Control of Rice Insect Pests

1. Control of Rice Insect Pests G.C. Jahn & Islam Zahirul Integrated Pest Management Training Course

2. LECTURE CONTENT • Introduction • Basics of Cultural Control • Single Field Cultural Control Practices • Community-wide Cultural Control Practices • Examples of Cultural Options Against Specific Insect Pests

3. Introduction What is CULTURAL CONTROL? • The modification of management practices so that the environment is less favorable for pest • invasion • reproduction • survival • immigration

4. Introduction Ecological Pest Management • “Cultural control” is referred to as “Ecological Pest Management” (EPM) by some authors (e.g. Speight et al. 1999) • This is because cultural control is a way of changing the ecological factors that affect pest numbers.

5. Introduction Is there a difference between EPM and Cultural Control? • In practice, they are the same. • In theory, they are different ways of looking at crop protection, i.e. . . . • EPM – looks for intervention points to manipulate the ecosystem • Cultural control – looks at each aspect of crop management and how it affects pests. • For our purposes the terms can be used inter-changeably.

6. Introduction Aims of EPM In EPM the crop is managed to: • Improve resistance of the crop to pests, by optimizing plant health • Enhance the proliferation and efficiency of natural enemies

7. Introduction Aims of Cultural Control • To achieve reductions in pest numbers through crop management. • Increase yield. • Improve grain and crop quality. • Improve seed viability (germination rates). • Decrease cost of pest management. • Reduce the negative impact of pest management on the environment and health by reducing reliance on pesticides.

8. Basics Basics of Cultural Control • Advantages vs. Disadvantages • Types of cultural control • Primary • Secondary • Examples of Cultural Control Practices • Adoption scale

9. Advantages: Inexpensive Slow development of resistance (compared to chemical control) Low environmental impact Compatible with other pest management Disadvantages May suppress some pests, but increase others May require community-wide adoption Generally slower than pesticides for controlling outbreaks. Basics Advantages vs. Disadvantages of Cultural Control

10. Basics Types of Cultural Control • Primary Cultural Control • those practices adopted specifically to control insect pests. • Secondary Cultural Control • those practices adopted for general crop health, but which also prevent pest build up.

11. Basics Examples of Primary Cultural Control • Draining a rice field to control caseworm. • Transplanting older seedling to prevent whorl maggot damage • Increasing the seeding rate to compensate for feeding by ants or birds • Adjusting the timing of planting or land preparation to avoid certain pests (e.g. chafer beetle, stem borer, rice root weevil)

12. Basics Examples of Secondary Cultural Control • Maintaining water in the field to prevent mole crickets, ants and other soil pests. • Land preparation – e.g. plowing to prepare the soil for planting while at the same time turning over stubble that harbors stem borers. • Weeding • Fertilization – splitting nitrogen applications to avoid build up of certain pests (e.g. brown planthoppers, gall midge)

13. Basics Examples of CULTURAL CONTROL PRACTICES • Rotations, intercropping, mixed cropping, barrier, trap crops • Tillage • Mulches • HPR • Phytosanitation • Water management • Fertilizer management

14. Basics Adoption Scale Some cultural practices offer direct benefits to the farmer if carried out at the farm level. However, some others require community-wide action to be effective. • Single field cultural practices • e.g. transplanting vs direct seeding for weed control • Community-wide cultural practices • e.g. crop rotation to break pest life cycle

15. Single Field Cultural Control Practices Single Field Cultural Control Practices • Overview • Planting methods • Seedling age • Clipping • Plant Density • Crop cover – using Azolla • Water management • Fertilizer management

16. Single Field Cultural Control Practices Overview of Single Field Cultural Control Practices • Works well when for pests that can be excluded from the field e.g. flooding eliminates dryland pests such as root aphids. • Works for avoiding pests in time. • Does not work well for reducing overall pest populations of species that readily move between fields such as adult rats or flying insects.

17. Single Field Cultural Control Practices Planting Methods • Transplanting into flooded fields suppresses dry land adapted pests such as white grubs, root aphids, termites, mole cricket, ants, and others. • Seed beds are easier to protect from pests, than entire fields, due to small area. • Delayed transplanting is may help avoid certain insects (e.g. stem borer) or diseases.

