الفهرس 
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Abstract
The almond moth, Cadra (Ephestia) cautella (Walker) (Lepidoptera: Pyralidae) is one of the major date palm pests in Egypt. The infestations begin in date palm plantations and continue in storehouse through infested dates and can go through multiple generations. Larvae cause considerable damage by feeding and/or by contaminating stored food with dead bodies and their own products, e.g. excreta, webbing, silk and feces.
The present study was aimed to study the following aspects on C. (E.) cautella in Upper Egypt:
1- Biology of the pest.
2- Suitability of semi- and dry-date fruit varieties to the pest.
3- Effect of extremely low and high temperatures on C. cautella:
1- Effect of constant temperatures:
The present investigations were carried out to study the effect of constant temperature regimes of 18, 22, 26 and 30ºC on developmental stages of the almond moth to determine the developmental threshold (t0) and thermal units (day-degrees) needed for the development of the immature stages as well as on the adult reproductive potential (longevity and fecundity) of the almond moth, C. cautella.
1.1-Effect of constant temperatures on the immature stages:
The results indicate that the pest developed successfully from egg to adult emergence over the temperatures ranged from 18º to 30ºC.
1.1.1-Egg stage:
The time required for completion of embryogenesis decreased gradually as temperature increased from 18º to 30ºC. The incubation period of the pest lasted 11.04±0.32, 7.72±0.18, 5.65±0.69 and 3.19±0.07 days at the constant temperatures of 18, 22, 26 and 30ºC, respectively.
The highest percentage of hatchability (50%) was recorded at 30º followed by (46%) at 22º, whereas the lowest (42%) was at 18º and 26ºC. The index of efficiency (IE) for the development of egg stage was markedly higher at 30ºC (15.67) followed by 26ºC (7.43). Developmental threshold of the egg stage was14.06ºC. The calculated thermal units, using this threshold as a base temperature, were about 55.85 day-degrees.
1.1.2-Larval stage:
Durations of the larval stage (103±10.25, 54.73±3.23, 45.87±4.89 and 31.71±3.56 days) were recorded at temperatures of 18, 22, 26 and 30ºC, respectively. The highest percentage of larval survival was achieved at 26ºC. The highest index of efficiency (1.94) recorded at 30ºC. It could be concluded from the data that temperature of 30ºC is the most suitable condition for the development and survival of the larval stage of this pest.
The calculated temperature threshold (t0) for the larval stage was 12.41ºC, consequently, this stage required about 582.15 day-degrees to complete its development.
1.1.3-Pupal stage:
The pupal stage lasted 32.86±2.74, 17.80±1.17, 10.87±0.47 and 8.44±0.64 days at 18, 22, 26 and 30ºC, respectively. The highest (IE) (11.36) was obtained at 30ºC, whereas the lowest value (3.04) was recorded at the lowest temperature of 18ºC. It could be concluded that temperature of 30ºC was the most suitable condition for development and survival of the pupae.
The estimated temperature threshold of pupal development was 14.20ºC. The thermal units required for the pupae to complete its development were 132.30 day-degrees.
1.1.4-from Egg to Adult emergence:
The longest time required for the insect to complete its life cycle (147.30±13.31 days) was recorded at 18ºC and decreased as temperature increased to reach 43.34±4.27 days at 30ºC. The highest index of efficiency (IE) (0.68) was also observed at temperature of 30ºC, whereas, the lowest value (0.11) was noticed at 18ºC. The foregoing results concerning, the duration, survival and index of efficiency in relation to temperature clearly indicate that temperature of 30ºC was the most preferable temperature for development of the almond moth.
The calculated developmental threshold (t0) was 12.92C. By using this value as a base temperature, an average of about 752.35 day-degrees is needed for the pest to complete one generation. Accordingly, about 6 generations of the pest could be developed in one year under Assiut conditions.
1.2-Effect of constant temperatures on the adult stage:
1.2.1-Longevity:
The preovipostion periods at the four tested temperatures were 0.83±0.71, 0.60±1.12, 0.07±2.26 and 0.13±0.34 days, respectively. The oviposition period decreased with the increase of temperature but remained relatively constant from 26º up 30ºC. The post-oviposition period ranged from 1.33±1.49 days at 18º to 0.33±0.49 days at 30ºC.
