Population studies of the Cabbage aphid Brevicoryne brassicae (L.) and its parasites, with special reference to synchronisation

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Effects of Host Fruit and Larval Density on Development and Survival of Bactrocera sp. (Malaysian B). (Diptera: Tephritidae)

The effects of five fruits (guava, mango, papaya, starfruit and tomato) on the larval survival, adult eclosion and size of Bactrocera sp. (Malaysia B) were investigated. The percentage pupation and adult emergence from pupae were not affected by different hosts, except for guava which gave the lowest percentage of adult emergence. Papaya and mango yielded the largest adult (>2mm head width). Comparison of composition of fruits indicates that a high percentage of carbohydrate and high pH in fruits would produce larger adults. High larval density reduced the percentage of larval survival, adult emergence and adult size

Molecular diagnostic method for rapid and accurate identification of Malaria parasite species

Four of the five malaria parasite species infecting humans have been recorded in Malaysia (Plasmodium vivax, P. fa/ciparum, P. malariae and P. know/es,) with P. know/esi most prevalent in Sabah. Although the fifth species P. ovale is reported in Malaysia occasionally, it is only an imported species brought in by an infected visitor. Plasmodium species are identified mainly by microcopic examination of blood film on glass slides, using mainly the ring stage of the parasite within the red blood cells as a distinguishing feature. This can be done in most hospitals, but the accuracy of the method depends highly on the skill of the technician/ doctor and idetification errors have been recorded. A molecular method of species identification using DNA of Singh et al. (1999) has become popular. However this method involves two stages of PCR protocol and takes consderable time. Using this method, various investigators have shown that errors have been previously made in the identification of Plasmodium based on microscopic examination alone. For example, P. vivax and P. malariae had been misidentified as P. fa/ciparum by microscopy, almost all P. knowlesi misidentified as P. malariae or Plasmodium vivaxor P. falciparum (Singh et al., 1999) In our research, we also used a molecular method, but we used four different genes, and various DNA markers which could provide more accurate and faster identification, with lower error rates. Our approach was to examine the DNA sequences from GenBank website (www.ncbi.nlm.nih.gov/nucleotide) and determine which markers can be used as a species identification tool. We have designed new primers, tested in single as well as multiplex amplication of the four malaria species. Our results showed the multiplex PCR method is able to identify any of the five malaria species. Finally we compared our method with Singh's method and the traditional microscopic method to analyse over 100 blood samples. Our comparison indicated our multiplex method is faster, cheaper and as accurate

Pattern of parasitism in the carambola fruit fly, Bactrocera sp.(Malaysian A)(Dipt., Tephritidae) by Biosteres vandenboschi (Fullaway)(Hym., Braconidae)

Studies with carambolas collected from the field indicated that the mean number of of B. vandenboschi emerging from a larval patch (indicated externally by an ovipuncture) and from a whole fruit was respectively 5.02 ± 0.51 and 20.14 ± 1.93. In both cases, parasitism by B. vandenboschi was found to be inverse density dependent, with the respective equations of y = 97.99 e-0.12x and y = 32.54 e-0.03x where y = parasitism rate and x = total adult insects emerging from each fruit piece or a whole fruit. Likely reason for the inverse density dependent parasitism is the “spreading the risk” strategy employed by the female B. vandenboschi

Nesting population and frequency of visits in Dermochelys coriacea in Malaysia

A total of 37,654 leatherback turtle visits were recorded over a period of 10 yrs (1967- 1976) on the east coast of peninsular Malaysia. The mean number of visits/yr was 3765 (range 1962-6721), made by 1924 individual turtles (1067-3103), with a mean number of visits/turtle/yr of 1.96 (overall general mean). The mean number of visits/yr made by a turtle tagged in any one yr was 2.89 (overall tagged mean). The number of visits declined somewhat during the last 4 yrs of the program. The turtles visited mostly between May and September, with a peak of 626 individuals and 1278 visits (34% of the mean annual total) recorded in July. The visit (nesting) frequency/mo/turtle increased from April (1.84 visits per month) to June (2.20) and tapered off in September (1.24). The breeding population was estimated to be 15,525 females, the yearly survival rate 0.89, and the proportion of return of tagged turtles 0.31. About 2039 newly matured females were calculated to join the breeding population every year, 65% of which (=1328 individuals) would return to this beach. Maximum use was recorded in the middle part of the nesting beach, and the highest number of nests/km was 886, recorded in 1972. 33.4% of the total tagged turtles (12,997) visited the beach only once (when they were tagged). Those that returned 2, 3, and 4 times constituted 19.9%, 15.6%, and 11.0% of all turtles that returned at least once in subsequent years. The maximum number of visits made by a turtle during the ten yrs was 14, recorded for 6 turtles. The number of visits was found to differ significantly among years, among months, and among sectors of the beach (P < 0.001)

