Unit 1: Insect Pest Management for Field & Forage Crops

1. Unit 1: Insect Pest Management for Field & Forage Crops

2. Unit 1: Insect Pest Management for Field & Forage Crops • Unit 1 Objectives: • Discussion of insect pest management for Illinois crops • Identification of proper pesticide choices for prevention and control • Understanding of control methods without the use of pesticides

3. Unit 1: Insect Pest Management for Field & Forage Crops • Integrated Pest Management (IPM) • comprehensive approach that uses combined methods to reduce pest densities to tolerable levels while maintaining a quality environment • uses several methods for pest control • host-plant resistance • cultural resistance • mechanical control • biological controls

4. Unit 1: Insect Pest Management for Field & Forage Crops • When should an insecticide be used? • When insect population has reached/exceeded and economical threshold • damage > cost of control • only after risks and benefits have been identified and evaluated • human • environmental

5. Unit 1: Insect Pest Management for Field & Forage Crops • Insecticides in this Chapter • Most common insecticides are included, however, label changes, generics, etc. may not be current • Insecticides cited will be of most common trade name and formulation • Refer to tables 2-8

6. Unit 1: Insect Pest Management for Field & Forage Crops • Managing Corn Rootworms • Pressure has been greatest in northern 2/3 of the state • Can have problems in corn after corn rotations • Control of rootworms needs to be a long-range plan that includes: • Crop rotations • Scouting • Effective use of insecticides

7. Unit 1: Insect Pest Management for Field & Forage Crops • Soil applied insecticides at planting are usually very effective • An aerial application may also be effective at preventing egg laying and have residual control • Only use in corn on corn situations • Long-range Corn Rootworm Mgmt. Strategies • Proper crop rotation where avg. # of adults/plant exceeds .75 or more, or if insecticide didn’t control in previous yr.

8. Unit 1: Insect Pest Management for Field & Forage Crops • If planting corn on corn, apply insecticide at planting time • Granular insecticides have provided the best control • Aztec • Counter • Force • Lorsban • Liquid insecticides have not been as effective • Environmental/pest conditions can still have an impact • Delayed larval hatch • Early planting

9. Unit 1: Insect Pest Management for Field & Forage Crops • Large #’s of larvae • Hot/dry conditions • Two seed treatments are labeled for control of larvae • Force ST & Prescribe • Applied to corn seeds before bagging • Effective control when rootworm pressure is moderate, however, control is not as effective if high risk areas

10. Unit 1: Insect Pest Management for Field & Forage Crops • Control egg laying adults • May take two applications • Caution should be taken: • Nebraska has observed the development of Corn Rootworms that are resistant to the insecticide • This mgmt. strategy should be used sparingly • Controlling egg laying and silk clipping is not the same thing • Silk clipping occurs much earlier than egg laying • Densities of 5+ adults/plant will reduce pollination

11. Unit 1: Insect Pest Management for Field & Forage Crops • Scouting: • Mid-July through September in corn fields • Soybean fields planned for corn the following yr. • Rootworms have started laying eggs in soybean fields in anticipation of corn the following yr. • Has increased the number of first-yr. rootworm damage • Can set traps in soybeans to evaluate rootworm populations • Treatment should be considered if no. of adults >5/trap/day

12. Unit 1: Insect Pest Management for Field & Forage Crops • Growers in western and southern IL are encouraged not to treat to prevent pest resistance • Corn Rootworm damage has not been reported in our part of the state

16. Unit 1: Insect Pest Management for Field & Forage Crops • Managing European Corn Borers • Has caused yield losses in many parts of IL • Larger populations have been supported by the trend to plant longer season corn earlier • Susceptible to both first and second generations • Reduced-tillage systems increase overwintering of corn borers

17. Unit 1: Insect Pest Management for Field & Forage Crops • Planning is difficult because an economic infestation is hard to predict • Densities of the population depend on: • Overwintering survival rate • Weather during egg-laying and the larval stage • Time of planting • Mgmt. w/ Bt Corn • Gene taken from soil bacterium Bacillus thuringiensis • Produces a protein that is toxic to some caterpillars

18. Unit 1: Insect Pest Management for Field & Forage Crops • Decision to plant Bt corn should be included in a long-term plan • Careful consideration should be given to the development of resistant corn borers to the Bt gene • Benefits of Bt corn will only be realized in yrs. where densities of corn borers will cause an economic yield loss • Decision to plant should be made when an economic yield loss is realized in 7 of 10 yrs. • Infrequent yield losses should not encourage growers to plant Bt corn due to increased cost and increased development of resistance

19. Unit 1: Insect Pest Management for Field & Forage Crops • Bt corn should provide 100% control • If some survive, growers should ensure that they mate w/ adults from areas that didn’t have Bt corn • Bt corn planting strategies • Provide one entire field of non-Bt corn just to ensure a population of unexposed corn borers • Alternating strips of Bt and non-Bt corn in the same field • A block of non-Bt corn within a Bt planted field (should not be less than 20%) • Non-Bt areas can still be treated if levels of corn borers exceed economic levels

