower and upper surfaces of leaves at three levels for both mites, respectively (T able 6). T he high build-up of the eriophyid mite population observed during summer months could be attributed to the weather conditions, viz., moderately high temperature and relative humidity. T his data will be useful for the sampling of the populations of eriophyid mite species on olive trees and also to evolve suitable strategies for the application of acaricides on this crop. 3.1.2 Predacious mite T he value of the predatory phytoseiid and stigmaeid mites for controlling eriophyoid mite populations has been well documented by several authors (A-A 1983; A-A and E -B  1986; A and C  1986; A-A et al. 1998; E -L 1999; S S and P 1999; A-A et al. 2000). T he distribution pattern of phytoseiid mite Neoseiulus cydnodactylon (Shehata & Zher) varied greatly from that of stigmaeid Agistemus olivi Romeih (R  2002) (Fig. 1). N. cydnodactylon abundance did not always strictly correlate with abundance of the two eriophyid olive mites. It could be found in about 79 and 45 % of the samples during the first and second years, respectively. T hese facts indicate that eriophyid prey types probably play an important part of the predator diet. Its population was noted from April or late May and reached its peak in August and late July being 1.16 and 0.56 individuals per leaf during the two successive seasons, respectively; while the seasonal dynamics of the predatory stigmaeid mite A. olivi having a peak in middle or late July averaging 1.68 and 95 and 50 % of samples containing predators during the two successive years, respectively. It is a predominant species on young olive trees and it occurred frequently in the presence of both eriophyid species. It can be concluded that the ecological study demonstrated that several factors may influence the eriophyid mite population on olive young trees. In this respect climatic conditions, action of predatory – prey relationship, shady and sunny zones, leaf age and vertical distribution are examples of important ecological factors. On the other hand, study in an abandoned olive nursery, which lasted two successive 296 Abou-Awad/Metwally/Al-Azzazy 3/05 PflKrankh. Fig. 4. Population trend of the olive rust mite Tegolophus hassani on abandoned young olive trees in Giza nursery from April 2000 to March 2001 in weather data for the corresponding period. PflKrankh. 3/05 Environmental management and biological aspects of two eriophyid olive mites in Egypt: 297 Fig. 5. Population trend of the olive bud mite Aceria oleae on abandoned young olive trees in Giza nursery from April 2000 to March 2001 and weather data for the corresponding period. 298 Abou-Awad/Metwally/Al-Azzazy T able 4. T able 5. Species T. hassani A. oleae T able 6. Species PflKrankh. Mean number of Tegolophus hassani and Aceria oleae per olive leaf at three vertical levels of olive bushes Levels T op Middle Bottom 3/05 Mite species T. hassani A. oleae 13.83 11.99 10.77 22.85 22.89 16.30 Percentage distribution of two eriophyid species on surfaces of olive leaves at three vertical levels of bushes T op Middle Bottom 43.23 56.77 36.42 63.58 35.19 64.81 Percentage distribution of two eriophyid species on the lower and upper (in parentheses) surfaces of olive leaf at three vertical levels of bushes T op Middle Bottom T. hassani 21.40 (70.31) 12.70 (74.80) 19.30 (56.30) A. oleae 78.60 (29.69) 87.30 (25.20) 80.70 (43.70) years till plants developed into young trees in the perforating stage of about 200 cm height under natural control, showed that the trees were almost protected against the damage of eriophyid infestation without the need for miticidal treatment in the second year. T his result agrees with that reported by E -L (1999) for other allied two eriophyid species (Aceria olivi Zaher & Abou-Awad and Oxycenus niloticus Zaher & Abou-Awad), with two predatory mites (Amblyseius swirskii Athias-Henriot and Agistemus exsertus Gonzales) in commercial olive nurseries. Likewise studies performed in abandoned fruit orchards (A and C  1990; A-A et al. 2000) indicated a stable mite community with positive relationship between phytophagous mites and their predominant predators. 