1.2.2-Egg laying capacity (fecundity):
The maximum number of eggs (123.50±70.17 eggs / female) was recorded at 30ºC. Females reared at 18ºC laid significantly fewer eggs (100.17±36.38 eggs / female) than those exposed to other temperatures. It seems that the range of 26º-30ºC is considered as the optimum zone for eggs laying activity.
1.2.3- Some life table parameters:
The generation time (GT) of this pest was shorter at 30ºC (55.61 days) as compared with those at 18, 22 and 26ºC.
The population doubling time (DT) of C. cautella had the capacity to double every 47.47, 19.97, 15.89 and 10.89 days at 18, 22, 26 and 30ºC, respectively. The shortest time (10.89 days) for population to double was recorded at 30ºC.
The calculated data for the net reproduction rate (R0) indicated that the pest can increase ca. 9.09, 17.87, 16.81, and 34.33 times after a single generation at 18, 22, 26 and 30ºC, respectively.
The data show that a constant temperature of 30ºC seems to be the optimum temperature among those tested, as it has the maximum intrinsic rate of increase (rm) value.
from the above mentioned results it could be concluded that temperature of 30ºC is the most suitable condition for the development and multiplication of the almond moth, C. cautella.
2- Suitability of some date fruit varieties to C. cautella:
The two date varieties (Sakkoti and Saidy) permitted reasonable development of the almond moth.
2.1-Egg stage:
The incubation period lasted 3.19±0.019 days for the eggs deposited by the females reared on semi-dry date and 3.91±0.05 days for the eggs laid by the females reared on dry-date. The highest percentage of hatchability was recorded on the eggs produced from females which their larvae reared on dry-date variety (75.10±14.35%), whereas the lowest (50±2.19%) was recorded on the eggs of semi-dry variety. The index of efficiency (IE) for the egg stage was higher (19.20) on dry-date as compared with 15.67 that on the eggs produced from the semi-dry date.
2.2-Larval stage:
The larval period was relatively short as for the larvae reared on semi-dry date (Saidy) (31.71±3.56 days) and relatively long (41.91±2.76 days) for those reared on dry-date (Sakkoti). The highest percentage of larval survival (74.00±16.46%) was recorded for C. cautella reared on dry variety; the lowest (61.67±18.99%) was recorded in the larvae reared on semi-dry variety. The Index of Efficiency (IE) for larvae reared on semi-dry-date variety (1.94) was relatively high as compared to that (1.76) on dry-date.
2.3-Pupal stage:
The duration of the pupal stage lasted 8.44±0.64 and 7.88±0.86 days when larvae reared on semi- and dry-date, respectively. Pupal survival (100±0.00%) was noticed on dry-date, whereas, it was (95.95±9.63%) on semi-dry with no significant difference. The relatively high IE (12.69) was obtained on the pupae of dry- date variety, whereas it was relatively low (11.36) on semi-dry date variety.
2.4-from egg to adult emergence:
The foregoing results concerning, the duration, survival and index of efficiency in relation to date varieties indicate that the dry variety (Sakkoti) was relatively preferable for development of the almond moth than the semi-dry date (Saidy).
2.5-Adult stage:
The pre- and post-oviposition periods were less than one day in both tested date varieties. The mean oviposition period ranged from 2.45 to 2.80 days for the adults emerged from semi- and dry date, respectively. It seems that adult emerged from dry-date (Sakkoti) survived longer as adults emerged from semi-dry (Saidy).
Fecundity of C. cautella was relatively high (127.73±57.03 eggs / female) for the female emerged from dry-date variety as compared to 123.50±61.71 eggs / female emerged from semi-dry date. In general, if the number of eggs laid per female of the almond moth is considered, the dry-date variety was relatively more suitable host than semi-dry date.
Life table statistic parameters:
The duration of one generation (GT) lasted for 44.44 and 55.53 days for the pest reared on semi-dry and dry-date varieties, respectively.
The population of this pest had the capacity to double (DT) every 11.48 and 11.22 days for the cohorts reared on semi- and dry-dates, respectively.
The number of female per female (mx) was 16.87 in the pest reared on semi-dry fruits and was 35.48 on dry date.
The values of net reproductive rate (R0) indicate that the population of the pest can increase ca. 14.62 and 30.85 times after a single generation on semi- and dry- date, respectively.
