J.H. Giliomee

Recent Establishment of Many Alien Insects in South Africa — A Cause for Concern

Any new alien insect that succeeds in reaching and establishing in South Africa is a cause for concern, especially if it is phytophagous and feeds on commercially important plants. It is important that this should be detected early and documented so that the status of the insect as a pest can be assessed. Where necessary, the agricultural sector, trading partners and neighbouring countries should be alerted and consideration given to the possibility of eradication. The rate at which these insects establish in a region gives an indication of the adequacy of phytosanitary procedures which are aimed at preventing this. The aim of this paper is to draw attention to the number of alien insect species (excluding pet insects and those introduced for the biological control of pest insects and weeds) which have recently (arbitrarily the last 12 years) established in South Africa, particularly in the Western Cape Province, and to consider possible pathways by which they have entered the country. Indications are that new introductions are taking place at an alarming rate, pointing to deficiencies in the regulatory procedures and constraints faced by the South African regulatory system.

Systematic revision of the mealybug genus Delottococcus Cox & Ben-Dov (Hemiptera: Pseudococcidae)

A systematic revision of the mealybug genus Delottococcus Cox & Ben-Dov is presented. Nine species are treated, including D. millari which is described as new. The eight previously described species are: Delottococcus aberiae (De Lotto), D. confusus (De Lotto), D. elisabethae (Brain), D. euphorbiae (Ezzat & McConnell), D. phylicus (De Lotto), D. proteae (Hall), D. quaesitus (Brain), and D. trichiliae (Brain). Adult females of all species are described and illustrated and a key for their identification is presented. In the past, specimens determined as D. elisabethae have been recorded from citrus and other hosts, but these appear to be misidentifications of D. aberiae. Delottococcus elisabethae is only known from the original collection. As invasive species, D. confusus is reported from California and Hawaii, D. aberiae from Spain, and D. euphorbiae from France, Italy, and Sicily.

A Survey of the Arthropod Pests Associated with Commercial Pomegranates, Punica granatum (Lythraceae), in South Africa

Little local information is available on pomegranate cultivation, especially on the pests affecting production and fruit quality. An extensive survey of the arthropods associated with commercial pomegranates, Punica granatum (Lythraceae), was therefore conducted over a period of 20 months from September 2006 to April 2008 in selected production orchards. Twelve orchards in nine districts of the Western Cape Province were inspected monthly and two spot surveys were done in the other major pomegranate-growing areas of the Northern Cape, North West, Mpumalanga and Limpopo Provinces of South Africa. A total of 35 insects and one mite species of economic importance was recorded. Of these, the most serious pests were the false codling moth, Thaumatotibia leucotreta (Meyrick), which damaged the fruit, the long tailed mealybug, Pseudococcus longispinus (Targioni Tozzetti), and various thrips species that affected both leaves and fruit. Small weevils of undescribed species were found to cause stunted growth due to larval and adult feeding on young shoots.

Fecundity and mortality of codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), under field conditions in South Africa

The fecundity of spring and summer adults and mortality of the egg, larval and pupal stages of codling moth, Cydia pomonella (L), were studied in sleeve cages in an apple orchard not treated with insecticides. There was a significant difference between the overall fecundity of the spring (137.2 eggs/female) and summer (159.3 eggs/female) moths. During the first third of October, spring moths produced significantly fewer eggs than in November. Egg mortality in spring was 8.2 %, and in summer 21.2%. The increased summer egg mortality was due to the egg parasitoid, Trichogramma luteum Girault (Hymenoptera: Trichogrammatidae). During spring and summer, mortality due to infertile and fertile but unhatched eggs was less than 5 %. In the absence of entomophagous insects, the failure of first instar larvae to penetrate the fruit ranged from 4.9 to 19.5 %. The mortality of larvae from egg hatch to emergence from the fruit ranged from 29.7 to 43.8 %. Mortality of fifth instar larvae in cocoons spun in corrugated cardboard after emerging from the fruit was low, ranging from 0 to 8.7 %. Pupal mortality varied from 0 to 3.5 %. These studies indicate that codling moth in South Africa probably has a higher biotic potential than in most other apple-producing countries.

Mediterranean black fig fly, Silba adipata McAlpine (Diptera: Lonchaeidae), recorded from South Africa

The black fig fly, Silba adipata McAlpine, 1956 (Lonchaeidae), an agricultural pest species previously known only from the Mediterranean and Middle East regions, has been found in South Africa for the first time. It has been reared from cultivated figs, Ficus carica L., collected at Hermanus, Somerset West, Stellenbosch, Klapmuts and Porterville in the Western Cape Province. During 2006, flies emerged initially on 15 November from the domestic fig cultivar White Genoa growing in a home garden at Somerset West.

