To account for the nutcrackers, Estron-type traps are used, which are placed on the surface of the soil. Attracted by the smell of pheromone, the nutcrackers rise up along the rough outer inclined plane of the insect receiver and fall inside (see Fig. 24 A). Before installing the trap, pheromone dispensers are unpacked and placed in the trap cage.
In the surveyed areas, for a Crimean nutcracker, one trap per 20 hectares, steppe – 15 hectares and sowing – 10 hectares. It is necessary to observe the uniform distribution of traps within the surveyed area. Extreme traps set at a distance of about 100 m from the boundaries of the site. In areas where inter-row treatments are carried out, traps are installed between the plants in a row in order to avoid damage.
Beginning of the flight of nutcrackers can be expected in the following terms: the second or third decade of June for the steppe, the end of April – the beginning of May in the southern zones of distribution of the species and the end of May – the beginning of June in the northern regions – for planting, the second or third decade of June for the Crimean. In order to determine the actual dates of the beginning of flight in each area of the range at observation points 10-15 days before the above dates, several control traps with pheromones of one or two common beetle snail beetles are established.
Attraction of single individuals serves as a signal for placing the required number of traps. Estimated duration of capture, counting from the beginning of flight for the Kuban nutcracker, is 40–45 days, steppe and sowing – 35–40 days. The attractiveness of the bait during the flight period of the beetles does not change, and its replacement is not performed.
The registration of attracted bugs is carried out weekly. Trapped beetles are removed from the receiver, counted and their number recorded in the log. To speed up and facilitate the counting of males with a large number of males, it is recommended to use measuring cylinders with a capacity of 50-100 ml. The volume corresponding to 10 ml contains 130 males of the Kuban nutcracker, 90 – of the steppe and 350 – of the sowing. The error in determining the number of males using a measuring cylinder does not exceed 8%. It is possible that some insects of other species (bread ground beetles, predatory ground beetles, dead-eaters, etc.) may fall into pheromone traps. When accounting for beneficial insects, it is necessary to release. The results of counting males in traps for the entire flight period are used in the following to determine the population density in the examined field. Moreover, it can be estimated as the density of the population as a whole,
The physical meaning of the forecast parameters and the value of the constant coefficients in the formula are given in table. eleven.
Parameters and constant coefficients in determining the number of clickers according to pheromone monitoring
|Notation in the formula||Physical meaning and method of obtaining||Values for identifying species of click beetles|
|Wed.||Pest population density (? = 1 – imaginal stage, i = 2 – imaginal and larval stages), ind./m 2||Estimated by the formula|
|V||The number of males caught on average per trap, ind.||Determined by capture into pheromone traps in the surveyed field|
|b||The rate of decrease in capture of males with distance from the trap (constant), m 1||-0,12||-0,053||-0,03|
|to||The degree of completeness of the extraction of males in the center of the trap (constant)||0,75||0,7||0,75|
|P||The coefficient of sexual and age structure of the population (permanent)||n = 3, n = 4, n = 5 for a 3-, 4- or 5-year cycle of pest development, respectively, when determining the total density of the imaginal and larval stages|