Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT:Chapter 1 - Mealybugs are tiny, soft-bodied insects which constitute the second largest scale insect family Pseudococcidae (Downie & Gullan 2004). The family comprises approximately 2000 species in 300 genera (Ben-Dov 1994), of which 20 species are pests of cultivated plants in South Africa (Annecke & Moran 1982). In South Africa, approximately 109 species of mealybugs have been recorded from 50 genera (Millar 2002). Chapter 2 - The effect of constant temperatures on the development, survival and fecundity of the oleander mealybug, Paracoccus burnerae on citrus was determined. Developmental time, rate of development, fecundity and survival were investigated at five constant temperatures and a 16L: 8D light: darkness regime. The rate of development increased linearly with an increase in temperature for the egg, 1st nymphal and pupal stages as well as the entire biological cycle (egg – adult), but was nonlinear for the 2nd and 3rd nymphal stages. Survival decreased with an increase in temperature. P. burnerae required 666.7 degree-days above a lower threshold of 8.7°C to complete one generation. The highest mean number of 68 eggs per female was reached at 22°C. A sex ratio of 0.52:0.48 (male:female) was obtained from the life table. The net reproductive rate (Ro) was >1 at all five temperatures, an indication that it is capable of increasing its population numbers despite the high mortality experienced in the 1st and 2nd nymphal stages. Chapter 3 - The oleander mealybug, Paracoccus burnerae (Brain) is a pest of citrus in South Africa. This study was carried out to determine the effect of temperature on development rate of P. burnerae and to investigate whether development rate is the reason why P. burnerae is out competing the citrus mealybug, Planococcus citri (Risso), in the Eastern and Western Cape Provinces of South Africa. The influence of temperature on life history traits of P. burnerae was determined at 20, 22, 25 and 27°C and compared with corresponding data for P. citri. The rate of development increased linearly with an increase in rearing temperature in the embryonic, first nymphal and pupal stages but reached a climax at 26.13 and 28.6°C in the second nymphal stage of both species, respectively. P. citri exhibited lower developmental thresholds except in first instar, shorter degree-days and higher developmental rates than P. burnerae. Results of the current study indicated that the dominance of oleander mealybug over the citrus mealybug is neither linked to developmental rates nor sum of effective temperatures. Chapter 4 - The importance of Paracoccus burnerae has risen over the years to an extent where it is now regarded as a quarantine pest for citrus fruit from South Africa. The field biology of P. burnerae on citrus in the Western Cape Province of South Africa was studied through periodic sampling of leaves from twigs enclosed in sleeve cages. The species composition and abundance of natural enemies was investigated. Both adult and immature stages attained maximum population peaks in March and P. burnerae had four generations. The highest level of mortality was experienced in the immature stages. Climate and an unidentified fungus were the key mortality factors. The level of abundance of the two observed predators, the harlequin beetle, Harmonia axyridis and the green lacewing, Chrysoperla sp. was relatively low. Although parasitism occurred in some cages, the level was low ranging between 1.62 to 9.43%. If biocontrol is the preferred method of controlling P. burnerae, suitable candidate parasitoids for inoculative biocontrol are Acerophagus sp., Leptomastix sp. and Microterys nietneri. The oleander mealybug does not share the same parasitoids with Planococcus citri, Pseudococcus calceolariae and Pseudococcus longispinus except the parasitoid Coccophagus sp. The most popular species of parasitoids used in the biolological control of mealybugs, Anagyrus sp. and Coccixenoides sp. were insignificant in the case of P. burnerae. Chapetr 5 - Biological control programs of mealybug species have relied on sprouting potatoes, pumpkins and butternut for rearing of both mealybugs and their natural enemies. In this study, the suitability of sprouting potatoes, butternuts and citrus as mass rearing substrates for the oleander mealybug, Paracoccus burnerae was investigated. Developmental times, rate and fecundity on each substrate were determined and compared at three different temperatures. The developmental time on sprouting potatoes was shorter than on citrus. P. burnerae was unable to complete its life cycle on butternut. The rate of development increased linearly with an increase in temperature on both sprouting potatoes and citrus. P. burnerae required 666.7 degree-days on citrus and 434.8 degree-days on sprouting potatoes above lower developmental thresholds of 7.6°C and 10.4°C respectively to complete one generation. The mean number of eggs per female was higher on sprouting potatoes (121.3) than on citrus (68), but declined with an increase in temperature from 22 to 27°C. Despite the shorter shelf life, sprouting potatoes are the preferred host for mass rearing of the oleander mealybug. Chapter 6 - general conclusions Chapter 7 - Researchers often present impressive results of their studies on the biology of the Coccoidea without mentioning the problems they came across and had to solve. In this paper the practical problems encountered during a study of the biology of the oleander mealybug, Paracoccus burnerae (Brain), an endemic pest of citrus in South Africa, are discussed. / AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.

Please read the abstract in the section 00front of this document / Dissertation (M Inst Agrar (Sustainable Insect Management))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted

Capsicum baccatum var. pendulum was first grown in the Makana District in 2005. Extremely little was known about best practices for cultivation or the insects and diseases associated with the crop in this area. The study was conducted during the second year of production, November 2005 and November 2006, in an attempt to identify the composition and phenology of insects occurring on C. baccatum. In the more rural parts of the Eastern Cape, and more particularly in Grahamstown, there are very few industries. With the advent of this new agricultural venture, a processing factory has been opened in Grahamstown creating more than 600 seasonal jobs in the factory and 1000 seasonal jobs on farms for local people. This business enterprise has not only brought about the creation of jobs, but also training and skills development and empowerment, generating much-needed income in this area. An extensive literature review yielded limited information on insect pests associated with Capsicum. Data from a pilot sampling trial undertaken were statistically analyzed to establish the number of plants to be scouted per site and the most effective scouting techniques to use. Based on the data available and insects collected during the pilot sampling trial, a surveillance programme was designed. Five different types of monitoring traps were placed in each of the eight study sites. Collection of trap catches and scouting of fifteen individual plants per site was undertaken on a weekly basis over the 52-week study period. The most commonly occurring potential insect pests were African Bollworm Helicoverpa armigera (Hübner), False Codling Moth Thaumatotibia leucotreta (= Cryptophlebia leucotreta) (Meyrick), Mediterranean Fruit Fly Ceratitis capitata (Wiedemann) and several species of thrips. Population densities of these pests and their phenology on Capsicum were determined. Statistical analyses established the efficacy of the monitoring traps for each pest, tested for differences among and between study sites, calculated an estimate of the number of pods damaged and a measure of plant damage.The results show that the majority of damage caused to the Capsicum baccatum cropping system was due to Mediterranean Fruit Fly populations. It was established that, although African Bollworm and False Codling Moth were present during the study period, their numbers were negligible and only nominal damage was caused by these pests. Damage caused by thrips species was apparent but not quantifiable. Intervention strategies using an Integrated Pest Management approach, are discussed.