The value of rm for the pest reared on the dry date was relatively higher than that of the pest reared on semi-dry date variety. The data indicate that dry date variety (Sakkoti) is relatively more suitable for the pest than semi-dry variety (Saidy).
from the above mentioned results, it could be concluded that the developmental time of the immature stages of C. cautella as well as adult fecundity are influenced by the date fruit variety on which they were reared and Sakkoti (dry-date) is relatively more suitable for C. cautella feeding than Saidy variety (semi-dry).
3-Effect of exposure to low and high temperatures on C. cautella:
3.1-Effect of exposure to low temperature of -5ºC:
The immature stages of the pest were exposed to low temperature of (-5ºC) for different exposure times.
The obtained results could be summarized as follows:
3.1.1-On the egg stage:
Exposure times to 60,90, 120, 180 and 240 minutes at -5ºC were able to kill 40.00, 60, 86.25, 92.50, and 100% of the eggs, respectively. Mortality increased with the exposure time increased. Exposure time from 240 to 360 minutes is an effective to get 100% mortality for this stage.
The LT50 and LT95 were calculated as 65.26 and 156.99 minutes.
3.1.2-On the early larval instars:
Exposed small larval instar to low temperature (-5ºC) for 180 minutes is an effective to achieve (100%) mortality for the early larval instars. The LT50 and LT95 were calculated as 96.94 and 157.34 minutes, respectively.
3.1.3-On the late larval instars:
Late larval instar of C. cautella was exposed to different times to low temperature of -5ºC. Data show that mortality values were 6.25, 17.50, 75.00, 95.00 and 100% for the larvae exposed to 90, 120, 180, 240 and 300 minutes, respectively. Exposure time to 300 and/or 360 minutes is an effective to achieve complete mortality for the late larval instars of the pest.
The calculated LT50 and LT95 were 143.11 and 226.53 minutes.
3.1.4-On the pupal stage:
Data reveal that mortality of pupae exposed to 90, 120, 180, 240 and 300 minutes were 14.00, 63, 81.48, 92.59, and 100%, respectively.
The calculated LT50 and LT95 were 113.73 and 208.64 minutes. Thus exposure of pupae to 300 minutes or more is an effective to get complete mortality for the pupal stage.
3.2-Effect of high temperatures:
High temperatures of 45º, 50º, 55º and 60ºC were tested against egg, large larvae and pupal stages of C. cautella.
3.2.1-On the egg stage:
Mortality tended to be increased with the increasing of temperature and exposure time. Means mortality of 24, 28, 36, 48 and 88% were recorded at the high temperature of 45ºC; 76, 88, 92, 96 and 100% were recorded at the high temperature of 50ºC; 88, 92, 96, and 100% were recorded when exposed egg stage to the high temperature of 55ºC for 5, 10, 15, 20 and 25 mints, respectively. Exposure time for for 20 minutes at 55ºC is an effective to get complete mortality for the egg stage
The calculated LT50 and LT95 were 13.52 and 59.06 minutes for the temperature of 45ºC; 1.37 and 12.59 minutes for the temperature of 50ºC and 0.33 and 7.88 minutes for the temperature of 55ºC. Thus exposure time for more than one hour at 45ºC, 15 minutes at 50ºC and 10 minutes at 55ºC were more aggressive and led to 95% mortality for the egg stage of C. cautella.
3.2.2-On the late larval instars:
The calculated LT50 and LT95 were 40.15 and 97.22 minutes at 45ºC; 10.95 and 72.17 minutes at 50ºC and 2.87 and 17.65 minutes at 55ºC, respectively. Thus exposure time for more than 97.22, 72.17, 17.65 minutes at 45, 50 and 55ºC are sufficient to achieve more than 95% mortality for the late larval instars as indicated by LT95 values.
3.2.3-On the pupal stage:
The exposure times of 5, 10, 15, 20 and 25 minutes to temperature of 45ºC were able to kill 15, 22, 33, 44 and 58%, respectively. At 50ºC and 55ºC, mortality increased with the increase of the exposure time. Exposing the pupae to 25 minutes at high temperatures of 50ºC and to 15 minutes at 55ºC is an effective to get complete mortality for the pupal stage.
The calculated LT50 and LT95 were 23.18 and 90.29; 6.13 and 33.58; 1.82 and 11.67 minutes in case of exposure the pupal stage to 45, 50 and 55ºC, respectively. Thus exposure time for more than 90 minutes at high temperature of 45ºC; 33 minutes at 50ºC and/or 11.67 minutes at 55ºC were more effective to achieve more than 95% mortality of the pupal stage of C. cautella.