Beziehungen zwischen dem Bakterium Serratia marcescens (Biz.) und der in den Raupen von Sesamia cretica. Led. (Lep., Tortricidae) sich entwickelnden Schlupfwespe Bracon brevicornis Wesm. (Hym., Braconidae)

Laboratory experiments were undertaken to study the interrelationships which may be detected when rearing the ectoparasitoid,Bracon brevicornis onSesamia cretica larvae after being injected with the bacterial pathogen,Serratia marcescens at five constant temperatures. Many effects detrimental to the parasitoid were found through rearing onSerratia-infected larvae ofSesamia e.g. decreased the deposited eggs especially at 35°C; reduced the formed cocoons and produced adults at all temperatures (15–35°C); and prolonged developmental, repriod especially at 20 or 25°C. Number of infected host larvae which allowed complete successful development for the parasitoid was significantly decreased especially at the extremes of temperatures.     

Übertragung zweler bakterieller Pathogene in den Körper von Sesamia cretica Led. (Lep., Tortricidae) mittels des Legebohrers von Bracon brevicornis Wesm. (Hym., Braconidae)

Laboratory trials were undertaken to investigate the transmission of 2 bacterial pathogens (Serratia marcescens Bizio andBacillus thuringiensis Berliner) by the ovipositor of a braconid parasitoid,Bracon brevicornis Wesmael into the body cavity ofSesamia cretica Lederer. The braconid's ovipositor was able to transmit the 2 bacterial pathogens and plays as inoculating needle. The host larvaeS. cretica were significantly immobilized faster by the contaminated ovipositor of a parasitoid (in case of the 2 pathogens). After successful transmission of the bacterial pathogen into the body cavity of host larvae, different deleterious effects were significantly found for the parasitoid and its progeny specially in case ofS. marcescens. Through contamination of the ovipositor, the non-sporeforming bacterium,S. marcescens has more pathogenic effects on the parasitoid and its progeny than the sporeforming bacterium,B. thuringiensis.     

Temperature-dependent survival,development, and adult longevity of the koinobiont endoparasitoid <Emphasis Type="Italic">Venturia canescens</Emphasis> (Hymenoptera: Ichneumonidae) parasitizing <Emphasis Type="Italic">Plodia interpunctella</Emphasis> (Lepidoptera: Pyralidae)

The effect of various constant temperatures on survival, development, and adult longevity of Venturia canescens Gravenhorst (Hymenoptera: Ichneumonidae) parasitizing larvae of Plodia interpunctella Hübner (Lepidoptera: Pyralidae) was studied under laboratory conditions. The following temperatures were tested: 15, 17.5, 20, 22.5, 25, 27.5, 30, and 32.5°C. The percentage of parasitoids that completed development at each temperature as well as the days needed for the emergence of the parasitoid’s pupa and adult eclosion was measured. Adult longevity was estimated under the same conditions. Survival of V. canescens was significantly higher at 25 and 27.5°C compared to 17.5, 20, 30, and 32.5°C. No individual of V. canescens managed to complete development at 15°C. Overall, developmental time decreased significantly with increasing temperature within the range of 17.5–27.5°C. The lowest developmental time was observed at 27.5°C while the highest at 17.5°C. Upper and lower threshold temperatures for total development were estimated at 36.2 and 13.2°C, respectively. Optimum temperature for development and thermal constant were 30.6°C and 312.5 degree days, respectively. Adult longevity was also affected by temperature, as it was significantly reduced at higher temperatures compared to the lower ones. This information would be useful in determining the potential of using V. canescens as a biological agent in IPM programs, by optimizing mass rearing and release techniques of the parasitoid.     