18. Single Field Cultural Control Practices Seedling Age Transplanting older seedlings: • Reduces seedling time in the field. • Reduces population buildup of pests that prefer the vegetative stage. • Reduces damage from caseworms and whorl maggots • Avoid one generation of stem borers, leafhoppers, and brown planthoppers.

19. Single Field Cultural Control Practices Plant Density • The effect of plant density on insect pest abundance is varied and complex. • Dense plantings change crop growth, development, and microclimate, which in turn has an effect on pests and their natural enemies. • Sparse planting encourages weeds and indirectly has an effect on insect abundance.

20. Single Field Cultural Control Practices Clipping • Clipping the tops of bundled tall seedlings prevents lodging and removes stem borer and hispa eggs, if present. • Not commonly used with modern rice varieties. • During the wet season, removal of the top third of a standing crop at the vegetative stage can remove leaf folders and stem borer egg masses, hispa eggs and grubs, and thrips.

21. Single Field Cultural Control Practices Crop Cover - Azolla • Covering the paddy water surface with Azolla (water fern) reduces incidence of whorl maggot. • Azolla cover also assists predators move from hill to hill in search of prey (e.g. planthoppers).

22. Single Field Cultural Control Practices What is Azolla? A. nilotica • Azolla is an aquatic fern (pteridophyte), that floats on the water surface of flooded rice fields, small ponds, and canals. • 1-5 cm, except for A. nilotica of Africa which reaches 15 cm. • Multiplies vegetatively and sexually. • Seven Azolla species are recognized • Distributed widely from temperate to tropical regions.

23. Single Field Cultural Control Practices Uses of Azolla • Symbiotic nitrogen fixation, thus high N content • Used for green manure in wetland rice in China, Vietnam, and Philippines • Weed suppression in rice

24. Single Field Cultural Control Practices Water Management • Draining field 1-2 days suppresses: • Whorl maggots, • root feeding midges, • water weevils, • caseworms • Alternate draining and flooding for 5-7 days helps control black bugs, planthoppers, gall midge, hispa, and stem borers

25. Single Field Cultural Control Practices Fertilizer Management IPNM = Integrated Pest & Nutrient Management = Managing soil nutrients and pests in a complementary fashion, i.e. • pest management has a neutral or positive effect on soil quality • soil nutrient management has a neutral or positive effect on pest levels

26. Single Field Cultural Control Practices Why do we need Integrated Pest and Nutrient Management (IPNM)? • Some nutrient management causes pest outbreaks • Some pest management techniques degrade the soil • IPNM could reduce pest problems and enhance soil fertility

27. Single Field Cultural Control Practices IPNM FOR A CHANGING RICE ECOSYSTEM • New cultivars & GMOs • Increased amounts of fertilizer being used • Interactions poorly understood, therefore the potential for disaster (e.g. outbreaks) - note pesticides • Current pest problems related to fertilizer use may be exacerbated

28. Single Field Cultural Control Practices EXAMPLES: PEST MANAGEMENT THAT REDUCES SOIL QUALITY • Burning straw to control insects and diseases • Plowing fallow land to hinder weeds and the insect pests they harbor • Draining fields

29. Single Field Cultural Control Practices EXAMPLES: PEST MANAGEMENT THAT IMPROVES SOIL QUALITY • Flooding fields to prevent infestations of thrips mole crickets or weeds • Crop rotation with a legume • Using fish and ducks to help regulate pests

30. Single Field Cultural Control Practices EXAMPLES OF PEST PROBLEMS CAUSED BY FERTILIZER • Nitrogen (N) applications tend to increase populations of: • weeds • sheath blight • leafhoppers • gall midge • N applications lead to heavier stem borer larvae, which presumably cause more damage • High N levels associated with pest outbreaks

31. Single Field Cultural Control Practices EXAMPLES OF USING FERTILIZER TO HELP MANAGE PESTS • N applications decrease thrips populations • Phosphorous (P) improves tolerance for root pests • Potassium (K) tends to suppress pests • Silicon increases resistance to blast, bacterial blight, planthoppers and stem borers • Zinc reduces stem borer damage

32. Single Field Cultural Control Practices FERTILIZER APPLICATIONS CAN: • Raise pest levels • Lower pest levels • Raise the levels of some pests and lower the levels of others • Have no effect on pest levels Depending on several factors. . .