Development of the Oleander Mealybug, Paracoccus burnerae (Brain) (Hemiptera: Pseudococcidae), on Citrus at Five Temperatures

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:dark regime. The rate of development increased linearly with an increase in temperature for the egg, first nymphal and pupal stages as well as the entire development cycle from egg to adult, but was nonlinear for the second and third nymphal stages. Survival decreased with increase in temperature. Paracoccus 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 recorded at 22 °C. A sex ratio of 1:0.92 (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 first and second nymphal stages.

Validation of the phenology model for the codling moth, Cydia pomonella (Lepidoptera: Tortricidae), in South African pome fruit orchards

The codling moth, Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae), is a key pest of pome fruits in the Western Cape, South Africa. Up to 1993, the industry recommendation for commencement of the codling moth spray programme was at 75 % petal fall in order to avoid the negative impact of organophosphate sprays on bees during bloom. However, codling moth can emerge, mate and oviposit before and during full bloom in pome fruit orchards. Consequently, petal-fall does not necessarily correspond with the commencement of egg-laying or first egg hatch. The availability of insecticides with a softer environmental profile made it possible to apply sprays earlier than 75 % petal-fall. The development of phenology models provided a means of accurately predicting biological events such as the initiation of egg-laying and first egg hatch. Using lower and upper development thresholds of 10 °C and 32 °C, respectively, and hourly temperature recordings, phenology models were evaluated by comparing the number of degree-days (°D) accumulated using a selection of three biofixes, and date of first egg hatch. The number of °D accumulated from the selection of biofixes to first observed egg hatch varied from 130.7 to 179. The least variation in the number of °D between biofix and first egg hatch occurred when the second trap catch was used as the biofix. A biofix based on the first evening when the temperature reached or exceeded 17 °C at 18:00 after first trap catch also showed less variation than when the biofix was based on first trap catch. The mean number of °D at which 50 % of the moths of the first flight emerged was 166.6 °D, while the mean number of °D at which 50 % oviposition occurred was 290 °D following biofix. The number of °D between the second and third flight biofixes varied between 488.7 and 531.2 °D, with a mean of 508.1 °D. The results are of significance in improving the timing and reducing the number of insecticide sprays for codling moth control.

Availability and location of cocooning sites for diapausing codling moth larvae (Cydia pomonella (L.)) (Lepidoptera: Tortricidae) on mature and young apple trees

Mature larvae of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), a key pest of apples and pears, leave infested fruit and spin cocoons in which they transform to pupae. These larvae may either immediately transform to pupae from which moths emerge two to three weeks later, or they overwinter in a state of diapause (Headlee 1929; Steiner 1929; Cutright 1937; Gould & Geissler 1941; Yothers & Carlson 1941; MacLellan 1960; Geier 1963; Wearing & Skilling 1975a,b; Howell 1994; Lacey et al. 2006).

The Woolly Whitefly, Aleurothrixus floccosus (Maskell) (Hemiptera: Aleyrodidae), a Potentially Serious Citrus Pest, Recorded from South Africa

A whitefly that has been noticed over the last two years on many lemon trees in suburban gardens of Cape Town and in Stellenbosch, has been identified as the woolly whitefly, Aleurothrixus floccosus (Maskell). This is the first record of this species from South Africa. Subsequently, it has been found all the way along the broad coastline from Stellenbosch to Port Elizabeth, and is apparently even more widespread in South Africa, as it was found on a lemon tree in a Pretoria garden during May 2009.

The Acaricidal Effect of Ethanolic Extracts of Chenopodium quinoa Willd. on Tetranychus urticae Koch (Acari: Tetranychidae)

Ethanolic extracts obtained from the seed coat of Chenopodium quinoaWilld. were evaluated for their acaricidal effect on different stages of the carmine spider mite Tetranychus urticae Koch. At 72 h after application of the extracts directly on the adult females, mortalities ranged from 30%to 93%, with concentrations of 6.11, 7.61 and 9.11%w/v producing the best results. The lethal effect of the extracts on the nymphs of T. urticae manifested at 24 h after inoculation, with mortality rates ranging between 50 % and 99 %. The extracts of C. quinoa had no lethal effect on the eggs of T. urticae. At 120 h post-application, between 76%and 89%of the larvae had hatched. The extracts showed a repellent effect on adult females of T. urticae. Oviposition by femaleT. urticae was not affected by application of sublethal concentrations of the extract. The survival of juveniles whose mothers were sprayed with the extracts ranged between 17 % and 48 %, showing a sublethal effect of the extracts on the offspring. Lethal concentrations of the extract of C. quinoa for adult females of T. urticae were determined as 1.24 % w/v (LC50) and 4.34 % w/v (LC90).