Laboruntersuchungen zur Wirtshabitat-Wahl von Bracon brevicornis Wesm. (Hym., Braconidae), einem Parasitoiden der Raupen von Sesamia cretica Led. (Lep., Noctuidae) in Sorghum-Stengeln

Females of the parasitoid,Bracon brevicornis were more strongly attracted to “live” larvae ofSesamia cretica (themselves) than any other accessible materials (e. g. “stalk”, “frass”, “paralyzed larva” or control). They were also attracted to paralyzed larvae but only when live larvae were absent. On the other hand, males were more strongly attracted to “stalk” than to “live” larvae or any other available material. Apparently “stalk” exhibited an important cue that directed the parasitoid males.     

Über die Fähigkeit vonBracon brevicornis Wesm. (Hym., Braconidae), zwischen nicht infizierten und von Bakterien infizierten Raupen vonSesamia cretica Led. (Lep., Noctuidae) zu unterscheiden

Sesamia cretica larvae infected with the bacterium,Serratia marcescens orBacillus thuringiensis were exposed toBracon brevicornis females, separately and in combination with non-infected larvae in the laboratory. Host larvae were exposed to the parasitoid under two manipulations “the larvae still alive or dead completely”. Bracon brevicornis females could not absolutely discriminate between healthy and moribund larvae (due toB. t. orS. m.) when those larvae exposed in a live appearance separately or jointly. However, they could discriminate between dead larvae (due to parasitoid's venom) and dead larvae due to Bacteria (B. t. orS. m.).     

Über Eignung und Reaktion überwinternder und aktiver Raupen von Sesamia cretica Led. (Lepid., Noctuidae) in bezug auf den Parasitoiden Bracon brevicornis Wesm. (Hymen., Braconidae)

Laboratory studies were undertaken to determine the differential response and suitability of 2 types of host larvae ofSesamia cretica (hibernating and active) to the development of the braconid,B. brevicornis. The parasitoid was able to immobilize the 2 forms of larvae. However, hibernating larvae were significantly less sensitive to the parasitoid's venom than active larvae. Parasitoid parents (specially females) which associated with hibernating larvae were significantly longer-lived than those kept with active larvae. Life cycle period of the parasitoid did not affect with any of the 2 types of larvae. However, numbers of each of cocoons and emerged adults/larva were significantly higher in case of hibernating than in case of active larvae. Moreover, the produced adults from hibernating larvae were significantly larger in their size. Therefore the hibernating host larvae will serve better for mass colonization of this braconid.     

Mass rearing of <Emphasis Type="Italic">Neochrysocharis formosa</Emphasis> (Westwood) (Eulophidae: Hymenoptera), a parasitoid of leafminers (Agromyzidae: Diptera)

A method for mass rearing the parasitoid Neochrysocharis formosa (Westwood) was developed, using the leafminer Liriomyza huidobrensis (Blanchard) as insect host, and the Phaseolus vulgaris L. bean as host plant. About 1,500 parasitoids per tray of 84 plants emerged from about 2,000 leafminer larvae; 70% of these were females. The most suitable release density of host was two pairs of leafminer adults per bean plant, and that of parasitoid was three pairs per 24 leafminer larvae. Adult parasitoids were harvested based on positive photo-tactic response with 94.5% efficiency. Plants were improved by trimming their tips to increase the leaf area. The trimming process increased the number of leafminer larvae by about 32%. Furthermore, nitrogen fertilization of plants overcame the size reduction of the insects due to continuous rearing. Rearing of leafminer under light—dark (16:8 h) cycle decreased the development period of larvae and pupae. In addition, it restricted the time and duration of larval emergence and adult eclosion. Storage of parasitoid males and females at 7 and 10°C ± 0.5, respectively, proved to be optimal. The fertility of the mass-produced parasitoids after 1 year of rearing reduced by about 23%, and the sex ratio shifted toward males. In conclusion, successful mass production of N. formosa was achieved through designing suitable rearing cage and an efficient harvesting device, improving the host plant, and determining the age and the conditions for cold storage of the parasitoid and its host. Next, we checked the characteristics of the mass-produced wasps to ensure the efficacy when used in the field.     