33. Single Field Cultural Control Practices FACTORS TO CONSIDER • Fertilizer • Composition • Timing • Amount • Cultivar • Hybrid • New plant type • Transgenic • Duration

34. Single Field Cultural Control Practices How would Nitrogen effect . . . Nn = Nt + B – D + I - E • Birth rate? • Mortality? • Immigration • Emigration?

35. Single Field Cultural Control Practices FERTILIZER AND BIRTH RATE • N increases birth rate ( = fecundity) of many phloem-feeding insects (e.g. planthoppers and leafhoppers insects) More babies!

36. Single Field Cultural Control Practices FERTILIZER AND DEATH RATE • N tends to lower insect death rate ( = mortality) • N increases insect tolerance to stress, therefore lowers mortality • Some parasitoids concentrate attacks on insect hosts that feed on the leaves with the highest N content

37. Single Field Cultural Control Practices FERTILIZER AND IMMIGRATION • Rice treated with high N attracts more pests

38. Single Field Cultural Control Practices FERTILIZER AND EMIGRATION • N tends to soften plant tissue, making penetration of the plant easier. • Therefore insects should tend to stay in a field with high N. • . . .which should reduce emigration. Comfortable animals tend to stay at home

39. Single Field Cultural Control Practices WHAT IS KNOWN? Nitrogen & insects • Increase insect tolerance to stress • Greater insect fecundity (e.g. sucking insects) • Increases insect feeding rate • More abundant, e.g. brown planthopper • Less abundant, e.g. thrips and whorl maggot • Rice attracts more pest • Promotes recovery from pest damage

40. Single Field Cultural Control Practices THE KNOWN: Weeds & Pathogens • Sheath blight - increased severity with increased N • Blast - use silica to increase resistance • Low density of Echinochloa can out-compete rice at high N

41. Single Field Cultural Control Practices THE KNOWN: Balance is important! • Studies in India, China, Indonesia, the Philippines, and Vietnam have found lower pest incidence in fields with site-specific nutrient management, compared to farmers’ practice • Why? • Farmers tend to apply unbalanced fertilizer regimes

42. Single Field Cultural Control Practices THE KNOWN: N effects • N increases number of eggs produced by some insects, (i.e. increase birth rate) • High N can attract ovipositing insects (i.e. increase immigration). • N augments plant growth rate, therefore softer tissues and easier penetration (reduces emigration).

43. Single Field Cultural Control Practices THE KNOWN: P effects • P (Phosphorus) improves root development, therefore greater tolerance to root pests (e.g. root weevil)

44. Single Field Cultural Control Practices THE KNOWN: Potassium (K) Effects • Lowers plant sugar • Lowers amino acids • Promotes thicker cell walls • Increases silica uptake • Therefore suppresses many pests

45. Single Field Cultural Control Practices APPLICATIONS of IPNM knowledge to date • Avoid fast pest build up by splitting applications of N, with a basal application for slow release. • Plow straw into soil to increase silica uptake and reduce stem borer • Apply N to promote recovery following a pest attack

46. Single Field Cultural Control Practices THE UNKNOWN • Quantifying the balance between pest & yield increases when fertilizer is used • Multiple effects: Fertilizer combinations on different soil types, with multiple pests on different cultivars

47. Single Field Cultural Control Practices THE UNKNOWN • How will pests respond to fertilizer on new cultivars? • How do natural enemies respond to fertilizer applications? (How do fertilizers effect the rate of death of pests?) • How do grain sucking insects respond to fertilizer applications and does this effect grain quality?

48. Single Field Cultural Control Practices OBJECTIVES OF IPNM RESEARCH • Understand processes involved in how fertilizers effect crop losses due to pests on different • cultivars • soil types • Predict the consequences of intensified rice production on crop losses due to pests.

49. Single Field Cultural Control Practices DESIRED OUTPUTS • Identify situations where outbreaks are likely to occur • Predict effectiveness of pest control strategies and soil nutrient management under different circumstances • Integrate pest and nutrient management strategies

50. Community-wide cultural control Community-wide Cultural Control: Overview • Eliminating or drastically reducing a pest population by removing its habitat. • Preserving a high diversity of natural enemies by maintaining habitats. • Can use indicator species for diversity of natural enemies (e.g. dragonflies in rice). • Rely on taxonomy and phylogenetics to define biodiversity (Douglas and Brunner 2002, May 1990)