Some biological characteristics of the Batrachedra amydraula Meyrick (Lepidoptera: Batrachedridae) on main varieties of dry and semi-dry date palm of Iran

Although Iran is the leading producer of dates in the world, only 10% of its product is exported. One of the factors which limits exportation is postharvest pests. Lesser date moth (Batrachedra amydraula) is one of these postharvest pests. This pest is found in all date palm plantations of Iran. The biology of this pest has not been studied under laboratory conditions on main varieties of stored date in Iran. In this research some biological characteristics including survivorship, developmental time, fecundity, oviposition and postoviposition period, and longevity of adults on date palm varieties Zahedi, Ghasb, Rabbi, Deyri and a semi-artificial diet were studied. All experiments carried out at constant temperature room (30 ± 0.5 °C and 55 ± 5% r.h.). Highest survivorship of egg and combined larval and pupal stages were 86 and 85% respectively on semi-artificial diet. Shortest total development time from egg to adult was 43 days for males and 43 days for females on semi-artificial diet. Longest total development time was 69 days for male and 65 days for female on Ghasb variety. The highest (45 eggs per female) and lowest (25 eggs per female) fecundity occurred on the Deyri variety and semi-artificial diet, respectively. Results of this study would be useful for making pest management decisions in date palm storage.Keywords: Lesser date moth, Batrachedra amydraula, Biology, Date pal

Sequential sampling plan of Metopolophium dirhodum (Hemiptera: Aphididae) in wheat fields

Sequential sampling plans of rose-grain aphid, Metopolophium dirhodum (Walker) were developed in wheat fields of Jalilabad region of Varamin, Iran. The aphid population was weekly sampled during 2000-2001. Each sample included 50 wheat stems, which were chosen randomly and the number of aphids was counted. This data was used to describe spatial distribution pattern of M. dirhodum by Taylorâs power law (TPL) and Iwaoâs patchiness regression methods. The results indicated aggregated dispersion pattern of rose-grain aphid population in wheat fields, based on both methods. The TPL provided a better description of the aphidâs spatial distribution. Estimates of two mentioned models led to development of sequential sampling plans, using Green and Kuno methods at precision levels of D = 0.20 and D = 0.30 in terms of confidence interval, respectively. In both sequential sampling plans, the higher sample size obtained as population density decreased and it decreased when precision level increased from 0.30 to 0.20. The required sample size for the estimation of mean aphid density was approximately identical at 0.8 and 8 aphids per tiller in both Greenâs and Kunoâs plans. Greenâs plan was more efficient than Kunoâs model for both lower (⤠0.8 per tiller) and higher (⥠8 per tiller) aphid densities due to its small sample size required and less time needed for sampling. Kunoâs model required fewer samples at the intermediate density range (0.8-8 aphids per tiller) and is considered more effective than Greenâs plan at this aphids' density range. However, Kunoâs model is not recommended when low aphid population density exists because it requires enormous samples of aphids

Demography of Habrobracon hebetor (Hym.: Braconidae) on Galleria mellonella (Lep.: Pyralidae) at different temperatures

Demographic parameters of Habrobracon hebetor Say (Hym.: Braconidae) reared on the last larval instars of Galleria mellonella (L.) were studied at 20, 25, 28, 30 and 35 ± 0.5°C, 60 ± 5% R.H. and 16L: 8D h conditions. The gross fecundity rate of the parasitoid was 43.17 eggs at 20°C that was approximately half of it at other temperatures. Net fecundity and net fertility rates increased as the temperature increased. Their lowest values were 8.49 and 8.405 at 20 ± 0.5°C and the highest values were 30.47, 30.47 eggs at 30°C, respectively. Their values decreased more than 30% and amounted to 21.49 and 20.63 eggs at 35, respectively. Reproductive value (Vx) was at maximum value at the early period of female reproduction and decreased as females aged. In other words, it was at peak, when females were 30, 18, 14, 14 and 11 day-old at above temperatures. The highest value of net reproductive rate (R0) was 17.06 at 30°C and the lowest (6.27) at 35°C. The intrinsic rate of increase (rm) had the highest value (0.17) at 30°C and the lowest (0.039) at 20°C. The highest value of finite rate of increase (λ) was 1.186 at 30°C and the lowest (1.04) at 20°C. In other words, the parasitoid population would increase 11.86% daily at 30°C. Mean generation time (T) was the longest (41.81 days) at 20°C and the shortest (14.93 days) at 35°C. The longest doubling time (DT) (17.82 days) was obtained at 20°C and the shortest (4.072) was at 30°C. These results showed that the temperature at 30°C would provide a more favorable condition for mass rearing of H. hebetor

