Continental comparisons of the interaction between climate and the herbivorous mite, Floracarus perrepae (Acari : Eriophyidae)

The Old World climbing fern, Lygodium microphyllum, is an invasive weed in the Florida Everglades and the leaf roll galling mite, Floracarus perrepae, is a proposed biological control agent. Field studies were conducted for one to two years at sites in its native range in Australia, New Caledonia, and India to evaluate the effect of climate on F perrepae. Monthly counts of the proportion of L. microphyllum subpinnae (leaflets) with leaf roll galls were used to measure the incidence of damage caused by F perrepae. Between sites the most significant weather variable was rainfall 14 to 28 days prior to sampling, with higher levels having a depressive effect on the incidence of leaf rolls. Within sites the mean maximum temperature was the only significant weather variable, showing a decrease in the incidence of leaf rolls above 27 degrees C, and it was predicted that no leaf rolls would form above 35 degrees C. The weather parameters in Homestead, Florida for 2002 were within the range of those evaluated in the eight native range field sites. Thus, we do not predict that climate will prevent the establishment of this biological control agent for L. microphyllum in southern Florida

Maximising the contribution of native-range studies towards the identification and prioritisation of weed biocontrol agents

Effective study in the native range to identify potential agents underpins all efforts in classical biological control of weeds. Good agents that demonstrate both a high degree of host specificity and the potential to be damaging are a very limited resource and must therefore be carefully studied and considered. The overseas component is often operationally difficult and expensive but can contribute considerably more than a list of herbivores attacking a particular target. While the principles underlying this foreign component have been understood for some time, recently developed technologies and methods can make very significant contributions to foreign studies. Molecular and genetic characterisations of both target weed and agent organism can be increasingly employed to more accurately define the identity and phylogeny of them. Climate matching and modelling software is now available and can be utilised to better select agents for particular regions of concern. Relational databases can store collection information for analysis and future enquiry while quantification of sampling effort, employment of statistical survey methods and analysis by techniques such as rarefaction curves contribute to efficient and effective searching. Obtaining good and timely identifications for discovered agent organisms is perhaps the most serious issue confronting the modern explorer. The diminishing numbers of specialist taxonomists employed at the major museums while international and national protocols demand higher standards of identity exacerbates the issue. Genetic barcoding may provide a very useful tool to overcome this problem. Native-range work also offers under-exploited opportunities for contributing towards predicting safety, abundance and efficacy of potential agents in their target environment

Continental comparisons of the interaction between climate and the herbivorous mite, Floracarus perrepae (Acari : Eriophyidae)

The Old World climbing fern, Lygodium microphyllum, is an invasive weed in the Florida Everglades and the leaf roll galling mite, Floracarus perrepae, is a proposed biological control agent. Field studies were conducted for one to two years at sites in its native range in Australia, New Caledonia, and India to evaluate the effect of climate on F perrepae. Monthly counts of the proportion of L. microphyllum subpinnae (leaflets) with leaf roll galls were used to measure the incidence of damage caused by F perrepae. Between sites the most significant weather variable was rainfall 14 to 28 days prior to sampling, with higher levels having a depressive effect on the incidence of leaf rolls. Within sites the mean maximum temperature was the only significant weather variable, showing a decrease in the incidence of leaf rolls above 27 degrees C, and it was predicted that no leaf rolls would form above 35 degrees C. The weather parameters in Homestead, Florida for 2002 were within the range of those evaluated in the eight native range field sites. Thus, we do not predict that climate will prevent the establishment of this biological control agent for L. microphyllum in southern Florida