AN INSECT HOST–PARASITE POPULATION

1960 ◽  
Vol 38 (1) ◽  
pp. 57-75 ◽  
Author(s):  
Thomas Burnett
Keyword(s):  
General Trend ◽  
Trialeurodes Vaporariorum ◽  
Parasite Population ◽  
Insect Host ◽  
Growth Forms ◽  
Encarsia Formosa ◽  
Tomato Plants ◽  
Sources Of Variation ◽  
Host Parasite

Eight populations of Trialeurodes vaporariorum and Encarsia formosa were propagated on tomato plants in the greenhouse for about eight months. Although there was some variation in the growth-forms of host and parasite among the experiments, the general trend in each experiment was one of fluctuations of slightly, but distinctly, increasing amplitude. As extraneous sources of variation had only a slight influence on the growth-forms, the fluctuations resulted from host–parasite interaction. The T. vaporariorum – E. formosa system, is well suited for an investigation of the principles of host–parasite interaction.

HOST LARVAL MORTALITY IN AN EXPERIMENTAL HOST–PARASITE POPULATION

1964 ◽  
Vol 42 (5) ◽  
pp. 745-765 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Larval Mortality ◽  
Trialeurodes Vaporariorum ◽  
Parasite Population ◽  
Rapid Decline ◽  
Encarsia Formosa ◽  
Host Protection ◽  
Host Mortality ◽  
Host Parasite ◽  
Parasite Populations ◽  
Two Populations

Two populations of Trialeurodes vaporariorum (Westw.) and its chalcid parasite Encarsia formosa Gahan were reared on tomato plants in the greenhouse at 72–76 °F for 26 weeks. Although the abundance of both species fluctuated with peaks of increasing amplitude, the population that was initially larger remained so throughout the period of sampling because the parasite inflicted similar rates of mortality in both cases. The fluctuations of the two separate populations were synchronized throughout the period of propagation. Host mortality, which resulted either from almost immediate killing of host scales following attack by adult parasites or from death of host larvae following parasitization and development of parasite progeny, was determined by parasite density, host size, and possibly by a number of other factors such as the age structure of host larval populations, age of adult parasites, and succulence of leaves on which the host larvae developed. The interaction of host and parasite produced cycles in the age structures of host and parasite populations that, in turn, influenced the interaction of the two species. The death of host larvae following attack by adult parasites was a form of host protection, as it ensured the rapid decline in the abundance of the parasite population and was, therefore, the primary factor in the maintenance of the host–parasite system.

EFFECTS OF INITIAL DENSITIES AND PERIODS OF INFESTATION ON THE GROWTH-FORMS OF A HOST AND PARASITE POPULATION

1960 ◽  
Vol 38 (6) ◽  
pp. 1063-1077 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Trialeurodes Vaporariorum ◽  
Parasite Population ◽  
Growth Forms ◽  
Encarsia Formosa

Initial densities and periods of infestation of adults of Trialeurodes vaporariorum and its chalcid parasite Encarsia formosa influence subsequent fluctuations in numbers of adults of both host and parasite.

ASPECTS OF THE INTERACTION BETWEEN A CHALCID PARASITE AND ITS ALEURODID HOST

1967 ◽  
Vol 45 (4) ◽  
pp. 539-578 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Larval Mortality ◽  
Trialeurodes Vaporariorum ◽  
Host Population ◽  
Population Variation ◽  
Encarsia Formosa ◽  
Greenhouse Whitefly ◽  
Parasite Abundance ◽  
Tomato Plants ◽  
Host Mortality ◽  
Dominant Process

Three populations of the greenhouse whitefly, Trialeurodes vaporariorum, and its chalcid parasite Encarsia formosa were propagated each year for three consecutive years on tomato plants in the greenhouse. The abundance of the host and parasite species fluctuated either with peaks of increasing amplitude, with peaks of decreasing amplitude, or with irregular peaks. The dominant process in the interaction was the occurrence of two qualitatively different types of host larval mortality: (a) parasitization, and (b) almost immediate killing after attack by adult parasites. Fluctuations in host and parasite abundance resulted from the almost immediate killing of small host larvae and the death of the short-lived adult parasites. The parasite population tended to destroy similar percentages of host populations of different densities but host mortality was also related to the age structure of the host population. Variation in host reproduction, caused by differences in rearing temperature and by seasonal variation in the physical environment, influenced host and parasite densities.

An Effect of Parasite Attack on Host Mortality, as Exemplified by Encarsia formosa and Trialeurodes vaporariorum

1962 ◽  
Vol 94 (7) ◽  
pp. 673-679 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Field Tests ◽  
Trialeurodes Vaporariorum ◽  
Host Feeding ◽  
Encarsia Formosa ◽  
Mature Adult ◽  
Bracon Hebetor ◽  
Black Scale ◽  
Host Mortality ◽  
Host Parasite ◽  
Juvenilizing Effect

It is not unusual for parasite attack on insect hosts to have different consequences for individuals of the same species. An indication of the variation in types of alternative effects is given by a consideration of three host-parasite relationships. First, although most hosts in a population are susceptible to parasitization, some are immune to attack: about one in 3,000 larvae of the Mediterranean flour moth, Anagasta kühniella (Zeller), was found by Payne (1934) to be immune to attack by Bracon hebetor Say. Second, tile morphology of hosts may be modified differentially by parasitism: unhatched eggs of Aphdius platensis Brethes exert a juvenilizing effect on nymphs of Aphis craccivora Koch whereas parasite larvae sometimes cause the appearance of adult characters (Johnson, 1959). Third, some hosts are successfully parasitized whereas others are killed long before parasite progeny can mature: adult females of Metaphycus helvolus (Com.) kill the black scale, Saissetin oleae (Bern.), by parasitization, by mutilation with the ovipositor, and by host-feeding at wounds made by the ovipositor. Field tests showed that up to 97 per cent of a black-scale infestation may be killed by the parasite over a period of several months.

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