Biological parameters of the egg parasitoid Trissolcus grandis (Hym.: Scelionidae) on Eurygaster integriceps (Hem.: Scutelleridae)

Trissolcus grandis Thomson is a solitary egg parasitoid of Sunn pest, Eurygaster integriceps Puton. Although widely distributed, it has often been overlooked in field surveys. Our objectives were to develop an efficient rearing technique for T. grandis, and to determine the basic bionomics and demographic parameters, necessary for future augmentative biological control programs. Exposure of 0-4 h-old Sunn pest egg masses to parasitoids at 1:1, 2:1 and 3:1 host-parasitoid ratios resulted in a parasitism rate of > 80%. The results demonstrated that the age of the host and the exposure time affected parasitism rate. However, parasitism rate did not differ significantly among 24, 48 and 72 h-old Sunn pest eggs. The percent of emerged parasitoids during the 24-h host exposure period was relatively high when host eggs were 24 h old. Moreover, the mean sex ratio showed a definite trend, suggesting that host age had an effect on the sex ratio of the T. grandis offspring. The mean developmental time obtained as 11.091 ± 0.1 and 9.68 ± 0.15 d. for female and male progenies, respectively. The longevity of females was ~ 30% lower compared to that of males. The average net fecundity reached 181.83 eggs per female. On the other hand, a female laid averagely ~ 7 eggs per day. Similarly, the daily population increase and mean generation time were 34.2%, and 14.61 d, respectively. The developing population consisted of 99% immature (egg, larvae, pupa), and only 1% adults. The importance of these findings to the population biology of this parasitoid is discussed

Temperature-dependent development of Habrobracon hebetor (Hym.: Braconidae) reared on larvae of Galleria mellonella (Lep.: Pyralidae)

The development times and the survival rates of different stages of Habrobracon hebetor Say reared on the last instar larvae of Galleria mellonella (L.) were compared at ten different constant temperatures (16 - 38 ºC). The development time of immature stages of the parasitoid, H. hebetor, decreased as the temperature increased in the range of 16 to 38 ºC. However, no larvae could survive and develop at 16 ºC. Development time from egg to adult females was the shortest (8.368 ± 0.069 days) at 35 ºC and the longest (32.667 ± 0.33 days) at 18 ºC. Egg incubation period, larval and pupal development times were significantly different at various constant temperatures. No significant difference was found between two sexes in their developmental periods from eggs to adult stage. The survival rate of the egg stage ranged between 94.90 and 100% at all temperature levels, but larval survival rates was significantly different at various temperatures. Although significant difference was found in the survival rate of pupal stage (P < 0.05), the trend of survival rate for pupae was similar to those of larvae. The relationship between temperature and the developmental rate of the parasitoid well described by linear regression model (R2 = 0.89, P = 0.0001, at the egg stage and R2 = 0.95, P = 0.0001, at the egg-adult stage). The lowest threshold temperature was obtained for all developmental stages of the parasitoid. Degree-days requirements (DD) for egg, larva, pupa and egg-female stages were 22.73, 56.82, 109.89 and 188.68, respectively. The results in this study showed that the temperature range between 25 and 32 ºC provide a favourable condition for mass rearing of this parasitoid

Biological characteristics of Cadra cautella (Lep.: Pyralidae) on different varieties of stored date palm fruit of Iran

The postharvest pests, including the dried fruit moth Cadra cautella Walker, are important limiting factors in the exportation of dates. The biology of C. cautella, its survivorship, developmental time, fecundity, oviposition, post oviposition period, as well as longevity of the adults were studied on four date palm varieties of Zahedi, Piarom, Rabbi, and Deyri under laboratory conditions in Iran. The experiments were carried out at constant temperature room (29 ± 1 °C, 60 ± 5% RH and photoperiod 16L: 8D hrs.). The highest survivorship of egg and larval stages was recorded 92.66%, 85.89% on Zahedi and 100% for pupal stage on Rabbi. The shortest larval period was 32.93 ± 1.41 days and 33.37 ± 1.87 days on Deyri and Zahedi respectively. The shortest total development time for males from egg to adult was 40.91 ± 1.15 days and 40.97 ± 1.59 days on Zahedi and Deyri respectively and for females was 43.76 ± 2.47 days on Deyri. The longest total development time for males was 47.61 ± 1.50 days on Piarom and for female was 55.88 ± 2.31 and 55.37 ± 3.87 days on Piarom and Rabbi respectively. The highest (247.00 ± 8.53 eggs per female) and lowest (147.40 ± 12.06 eggs per female) fecundity occurred on Zahedi and Piarom, respectively. The date palm varieties Zahedi, Deyri, Rabbi and Piarom are found to be on preferrence order for C. cautella. The results of this study would be useful for planning pest management strategies in date palm fruit storages

