FR2635254A1 - METHOD OF INTERRUPTING THE COUPLING OF INSECTS - Google Patents

Abstract

Method for the interruption of mating of harmful insects which attack crops, by releasing, on the field where the plants are cultivated, of the sex pheromone of the species of insect, characterized in that it surrounds the field at least partially of a fence net.

Description

l Method for interrupting insect mating Present

  The invention relates to a method for interrupting the mating of insects, in particular to a method for interrupting

  mating insects using the sex pheromone of the species.

  with the objective of controlling the pest population.

  A method developed in recent years in agriculture and forestry, for the control of the pest population, uses the sex pheromone of the insect species considered, as an agent for interrupting the mating of insects, in order to reduce the consumption of insecticides which inevitably causes environmental pollution problems and harmful effects on human health.

  rapid development of this method in the near future.

  We know, however, that this method poses problems and has drawbacks of two kinds; first, the effect of the method cannot be fully exploited if the insect population per unit area is not sufficiently low at the start of the use of the sex pheromone; second, the active concentration of pheromone in the atmosphere can be

  difficult to maintain above an area where a strong wind is blowing.

  A proposal has been made to resolve the problems mentioned above.

  above, according to which the zone in which it is desired to control the population of harmful insects is covered with a large doe in order to maintain the concentration of pheromone in the atmosphere at an effective level and to avoid that individuals of the same species of insects do not enter the area from the outside. This method, however, has little practical interest, because of the high cost of a tarpaulin large enough to cover the entire area. Consequently, the present invention aims to provide an effective method for interrupting the coupling. of insects, by use of the sexual pheromone compound of the species, which is free from the problems and drawbacks mentioned above of the prior art The method of the invention, developed in the course of considerable work by the inventors on the field, consists of protecting a crop from attack by harmful insects by interrupting the coupling of insects using the sex pheromone of the species to which the insect in question belongs, by surrounding the field where it grows the crop plant considered with a fence net, of a height greater than or equal to the flight height of the insects and by releasing the sex pheromone in the space surrounded by the net of fence The material of the net used according to the method of the present invention is not particularly critical, provided that the material has sufficient resistance to weathering, and includes synthetic fibers of acetylated polyvinyl alcohol, of polyester. polypropylene and the like. It is important that the net has a mesh opening which is in an appropriate range. A net with too fine a mesh opening is undesirable due to the economic disadvantages due to the high cost and the possible reduction of ventilation in the area surrounded by the fencing net, which can affect crop growth. On the other hand, a fence net with too large a mesh opening is also undesirable, since the net is less effective in preventing the penetration of harmful insects into the area surrounded by the fence net, and also because the diffusion of pheromone through the net is so rapid when carried by the wind, that the effectiveness of interrupting the mating of insects by the pheromone is significantly reduced. In summary, the net should have a mesh opening in the range of 0.01 to 5 mm. preferably from 0.1 to 2 mm According to the preferred embodiment of the present invention, the upper part and the lower part of the fence nets may have different mesh openings. The net of the lower part, starting from the ground and reaching up to 10 to 60 cm in height, has a relatively fine mesh opening, of 0.01 to 2 mm, and that of the upper part, of a height of 10-60 cm to 60-200 cm, has a relatively large mesh opening of 0.1 to 5 mm, simply preventing the penetration of insects from the outside. It is of course possible that the net is made up of more than two parts having successively increasing mesh openings from the lower part to the upper part. In this way, the advantage is obtained that the concentration of pheromone is maintained in the atmosphere at a level effective in controlling the population of insects, without affecting the growth of

  crops by reducing aeration in the area surrounded by the field.

  The fence net must have a chosen height so

  appropriate according to the flight height of the insects targeted by the method.

  When the insects are species of the tea budworm (Homona magnanima) or small tea budworm (Adoxophyes sp.). for example, the lower part of the fence net, up to a height of 30 cm from the ground, consists of a net having a fine mesh opening and its upper part. up to a height of 120 cm above the bottom. consists of a relatively coarse net. When the insects are of the moth type of cabbage (Plutella xylostella), the lower part of a relatively thin net should be 20 cm high. and a relatively coarse net constituting the part

  upper must have a height of 90 cm.

  The fence net must completely surround. as much as possible.

  the field where the plants in question are grown. Regarding the cost of the fence net, sometimes it is enough to set up the net on a boundary perimeter around the field. for example around the part facing the plants or trees which are the hosts of the harmful insects. and around the windward parts and

downwind.

