Effects of host stages and temperature on population parameters of Oomyzus sokolowskii, a larval-pupal parasitoid of Plutella xylostella

Oomyzus sokolowskii is alarval-pupal parasitoid of diamondback moth, Plutella xylostella. In a host stage preference test, the parasitoid parasitised all larval and pupal stages, but exhibited a strong preference for larvaeover prepupae or pupae, and did not show a preference among the larval instars. At 25°C, the developmental time, number and sex ratio of offspring per host pupa, and successful parasitism did not differ significantly among parasitoids reared from host larvae of different instars, indicating similar host suitability between larvae of different instars. Mean developmental times from egg to adult at 20, 22.5, 25, 30, 32.5, and 35°C were 26.5,21.0, 16.0, 12.7, 11.9 and 13.4 days, respectively. The favourable temperature range for development, survival, and reproduction of the parasitoid was 20--30°C. However, wasps that developed and emerged at a favourable temperature could parasitise effectively at 32--35°C for 24 hours. Life-fertility table studies at 20, 25, and 30°C showed that each female wasp on average parasitised 3.1, 13.2, 6.8 larvae of diamondback moth and produced 20.5, 92.1, 50.4 offspring, respectively, during her lifetime. The highest intrinsic rate of natural increase (r _m) of 0.263 female/day was reached at 30°C as a result of the short mean generation time at this temperature compared to that at 20 and 25°C, suggesting that the parasitoid had the highest potential for population growth at relatively high temperatures. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of temperature on the life history of <Emphasis Type="Italic">Eretmocerus</Emphasis> sp. nr. <Emphasis Type="Italic">furuhashii</Emphasis>, a parasitoid of <Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Eretmocerus sp. nr. furuhashii (Hymenoptera: Aphelinidae) is an indigenous parasitoid of Bemisia tabaci (Gennadius)(Hemiptera: Aleyrodidae) from southern China; the effects of constant temperatures on the life history of E. sp. nr. furuhashii were examined in the laboratory. The developmental period ranged from 39.2 days at 20°C to 12.40 days at 32°C. A total of 263.4 degree-days were required to complete development with a lower developmental threshold temperature of 11.1°C. Of the eggs produced, 59.3% completed development at 20°C with completion increasing to 71.5% at 26°C. Adult female longevity was 10.8 days at 20°C and 5.2 days at 32°C while the mean daily offspring reproduced per female was highest at 29°C with 5.9 offspring. Adult oviposition peaked three days after emergence at 26, 29 and 32°C, and four days post-emergence at 20°C and 23°C. The total numbers of offspring produced per female ranged from 25.7 individuals at 32°C to 41.1 individuals at 20°C. The sex ratio had a female bias and ranged from 0.72 at 17°C to 0.51 at 35°C. The intrinsic rate of increase was 0.1727 at 29°C followed with 0.1606 at 32°C. Results indicated that E. sp. nr. furuhashii reaches its maximum biological potential at temperatures ranging from 26°C to 32°C.     

Life histories ofPsyllaephagus yaseeni (Hym., Encyrtidae) andTamarixia leucaenae (Hym., Eulophidae), parasitoids of the leucaena psyllidHeteropsylla cubana

Age specific fecundity of two parasitoids,P. yaseeni andT. leucaenae, of the leucaena psyllidH. cubana, were studied under laboratory conditions. At 25 °C,P. yaseeni had a greater fecundity (R₀=192.9)_thanT. leucaenae (R₀=71.2);T. leucaenae however had a lower sex ratio (about 99 % females) thanP. yaseeni (about 50 % females). Innate capacity for increase (r_m=0.236) ofT. leucaenae was higher thanP. yaseeni (r_m=0.188). Developmental rates of the parasitoids were examined at constant and fluctuating temperatures and equations of the rate of development against temperature were calculated. At 25 °C, mean generation times were 28.0 and 18.1 days forP. yaeseeni andT. leucaenae respectively. At temperatures of 21.5, 25, and 30 °C total development times (egg to adult) were 28.5, 21.9, and 14.7 days inP. yaseeni and 19.2, 12.6, and 9.5 days inT. leucaenae respectively. The level of parasitism was low and pupal mortality was high at the lower temperature of 21.5 °C for both parasitoids. Both parasitoids showed poor survivorship at 100 % RH,P. yaseeni survived particularly well (32 days) at a temperature of 21.5 °C and 44 or 76 % RH. P. yaseeni allocated about 58 % females to first instar psyllid nymphs but only 12 % females to second instars. About 99 % of allT. leucaenae births were females. Significantly largerT. leucaenae females emerged from fifth instar parasitized nymphs than third or fourth instars.     

