1. Resurgence Mostly documented with insect pests
Mostly associated with indirect, secondary/minor pests for several reasons.
Key pests are watched too closely to resurge
Direct pests are mainly late-season pests & there isn’t time to resurge
Pest must be held at least partially in check by some agent that is affected by the pesticide
Note Fig in book.

2. Pest Resurgence
Pest (8)
Natural Enemy

3. Pest Resurgence
Pest
Natural Enemy

4. Pest Resurgence
pest
pest

5. Pest Resurgence
Note: 14 pests/leaf

6. Four processes contribute to resurgence
Reduced Biological Control (Secondary) – most common with insects
Reduced Competition – most common with weeds (mono vs. dicots)
Direct Stimulation of Pest – usually due to sub-acute doses
Improved Crop Growth

7. Resistance
Mostly a problem with pesticides (so far) but applies to all management tactics. Ex:
Biological Control – Rabbits & virus, Bt
Cultural Control – corn rootworms & rotation
Host Plant Resistance – many examples
Most serious, general problem in IPM
Arises because all management actions are selection pressures
Problem is rapidly getting worse

9. Read about Kentucky’s Herbicide Resistant Weeds Here

10. Resistance is best understood as a process
Initially, a small proportion of population has a resistant mechanism by chance.

11. The Resistance Process
These individuals survive at a higher rate than others

12. Resistance as a process
Resistant individuals increase in frequency

13. Resistance as a process
Eventually, the pesticide or other management tactic causes too little control to be effective.

14. Need to monitor resistance
The process has three general stages, each with its own Management Strategy
Abandon Pesticide/Management Tactic
Manage or Reverse
Prevention
Need to monitor resistance

15. Impact of Resistance
Overall agricultural productivity (during build phase)
Increased pesticide usage
Increased damage
Environmental impact
Increased use of non-renewable resources
Increased acreage
Pest management flexibility
Loss of pesticide tactic
Constraint on new pesticides

16. Causes of Resistance Independent of Pesticide Genetic Factors
Ecological Factors
Severity of Selective Pressure

17. 1. Genetic Causes of Resistance
Genetic Factors
Relative dominance – More dominant is bad
Linkage to phenotype – Fewer genes is bad
Initial resistant pop – Prior exposure
Broad diversity & diversity-maintenance
Low diversity associated with foreign pests
Sexual reproduction
Haplo-diploidy

18. 2. Ecological Causes of Resistance
Population Isolation
More isolated develop resistance more rapidly
Less isolated allow resistance to spread more rapidly
Narrow host range – more selective pressure
Intrinsic population factors
Voltinism
Generation time
Fecundity
Behavioral factors

19. 3. Selection Pressure
Selective pressure is “high” if a “low” percentage of susceptibles survive to reproduce
Reduce pressure by: (1) reduce dosage & (2) reduce frequency
Site of action
Alternating modes of action reduces pressure
Spatial coverage – reduce pressure by reducing coverage
Timing – Using pesticides after reproduction reduces selective pressure

20. Resistance Categories
Resistance to individual pesticides
Delayed entrance of toxicant
Increased deactivation/decreased activation
Decreased sensitivity
Behavioral avoidance
Resistance to multiple pesticides
Cross-resistance & class resistance
Multiple resistance
Multiplicate resistance

21. Resistance Management
Strategy
Saturation
Moderation
Multiple Attack
Tactics
Prevention
Reversal

22. Specific Tactics Prevention Reversal Use pesticides only as needed
Time/target applications precisely
Combine chemical & non-chemical controls
Reversal
Cease use of pesticide causing resistance. Problems
Probably the preferred control
May be used for other pests
Area-wide enforcement usually necessary
Refugia
Use synergists
Genetically manipulate the pest population (Gene Driving)