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Threshold equation for the harmfulness of larvae of plate phytophages

Author(s) Korenchuk E., , ,
Fokin A.V., Doctor of Agricultural Sciences, ,
Drozd V.F., Doctor of Agricultural Sciences, ,
Category The Agronomy
year 2019 issue Issue number 95. Part 1
pages 226-236 index UDK 632: 595.7
DOI 10.31395/2415-8240-2019-95-1-226-236 (Link)
Abstract Modern developments regarding the threshold values of the number of soil phytophages in agrocenoses are most often based on energy indicators of the estimated need, consumption and assimilation of trophic resources, phytophage and plant biomass. The problem of determining valid threshold values of the load of larvae of larvae on forest crops is significantly complicated by the long-term nature of the latter. To determine the level of harmfulness of soil phytophages, it is important to assess at what number of larvae of different ages a two-year-old seedling of common pine is able to survive during the critical period - the period of trophic activity of the pest. A model of thresholds for harmfulness of larvae of phytophage phytophages, based on the principles of combinatorics, is suggested, assuming that the root system of seedlings of tree species can be represented as an energy matrix of dimension n x n that includes two trophic zones: risk and adaptive (resistance) and the level of maximum damage. The consumption of the trophic resource of the adaptive zone by larvae of the lamellar phytophage is represented as the route through the energy squares of the matrix (by determining the number of possible route scenarios). It was established that the zone of adaptation of the energy matrix of the pine root system with an ordinary dimension of 3 x 3 and 6 x 6 can withstand the pressure of 4 units of mass of larvae of the western and eastern May chrysanthemums of the first age and 4-5 of the second and third ages, respectively. The differences in the capacity of the adaptive part of the matrix depends on the proportion of the plant component of nutrition of larvae of May beetles of different ages. To determine the threshold levels, we used the method of representing the dependence in the form of straight lines. Moreover, the transition of one linear section to another characterizes the critical point. The threshold values of the ratio of the biomass of the root system of two-year-old seedlings of Scots pine and larvae of lamellar phytophages were determined - 1.71 for larvae of the first and 0.75 for larvae of the second and third ages.
Key words soil pests, trophic resources, feeding of larvae, maximum weediness, biomass, root system, Scotch pine, seedlings of tree species
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