Pest monitoring methods

Learning Outcomes:

• Understand and distinguish Economic and Action threshold level.
• Understand the differences among different pest monitoring methods.
• Choose and implement the monitoring of the most common pests, decide on actions that need to be taken in order to preserve yield and prevent economic damage..

Protection against pests in organic farming is not possible without regular monitoring of the occurrence and determination of the level of the population of pests and natural enemies, as well as the determination of damage to plants. The data collected are the basis for determining the decision threshold and deciding whether to use direct pest control measures.

The economic threshold level (ETL) is the point at which the economic damage caused by harming a particular pest population equals the cost of controlling the same population (which includes the cost of environmental damage). The ETL takes into account the amount of damage prevented, the cost of the action and the environmental damage. Since in organic farming we use methods and means that have minimal (or no) impact on the environment, the environmental damage is minimal.

The action threshold is the level of pest infestation, or the constellation of factors on which the occurrence of a pest depends, at which the expected value of prevented damage is equal to the sum of the application cost and the value of environmental damage. The action threshold represents the level of infestation at which suppression is approached. Proper assessment of the action threshold also requires information on the population of natural enemies, the presence of which may reduce the need for direct control. Data on action thresholds for most economically important pests in integrated agricultural production are well known and are based on studies of the harmfulness of certain species under certain production conditions, calculation of yield and price of agricultural products from integrated farming, and economic calculation of the cost of classical means of plant protection (which are cheaper, but for which the environmental damage is higher). Since the expected yields and prices of organic products vary and the prices of plant protection products are higher in organic farming and the environmental damage, they cause is much lower, the action thresholds for organic farming can vary considerably. In most cases they are not known, so decisions are often made based on the producer's experience.

Successful pest management in organic farming is not possible without regular and systematic monitoring of the pest population and crop damage, as well as beneficial insect monitoring. These ultimately allow assessment and decision making depending on the stage of development of the crop, the general condition of the crop, the presence and level of populations of natural enemies, and the level of pest population and damage present and/or expected.

In addition to regular monitoring, for successful insect monitoring, it is important to monitor climatic conditions. For some pests and natural enemies, temperatures at which insect development begins have been determined, and developmental models have been created based on summing effective air or soil temperatures (depending on where the particular stage of the insect develops). Effective temperatures represent the difference between the average daily temperature and the thermal threshold of development and are summed over a period of time until their sum reaches what is known as the. Thermal constant, i.e. the number of thermal units that have been shown to be necessary for a species (or developmental stage) to complete its development.

The most common methods of pest monitoring are shown in Figure 3.40. They differ depending on whether we are inspecting crops or looking for insects. When inspecting crops one can determine the damage caused by insects in addition to the insects, while when collecting insects, one can use a method that attracts insects in addition to direct inspection.

Figure 3.40.Schematic overview of the available pest monitoring methods

Some monitoring methods are carried out according to certain prescribed protocols for crop and pests. Table 3.2. shows how each method is carried out.