The parasite complex of Saissetia nigra in Malaysia

The percentage parasitism of Saissetia nigra (NIETNER) by chalcidoid parasites and the relative abundance of individual parasites were studied in the field usingHibiscus rosa-sinensis L. as the host plant. In order of abundance (on the basis of percentage recorded) the primary parasites wereAnysis saissetiae ASH.,Aneristus ceroplastae HOW., and Microterys newcombi (GIR)., while the hyperparasites wereMarietta exitiosa COMP.,Cheiloneurus saissetiae NOYES & CHUA andEupelmus catoxanthae FERR. The efficiency ofA. saissetiae (the larvae of which feed on the scale eggs) to control the scale population is doubtful because it is often parasitised by all 3 hyperparasites mentioned and each larva during development causes only 58% egg mortality of the parasitised host, leaving many scale eggs unconsumed.A. ceroplastae appears to be more useful parasite because it attacks the 2nd instar scales which cause significant damage to the host plant and it is free from attack by hyperparasites

Population studies of Brevicoryne brassicae (L.), its parasites and hyperparasites in England

Brevicoryne brassicae (L.) is a cosmopolitan aphid, feeding mainly on Crucifers (BONNEMAISON, 1965). It normally overwinters as eggs, but small colonies may survive mild. winters (PETHERBRIDGE and WRIGHT, 1938). In the spring, freshly planted Cruciferous crops are colonized by fundatrices or immigrant alates. Throughout spring, summer and autumn, B. brassicae reproduces parthenogenetically. Later in the year, however, owing to low temperatures and shorter photoperiods, sexual forms begin to appear and overwintering eggs are laid on the Cruciferous hosts. In the Netherlands, HAFEZ (1961) has shown that the number of generations per year to be between 6 and 11

Effects of prey number and stage on the biology of Cyrtorhinus lividipennis (Hemiptera: Miridae): A predator of Nilaparvata lagens (Homoptera: Delphacidae)

When given 30 eggs of Nilaparvata lugens (Stal) daily, males and females of Cyrtorhinus lividipennis Reuter took 10.8 and 13.0 d, respectively, to develop from first instar. The males consumed 49.0 eggs and the females, 59.2 eggs. The mean body length of adult males was 2.6 mm and females, 3.1 mm; mean longevity was 9.6 d for the males and 14.4 d for the females. Lifetime egg consumption was 43.8 eggs by the males and 123.6eggs by the females. Mean lifetime fecundity by unmated females was 34.0 eggs. When 20 or fewer eggs or 10 or fewer first-instar N. lugens were given daily as food, nymphal survival, adult longevity, and fecundity decreased. Individuals offered 20 or more N. lugens eggs consumed significantly more than those offered fewer eggs, but this did not result in a decrease in development time or in adult size. C. lividipennis adults that were fed daily with N. lugens nymphs (5 or 10 first, second, or third instars) also had a shorter life span and laid no eggs. Adults offered 10 second or third instars lived significantly longer than those on other regimes. Our results suggest that C. lividipennis nymphs need only small amounts of food to survive to adulthood under field conditions, especially at the beginning of the rice growing season, when N. lugens eggs are relatively scarce

Preference for sites within plant by larvae of the cabbage webworm, Hellula undalis (Fabr.)(Lep., Pyralidae)

A comparative study on the cabbage webworm (CWW), Hellula undalis, with respect to larvae feeding either on the shoot or leaf of cabbage was carried out both in the laboratory and in the field. For the first 2 days after eclosion from the egg, a CWW larva would tend to remain within the mine in the leaf where the egg was deposited. The Lloyd patchiness index (x*/x) suggested that the larval distribution was contagious, although the degree of contagiousness tended to decrease as the larvae grew due to their dispersal movement. This was indicated by the inter-plant larval movement study, in which most of these larvae were found in the shoot: 84.6% on the source plant and 40% on the neighbouring plants by the ninth day of experiment. For the larvae that fed on the shoot, the duration of the larval and pupal stages were significantly shorter and adult longevity was significantly longer, although the females laid a significantly lower number of eggs than those from larvae that fed on the leaves. However, there were no differences in the size of adults reared either on the shoot or the leaves (body lengths were 7.96 ± 0.12 and 7.82 ± 0.08 mm, respectively), and in the survivorship patterns of the adults. The moths emerging from larvae collected from the cabbage shoot in the field also lived slightly longer but laid fewer eggs than those from the leaves, with the intrinsic rate of increase (rm) of 0.11 and 0.07, respectively. The results indicated that the CWW larvae preferred the cabbage shoot (to the leaves) which provides a natural refuge and protection for the CWW larva under field conditions, although it is relatively a poorer food type (3.47 ± 0.17% nitrogen) than the leaf (4.31 ± 0.30% nitrogen) (P < 0.05). The higher fertility of CWW bred from the leaves could possibly be related to the relatively higher percentage nitrogen in the leaves. After eclosion from the eggs, there was initial grouping of larvae in the shoot, and then an eventual decrease which could be due to the limited carrying capacity of the shoot to accommodate more than one larva