3.2 Acaricide management of mite populations Eriophyid mites offer some of the best opportunities for pest management in permenant crops such as fruit orchards. On the basis of a population dynamic study, the suitable timing of acaricide application to suppress outbreak of eriophyid olive nursery can be approached. T he system relies heavily on the use of available naturally occurring enemies (predatory mites) and the occasional use of a specific compound (Acaricides). At Giza nursery and in the first season (2001), study revealed that the prevailing phytoseiid and stigmaeid predators on the young olive trees are ineffective in reducing the populations of A. oleae and T. hassani to below economic injury levels. T he data of the present work showed that one spring application of abamectin in mid April, when the eriophyid populations start to increase, was sufficient to control injurious mites for the entire year. T his allows for the longest possible period of biological control, especially because the predacious mites were almost absent or present in very low numbers at the time of application. PflKrankh. 3/05 Environmental management and biological aspects of two eriophyid olive mites in Egypt: 299 T able 7 shows the effect of abamectin on eriophyid olive mites in Giza nursery during the first season (2001). T he results indicate that abamectin is a promising control against the two eriophyid species. It caused a reduction of 85.40 % and 88.90 % in the population of A. oleae and T. hassani on leaves, respectively, during the 35-day period following applications. Similar affects of this products against eriophyid mites have been found on fig trees in Egypt (A-A et al. 2000) and on citrus in Florida orchards (C  1986). Many workers (such as W  et al. 1978; B  1982; E  1984; A-A et al. 2000) have shown that if spray could be eliminated, or at least greatly reduced, orchard mites would not be a problem. 3.3 Biology 3.3.1 The olive bud mite, Aceria oleae A. oleae was able to develop successfully from egg to adult through entire life history without problems. Eggs were deposited together in groups of three to five or even more in sheltered depressions made by the fertilized female under the scales on the lower surfaces of the leaves and apparently cemented to the plant tissue. Eggs are 44–47 µm in diameter and translucent when the first laid, later becoming creamywhite. Embryos develop within the eggs; the eggs turn darker, then hatched into a first instar nymph, which resembles the adult in many respects, but is smaller, without external genitalia and with fewer annulations, which may be slightly different in nature and in microtuberculation. T he first nymph is translucent, 73–99 µm long, relatively active and only vagrants around the scales. It passes through nymphochrysalis before moulting into the second instar nymph, which is very much similar to the first, creamy-white in colour, 103–111 µm long, more active and vagranting on the entire lower surface of the leaf. T he second nymph passes through an imagochrysalis before moulting and giving rise to the adult. It was observed that during the quiescent stages, the individual stretched its legs directly forward parallel to each other, and the mite fastened itself slightly to the plant surface at the same site as the mite feeds and lay eggs or any other sheltered site on the under surface of the leaf. T he moulting form has a pearly luster and is motionless. In the moulting process, a transverse rupture occurred at the anterior region behind of the cephalothoracic shield, hence legs and the cephalothorax were the first parts to the plant surface; the anterior parts were then elevated and mite moved to get rid of the exuvia. T he female life cycle lasted 13.86, 9.36 and 6.58 days at 20, 25 and 31 °C, respectively, while the male developed faster (T able 8). Insemination took place soon after female emergence from the last quiescent stage. It was noted that the mating process was essential for the maximum reproduction of the females, as unmated females deposited lower numbers of eggs compared to mated ones. Unfertilized females were found to produce only male offsprings, while both males and females were produced by fertilized females. Similar findings were reported on Phyllocoptruta oleivorus (Ashmed) and Aculus pelekassi Keifer (B  et al. 1963) and on Aceria ficus (Cotte) (A-A et al. 2000). Oviposition period was the shortest at 20 °C, while it was the longest at 31 °C. Female deposited an average of 7.4, 15.0 and 21.4 eggs during the average oviposition period of 7.60, 10.00 and 10.40 days. T hen survived for 3.40, 2.20 and 1.40 days before