Effect of storage temperature on the insecticidal activity of a wettable powder formulation ofBacillus thuringiensis var.israelensis onCulex pipiens molestus larvae

Bactimos was incubated for 30 days under 7 constant temperatures (i. e. ?20, ?10, 5, 25, 35, 40 and 45°C). The insecticidal activity of the compound was evaluated against 2nd and 4th instar larvae ofCulex pipiens molestus after 1, 3, 7, 10, 15 and 30 days of storage. No loss in the insecticidal activity of the Bactimos was detected after 30 days at ?20, ?10 and 5°C. At temperatures above 25°C the insecticidal activity reduced as the storage period increased. The LT₅₀ value of Bactimos for the 2nd and 4th instar larvae at 24 h and 48 h exposure was found to decrease as the temperature increased.     

Zur Biologie von Trogoderma variabile Ball. (Col. Dermestidae): Larvalentwicklung und Larvaldiapause

Larval development ofT. variabile under various environmental conditions is examined to estimate the potential damages in storehouses in Central Europe. Larvae develop between 21 and 37°C, lower temperatures considerably prolong the time of development: at 25° it lasts 48.3 days (♂ ♂) and 60.8 days (♀ ♀), at 30° 29.3 days (32.9 resp.), and at 35° 27.5 days (34.6 resp.). Female larvae on an average pupate after six larval instars, males after five. From this results the earlier pupation of the males. Isolated larvae do not pupate; they grow up to big and resistant dauerlarvae and possibly pass through a diapause of several years. Reared in groups larvae pupate promptly and diapause is terminated. Longevity, cold resistance and ability of starvation of dauerlarvae are examined. The results indicate that a development ofT. variabile in unheated rooms is possible. Because of the very slow development at lower temperatures economic important damages are unlikely.     

Entwicklung und Überlebensdauer von jungen Larven der vorratsschädlichen MottenEphestia cautella Walker,Ephestia elutella Hübner undPlodia interpunctella Hübner (Lepidoptera,Pyraloidea) bei niedrigen Temperaturen

The longevity of new-hatched larvae ofEphestia cautella, Plodia interpunctella andEphestia elutella was investigated at temperatures of 2°C, 4°C, 6°C, 8°C and 10°C. While larvae ofEphestia cautella were killed at 10°C within 35 days, larvae ofPlodia interpunctella survived at 10°C and died at 8°C within 21 days. Larvae ofEphestia elutella survived at 8°C and were killed at 6°C in 35 days. A further decline of temperature reduced the longevity. After a gradual cooling down to 10° larvae ofEphestia cautella survived longer than after being cooled down abruptly.     

Zur Morphologie und Entwicklung von Bracon instabilis Marsh. (Hym., Braconidae), eines Parasiten der Kartoffelmotte,Phthorimaea operculella Zell. (Lep., Gelechiidae) in Ägypten

Bracon instabilis Marshal is an ectoparasite attacking the larvae ofP. operculella in Egypt. According to available literatures, this is the first study onB. instabilis. The laboratory rearing of this parasite was undertaken on the third and fourth larval instars ofP. operculella and the method was mentioned in details. Certain aspects of the morphology of the immature and adult stages were given. The durations of the immature stages of the parasite were estimated at 15 and 25°C and 60±5% R.H. The total durations of the immature stages (from egg to adult) were 39.62 and 11.19 days at 15 and 25°C, respectively.     

Parasitism byMeteorus rubens onAgrotis ipsilon as affected by supplementary food and kairomone, field studies

Field experiments in clover field showed that releasing of 10 matedM. rubens females/m², increased parasitism amongA. ipsilon larvae from 16.7% at 0 to 43,3% after 10 days. Also, releasing 10 females/m² after spraying 3% molasses in tomato field increased parasitism from 4% at 0-day to 27.5% after 10 days amongA. ipsilon larvae. Spraying molasses and kairomone together on maize plants, increased markedly the rate of parasitism amongS. cretica larvae comparing with parasitism obtained when each of them was sprayed alone. The release ofM. rubens in a rate of 10 females/m² after spraying molasses and kairomone induced a significant increase in the rate of parasitism amongS. cretica larvae after 10 and 15 days compared to releasing 3 or 4 females of the parasitoid. A significant increase in parasitism amongS. cretica larvae on tomato after 10 and 15 days was recorded whenM. rubens was released at the rates of 5 and 10 females/m², after spraying molasses and kairomone, compared to other treatments.     

