Kamis, 08 Januari 2009
The effect of development time on the fitness of female Trichogramma evanescens
Josée Doyon1,2 and Guy Boivin1
1Horticultural Research and Development Center, Agriculture and Agrifood Canada, St-Jean-sur-Richelieu, Québec, Canada
2Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Québec, Canada
Abstract
Trichogramma are facultative gregarious egg parasitoids that attack a wide range of lepidopterous eggs. Because hosts in which parasitoids develop vary in terms of available food, the progeny produced by parasitoid females vary in size and fitness. While one might expect that the developmental rate and emergence rhythm should be similar for all individuals reared under the same environmental conditions, variations in the duration of development of individuals reared under uniform conditions have been found in several insect species. In the Hymenopteran egg parasitoid Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) adults emerge at the beginning of the photoperiod on two consecutive days. Longer development may influence the fitness of adults and have an impact on mating opportunities. Size, longevity and daily and lifetime fecundity were measured for female T. evanescens that developed in nine and ten days. We observed a significant relationship between size and both longevity and lifetime fecundity. While early emerging females did not live longer and did not produce progeny with a different sex-ratio than females that emerged later, they were larger and produced more
progeny than late females. We conclude that early emerging females have a higher fitness than late emerging females T. evanescens.
Keywords: emergence, fecundity, longevity, parasitoid, sex-ratio, size
Journal of Insect Science, 5:4, Available online: insectscience.org/5.4 Read More..
1Horticultural Research and Development Center, Agriculture and Agrifood Canada, St-Jean-sur-Richelieu, Québec, Canada
2Département des Sciences Biologiques, Université du Québec à Montréal, Montréal, Québec, Canada
Abstract
Trichogramma are facultative gregarious egg parasitoids that attack a wide range of lepidopterous eggs. Because hosts in which parasitoids develop vary in terms of available food, the progeny produced by parasitoid females vary in size and fitness. While one might expect that the developmental rate and emergence rhythm should be similar for all individuals reared under the same environmental conditions, variations in the duration of development of individuals reared under uniform conditions have been found in several insect species. In the Hymenopteran egg parasitoid Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) adults emerge at the beginning of the photoperiod on two consecutive days. Longer development may influence the fitness of adults and have an impact on mating opportunities. Size, longevity and daily and lifetime fecundity were measured for female T. evanescens that developed in nine and ten days. We observed a significant relationship between size and both longevity and lifetime fecundity. While early emerging females did not live longer and did not produce progeny with a different sex-ratio than females that emerged later, they were larger and produced more
progeny than late females. We conclude that early emerging females have a higher fitness than late emerging females T. evanescens.
Keywords: emergence, fecundity, longevity, parasitoid, sex-ratio, size
Journal of Insect Science, 5:4, Available online: insectscience.org/5.4 Read More..
Impact of release rates on the effectiveness of augmentative biological control agents
David W. Crowder
Department of Entomology, University of Arizona, Tucson, AZ
Abstract
To access the effect of augmentative biological control agents, 31 articles were reviewed that investigated the impact of release rates of 35 augmentative biological control agents on the control of 42 arthropod pests. In 64% of the cases, the release rate of the biological control agent did not significantly affect the density or mortality of the pest insect. Results where similar when parasitoids or predators were utilized as the natural enemy. Within any order of natural enemy, there were more cases where rates did not affect augmentative biological control than cases where release rates were significant. There were more cases in which release rates did not affect augmentative biological control when pests were from the orders Hemiptera, Acari, or Diptera, but not with pests from the order Lepidoptera. In most cases, there was an optimal release rate that produced effective control of a pest
species. This was especially true when predators were used as a biological control agent. Increasing the release rate above the optimal rate did not improve control of the pest and thus would be economically detrimental. Lower release rates were often optimal when biological control was used in conjunction with insecticides. In many cases, the timing and method of biological control applications were more
significant factors impacting the effectiveness of biological control than the release rate. Additional factors that may limit the relative impact of release rates include natural enemy fecundity, establishment rates, prey availability, dispersal, and cannibalism.
Journal of Insect Science 7:15, available online: insectscience.org/7.15 Read More..
Sabtu, 03 Januari 2009
menyikapi org yang tak menghargai kebaikan kita
Apa anda pernah merasakan kecewa?? mungkin hampir semua dari kita menjawab iya.
Truz apa anda pernah merasa tak di hargai?? sekali lagi anda pasti menjawab iya.
Kadang kita tlah berbuat baik/ kasih perhatian pada seseorang bukan sekali bahkan tlah berkali-kali tapi apa yang kita dapat? sekali lagi bukan ucapan terima kasih, karena itu memang bukan tujuan kita berbuat baik padanya. Mungkin yang kita ingin dari dia hanyalah menghargai maksud baik kita.
Tetapi kadang kita mendapatkan sebaliknya. Bahkan ada yang mengatakan bahwa kita tlah mengganggunya, sungguh hati kita menjadi hancur saat mendengar hal itu. Truz apa yang harus kita lakukan?? apakah merasa dendam?? mungkin pada saat dia mengatakan itu hati kita kecewa sangat2 kecewa.. itu wajar. Apa kita merasa dendam, ternyata dendam tidak menyelesaikan masalah. Dendam hanya berlaku buat orang yang tak mengerti. Malah sebaliknya kita harus memaafkan&mendoakannya.
Selalulah berbuat baek pada smua orang.. tak peduli mereka menghargai niat baek kita atau malah sebaliknya.
Yang pasti dengan berbuat baik/ kasih perhatian hati kita bisa DAMAI
Read More..
Truz apa anda pernah merasa tak di hargai?? sekali lagi anda pasti menjawab iya.
Kadang kita tlah berbuat baik/ kasih perhatian pada seseorang bukan sekali bahkan tlah berkali-kali tapi apa yang kita dapat? sekali lagi bukan ucapan terima kasih, karena itu memang bukan tujuan kita berbuat baik padanya. Mungkin yang kita ingin dari dia hanyalah menghargai maksud baik kita.
Tetapi kadang kita mendapatkan sebaliknya. Bahkan ada yang mengatakan bahwa kita tlah mengganggunya, sungguh hati kita menjadi hancur saat mendengar hal itu. Truz apa yang harus kita lakukan?? apakah merasa dendam?? mungkin pada saat dia mengatakan itu hati kita kecewa sangat2 kecewa.. itu wajar. Apa kita merasa dendam, ternyata dendam tidak menyelesaikan masalah. Dendam hanya berlaku buat orang yang tak mengerti. Malah sebaliknya kita harus memaafkan&mendoakannya.
Selalulah berbuat baek pada smua orang.. tak peduli mereka menghargai niat baek kita atau malah sebaliknya.
Yang pasti dengan berbuat baik/ kasih perhatian hati kita bisa DAMAI
Read More..
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