Biological and predatory characteristics of Andrallus spinidens (Hem.: Pentatomidae) on fourth instar larvae of Spodoptera littoralis (Lep.: Noctuidae), under laboratory conditions

Biological and predatory characteristics of Andrallus spinidens (F.) on fourth instar larvae of Egyptian cotton leafworm, Spodoptera littoralis (Bois.), were investigated, under laboratory condition, at 25 ± 1°C, 60 ± 5% RH and a photoperiod of 16: 8 L: D h. The analysis was based on an age-stage, two-sex life table. The intrinsic rate of increase (rm), finite rate of increase (λ), net reproductive rate (R0), gross reproductive rate (GRR) and mean generation time (T) of A. spinidens on S. littoralis were 0.0821 day-1, 1.0821 day-1, 102.77 offspring, 192.61 eggs and 58.68 day, respectively. The mean reproductive value of A. spinidens was estimated as 342.58 ± 48.18 eggs per female. The intrinsic birth rate (b) and intrinsic death rate (d) for A. spinidens on S. littoralis were 0.0894 and 0.0073, respectively. The first stage nymphs of A. spinidens live only on water but the second, third and fourth stage nymphs fed on 12.22, 26.22 and 41.28 of S. littoralis larvae, respectively. The fifth stage nymphs were more voracious and preyed on more than 70% of the larvae (94.36). At the adult stage, both male and female of A. spinidens were able to kill up to 85% of the larvae. In conclusion, the results prove that this predator pentatomid bug can be used as an efficient biological control agent against the noctuid pest, S. littoralis

Demography of Habrobracon hebetor (Hymenoptera : Braconidae) on two pyralid hosts (Lepidoptera : Pyralidae)

Demography of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) on two pyralid host species [Galleria mellonella (L.) and Ephestia kuehniella Zeller] (Lepidoptera: Pyralidae) was studied at 28 degrees C in the laboratory. Data were analyzed based on an age-stage, two-sex life table, to take both sexes and variable development into consideration. The intrinsic rate of increase (r), finite rate of increase (A), net reproductive rate (R,), gross reproductive rate (GRR), and mean generation time (T) of H. hebetor on G. mellonella were 0.1520 d(-1), 1.1640 d(-1), 12.5 offspring, 50.1 offspring, and 16.8 d, respectively. These values were not significantly different from the values obtained for E. kuehniella, i.e., 0.1375 d(-1), 1.1473 d(-1), 11.9 offspring, 54.9 offspring, and 18.2 d. The life expectancy of an H. hebetor egg was 10.6 d on E. kuehniella and 10.4 d on G. mellonella. On both host species, the maximum reproductive value of female H. hebetor occurred on the 12th day

Estimating development and temperature thresholds of Ephestia kuehniella: Toward improving a mass production system

The development of the Mediterranean flour moth, Ephestia kuehniella (Zeller), was evaluated at 10, 15, 17.5, 20, 22.5, 25, 27.5, 30 and 32.5°C with no lighting. None successfully completed development at 10 and 32.5°C. The total development time from egg to adult emergence was 164, 140, 98, 76, 61, 62 and 50 days, respectively, at the remaining temperatures. The developmental rate of E. kuehniella was described by the common linear model and six non-linear models. The lower temperature threshold for the immature stages and the thermal constant for E. kuehniella were 9°C and 1111 degree-days (DD) to complete development from egg to newly emerged adult. Non-linear models estimated the lower and upper thermal thresholds (T and T) and optimal temperature (T). The values of T calculated by three nonlinear models ranged from 34°C to 46°C; T for each stage of development varied from 24 and 31°C, consistent with the temperature (30°C) at which the most rapid development occurred. Information on the threshold temperatures for development and thermal requirements can be utilized to predict E. kuehniella population dynamics and phenology and to evaluate optimal temperature conditions for mass rearing in stored products