Dissertation•
Pine Weevil Feeding Behaviour in Relation to Conifer Plant Properties
01 Jan 2014-
TL;DR: The results from a no-choice and a choice experiment indicate that the protective effect of MeJA-induced defences is, besides an overall reduction of feeding, mainly due to the reduced amount that a pine weevil can feed at one place.
Abstract: The pine weevil (Hylobius abietis (L.)) is a forest insect distributed over the Palearctic region. The adults feed on the phloem of young conifer plants causing high economic losses for the European forest industry. Still, there is very little knowledge about the structure of its feeding behaviour. Feeding behaviour can be studied in several different temporal resolutions, from differences in feeding after several weeks to diel patterns and short-term feeding, i.e. feeding patterns at the level of feeding events and meals. The aim of this thesis was to increase the knowledge about the pine weevils’ feeding patterns and the underlying behavioural mechanisms.
I studied the pine weevils’ time budget and diel behaviour as well as its short-term feeding behaviour based on video recordings. In addition, I assessed how changes in plant properties due to girdling or induction of plant defences with a chemical elicitor, methyl jasmonate (MeJA), affect the feeding pattern and preferences of the pine weevil.
Pine weevils allocated only 6 % of the time to feeding. Most of the time was spent away from the plant (70 – 80 %). Damaged plants appeared to attract the weevils because they spent more time while not feeding on damaged plants than on undamaged plants. Feeding behaviour was mostly concentrated to the second half of the dark phase, after a peak of locomotion behaviour during the first part of the dark phase. During the light phase, pine weevils mostly rested. Analysis of the short-term feeding behaviour showed that pine weevils made 4-5 meals per day, removing about 13 mm2 during about 24 minutes in each meal. Some of the feeding properties, such as how much time was spent not feeding during a meal, differed between male and female weevils. Girdling did not affect the time budget or feeding properties.
The induced plant defences with MeJA caused a reduction in meal duration. When meals consisting of only phloem, only needles or both were compared, the meal duration and the time until the initiation of a meal were more similar between the different meal contents on induced plants. In addition, the results from a no-choice and a choice experiment indicate that the protective effect of MeJA-induced defences is, besides an overall reduction of feeding, mainly due to the reduced amount that a pine weevil can feed at one place. Thus the risk of girdling and death of the plant is reduced.
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149 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...Girdling can refer to the removal of an entire ring of bark or a thin incision in the bark (Noel, 1970)....
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...Depending on the tree species, the kind and extent of the girdling, trees can experience a range of negative effects from girdling, which might result in their death (Noel, 1970)....
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...By this, not only were the defences induced but also the nutrition and water flow in the plants affected (Noel, 1970)....
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...If bark is manually removed, girdling can further be distinguished into whether or not tissues internal to the vascular cambium are removed (Noel, 1970)....
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...Girdling means the complete severing of the phloem of a tree (Noel, 1970)....
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TL;DR: A method that models the frequency distribution of log-transformed interval lengths and obtained meaningful meal criteria for all individuals by fitting either a double, or a triple, log-normal model to the frequency distributions of the lengths of intervals between feeding.
146 citations
TL;DR: Terpenoid resin production was tissue‐specific, but generally increased after MJ treatments, which means that this compound may offer potential protection of conifers against herbivores.
Abstract: Scots pine (Pinus sylvestris L., Pinaceae) produces a terpenoid resin which consists of monoterpenes and resin acids that offer protection against herbivores and pathogen attacks. Methyl jasmonate (MJ) is a potential plant elicitor which induces a wide range of chemical and anatomical defence reactions in conifers and might be used to increase resistance against biotic damage. Different amounts of MJ (control, 10 mM, and 100 mM) were applied to Scots pine to examine the vigour, physiology, herbivory performance, and induction of secondary compound production in needles, bark, and xylem of 2-year-old Scots pine seedlings. Growth decreased significantly in both MJ treated plants, and photosynthesis decreased in the 100 mM MJ treated plants, when compared to 10 mM MJ or control plants. The large pine weevil (Hylobius abietis L.) (Coleoptera: Curculionidae) gnawed a significantly smaller area of stem bark in the 100 mM treated plants than in the control or 10 mM treated plants. The 100 mM MJ treatment increased the resin acid concentration in the needles and xylem but not in the bark. Furthermore, both MJ treatments increased the number of resin ducts in newly developing xylem. The changes in plant growth and chemical parameters after the MJ treatments indicate shifts in carbon allocation, but MJ also affects plant physiology and xylem development. Terpenoid resin production was tissue-specific, but generally increased after MJ treatments, which means that this compound may offer potential protection of conifers against herbivores.
139 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...Additionally, the efficiency of treatments for plant protection has been tested (Heijari et al., 2005; Moreira et al., 2009; Sampedro et al., 2011; Paper III)....
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TL;DR: The probability of cows ending and starting a meal increased with meal length and interval between meals, as predicted by the satiety concept, and meals are, therefore, a biologically relevant unit of short-term feeding behavior and visits are not.
135 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...On a shorter time scale than diel behaviour, short-term feeding behaviour can be used to investigate feeding patterns at the level of feeding events and meals (Tolkamp et al., 2000; Howie et al., 2009)....
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TL;DR: This review aims at providing an overview of the current knowledge on elicitors and will highlight their potential efficacy from the laboratory in controlled conditions to vineyards, to determine their practical and effective use in viticulture and to propose ideas for improving their efficacy in non-controlled conditions.
Abstract: Development and optimisation of alternative strategies to reduce the use of classic chemical inputs for protection against diseases in vineyard is becoming a necessity. Among these strategies, one of the most promising consists in the stimulation and/or potentiation of the grapevine defence responses by the means of elicitors. Elicitors are highly diverse molecules both in nature and origins. This review aims at providing an overview of the current knowledge on these molecules and will highlight their potential efficacy from the laboratory in controlled conditions to vineyards. Recent findings and concepts (especially on plant innate immunity) and the new terminology (microbe-associated molecular patterns, effectors, etc.) are also discussed in this context. Other objectives of this review are to highlight the difficulty of transferring elicitors use and results from the controlled conditions to the vineyard, to determine their practical and effective use in viticulture and to propose ideas for improving their efficacy in non-controlled conditions.
121 citations
"Pine Weevil Feeding Behaviour in Re..." refers background in this paper
...It can be used as an elicitor to induce the plant defence system, which can result in a more efficient defence reaction during subsequent stresses (Goellner & Conrath, 2008; Bruce, 2010; Delaunois et al., 2014)....
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