Paper No. 14 



A STUDY OF THE PHENOLOGY AND GERMINATION OF EREMOPHILA 

 GILESII IN SEMIARID QUEENSLAND 



By W. H. Burrows 2 



Abstract 



The status of Eremophila gilesii as a weed in 

 semiarid Queensland was examined. The studies 

 show that E. gilesii is restricted in distribution to 

 those areas receiving both summer and winter 

 rainfall. The species is increasing in density, ap- 

 parently due to light stocking. Frequent flower- 

 ing in summer is not necessarily followed by 

 abundant fruit production. Fruiting may only 

 be significant following rains of more than 40 

 mm. in the cooler months of the year. High ger- 

 mination percentages only occur following pro- 

 tracted fruit weathering in the field. Germina- 

 tion may be severely inhibited by soil tempera- 

 tures in excess of 40° C. On the basis of the pre- 

 ceding information, a management system to 

 control E. gilesii is proposed. It is suggested that 

 from March to September inclusive land on which 

 E. gilesii is a weed should be heavily stocked fol- 

 lowing rainfalls greater than 40 mm. The need 

 to consider the ecological system as a whole when 

 formulating control measures is discussed. 



Additional key words: Green turkey bush, shrub 

 control 



Introduction 



Woody plants are troublesome weeds in much 

 of the world's range-lands (14, 15, 22, 24, 33). 

 There appears to be general agreement about the 

 processes leading to increases in shrub density. 

 Usually these increases are attributable to over- 

 grazing (9) and the process is described suc- 

 cinctly by Weaver and Clements (40). The ab- 



1 Financial assistance for this study was provided by 

 the Wool Research Trust Fund. 



2 Agrostologist, Charleville Pastoral Laboratory, De- 

 partment of Primary Industries, Charleville, Queensland. 

 4470, Australia. 



160 



sence of fire {42) is also considered a major cause 

 of brush encroachment, although in some circum- 

 stances repeated burning may lead to increase in 

 woody plants {15.) 



Regeneration of unpalatable trees and shrubs 

 is presently widespread in summer rainfall zones 

 of semiarid Australia (25). The increase is not 

 so much an invasion of new territory as an in- 

 crease in density of the stand in the vicinity of 

 parent plants. 



High costs limit the use of chemical and me- 

 chanical weed control measures on semiarid 

 rangelands. Naveh (28) considered that ecologi- 

 cal and biological methods, such as grazing and 

 burning, will be for a long time to come the chief 

 tools for the economic management and improve- 

 ment of East African rangelands. This approach 

 was supported by Whyte (44): w ho advocated 

 the use of cheap methods for broad scale improve- 

 ments and the concentration of limited resources 

 on particularly favorable areas. 



In South Africa, Scott (33) urged greater em- 

 phasis on autecological studies to determine new 

 lines of ecological control of unwanted species. 

 Few detailed studies of the germination and dor- 

 mancy characteristics of seeds of pasture weeds 

 have been made in Australia despite their rele- 

 vance to weed control methods (21). 



Observations on morphogenesis and phenology 

 of woody plants in semiarid Australia are lim- 

 ited. Davies (7) and Slayter (34) studied growth 

 of mulga (Acacia aneura F. Muell.), an impor- 

 tant fodder tree. Published work on morphogene- 

 sis and phenology of woodj T weeds appears re- 

 stricted to A. harpophylla F. Muell. (16, 43), 

 which is a problem in more mesic parts of the 

 summer rainfall semiarid zone. 



An important woody weed of semiarid Queens- 

 land is green turkey bush (Eremophila gilesii 

 F. Muell.). This is a small shrub wrich grows up 



