As mentioned earlier, sex and aggregation pheromones provide the rapprochement of insects, originally separated by a certain space. At a distance, pheromone is the connecting thread between individuals of the same species. It can be cut off using synthetic pheromone analogues. Since synthetic pheromones are used in amounts thousands of times higher than the amounts released by live insects, they effectively suppress the chemical communication of pests (Fig. 22).
There are two main ways to use synthetic pheromones against harmful insects. Firstly, synthetic pheromones allow you to record the beginning of the flight of pests, obtain data on the number of pest populations in an agrobiocenosis, or determine its range, that is, monitor.
Secondly, synthetic pheromones are used directly to control pests. After saturating the air with synthetic pheromone, you can prevent the insect from finding sexual partners; you can attract an insect with a pheromone and destroy it before it can detect a natural source of pheromone. In both cases, the reproduction of insects will be impaired. The following are the main ways to use synthetic pheromones to protect plants from pests.
Fig. 22. Comparison of sex pheromone emission levels (according to Witzgal et al., 2008):
1 – female codling moth; 2 – a rubber dispenser used in pheromone adhesive traps; 3 – a plastic dispenser used for disorientation
The use of synthetic pheromones for pest monitoring
The use of synthetic pheromones for monitoring pests and signaling treatments with insecticides and biologicals is the most effective and cost-effective method of monitoring many types of pests, such as various types of moths and leafworms, scoop, meadow moth, nutcracker beetles, fruit flies, etc. For example, the use of pheromone traps to determine the number of codling moth only (the Cydia pomonella L.) three times increases productivity compared with other IU odov accounting and use of traps for two pest species – already six times. The use of pheromone traps to determine the number of bunch of leaves in vineyards using pheromone traps is 15-20 times more effective than other methods of accounting.
The advantages of synthetic pheromones when used for monitoring are their high species specificity and attractiveness.
Synthetic analogues of pheromones are also widely used by the phytosanitary service to detect quarantine species and determine their ranges, since this method is highly effective for detecting foci of quarantine pests even at low numbers. Synthetic pheromones are used in traps for monitoring such quarantine pests of plants as California scabbard ( Quadraspidiotus perniciosus Comst.), Mulberry scallop ( Pseudaulacaspis pentagona Targ.-Tozz.), Capoe beetle ( Trogoderma granarium Everts), peach wortis fruit. , American White Butterfly (Hyphantria cunea Drury), Mediterranean Fruit Fly ( Ceratitis capitataWied.), A brown-marble bug of C Halyomorpha halys Stal) and some others.
The first use of pheromone preparations for monitoring pests and signaling insecticide treatments began in the early 60s. XX century Prior to that, in the 1940s. in the US, female abdomen extracts were used in traps to monitor unpaired silkworms.
To implement pheromone monitoring, pheromone traps are used, which can have a variety of designs, but they can be divided into two main types. The first type is pheromone glue traps, which consist of three main elements: the trap body (usually made of laminated cardboard or plastic), the glue liner covered with non-drying glue, on which the lured insects are caught, and the dispenser with pheromone (Fig. 23).
Glueless traps of the second type also consist of a body and a dispenser, but do not have a glue liner, and for catching insects they use various reservoirs (receivers) from which insects are not able to get out (Fig. 24). Using these traps, you can catch live specimens of pests. At the same time, some modifications of these traps can be equipped with an insecticidal liner to kill insects.
Pheromone dispensers are made of various materials that can hold and evaporate pheromone for a long time, mainly from different grades of rubber or cardboard, but sometimes they use skin, beeswax, etc. The dispenser is impregnated with pheromone (usually 1-2 mg of substance per dispenser), which is dissolved in a small amount of a rapidly evaporating solvent (hexane is often used as such a solvent). The latest generation pheromone dispensers are capsules or multilayer sachets (foil-like) and, in addition to synthetic pheromone, contain a solvent (e.g. alcohol), which provides a longer and more stable evaporation of pheromone, and therefore increases the monitoring efficiency.
Fig. 23. Pheromone glue trap (original)
Consider pheromone monitoring using the example of the codling moth, the main pest of apple trees in Russia and the world.