death at the same previous temperatures, respectively (T able 8). It could be concluded that the highest temperature and relative humidity accelerated the rate T able 7. Eriophyid mites A. oleae T. hassani Abamectin effect on eriophyid olive mite species in Giza nursery within 35 days after application in 2001 season Abamectin concentrations (%) 0.04 0.04 Number of mites/leaf Pre-spray count* Average postspray count Reduction (%)** 94.65 57.20 14.95 09.2 85.40 a 88.90 b * Counts made 1, 3 days and 5 weeks post treatment. ** Mortality values calculated with Henderson-T ilton equation. Different letters in vertical column denote significant difference (t-test, P < 0.05). 300 Abou-Awad/Metwally/Al-Azzazy T able 8. 3/05 PflKrankh. Average duration (in days) of various stages and oviposition rate of Aceria oleae at different temperatures and relative humidities Mite stage Egg First stage nymph Nymphochrysalis Second stage nymph Imagochrysalis T otal Pre-oviposition O viposition T otal fecundity Post-oviposition Life span % Surviving Number of observations Sex Female Male Female Male Female Male Female Male Female Male Female Male Female Female Female Female Female Male Female Male Female Male A. oleae Mean ± S. D. T emperatures °C and relative humidities 20 ± 1 & 50 % 25 ± 1 & 70 % 31 ± 1 & 80 % 05.60 ± 0.24 05.00 ± 0.22 03.60 ± 0.24 03.20 ± 0.02 00.35 ± 0.05 00.30 ± 0.02 04.00 ± 0.20 03.60 ± 0.24 00.31 ± 0.02 00.30 ± 0.04 13.86 ± 0.20a 12.40 ± 0.39a 04.60 ± 0.24 07.60 ± 0.50a 07.40 ± 0.81a 03.40 ± 0.50 29.46 ± 0.19a 27.00 ± 0.49a 100 100 020 010 04.20 ± 0.20 03.40 ± 0.24 02.40 ± 0.50 02.20 ± 0.20 00.26 ± 0.40 00.28 ± 0.20 02.20 ± 0.20 02.60 ± 0.24 00.30 ± 0.02 00.30 ± 0.21 09.36 ± 0.57b 08.78 ± 0.37b 03.00 ± 0.44 10.00 ± 0.31b 15.00 ± 1.30b 02.20 ± 0.20 24.59 ± 0.43b 21.58 ± 0.70b 100 100 021 009 03.00 ± 0.02 02.40 ± 0.24 01.60 ± 0.24 01.60 ± 0.24 00.28 ± 0.01 00.23 ± 0.02 01.40 ± 0.24 01.20 ± 0.20 00.30 ± 0.02 00.25 ± 0.03 06.58 ± 0.13c 05.68 ± 0.19c 01.80 ± 0.20 10.40 ± 0.24b 21.40 ± 1.40c 01.40 ± 0.24 20.18 ± 0.37c 17.68 ± 0.35c 100 100 022 008 Different letters in horizontal columns (between females of the different treatments or male of the different treatments) denote significant difference (F-test, P < 0.05, P < 0.01). of development and induced more reproduction of A. oleae. T hus, warm and humid climatic conditions are the most important factors favouring a population increase. T his notation is supported by the large populations frequently recorded for A. oleae in summer months (A-A 2000). Many authors are in agreement either for phytophagous or predacious mites (S-M  1981; J  1990; J  and T  1992; T  and J  1993). 3.3.2 The olive rust mite, Tegolophus hassani T. hassani was able to develop successfully from egg to adult with the same technique. Eggs are spherical, translucent after being laid. T hen become dark yellow as a result of the development of the embryo. T he fertilized female lays eggs scattered on the upper surface of the leaves and in the same place as the mite feeds. Eggs are 61–63 µm in diameter. Embryo develops within the egg, then hatches into a first instar nymph which resembles the adult, but it is smaller, without external genitalia and with fewer annulations. T he first nymph is translucent, 69–84 µm long. It passes through nymphochrysalis before moulting into the second instar nymph, which is very similar to the first, yellow-white in colour, 111–123 µm long and more active. T he second nymph passes through an imagochrysalis before moulting, giving rise to adult. Unfertilized females, fertilized females and moulting behaviour of T. hassani were similar to the olive bud mite A. oleae. In the light of the information obtained in this study, developmental times of T. hassani females were as follows: Eggs 6.4, 4.2 and 3.0 days, first instar nymph 3.8, 2.2 and 2.0 days, nymphochrysalis 0.35, 0.30 and 0.25 days, second instar nymph 4.2, 3.0 and 1.8 days and imagochrysalis 0.40, 0.23 and 0.27 days at 20, 25 and 31 °C, respectively. Males developed faster (T able 9), the total life cycle being PflKrankh. 