Influence of larval rearing temperature on the quality of cold‐stored Oomyzus sokolowskii Kurdjumov (Hymenoptera: Eulophidae)

Oomyzus sokolowskii, an important parasitoid of Plutella xylostella, has great potential for use in biological control. Storage at suboptimal temperature is valuable for increasing the shelf‐life of insect parasitoids. In this study, O. sokolowskii larvae were reared at 30/25, 25/25 and 25/20°C light/dark (65 ± 5% RH, 16 : 8 h L : D) until pupation. The pupae were then cold‐stored at 4 ± 1°C (60 ± 5% RH, full darkness). The pupae were removed out from the storage at 10, 20, 30 and 40 days after storage (DAS) and maintained at 25 ± 2°C until adults emerged or pupae died. Quality of the emerging adults and their F₁ offspring were assessed. Incidence of parasitism by O. sokolowskii was higher at 30/25°C than at 25/20°C. Cold storage of O. sokolowskii pupae greatly affected the fitness of the parasitoid: adult emergence rates were lower in the 40 DAS treatment than in other treatments; when O. sokolowskii larvae developed at 25/25°C, female proportions of the emerged adults were lower in the 40 DAS treatment than in the 0 and 10 DAS treatments. Larval rearing temperature mildly affected the adult emergence rate, post‐storage developmental time and female proportion with a few exceptions. Number of parasitoids emerged per host pupa, and incidence of parasitism by the females were neither affected by larval rearing temperature nor cold storage duration. Trans‐generational effects on F₁ offspring were evident in adult emergence rate, egg‐adult developmental time and female proportion which were negatively affected by long duration of storage (40 days), but not by larval rearing temperature with a few exceptions. In conclusion, O. sokolowskii pupae could be stored at 4°C for up to 30 days without significant fitness loss.     

Studies ontrichogramma buesi as a biocontrol agent againstPieris rapae in Egypt

Trichogramma buesi was reared in the laboratory on eggs of the Mediterranean flour moth,Anagasta kuehniella. The incubation period of the parasite's egg was 27 h at 23 °C and 22 h at 27 °C. The larval stage lasted 3.6 and 3.2 days, the pre-pupa lasted 16 and 23 h, and the pupa lasted 5.4 and 4.6 days at 23° and 27°C, respectively. The total developmental time (from egg to adult) averaged 9.2, 9.4, and 9.1 days when the parasite was reared on eggs ofPieris rapae, Spodoptera littoralis, andA. kuehniella, respectively, at 27 °C. Sex ratio inT. buesi was 1 ♂: 1 ♀ in nature and 1 ♂: 1.3 ♀ in the laboratory. The daily and total numbers or progeny produced/female were 5.1 and 98.2 adults, respectively. The parasite female, fed on honey, lived 10.7 days at 27 °C and 12.1 days at 23 °C. Percentages of parasitism byT. buesi on eggs ofP. rapae collected from cabbage fields ranged between 0 and 31.5 % in 1985 and betwcen 0 and 36.4% in 1986 during July through December. The respective figures on eggs collected from turnip fields were 16–42.2% and 12.5–32.1% during November and December.      

Parasitism of frozen Halyomorpha halys eggs by Trissolcus japonicus: applications for rearing and experimentation

The brown marmorated stink bug, Halyomorpha halys (Stål), has become a well-known pest to growers and homeowners since its 1996 introduction to the United States. A classical biocontrol programme is under development using the egg parasitoid Trissolcus japonicus. Widespread implementation of biocontrol requires efficient mass rearing, which is constrained by the availability of fresh H. halys eggs. In this study, parasitism rate, developmental time, sex ratio and size were compared between wasps reared on fresh versus frozen, newly laid (<1 d old) versus variably aged (0–3 d old), and frozen egg masses stored ≤4 y. Frozen eggs yielded 56–65% fewer wasps, with parasitism rate decreasing 1–3% per month stored. Parasitism rate, sex ratio and developmental time were comparable between newly laid and variably aged eggs. Freezing eggs for any duration did not affect sex ratio or weight of emerged wasps, but delayed emergence 5–6 d. To simulate deployment of sentinel eggs in the field, we incubated frozen eggs at 20°C and 30°C for 1–9 d before exposing them to T. japonicus, then evaluated parasitism trends. Trissolcus japonicus parasitism rate decreased 5–8% per day incubated, unhatched wasps increased 9% per day incubated and sex ratio was not impacted. Variably aged, frozen and longer stored eggs can be used for T. japonicus rearing and experimentation without affecting emerged wasp sex ratio or size within one generation, but have lower parasitism and slower development. Frozen sentinel eggs are effective <3–5 d, especially in hot conditions.     

