Pest, disease and weed management

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Environmental factors affecting Adelina in the Burdekin region : final report CE004
(BSES, 2003) Dall, D; Logan, D
The project aimed to determine why the canegrub pathogen Adelina does not infect a significant proportion of the canegrub population in the Burdekin Delta area. It examined the effect of physical characteristics of soil (pH, sodicity and composition) and three other environmental parameters (temperature, relative humidity and compaction) on retention of oocyst infectivity for larvae over periods corresponding to one and two cycles of grub infestation of crops in the field. In addition, the project raced the establishment and persistence of Adelina infection in two experimentally inoculated field plots in the Burdekin canegrowing area. A ‘sentinel larva’-based bioassay that allows examination of the effect of various environmental factors on the retention of infectivity of Adelina was developed. Results of such a bioaasay showed no differences between the three types of soils tested, despite one soil coming from a region where the pathogen is very common (Bambaroo), and another from a region where it is quite rare (Burdekin Delta). The test did clearly show that drying conditions can be highly detrimental to retention of infectivity of the pathogen. Extrapolation from these results would suggest that field locations where there are prolonged periods of dry soil conditions would be at a relative disadvantage as regards maintenance of high levels of the pathogen in grub populations. Under field conditions in the Burdekin, Adelina did survive at levels sufficient to cause infection in the following generation of canegrubs in some areas and in one of two years; in the other plots and year, there was no subsequent infection. These results thus show that while oocysts of protozoan pathogens such as Adelina have robust external walls, they are, nevertheless, susceptible to the influence of adverse environmental conditions. Under field conditions, where exposure to any potential inoculum is likely to be more transient, the influence of an adverse environmental factor is even more acute. Improved understanding of the physical tolerances of the infective stages of Adelina has assisted in the design of crop-management strategies that maximise the impact of the pathogen on canegrub populations. These strategies have been incorporated into the GrubPlan program that has been successful in reducing the impact of greyback canegrub.
Viability of the seed of itch grass (Rottboellia cochinchinensis) in the Burdekin district
(BSES, 1990) Freshwater, IT; Benson, AJ
Itch grass, raoul grass, or guinea fowl grass emerged as a problem weed of sugarcane fields in the Burdekin district of North Queensland during the late 1970s - early 1980s. It is considered to be a native of tropical Asia, but has become endemic to many other tropical areas, and is a major weed of sugarcane in Eastern Africa, the Philippines, West Indies, Trinidad, Florida and Louisiana. Itch grass has been recorded in Colombia, Venezuela, Puerto Rico, New Guinea, Mississippi and Texas and has been described as rapidly becoming one of the world's worst weeds. In the Burdekin canegrowing district, itch grass occurs in varying degrees of infestation over an assigned area of 1 600 ha. From the intital infestation on one farm in 1964, the grass has been recorded on 33 farms in the Pioneer Mill area, one in the Kalamia Mill area, and three in the Inkerman Mill area (see Map, Appendix 1). The project described in this paper was initiated early in 1983 to determine the viability of itch grass seed under field conditions. It was reasoned that the results from the project could be used to define more clearly strategies necessary to effect efficient control of this weed.

Pest, disease and weed management

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