Phenology and relative abundance ofCeroplastes destructorandC. sinensis(Hemiptera: Coccidae) on citrus in Northland, New Zealand

Abstract

The main scale insect pest in citrus orchards in Northland, New Zealand was Ceroplastes destructor although C. sinensis was more widespread. We studied the phenology of both species over 3 years by regularly sampling scales on leaves and wood for laboratory examination. Both species were univoltine. The start of C. destructor crawler emergence varied by c. 7 weeks o ver 6 years, and was inversely correlated with annual degree-days. Egg hatching occurred c. 2 months earlier in C. destructor than C. sinensis. The development of successive instars continued to be earlier in C. destructor so it passed through the first and second instar stages by autumn and Received 13 November 1995; accepted 4 October 1996 4 months faster than did C. sinensis. First and second instars are vulnerable to adverse weather and predation and their longer duration in C. sinensis may partly account for its lower abundance. We predict that control by insecticides should be most effective in late January for C. destructor and in late March for C. sinensis. H95064

Toxicity of pesticides toHalmus chalybeus(Coleoptera: Coccinellidae) and the effect of three fungicides on their densities in a citrus orchard

“…Tangelo fruit are most susceptible to fungal diseases (and hence require most frequent spraying) during the 3-5 months following fruit set in November (Olson et al 1992). This period coincides with the presence of first-and second-instar C. destructor (Lo et al 1996), which are the stages that are vulnerable to predation by H. chalybeus (Lo & Chapman 2001). The results of these experiments suggest that the use of fungicides, particularly copper-based ones, should be minimised from about November to February, where C. destructor is a pest.…”

“…This will help reduce disruption to ladybird predation of the vulnerable scale stages. C. sinensis should be less susceptible to any negative effects of fungicides on H. chalybeus because its first-instars do not appear until February (Lo et al 1996), when fruit are less susceptible to diseases.…”

“…Two species of wax scale are pests of citrus in New Zealand. Ceroplastes sinensis Del Guercio (Chinese wax scale) is more widespread, but C. destructor (Newstead) (soft wax scale) is more prone to outbreaks (Lo et al 1996). In Northland, C. destructor occurred at higher densities on a greater proportion of citrus orchards where organophosphate insecticides had been used compared with other orchards (Lo et al 1996).…”

“…Ceroplastes sinensis Del Guercio (Chinese wax scale) is more widespread, but C. destructor (Newstead) (soft wax scale) is more prone to outbreaks (Lo et al 1996). In Northland, C. destructor occurred at higher densities on a greater proportion of citrus orchards where organophosphate insecticides had been used compared with other orchards (Lo et al 1996). It was thought that these outbreaks were caused by the destruction of natural enemies, which is a common side effect of insecticide applications (Croft 1990;DeBach & Rosen 1991).…”

Species and abundance of ladybirds (Coleoptera: Coccinellidae) on citrus orchards in Northland, New Zealand, and a comparison of visual and manual methods of assessment

“…Firstly, both larvae and adults can greatly reduce populations of C. destructor and C. sinensis by feeding on crawlers and settled first and second instars (Lo 1994). Secondly, its phenology is well synchronised with that of its prey.The emergence and settlement of first instar C. destructor occurs in early summer (Lo et al 1996), which coincided with the presence of large numbers of H. chalybeus larvae. Thirdly, the year-round presence of H. chalybeus means that it does not need to become re-established on orchards each year.…”