  One of the advantages obtained by the method of the invention is that by surrounding the crops, which would otherwise be subjected to the attack of harmful insects, by a fencing net, the sex pheromone released in the area can develop all of its activity even when the insect population in the area adjacent to the target area is high at the start of the use of the sex pheromone. Although this characteristic is less important in areas where it is very cold in winter. because the sex pheromone can develop a very high activity of interruption of the mating of the harmful insects even without using a fence net, one due to the very low population of insects in this season, the advantage is considerable in climates tropical and subtropical or the effectiveness of the method using the sex pheromone cannot be sufficiently high, because in addition to the high temperature prevailing in these areas, the cultures of the same species are found at different degrees of growth. so that the pest population in an area is already very high at the start of the use of the sex pheromone in the adjacent areas. Even under these difficult conditions, a very high efficiency of the sex pheromone can be obtained according to the method of the present invention, since the zone where the pheromone is released is surrounded by a fencing net, after the zone has been left fallow for I or 2 weeks following

  previous harvest, so that. reduce the insect population.

  When the sex pheromone of the insect pest, which naturally attracts insects of the species considered, is used according to the method of the present invention, by using a fencing net surrounding the area, an efficiency can be obtained. total mating interruption even if the pheromone quantity is considerably reduced compared to conventional methods using no fence net In addition to the cabbage moth, the tea bitter and the small tea bitter mentioned above, the method of the present invention can be successfully applied to insect species belonging to the genus of spodoptera such as tobacco worm (Spodoptera litura), beet worm (Spodoptera exigua), the leaf of Egyptian cotton (Spodoptera littoralis)

and others.

  The invention will be better understood using the examples and comparative examples described below, without the scope of the invention being limited to these.

particular embodiments.

  Example 1 A square tea plantation, of 10 ares (1000 m2), where 50 females of tea budworm have been fixed, is completely surrounded by a fence with a height of 120 cm and made of a net of synthetic fibers of acetalized polyvinyl alcohol (Vinylon, trade name) having a mesh opening of 0.2 mm. Distributors of pheromone from the tea budworm (produced

  by Shin-Etsu Chemical Co.), each containing 80 mg of Z-ltetradecenylacetate.

  as pheromone of the genus, are distributed in the plantation with a density of -300 or 250 for 10 ares, being suspended in the twigs The proportion, of mating of the fixed females is counted, and the results are 36% and 42 % when the proportion of pheromone dispensers is 300 or 250 for 10 ares. respectively For comparison. the same test as above is carried out simultaneously in other plantations, except that the fence net is not placed around the plantation, to find that the percentage of mating in fixed females is 68% or 88 % when the proportion of pheromone distributors is 300 per 10 ares or when no pheromone distributor

is used, respectively.

Example 2

  Cabbage plants are planted on a 10 ares square field.

  completely surrounded by fences made of a net, the lower part of which, 30 cm above the ground, has a mesh opening of 0.1 mm and the upper part of which, 90 cm above the lower part, has a mesh opening of I mm Ten days after planting the cabbage plants, distributors of pheromone for ringworm of cabbage, in a tubular form, each containing 0.25 g / m of a 1: 1 mixture of acetate Z-11-hexadecenyl and Z-11-hexadecenal. are spread all over the field. with a density of 100 m for 10 ares. A month later, the number of caterpillars is counted to calculate the density of these per unit area or the average number of caterpillars assembled on a single cabbage plant, to find that the average number is 0.4 As for comparison, the same test is carried out as above simultaneously. in the neighboring cabbage field, except that the fence net is not in place, and there are an average number of caterpillars on a single plant

cabbage 1.6.

  For comparison, the number of caterpillars is counted in a cabbage field where no pheromone distributors have been placed, and there is an average number of caterpillars on a single cabbage plant of 6.2 in an open field , while this number is only 3.4 when the field is surrounded

  a fence net made up of the same net as above.

Example 3

  Fields of spring onions, each having a square shape of 10 ares in area, are surrounded by fences made up of different nets indicated in the table below, immediately after transplanting the plants, and five days later, we set up in the beet worm pheromone dispenser fields containing a 70. 30 mixture of ZE-9,12-tetredecadienyl acetate and Z-9-tetradecenol, with a density of 100 dispensers per 10 ares. The number of larvae per 10 spring onions is counted, and the results shown in the table are found as an average value. The corresponding number counts in the control test in an open field is 24, without the use of pheromone distributors. Note that the flight height of an adult beet worm is

supposed to be 120 to 150 cm.

Board

  Test Opening Height of the Average Number of n Mesh of the Net Closing Net Larvae per Scallion mm cm

1 0.3 10 0.4

2 0.3 40 0.2

3 0.3 120 0

4 0.3 200 0

2.0 130 6

(lower) 0.3 30

6 0.1

(higher) 2.0 100 7 - (none) 8

Claims (4)

  1. Method for the interruption of the mating of harmful insects which attack crops, by liberation, on the field or the plants are cultivated, of the sexual pheromone of the species of insect. characterized in that we surround   the field at least partially of a fence net.   2. The method of claim 1, wherein the fence net   has a mesh opening in the range of 0.01 to 5 mm.   3. The method of claim 2, wherein the fence net has a mesh opening in the range of 0.1 to 2 mm. 4. Method according to claim 1, in which the fencing net is divided into at least two parts comprising a lower part and an upper part, the mesh opening of the net constituting the lower part of the   fence being smaller than that of the upper part.