Encarsia formosa parasitizing the Poinsettia-strain of the cotton whitefly,Bemisia tabaci, on Poinsettia: bionomics in relation to temperature

Adult longevity, developmental time and juvenile mortality ofEncarsia formosa Gahan (Hymenoptera:Aphelinidae) parasitizing the Poinsettia-strain ofBemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) on Poinsettia (Euphorbia pulcherrima Willd.) were investigated in laboratory experiments at three temperatures: 16 °C, 22 °C and 28 °C. Furthermore, the parasitoid's preference for different larval stages of the whitefly was determined at 24.5 °C. The lifespan ofE. formosa decreased with temperature from one month at 16 °C to nine days at 28 °C. A lower temperature threshold of 11 °C for adult development was found. The development of juvenile parasitoids inB. tabaci lasted more than two months at the lowest temperature, but was only 14 days when temperature was 28 °C. The lower temperature threshold for immature development was 13.3 °C, yielding an average of 207 day-degrees for the completion of development into adults. Juvenile mortality was high, varying from about 50% at 16 °C to about 30% at 22 °C and 28 °C.E. formosa preferred to oviposit in the 4th instar and prepupal stages ofB. tabaci followed by the 2nd and 3rd instars. The preference for the pupal stage was low. The parasitoid used all instars of the whitefly for hostfeeding, with no apparent differences between the stages. The average duration of the oviposition posture was four minutes. Demographic parameters were calculated from life tables constructed from the data. The intrinsic rate of increase (r _m) and the net reproductive rate (R ₀) increased with temperature from 0.0279 day⁻¹ at 16 °C to 0.2388 day⁻¹ at 28 °C and from about 12 at 16 °C to about 66 at 28 °C, respectively.     

Influences of temperature and humidity on the life history parameters and prey consumption of <Emphasis Type="Italic">Anthocoris minki</Emphasis> Dohrn (Heteroptera: Anthocoridae)

Anthocoris minki Dohrn is a promising indigenous Anthocoris species for the biological control of Agonoscena pistaciae Burck. and Laut. (Homoptera: Psyllidae) in pistachio orchards in Turkey. The adult longevity, fecundity, life table parameters and prey consumption of A. minki fed on Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs were studied at combinations of three constant temperatures (20, 25 and 30 ± 1°C) with two relative humidity (RH) levels (40 and 65 ± 5%). Studies indicated that temperature and RH significantly affected adult longevity, fecundity and prey consumption of A. minki. The greatest adult female longevity was 116.0 days at 20°C and 65% RH; the shortest adult female longevity was 27.5 days at 30°C and 40% RH. At all tested temperatures, the oviposition period and prey consumption of both females and males significantly decreased at low RH compared to high RH. The highest and lowest total fecundities were 276.0 eggs (at 20°C and 65% RH) and 42.4 eggs (at 25°C and 40% RH), respectively. The intrinsic rates of natural increase (r _m) at 40 and 65% RH were 0.049 and 0.076 at 20°C, 0.072 and 0.096 at 25°C and 0.076 and 0.112 at 30°C, respectively. The highest mean numbers of E. kuehniella eggs consumed by females and males were 859.6 (at 20°C) and 515.3 (at 25°C) at 65% RH, respectively; the lowest were 183.3 (at 20°C) and 95.5 (at 25°C) at 40% RH, respectively.     