Efficacy of low temperatures for the control of all life stages of <Emphasis Type="Italic">Plodia interpunctella</Emphasis> and <Emphasis Type="Italic">Liposcelis bostrychophila</Emphasis>

The insecticidal effect of low temperatures for the control of all life stages of two stored-product insects, Plodia interpunctella and Liposcelis bostrychophila, was evaluated under laboratory conditions. The temperatures tested were 0, ??5, ??10 and ??15 °C, and, at these temperatures, the insects were exposed for 2, 4 and 8 h and also for 1, 2, 3 and 7 days. Regarding P. interpunctella, the most cold-tolerant life stage was larvae, given that 2 days of exposure were needed for complete (100%) mortality at ??10 °C. Moreover, all larvae were dead at ??15 °C even after 2 h of exposure. Eggs of P. interpunctella were susceptible to cold, as mortality was complete after 7, 1 day, 2 and 2 h at 0, ??5, ??10 and ??15 °C, respectively. L. bostrychophila was by far less susceptible than P. interpunctella. For this species, adults were still alive even after 7 days at ??10 °C, while complete mortality was achieved only after 1 day at ??15 °C. Eggs of L. bostrychophila were the most cold-tolerant life stage, as survival was observed even after 3 days at ??15 °C. The results of the present study provide the first data set on which all life stages of P. interpunctella and L. bostrychophila are evaluated for their susceptibility to cold treatments in a standardized series of exposures and temperatures. These results are expected to further encourage the “real world” application of cold treatments for the disinfestation of durable stored-products.     

Temperature-dependent differences in biological traits between two strains of <Emphasis Type="Italic">Trichogramma cacoeciae</Emphasis> (Hymenoptera: Trichogrammatidae)

Parasitoids’ efficiency in controlling pests depends not only on their ability to parasitize their hosts but also on how much they are adapted to climatic conditions (notably temperature) of the area where they are planned to be released. In addition, the optimal conditions for production of parasitoids used for inundative releases like Trichogramma spp. may also vary largely as a function of strains. Using the parasitoid Trichogramma cacoeciae Marchal as biological model, we studied how temperature affects important parasitoid efficiency-related biological traits under laboratory conditions. Emergence, mortality rates and fecundity of two strains of T. cacoeciae, one originating from France (Alsace) and the other one from Tunisia (Degache), were compared at constant temperatures of 15, 20, 25 and 30°C. The parasitoids of the French strain showed highest fecundity at 25°C with wasps that had been reared at 20 or 25°C. The Tunisian strain showed the highest fecundity at 25°C, but only when wasps were previously reared at 25 or 30°C. For both strains, the highest mortality occurred among wasps that had laid eggs at 30°C. Emergence rates were relatively high at all temperatures, although the French strain did better at 15–25°C and the Tunisian one at 20–30°C. Because of the differences in biological traits of these two T. cacoeciae strains in relation to the temperature, a judicious choice must be made among the various strains when using this species in biological control programs.     

Host discrimination ability in the tephritid parasitoid Psyttalia concolor (Hymenoptera: Braconidae)

Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) is a koinobiont larval-pupal endoparasitoid of many Tephritidae of economic importance. Little has been reported on the ability of females to discriminate between healthy and parasitized hosts, as well as parasitized versus superparasitized larvae. Two-choice bioassays were conducted to evaluate the preferences of P. concolor naïve females for healthy or single-parasitized/superparasitized C. capitata larvae, as well as the host discrimination ability among medfly larvae which had been superparasitized by the same wasp or by a conspecific one. Psyttalia concolor preferred to oviposit in a unparasitized C. capitata larva than in a self-parasitized one. Females also showed an innate ability to discriminate between larvae parasitized twice or only once, preferring the latter. This ability helps the female to optimise its oviposition decisions by deliberately avoiding superparasitized hosts, since it is known that they give a lower return in offspring number and quality than do singly parasitized hosts. Our findings contribute to a better knowledge of the P. concolor host location behaviour and also to improve its mass-rearing technique through a rational management of the host/parasitoid ratio and the host exposure time. Indeed, the proper setting of these parameters allows to reduce the fraction of single-parasitized and heavily superparasitized larvae and to enhance P. concolor rearing in terms of parasitoid offspring.     

Pupal diapause development and termination is driven by low temperature chilling in Bactrocera minax

Bactrocera minax is a major citrus pest in China, Bhutan, and India. It is univoltine and exhibits pupal diapause during winter. To better understand pupal diapause in this pest, we investigated pupal survival and pupal developmental duration under field and laboratory conditions. Specifically, we tested if pupal chilling was required for diapause development and termination. Nearly all mature larvae collected at the end of the citrus season entered pupal diapause. For pupae exposed in the field, natural chilling for less than 3 months resulted in more than 70 % mortality. However, exposure to winter conditions for 3 months or more both decreased pupal mortality and developmental duration when pupae were returned to the laboratory and held under constant temperature (25 °C). When pupae were gathered from the field in November and exposed to different chilling regimes in the laboratory, the chilling duration (30 vs 60 days) had significantly more impact on pupal survival than the specific chilling temperature (6, 8, 10, or 12 °C constant). However, both chilling duration and chilling temperature impacted on the pupal developmental duration, with longer chilling duration and higher temperatures decreasing pupal developmental duration. In conclusion, we demonstrated that pupal diapause development and termination in B. minax is strongly influenced by chilling conditions. Increasing cold exposure led to significantly and consistently faster adult eclosion and improved synchronization of adult emergence. This knowledge will help with the laboratory rearing of B. minax, an essential step in the long-term management of this pest.     

Temperature-dependent development and survival of Podisus maculiventris (Hemiptera: Pentatomidae): implications for mass rearing and biological control

The spined soldier bug, Podisus maculiventris (Say), is a generalist predator that can control >75 insect pests in various agroecosystems. Despite valuable results from the previous studies, thermal development and survival of P. maculiventris over a wide range of temperatures had not been elucidated completely. This study was conducted to investigate the stage-specific development and survival of P. maculiventris at eight constant temperatures (13.2, 18.4, 21.7, 23.7, 27.2, 32.7, 35.2, and 40.6 °C) covering the entire thermal range for P. maculiventris development. Completion of egg development was observed at 13.2–32.7 °C, whereas nymphs successfully developed into adults at 18.4–32.7 °C. Survival model using log-normal equations showed bell-shape patterns for all stages, and temperatures resulting in highest survival of P. maculiventris were 19.9, 24.3, and 24.5 °C for egg, nymph, and egg to adult, respectively. Developmental rates at the eight temperatures were fitted with a nonlinear Briere model, which estimated optimal temperatures for development as 31.2, 30.6, and 30.6 °C for egg, nymph, and egg to adult, respectively. Operative thermal ranges (i.e., in-between the lower and upper developmental thresholds) were estimated to be 8.9–35.2, 12.8–35.2, and 12.7–35.2 °C for egg, nymph, and egg to adult, respectively. In a linear model, the lower thresholds were 10.9, 13.1, and 13.0 °C for egg, nymph, and egg to adult, respectively. Findings herein provide comprehensive data and explanations on optimal temperature and thermal requirement for P. maculiventris, which can be used to optimize environmental condition in mass rearing and predicting phenology of P. maculiventris in the field.     

