Pest Management Decisions

IPM decision staircase Some basic information is essential Information must be obtained from bottom to top Missing information will lead to incorrect decisions Each step interacts with the other in some way

Major steps in the decision-making process Pest Identification Pest species must be correctly identified Tells us about biology, life cycle, control strategies, etc. Population Determination Monitoring to determine pest population size, pest distribution, stage of development, presence and distribution of beneficials Damage and Economic Loss Evaluate potential damage to crop relative to pest density Consider action, economic and/or damage thresholds

Major steps in the decision-making process Available Control Tactics Review what tactics are available and their efficacy Cost of implementing control vs. economic returns expected Current and projected market value Interactions Consider interactions among target pest and other pests and beneficials in the system Environmental and legal constraints Consider local, regional environmental and societal regulatory restrictions

Major steps in the decision-making process Make a decision No action Damage caused by pest doesn’t warrant action Reduce crop susceptibility to damage Change some aspect of the system to limit damage to an acceptable level Reduce pest population size Recommended action that will reduce pest population Combination of b. and c.

Monitoring Process by which number and life stage of pests present in a location are established (aka scouting) Key objectives are to determine: Pest stages present in the crop Phenology of pest Growth stages through which the pest passes in relation to time Density of pests in the crop Number of pests per unit area 2,000 seeds/m2 Number of pests per plant part 5 aphids/plant Number of pests per unit of sampling effort 10 beetles per 5 sweeps of a sweep net

Steps in Monitoring Record type of plant being monitored, its size, location, condition, and date and time inspection took place Monitor the crops for insects (using methods described above) on a regular or weekly basis, and note number of pests, their stage of growth, and distribution Identify any beneficial insects Take representative plant samples in the field Assess the growth status and general health of the crop Record the findings on field data sheets

Techniques for Assessing Pest Populations There is no single monitoring technique that works for all categories of pests Overall considerations Data required Actual pest numbers, presence/absence, phenology Time of day when samples are collected Weather conditions Windy, cool/hot, or rainy conditions can alter pest visibility Soil conditions Phenological development of organism Weed seeds vs. seedlings, 1st vs 5th instar larvae differ in size Pest location Soil/plant host, in-crop/field edges

Common Monitoring Techniques Direct Pest Observation/Counting Quadrats Organisms present within an area Weeds Plant Samples Samples of plant parts Egg and larval counts, estimating leaf/root damage

Common Monitoring Techniques Direct Pest Observation/Counting Knockdown Pests are dislodged from host onto a collecting surface/container Larvae and non-flying insects Sweep Nets Nets are strong, usually about 15 inches in diameter at opening Insects only http://www.youtube.com/watch? v=DGggRMwpnY8

Common Monitoring Techniques Damage Evaluation Sometimes looking at symptoms or injury is the only way to determine pest presence Signs or symptoms Pushed up soil Frass Slime trails Spores, sclerotia, mycelium Physical injury Remote sensing

Common Monitoring Techniques Trapping Primarily used for insects Can detect a presence but not usually reliable for population size Will help monitor population activity and frequency of insect vectors Visual Sticky traps Bait traps Pitfall traps Pheromone traps Blacklight

Common Monitoring Techniques Soil Sampling Soil-borne pests Can be time consuming, laborious Shovels, scoops, cores Water submersed, sieved http://www.youtube.com/watch?v=9bMxSDSYp3E

What do we need to consider when we are taking samples in the field? Field size Economic value of the crop Sample location Pest density Sample size Sampling patterns Goals of manager Mobility of the pest Timing of sampling Frequency of sampling

Assignment Choose two weeds, two insects and two diseases. List which technique is used to monitor each.

Economic Thresholds

Damage Concept Injury Damage The physical harm or destruction to a valued commodity caused by the presence or activities of a pest consuming leaves, tunnelling in wood, feeding on blood, etc. Damage The monetary value lost to the commodity as a result of injury by the pest spoilage, reduction in yield, loss of quality, etc. Any level of pest infestation causes injury, but not all levels of injury cause damage

Just how much damage can we tolerate? At some point, a pest begins to cause enough damage to justify the time and expense of control measures But how does one know when this point is reached? How much financial loss is the pest causing? How much will it cost to control the pest? Economic Injury Level The pest density where economic value of the crop loss prevented by the control action is equal to the cost of that control action Determined through extensive research

Economic Injury Level P=C/(V x I x D x K) P=Pest population expressed as a density (e.g., number of pests per plant) Point where damage equals cost of control (EIL) C=Management costs (i.e., costs of control) V=Market value per unit of production I=Injury per pest equivalent D=Damage per unit injury K=Proportion of damage that must be tolerated

Economic Threshold Threshold Economic Threshold Stimulus has reached a sufficient level to provoke a response Must be qualified further Economic Threshold Pest density at which control action must be taken to prevent the population from increasing to the EIL ET occurs at a lower population that the EIL…why? In weed science, the ET is equal to the EIL

Examples of thresholds?? What are some of the thresholds written in our insect fact sheets?

Limitations of Thresholds Environmental conditions can alter thresholds Some pathogen populations are impossible to count accurately There may not be any available controls for a pest once it reaches a detectable stage Some pests cannot be cured Multiple pests may attack a given crop Not enough data available to establish the thresholds

Other factors that affect pest management Cropping History Field Location and Size Weather Monitoring