3/05 Environmental management and biological aspects of two eriophyid olive mites in Egypt: 301 completed in 15.15 and 14.28, 9.93 and 9.68 and 7.32 and 6.73 days for female and male, respectively. T he life cycle results of E  (1978, 1979) on the pear rust mite Epitrimerus pyri (Nalepa) and the apple leaf mite Aculus schlechtendali (Nalepa) are nearly in agreement at the same temperatures. Females deposited an average of 5.6, 11.2 and 14.2 eggs, during an oviposition period that averaged 7.4, 9.8 and 8.4 days, and then survived for 3.0, 2.2 and 2.0 days at aforementioned temperatures, respectively (T able 9). It was observed that T. hassani females laid slightly fewer eggs than A. oleae. Rice and Strong (1962) reported that females of the tomato russet mite, Aculops lycopersici (Massee), laid 10-53 eggs, depending on environmental conditions. It is possible, however, that the reproductive capacity of T. hassani might be better under favourable conditions. T he life history took 29.95 and 28.28, 25.13 and 24.68 and 19.72 and 17.33 days for female and male at the same temperatures, respectively. In general, life histories studied by P (1939), K (1942), M  (1957), E  (1979), A-A et al. (2000) are in a agreement. It is of interest to note that the mating process in eriophyid mites has been described by O  et al. (1970). Males produce packets of sperm cells that are known as spermatophores. Occasionally, the spermatophore is pulled free from the plant and the base and stalk protrude from the female’s genitalia. Few days after fertilization, the progeny was predominantly females, with a sex ratio of 2 : 1, while unfertilized females produced only males. T his is in agreement with the results reported for this study (T able 10). A comparison of the life table parameters of the two dominant eriophyid species on olive trees (T able 10) revealed that the parameters differed greatly. For example, the population of the olive rust mite T. hassani multiplied 9.92 times in a generation time of 14.42 days at 31 °C and 80 % r. H. In regard to the olive bud mite A. oleae, the population increased 16.70 times in a generation time of 13.50 days at the same temperature and relative humidity. Consequently, A. oleae is considered to be a T able 9. Average duration (in days) of various stages and oviposition rate of Tegolophus hassani at different temperatures and relative humidities Mite stage Egg First instar nymph Nymphochrysalis Second stage nymph Imagochrysalis T otal Pre-oviposition Oviposition T otal fecundity Post-oviposition Life span % surviving Number of observations Sex Female Male Female Male Female Male Female Male Female Male Female Male Female Female Female Female Female Male Female Male Female Male T. hassani Mean ± S. D. T emperatures (°C) and relative humidities 20 ± 1 & 50 % 25 ± 1 & 70 % 31 ± 1 & 80 % 06.40 ± 0.24 05.80 ± 0.20 03.80 ± 0.20 03.60 ± 0.03 00.35 ± 0.04 00.34 ± 0.02 04.20 ± 0.20 04.20 ± 0.20 00.40 ± 0.04 00.34 ± 0.08 15.15 ± 0.20a 14.28 ± 0.40a 04.40 ± 0.40 07.40 ± 0.24a 05.60 ± 0.95a 03.00 ± 0.01 29.95 ± 0.20a 28.28 ± 0.24a 100 100 019 011 04.20 ± 0.20 04.20 ± 0.24 02.20 ± 0.20 02.40 ± 0.24 00.30 ± 0.05 00.23 ± 0.02 03.00 ± 0.31 02.60 ± 0.24 00.23 ± 0.24 00.25 ± 0.31 09.93 ± 0.24b 09.68 ± 0.14b 03.20 ± 0.02 09.80 ± 0.37b 11.20 ± 0.37b 02.20 ± 0.20 25.13 ± 0.56b 24.68 ± 0.52b 100 100 019 011 03.00 ± 0.01 02.80 ± 0.20 02.00 ± 0.01 01.80 ± 0.20 00.25 ± 0.03 00.27 ± 0.02 01.80 ± 0.20 01.60 ± 0.24 00.27 ± 0.02 00.26 ± 0.02 07.32 ± 0.16c 06.73 ± 0.74c 02.00 ± 0.31 08.40 ± 0.50c 14.20 ± 1.06c 02.00 ± 0.31 19.72 ± 0.37c 17.33 ± 0.19c 100 100 019 009 Different letters in horizontal columns (between females of the different treatments or male of the different treatments) denote significant difference (F-test, P < 0.05, P < 0.01). 302 T able 10. Abou-Awad/Metwally/Al-Azzazy 3/05 PflKrankh. Life table parameters of the olive bud mite Aceria oleae and the olive rust mite Tegolophus hassani at different temperatures and relative humidities Parameters Net reproduction rate (R o) Mean generation time (T ) Intrinsic rate of increase (rm) Finite rate of increase (erm) 50 % mortality (in days) Sex ratio (female/total) Sex ratio (female : male) A. oleae T emperatures (°C) and relative humidities T. hassani T emperatures (°C) and relative humidities 20 ± 1 & 50 % 25 ± 1 & 70 % 31 ± 1 & 80 % 20 ± 1 & 50 % 25 ± 1 & 70 % 31 ± 1 & 80 % 7.31 13.15 16.70 5.82 7.62 9.92 21.80 15.66 13.50 21.90 17.50 14.42 0.091 0.165 0.206 0.080 0.116 0.159 1.09 1.17 1.22 1.08 1.11 1.17 26 22 19 27.00 23.00 19.00 20 /30 21/30 22/30 19/30 19/30 21/30 2.00 : 1 2.33 : 1 2.75 : 1 1.73 : 1 1.73 : 1 2.33 : 1 disastrous mite on shrub and young olive trees compared with T. hassani. 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