摘要:

Benefits of trophobiosis betweenPheidole megacephala(F.) andCoccus viridis(Green) were studied in exclusion experiments in coffee. Treatments consisted of trees with ants and no scale natural enemies, no ants and no natural enemies, natural enemies and no ants, and ants and natural enemies. Ant foraging activity and scale populations were monitored weekly. There were no significant differences in green scale populations between ant-infested and ant-free trees when natural enemies were excluded. This demonstrated that scale survival was not due to sanitational benefits from the removal of honeydew by ants. Scale populations on ant-free trees with natural enemies were significantly different from those on ant-infested trees with natural enemies after 119 d. Ants had a positive influence on green scale survival by interfering with or preying on natural enemies. Ant foraging activity, and scale, coccinellid, and parasitoid densities were monitored on ant-infested and ant-free trees in a second experiment using different ant exclusion techniques. The results were a significant positive interaction between ants and scales and a significant negative interaction between ants and coccinellid larvae. There were no significant interactions between ants and adult coccinellids or parasitoids. Green scales declined after 50 d and were not present after 70 d on trees from which ants were excluded, but scales remained on ant-infested trees. This decline followed increases in four species of larval coccinellids. It was concluded that ants were necessary for the survival ofC. viridisin coffee. In the absence of ants, natural enemies, primarily larval coccinellids, eliminatedC. viridisfrom trees.

ISSN:1754-5692    

DOI:10.1093/ee/22.2.483

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

A 3-yr evaluation of the biological control agentNosema locustaeCanning on grasshoppers was conducted on the National Wildlife Refuge at Maxwell, NM. Six O.1-ha plots were treated with the microsporidian in 1988; grasshopper densities were monitored in treatment and control plots through 1990. In 1988, there was a significant time-by-treatment interaction; grasshopper densities were significantly reduced for several weeks, with as much as 50% reduction by the end the season. Infections were highest 6 to 8 wk after treatment. Infection rates differed significantly across developmental stages and subfamilies. Melanoplinae were most heavily infected and suffered the greatest rate of mortality. Three additional orthopteran species were added to the host range ofN. locustae. In the treated plots, in 1988, bird densities were significantly higher, and the parasitic waspScelio opacus(Provancher) was significantly more frequent in egg pods. Spores ofN. loeustaewere present in unhatched eggs and early instar nymphs, but no spores were observed on egg pods or foam plugs. In June of 1989, density of the treated population was similar to that of the controls, but from mid-July through mid-August the population density was significantly lower in the treated plots. Based on infection and demographic data, this second-year population suppression seems to have been the result ofN.loeustae. In 1990, treated and control populations did not differ significantly, and both were reduced below the standard treatment threshold of 9.6 grasshoppers per square meter.

ISSN:1754-5692    

DOI:10.1093/ee/22.2.489

出版商:Oxford University Press    

年代:1993

数据来源: OUP

ISSN:1754-5692    

DOI:10.1093/ee/22.2.498a

出版商:Oxford University Press    

年代:1993

数据来源: OUP