At the end of the flowering of the apple tree, when the flight of the moths begins (in the conditions of the Moscow region, this period falls at the end of May. – Note, ed.)pheromone traps are posted in the gardens at the rate of one trap per 3 hectares of the garden. Traps periodically (at least once a week) check and take into account captured males. The signal for chemical treatments against the first generation of the moth is the catch of at least five males per trap in five days, for the second generation – the capture of two or three males per week (Fig. 25). In the conditions of the Krasnodar Territory, in areas with a low number of apple codling moths (catching five to ten butterflies per trap per week), two are sprayed against the first generation – before the caterpillars hatch, Dimilin (wettable powder – SP) (1 kg / ha) or Insegar ( water-dispersible granules – EDC) (0.6 kg / ha) in alternation with Dursban (emulsion concentrate – CE) (2 l / ha).
Fig. 24. Pheromone glueless traps of various designs (according to various authors):
A – for catching nutcrackers: 1 – trap body, 2 – camera for dispenser, 3 – pheromone dispenser, 4 – air flow dividers, 5 – cork closing the dispenser chamber, 6 – hatch for removing captured insects; B – barrier trap for catching bark beetles: 1 – pheromone dispenser, 2 – barrier part,
3 – funnel, 4 – hairpin for mounting the tank, 5 – tank for collecting trapped insects, 6 – suspension for placing the trap on trees
Fig. 25. Flight dynamics of males of the apple codling moth in pheromone traps (Moscow region, 2006) (original)
The use of pheromone monitoring is included in the integrated protection systems of many crops and allows to increase the economic efficiency of the use of insecticides and other protection methods by two to three times, as well as minimize their number. So, in the conditions of Russia, the use of pheromonitoring of the apple codling moth makes it possible to reduce the volume of the use of chemical treatments in the summer period by 50–70%. Observations of the intensity of flight also make it possible to determine the economic thresholds of pests and predict harmfulness and, therefore, the feasibility of protective measures (Fig. 26, Table 3).
Signaling scheme for protective measures against cotton scoops on fine-fiber cotton in Central Asia and Azerbaijan based on the results of catches in pheromone traps *
|Event||Catch per 1 trap in 3 days, ind.|
|The first issue of trichogram within 3 days after accounting for butterflies||1—5|
|The beginning of regular surveys of the number of eggs and caterpillars on plants||1—5|
The end of the table. 3
|Event||Catch per 1 trap in 3 days, ind.|
|Cancellation of chemical protection of cotton within 3 days after males||less than 1-5|
|Alarm protection according to the standard method (with a threshold number of eggs and caterpillars)||5—20|
|Obligatory protection by biological (Gabro-Bracon, biological products) or chemical means within 3 days after accounting for butterflies||20-30 and more|
|Implementation of agricultural and biological preventive protective measures||5—10|
* According to Grichanov, Ovsyannikova, 2005.
Fig. 26. Dependence of damage to apple fruit on the intensity of flight of the apple codling moth into traps with synthetic sex pheromone (cultivar Antonovka ordinary, 2003-2005) (original)
When conducting pheromone monitoring, it is necessary to take into account a number of factors affecting its effectiveness. The effectiveness of pheromonitoring depends not only on the properties of pheromone preparations, but also on the characteristics of the placement of traps in the agrocenosis, weather conditions, the state of the pest population, and other factors (Fig. 27). Since pheromone is heavier than air, a higher trap placement is preferable for monitoring fruit crop pests at a height of not less than 1.5 m. When monitoring pests of field and row crops (for example, different types of scoops) traps are placed on poles. Nutcracker traps are placed on the surface of the soil.
The orientation of the traps may have some effect on catches. Thus, a number of domestic researchers recommend placing traps for monitoring the codling moth on the southwestern or western side of the crown of the apple tree, as it warms up during sunset, and butterflies concentrate here.
Fig. 27. The main factors affecting the effectiveness of pheromone monitoring (orig.)
The color of the trap may influence the amount of catch. The material (cardboard or plastic) the trap is made of must not emit any odors that can reduce the entrapment of insects. Particular attention should be paid to the condition of the glue liner, since the liners contaminated with captured insects and dust significantly reduce catches. The liners must be changed periodically. The quality of the glue used in the traps also has a big impact on the monitoring efficiency.
Traps for lepidopteran fruit pests must be placed at least 1.5 m above the ground, on tree branches, but it is known that the catches in pheromone traps are greater, the higher they are located, since pheromone is heavier than air, although it can be detected at a height up to 6 m if there is a slight wind. With a decrease in air temperature and with precipitation, as well as with a strong wind, catches in traps, as a rule, decrease.