Table 3.2.Monitoring methods and their implementation

Monitoring method		Implementation
Survey of the crop	Regular visual survey	At specified intervals, a certain number of plants are inspected, the presence and number of pests and natural enemies are determined, and damage is assessed using various scales If necessary, samples are taken and the species found are determined in the laboratory. Records of each survey shall include the following: 1. date, time of survey, weather conditions 2. assessment of general condition of crops/plantations 3. number of pests by species 4. damage assessment and type of damage 5. number of beneficial insects by species 6. presence of parasitic pest individuals 7. stage of development of crops/plantations
	Targeted visual survey	It is carried out at certain stages of development of the crop according to the protocol for each individual pest. The exact timing of the survey can be further determined by monitoring of insects, such as by pheromones or yellow panels. Targeted surveys are often conducted by taking a specific number of samples (e.g. branches of the exact length for perennial species, a specific number of flower buds or leaves).
Collecting the insects	Non-targeted sampling	Entomological net	For species that reside on above-ground organs, an entomological net is used on low crops (arable, vegetable crops) to make a certain number of catch sweeps over the plants, walking diagonally across the field. Catches from the net are determined by species, the number of individuals of each pest and beneficial species determined in the sample is recorded. Catches from nets are determined by species in the laboratory using a magnifying glass (depending on the skill of the person determining) and the number of individuals is recorded.
		Shaking the branches	It is performed on fruit trees. The branches are struck with a rubber stick, and the falling insects are collected in a fixed entomological net (trap). The protocols prescribe the number of branches to be shaken and the number of strikes for each branch. Catches from the net are identified to species in the laboratory using magnifying glasses (depending on the skill of the person determining). The number of individuals of each harmful and useful species determined in the sample is recorded
		Aspirator	Depending on the type of aspirator, it is possible to use it on all types of crops. The aspirator sucks in all insects that are on certain parts of plants or whole plants that are aspirated. The catches from the aspirator are determined to the species in the laboratory using a magnifying glass ((depending on the skill of the person determining). The number of individuals of each pest and beneficial species identified in the sample is noted.
		Pitfall traps	Pitfall traps are containers of liquid (usually water to which common salt is added) buried in the ground so that the top of the container is at ground level. Insects that walk on the soil surface fall into the traps, which must be emptied regularly. Catches from the traps are identified to species in the laboratory using a magnifying glass (depending on the skill of the person determining). The number of individuals of each harmful and useful species determined in the sample is recorded.
	Targeted sampling	Visual attractants	Colored baits	It is performed for species that fly and that attract certain colors. The most commonly used colored sticky boards are blue, yellow, or white. In some cases, hunting pots are used, painted on the inside and filled with water in which the insects drown. The color of the sticky or colored bait adapts to the species whose presence we want to detect, blue tends to attract thrips, yellow effectively attracts aphids, various types of flies, moths, crickets... white attracts wasps (which lay their eggs on white flowers). Colored sticky boards have standard dimensions and are placed so that the bottom edge of the board is just above the canopy - as plants grow, the board must be moved. Several species of insects (and in some cases beneficial insects) are caught on the colored boards, so when checking, the species found and the number of each pest must be determined. Colored baits placed in large numbers can also be used to control some pests.
			Light traps	Performed for species that fly and are attracted to light. The most commonly used lamps that draw their power from solar sources. Light traps catch several species of insects (in some cases useful species too), so when inspecting the caught insects, it is necessary to determine the species found and their number.
		Olfactory attractants	Feeding attractants	It is performed for species that are attracted to a particular type of food. Food attractants used are plants and parts of plants, food (honey, sugar), products of animal origin (e.g. fish) or special synthesized products (e.g. hydrolyzed protein, buminal). The attractants are placed in different types of traps. The attractants are usually species-specific so that individuals of the species we monitor, whose numbers we determine during inspection, can be easily found. When the attractants are placed in large numbers, they can also be used to control some pests (e.g. olive flies, wasps, hornets, ants...).
			Pheromones	Pheromones are produced by insects themselves. There are several types of pheromones, but for pest monitoring we use aggregation and sex pheromones. Aggregation pheromons are secreted by social insects (ants, bees) and some other insects (palm weevils, beet weevils). Normally, sex pheromones are secreted by females to attract males of the same species. The pheromones are synthetically produced and formulated for monitoring purposes in the form of capsules that are placed in traps of various shapes. The design of the traps is adapted to the behavior of the pest species. Due to their high specificity, insects trapped with pheromones do not need to be specifically identified. Pheromones determine the time limits for the appearance of a particular pest species, and for some pests (e.g. codling moth, grape berry moth, etc.), population size and control needs can be determined. Pheromone capsules and / or traps with pheromone baits placed in large numbers can also be used to control some pests using the confusion method or the mass trapping method (see Chapter 3.4.2.).