Effect of different cold storage periods on parasitization performance of Trichogramma cacoeciae (Hymenoptera,Trichogrammatidae) on eggs of Ephestia kuehniella (Lepidoptera,Pyralidae)

The parasitism rates by Trichogramma cacoeciae Marchal (Hymenoptera, Trichogrammatidae) using Ephestia kuehniella Zell. (Lepidoptera, Pyralidae) eggs held at 0, 4 and 8°C and for up to 31 days was measured. Parasitism was lowest on eggs held at 8°C and highest on eggs held at 0°C. The highest parasitism, 97.8%, was measured for parasitoids attacking eggs held for 3 days and stored at 0°C. Parasitism of eggs stored at all three temperatures decreased with increasing duration of storage. The number of T. cacoeciae successfully developing and emerging as adults after storage in E. kuehniella eggs held at 0, 4 and 8°C was measured. Parasitoid emergence was >83% from E. kuehniella eggs stored at 8°C for 3 weeks. Storage at 0°C caused a significant decline in parasitoid emergence after 2 weeks (P<0.05). Storage at 0°C for more than 4 weeks reduced fecundity by 50%. T. cacoeciae parasitized the highest number of E. kuehniella eggs 1 day after adult emergence. The oviposition period lasted 6–7 days, although the parasitoids lived up to 13–14 days. Impact of storage time and temperature on parasitism rates by T. cacoeciae stored while in E. kuehniella eggs was measured. As storage time and temperature increased, subsequent parasitism rates of resulting adult T. cacoeciae decreased. Eggs of E. kuehniella can be stored at 0°C for up to 31 days. Trichogramma cacoeciae developing in eggs of E. kuehniella can be stored at 4°C for up to 5 weeks prior to release.     

Effects of temperature on biology and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama (Homoptera: Psyllidae)

The development, survivorship, longevity, reproduction, and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama were evaluated at 10°C, 15°C, 20°C, 25°C, 28°C, 30°C and 33°C. The populations reared at 10°C and 33°C failed to develop. Between 15°C and 30°C, mean developmental period from egg to adult varied from 49.3 days at 15°C to 14.1 days at 28°C. The low‐temperature developmental thresholds for 1st through 5th instars were estimated at 11.7°C, 10.7°C, 10.1°C, 10.5°C and 10.9°C, respectively. A modified Logan model was used to describe the relationship between developmental rate and temperature. The survival of the 3rd through 5th nymphal instars at 15–28°C was essentially the same. The mean longevity of females increased with decreasing temperature within 15–30°C. The maximal longevity of individual females was recorded 117, 60, 56, 52 and 51 days at 15°C, 20°C, 25°C, 28°C and 30°C, respectively. The average number of eggs produced per female significantly increased with increasing temperature and reached a maximum of 748.3 eggs at 28°C (P<0.001). The population reared at 28°C had the highest intrinsic rate of increased (0.199) and net reproductive rate (292.2); and the shortest population doubling time (3.5 days) and mean generation time (28.6 days) compared with populations reared at 15–25°C. The optimum range of temperatures for D. citri population growth was 25–28°C.     

Biology of Microplitis kewleyi (Hymenoptera: Braconidae): A parasite of Agrotis ipsilon (Lepidoptera: Noctuidae) larvae

Microplitis kewleyi Muesebeck is a gregarious internal parasite of larvae of the black cutworm Agrotis ipsilon (Hufnagel). Studies of the biology of the parasite revealed that there was an inverse relationship between host instar and parasite preference. Duration of development from egg to pupa ranged from 18 days at 27°C to 68.7 days at 16°C. Development from egg to pupa took 13.5–21.6 days when fourth and first instar host larvae, respectively, were parasitized. A larger number of parasites emerged from hosts parasitized in the fourth instar (22.4) than the first instar (11.5). Parasite pupation occurred when the host was in the fifth/sixth instar, depending on the instar parasitized. Thirty‐nine per cent of host larvae exposed as first instars to parasites died before parasite emergence. This decreased to 0% for host larvae exposed as fourth instars. The sex ratio was 1:1.2 (M:F). Thirty‐seven per cent of hosts exposed diurnally were stung, compared to 24% exposed nocturnally. Mean daily progeny was highest (12) on the first day, decreasing to zero after 20 days. Percent host parasitism was also highest on the first day (35%) decreasing to nearly 0% after 18 days. There appear to be three parasite larval instars. Host larvae often remained alive after parasite emergence.     

