Novel Encapsulated Herbicide Delivery Mechanism: Its Efficacy in Mimosa Bush (Vachellia farnesiana) Control

Mimosa bush (Vachellia farnesiana) is an invasive woody weed widely distributed in Australia. While it can be controlled using several mechanical and chemical techniques, this study evaluated a novel herbicide delivery mechanism that minimizes the risk of spray drift and potential non-target damage. This method, developed by Bioherbicides Australia, involves the implantation of encapsulated granular herbicides into the stem of intact plants or into the stump after cutting off plants close to ground level (cut stumps). Trials were implemented near Moree (New South Wales, Australia) on intact (two experimental runs) plants and cut stumped (two experimental runs) plants. For each trial, an untreated control plus the conventional basal bark application of a liquid formulation of triclopyr + picloram mixed with diesel was included for comparison. Encapsulated glyphosate, aminopyralid + metsulfuron-methyl, hexazinone and clopyralid were also tested in all trials. In addition, encapsulated triclopyr + picloram, and metsulfuron-methyl were included in one of the intact plant trials. Aminopyralid + metsulfuron-methyl was consistently most effective on cut stump and intact plants, whilst clopyralid provided highest mortality when applied to cut stumps and single-stemmed intact plants. Particularly for multi-stemmed intact plants, clopyralid should be applied to each stem. Overall, the highest efficacy was achieved on single stemmed plants, but with further refinement of the technique, it should be possible to achieve similar results for multi-stemmed individuals. This method resulted in a reduction in the use of herbicide and environmental contamination while significantly improving speed of treatment.

Susceptibility of Small-Diameter Norway Spruce Understory Stumps to Heterobasidion Spore Infection

Heterobasidion spp. cause economically important losses in conifer forests in the Northern Hemisphere, especially in Norway spruce stands. Freshly cut stumps are the main route for Heterobasidion spp. infection. Even small stumps of spruce seedlings are known to be susceptible to spore infection, however, very little is currently known about the susceptibility of small stumps of understory spruce to Heterobasidion spore infection. To determine the frequency of spore infections among stumps of understory trees, we analyzed 756 Norway spruce stumps in eight sample plots in eastern Latvia. Understory trees 35–68 years of age, with a stump diameter of 2–10 cm, were felled 33–48 weeks before sampling. In total, 514 (68%) of the spruce stumps were infected by Heterobasidion spores. The infection frequency among the plots varied from 56% to 86%. Both infection frequency and stump surface area occupied by Heterobasidion positively correlated with stump diameter, but neither correlated with the time span elapsed between felling and sampling. Colonization of trees by a competitor fungus, Phlebiopsis gigantea (Fr.) Jülich, was observed in 30 (4%) of investigated stumps, but did not have any effect on the frequency of Heterobasidion infections. Our data show that Norway spruce stumps can be highly susceptible to Heterobasidion spore infection. In order to control airborne Heterobasidion infections, stump treatment should be considered during the sporulation period of Heterobasidion spp.

Fungi in living and dead stems and stumps of Pinus mugo on coastal dunes of the Baltic Sea

Communities of xylotrophic fungi were studied in wood of Pinus mugo of different qualities: (i) living stems, (ii) cut stumps, (iii) burned snags, (iv) cut burned stumps, (v) stems recently killed by root rot, and (vi) old snags of root rot-killed trees. A total of 277 isolates representing 58 fungal taxa were obtained from 300 wood samples (50 samples per each substrate category). Results of the present study suggested that following different disturbances (tree felling, forest fire or root rot), fungal communities likely evolve in different directions: depending on its origin (cut, burned or killed by the disease), dead wood might be inhabited by principally different microbial assemblages, and that fire has less effect on community structures than tree felling or root rot.  

Life on deadwood: cut stumps as a model system for the succession and management of lichen diversity

Coarse deadwood provides an important habitat for a suite of niche-specialist lichens in old-growth forests, for example, snags (standing dead trees) and fallen logs. Conversely, the scarcity of deadwood in managed forests is a limiting factor to lichen diversity, though cut stumps may provide an alternative habitat for deadwood species. The surface of cut stumps is an ecologically useful study system, facilitating standardized sampling with which to determine the pattern and process of deadwood succession. This study examined vegetation patterns for the surface of cut stumps at Abernethy RSPB Reserve in northern Scotland. We demonstrate the interrelationship between key topographic, management and edaphic factors during a successional process of terrestrialization. Consequently, we recommend that deadwood diversity might be maximized by 1) creating managed plots with varying degrees of canopy openness for sites with different levels of topographic exposure, and 2) providing cut stumps at different heights within plots, to ensure that during a rotational period the process of terrestrialization operates at different speeds among individual microhabitats. The study examined successional processes on cut stumps using two recently accessible and powerful statistical methods: 1) nonparametric multiplicative regression (NPMR), and 2) multivariate regression trees (MRT). The principles on which these techniques are based are becoming the preferred statistical framework with which to provide robust interpretation of field-sampled data; they are unconstrained by prior assumptions as to the form of a species' niche response, and are data-led models evaluated based on cross-validated performance, thereby avoiding the complication of multiple hypothesis tests.