Laboratory rearing of the solitary egg-larval parasitoid, Chelonus oculator Panzer (Hymenoptera: Braconidae) on a newly recorded factitious host Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) is recorded as a new factitious host for the solitary egg-larval parasitoid, Chelonus oculator Panzer (Hymenoptera: Braconidae). A short biology and rearing method of the parasitoid on the new host were studied at 30±1°C, 60–70% relative humidity, with a photoperiod of 16:8 (L: D). Chelonus eclosed from 74.60% of parasitized hosts. No significant difference was found between development times of male and female parasitoids. Development of the parasitoid was completed in 28.14±0.47 days in male, and 28.87±0.58 days in female. However, a significant difference was found between adult sizes of male and female parasitoids. Adult dry mass was found 0.88±0.04 mg in male, and 1.99±0.11 mg in female. In addition, C. oculator was successfully reared from P. interpunctella in twenty generations with the explained method. Significant knowledge about biology of C. oculator is still lacking. However, the parasitoid can be candidate for future research as a biological control agent against some important lepidopteran pests, and P. interpunctella may be suitable factitious host for mass rearing of C. oculator.     

Über den Einfluß der Temperatur auf die Entwicklung und Vermehrung des Bekreuzten Traubenwicklers,Lobesia botrana Den. et Schiff. (Lepid., Tortricidae)

By breeding grape moth,Lobesia botrana Den. et Schiff., in laboratory conditions the effect of constant temperatures on the growth and reproduction of the pest was investigated. On the basis of collected data the sum of effective temperatures for every stage of growth as well as the threshold temperature for the growth were calculated. For the embryonic development the temperatures are 74,0°C±2,3°C and 8,8°C; for the larval development in males 384,6°C±30,1°C and 7,3°C, in females 362,3°C±20,9°C and 9,4°C; for the chrysalis stage in males 162,1°C±23,5°C and 7,1°C, in females 151,5°C±24,0°C and 9,1°C. The sums of effective temperatures of the particular growth stages were completed by their quantil values (Q₃₀, Q₅₀, Q₇₅, Q₉₅). The threshold temperature for the life of moths was set up as 11,0°C in males and 12,8°C in females. The reproduction activity in the majority of females begins at temperatures above 15°C. The effect of the temperature on the actual fertility has proved to be significant. The optimal temperatures for the oviposition are within the range of 20,0°C–27,0°C. The relation between the actual fertility and temperature is at these temperatures determined by the regression line equation Y=?5,75·X+293. Temperatures below or above the limits of this interval are less favourable for the oviposition because they lead to a decreasing of actual fertility. The limit temperature (15°C) of reproduction activity in the majority of females is considered to be the lowest extreme temperature for the oviposition.     

Temperature-dependent development of Sesamia nonagrioides

The effect of various constant temperatures on survival, development and adult longevity of Sesamia nonagrioides Lefébvre (Lepidoptera: Noctuidae) was studied under laboratory conditions. The following temperatures were tested: 14, 17, 21, 25 and 31 °C. The percentage of individuals that completed development at each temperature as well as the days needed for the emergence of the pupa and adult eclosion were measured. Adult longevity was estimated under the same conditions. Development time decreased significantly with increasing temperature within the range 14–25 °C. Survival was higher at medium temperatures (17–25 °C) in comparison with that at more extreme temperature regimens (14 and 31 °C). Egg and first larval instars were the stages where S. nonagrioides suffered the highest mortality levels at all temperatures. The highest survival was recorded with experimental individuals aging between the third and fifth larval instar. Thermal requirements of development (developmental thresholds, thermal constant, optimum temperature) of S. nonagrioides were estimated with application of linear and one nonlinear models (Logan I). Upper and lower developmental thresholds ranged between 31.2 and 36.2 and 7.0 and 10.3 °C, respectively. The optimum temperature for development (where maximum rate of development occurs) was estimated at between 28.1 and 30.3 °C. The thermal constant for total development was estimated at 1,000.0 degree-days. Adult longevity was also affected by temperature, as it was significantly reduced at higher temperatures (21–31 °C) compared to the lower ones (14 and 17 °C). This information would be useful in determining the critical temperatures which may affect the distribution of S. nonagrioides concerning potential climate change.