Temperature‐dependent developmental model of Neoseiulus californicus (McGregor) (Acari,Phytoseiidae)

The developmental time and survival of immature stages of Neoseiulus californicus were studied at nine constant temperatures (12, 16, 24, 24, 28 32, 36, 38 and 40°C), 60–70% RH, and a photoperiod of 16 : 8 (L : D) h. The total mortality of immature N. californicus was lowest at 24°C (4.5%) and highest at 38°C (15.2%). The total developmental time decreased with increasing temperature between 12°C (18.38 days) and 32°C (2.98 days), and increased beyond 32°C. The relationship between the developmental rate and temperature was fitted by five nonlinear developmental rate models (Logan 6, Lactin 1, 2 and Briere 1, 2). The nonlinear shape of temperature development was best described by the Lactin 1 model (r² = 0.98). The developmental variation of each stage was well described by the three‐parameter Weibull distribution model (r² = 0.91–0.93). The temperature‐dependent developmental models of N. californicus developed in this study could be used to determine optimal temperature conditions for its mass rearing, to predict its seasonal population dynamics in fruit tree orchards or greenhouse crops, or to develop a population dynamics model of N. californicus.     

On the biology and thermal developmental requirements of the cotton mealybug,Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) in Egypt

This study evaluated the thermal requirements for development of the cotton mealybug Phenacoccus solenopsis depending on different biological parameters on Okra leaves Abelmoschus esculentusat under two constant temperatures (20 and 30 °C) at (RH 65%, 12:12 h. light/dark). The effect of temperature on eggs was ineffective since it hatched shortly to first nymphal instars after deposition. While the tested temperature caused significant effects on nymphal durations, pupation rate (pre-male stage), females emergence %, pre-oviposition, longevity, post-oviposition periods and fecundity in females (egg deposition, ovisacs numbers and hatchability %). The thermal constant and developmental zero were calculated to be 7.29 °C and 79.9 degree-days (DDs) for eggs, 11.67 °C and 272.9 DDs for nymphal stages, 11.06 °C and 46.4 DDs for males and then 3.31 °C and 554.1 DDs for females, respectively. The duration of the life cycle was 65.6 ± 10.36 days at 20 °C; this was shortened to 35.51 ± 1.12 days at 30 °C. The thermal requirements to complete the insect development for one generation was 8.2 °C for the developmental zero and 774.1 DDs for the thermal constant. Based on the thermal requirements values, the average life cycle duration from January to December 2016 was 61.78 days and the number of annual generations was 7.143 when the average annual temperature was 23.29 °C.     

Assessment of life history parameters of Aspidiotus nerii (Hemiptera: Diaspididae) to improve the mass rearing of Aphytis melinus (Hymenoptera: Aphelinidae)

The biological control of Aonidiella aurantii (Maskell) on citrus can be achieved with periodic releases of the parasitoid Aphytis melinus DeBach. A. melinus is normally reared on parthenogenetic strains of the scale Aspidiotus nerii Bouché. The developmental rate, crawler production and survival of A. nerii were studied at two temperatures (25±1 and 30±1°C) and two levels of relative humidity (RH; 55±5 and 85±5%) on squash. Temperature had an important effect on developmental rate, but RH did not. At 30°C, no growth was observed and no crawlers were produced. At 25°C, development of the L1, L2 and young females’ stages required 24.4±0.7, 11.1±0.8 and 13.2±0.3 days, respectively. At 25°C, times until the appearance of mature females, the start of crawler production and the peak of crawler production were 48.7±0.1, 50.1±0.7 and 63.3±1.0 days, respectively. Crawler production lasted 42.6±1.9 days, and the 50% production level was reached on day 13. Initially, crawler survival was higher at 30°C (65.9±2.8%) than at 25°C (51.7±4.8%), but by the end of development survival was much higher at 25 than 30°C (88.0±2.1 vs. 22.9±2.7%). RH had no effect on either initial or final survival. Average progeny production was of 28.0±2.8 crawlers per female at 25°C. The relationship between the weight of groups of crawlers and their number was: Number=1031+835,500×weight of group (g) (R ²=0.826), which can assist in colony management. The importance of selecting the correct strain of A. nerii is emphasised.     

Biological parameters and thermal requirements of the parasitoid Praon volucre (Hymenoptera: Braconidae) with Macrosiphum euphorbiae (Hemiptera: Aphididae) as host

The effect of temperature on the biology of Praon volucre (Haliday, 1833) (Hymenoptera: Braconidae) in Macrosiphum euphorbiae (Thomas, 1878) (Hemiptera: Aphididae) hosts was studied and the thermal requirements of the parasitoid were determined. Experiments were carried out at 16, 19, 22, 25, and 28 ± 1°C with 70 ± 10% relative humidity and 12 h photophase. The developmental time of P. volucre males and females decreased between 16 and 23°C. The highest percentages of aphid parasitism and adult parasitoid emergence were observed at 16, 19, and 22°C. The sex ratio (expressed as % females) decreased between 16 and 23°C. Male and female longevity was high between 19 and 22°C and decreased strongly at 25°C. The lower temperature threshold for P. volucre was 5.17°C and the thermal constant was 243 degrees-days.     