20. Unit 1: Insect Pest Management for Field & Forage Crops • Managing Corn Borers w/ Insecticides • Scout for first-generation corn borers and injury in June • Unroll the whorl to find the borers • Examine at least 50 plants (10 plants from each of 5 areas in the field) • Avoid sampling only damaged plants • Scout for second-generation July through mid-August • Counting egg masses

21. Unit 1: Insect Pest Management for Field & Forage Crops • Signal to begin checking is when you observe moth flight • Most eggs laid in the ear zone (middle 7 leaves) • Mgmt. worksheets are provided to aid in decision-making • If eggs are examined on leaves, must calculate to account for eggs in other parts of the plant • Level of infestation, expected yield, value of the grain, cost of control are all included in the worksheet • Insecticide must be applied soon after egg hatch • Begin to tunnel into stalk ~10d after hatch

22. Leaf damage and damage near stalk

23. Hatching Larvae

25. Unit 1: Insect Pest Management for Field & Forage Crops • Other Insect Problems • White Grubs • Reports of damage to seedlings are increasing • Mild fall and winter weather likely aiding in their survival • “True” White Grub (3 yr. life cycle) • Trees are hosts for the adult • Infestations usually not widespread, but close to a food source

26. Unit 1: Insect Pest Management for Field & Forage Crops • Annual White Grub • Most problems attributed to the Japanese Beetle • No consistent pattern for infestation is established • Mode of Action • Devour roots and root hairs • Symptoms include: • Irregular emergence • Reduced stands • Stunting or wilting • Purple coloring due to reduced P uptake • Spotty areas of injury • Must be controlled w/ soil applied insecticides, rescue treatments not effective

27. Japanese Beetle Larvae

29. Unit 1: Insect Pest Management for Field & Forage Crops • Southwestern Corn Borer • Significant damage in southern IL from ’98-’02 • Most economic losses occurred south of I-64, but much south of I-70 • Can overwinter during mild winters • 2 generations/yr. • Eggs laid in June • 1st generation • Younger larvae feeds on whorls, cause little to no economic loss • Older larvae bore into stalks

30. Unit 1: Insect Pest Management for Field & Forage Crops • 2nd generation • Eggs laid in July • Tunnel into stalks and cause much more economic damage • Full-grown larvae tunnel to bottom of stalk and prepare to overwinter • Can cause severe lodging • Populations can be decreased by disking or shredding cornstalks after harvest • Infestations also decreased w/ early planting

31. Unit 1: Insect Pest Management for Field & Forage Crops • Insecticide treatment: • Should begin when 20-25% of crop infested from 2nd generation • Bt corn also provides good control

34. Unit 1: Insect Pest Management for Field & Forage Crops • Bean Leaf Beetle • High densities in last few yrs. • Problems associated w/ BLB • Clipped pods • Pod feeding • Disease introduction • BLB lifecycle • Adults can overwinter in debris and wooded areas • Feed on alfalfa & clover in the spring

35. Unit 1: Insect Pest Management for Field & Forage Crops • Colonize soybeans when they emerge • Lay eggs in soil • Feed on cotyledons, leaves, stems • Eggs hatch quickly • Larvae feed on roots and nodules • Peak adult populations occur in late July • Severe infestation will have leaves riddles w/ holes • 2nd generation emerges in September and can continue the infestation • This generation overwinters

36. Unit 1: Insect Pest Management for Field & Forage Crops • Scouting should occur: • At emergence • When 1st generation adults begin to feed • Pod-filling time is most critical • Economic damage: • Begins when beetles are >16/ft. of row • 5-10% injured pods • Control may be needed during pod-filling if defoliation >20%

39. Unit 1: Insect Pest Management for Field & Forage Crops • Soybean Aphids • Found for the 1st time in the U.S. in 2000 • Little is known about them • Eggs overwinter on buckthorn plants • Can have 18 generations/yr. • As colonies increase, they will spread • Usually found on leaves and stems • Feed by sucking fluid from the soybean leaves • Caused crinkled/cupped leaves

40. Unit 1: Insect Pest Management for Field & Forage Crops • Have reduced yields by as much as 28% in China • Very difficult to treat • Weather can cause a population crash quickly • Predatory control • Infestation can increase 10x in a week • Insecticide may only control for small period of time • May take 2 applications for control

42. Insecticide applied Not treated

43. Unit 1: Insect Pest Management for Field & Forage Crops • Wireworms • Have typically been a problem restricted to grass/sod • Becoming more of a problem in corn/soybeans • Feed on the seed and roots • Cause problems w/ germination, reduced stand, etc. • Usually localized infestation • Larvae will spend 2-6 yrs. in the soil developing • Adults are called “Click Beetles” and will live 10-12 mos. before laying eggs in grass

44. Unit 1: Insect Pest Management for Field & Forage Crops • Rescue treatment is not effective for control • Insecticide is recommended for high risk fields at planting time for good control • Highest risk fields are those that are coming out of pasture/CRP, or fields that might be adjacent to these