Effects of rearing conditions on the parasitism of Tetrastichus brontispae on its pupal host Octodonta nipae

Octodonta nipae (Maulik) (Coleoptera: Chrysomelidae) is currently a serious invasive pest of palm plants in southern China. Although previous studies reported that Tetrastichus brontispae Ferriere (Hymenoptera: Eulophidae) could successfully parasitize the pupae of O. nipae, little is known of the potential for T. brontispae to control this pest. To understand the interaction between T. brontispae and O. nipae, the effects of parasitoid feeding regimes, host age and density, parasitoid age and density, and cold storage on the parasitism of T. brontispae were investigated. Our results indicate that a supply of either glucose or sucrose increased the longevity and fecundity of T. brontispae. The parasitoid preferred one-day-old host pupae and its fecundity increased with increasing host or parasitoid female density. Extended cold storage negatively affected the parasitism of T. brontispae. These results demonstrate how to efficiently raise T. brontispae and will contribute to the effective management of O. nipae.     

Note on the life history of the magpie moth,Nyctemera annulata (Lepidoptera: Arctiidae)

Nyctemera annulata Boisduval was reared in the laboratory at 26±1°C and 50 ±5% RH on a host plant, ragwort (Senecio jacoboea L.), and on an artificial diet. On ragwort the average life cycle of 34 days embraced a larval period of 24 days, with up to 6 larval instars, and a pupal period of 9–11 days, depending on whether pupation occurred at the 5th or 6th instar. On the artificial diet the larval period of 56 days, involving up to 10 instars, was followed by a pupal period of 9 days, for an average life cycle of 65 days.     

Factors affecting the parasitism rate and the number and sex ratio of offspring of Asecodes hispinarum Bouček (Hymenoptera: Eulophidae), a biological control agent of Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae)

To optimise the production of Asecodes hispinarum Bou?ek (Hymenoptera: Eulophidae), a parasitoid of coconut leaf beetle, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae), some of the factors affecting rates of parasitism, number of offspring produced per host and sex ratio of A. hispinarum were investigated. The numbers and sex ratio of A. hispinarum offspring per host reduced significantly at extreme low humidity (30% relative humidity [RH]), but there was no significant effect on parasitism. Photoperiod had no significant effects on any of the life traits tested. A. hispinarum was able to reproduce via arrhenotoky, and while increasing the proportion of female parents increased the number of parasitoids produced, the proportion of female offspring decreased. Older females showed a lower rate of parasitism than young females, however, maternal age did not affect the number or the sex ratio of offspring. Increasing the number of hosts offered to a pair of parasitoids significantly increased the number of parasitised hosts but decreased the parasitism rate while the sex ratio of progeny was not affected. Present work showed that to maximise the production of female parasitoids, a parasitoid/host ratio of 1:1, using one-day old A. hispinarum at a female/male ratio of 3:1 and RH of at least 55% is recommended.     

Effects of constant and fluctuating temperatures on development of the coconut hispine beetle,Brontispa longissima (Coleoptera: Chrysomelidae) and two species of parasitoid

Abstract

The larval parasitoid Asecodes hispinarum Bou?ek has been used to control the coconut hispine beetle, Brontispa longissima (Gestro) in Vietnam. Although A. hispinarum has succeeded in suppressing B. longissima in southern Vietnam, biocontrol has not succeeded in central Vietnam. One factor underlying this failure might be the high temperature during the hot season. In the present work, we examined whether A. hispinarum parasitises the beetles within the range of temperatures that occur during the hot season in central Vietnam and we evaluated the potential use of the pupal parasitoid Tetrastichus brontispae Ferrière. Development of the beetle and two parasitoids was investigated at two constant temperatures (28 and 30°C) and at fluctuating temperatures from 25 to 35°C (corresponding to temperatures during the hot season in central Vietnam). B. longissima reached adulthood in all the temperature treatments. More than 70% of A. hispinarum emerged from hosts at 28°C, but none emerged at 30°C or under fluctuating temperature conditions, indicating that A. hispinarum cannot be used as a biological control agent in central Vietnam. However, T. brontispae could reproduce the next generation at all temperatures. These results suggest that T. brontispae is a potential agent for continuous biological control of B. longissima in central Vietnam.