Rice IPM: Module 3

Module 3. The Second Rule of Rice IPM – Observe Fields Weekly

Module Overview

It has been proven consistently that the most successful farmers, and the ones with the least amount of pest problems, share two characteristics.

  • They have a good understanding of the biological processes that determine the health of the crop agroecosystem and their crops.
  • They spend a significant amount of time in their fields observing their crops and the various organisms that make their home there.

These characteristics are what rule 2 is all about – observing the crop frequently and accurately, being able to identify the various organisms observed and knowing something about these organisms’ biology and ecology. Key considerations are being able to tell friend from foe and in knowing how friends and foes interact.

Although you will be asked to look through and become familiar with a great deal of material in this module you shouldn’t find it particularly difficult. Most of the information here is really just reference that you may find useful in future IPM activities you may be involved in or in answering questions that may be put to you.

Lesson 3.1: Scouting

Farmers, and agricultural professionals, must understand and become familiar with the natural processes going on in the crop and the organisms present in the rice ecosystem in order to make good judgments on whether to take action, when and how. Periodic scouting (looking carefully and systematically at the crop) gives farmers the kind of information needed before deciding whether actions are necessary and what kinds of actions will have the most success. The purpose of scouting is to determine whether and which pests are present and if the application of a pest management procedure is justified. Scouting is also beneficial to determine whether nutrient deficiencies, soil compaction or other disorders are affecting crop health.

Scouting should be carried out each week or more frequently. It means walking through the crop and stopping 10 – 20 times to examine the leaves/stems/panicles for pests, disease and nutrient deficiency symptoms and natural enemies. The numbers and types of organisms (pests, parasites, predators, weeds) and disease should be noted as well as any abnormalities like discolorations or yellowing. On the basis of this information and a consideration of the time of the year, stage of growth of the crop, and weather conditions, an experienced grower can predict population trends and potential damage based on an understanding of such processes as plant compensation, fertilizer effect, and plant development.

Based on the information collected each week, the grower thinks about (predicts) current and potential economic losses and chooses the most economic management practice (e.g. remove water, add water, add fertilizer, weed, spray and continue observation, continue observation without sprays, change variety next season, organize community rat campaign, set up rat barriers, etc.). After all, the ultimate goal of IPM is to improve the decision-making skills of the grower for better production and profits.

A well-designed scouting program includes three main activities:

  1. Sampling to provide an accurate estimate of pest densities and crop health.
  2. Identification of pests or diagnosis of the cause of crop injury based on observable symptoms.
  3. Comparison of observed pest pressure or crop injury to an assessment of the most likely outcome if nothing is done.

It is not practical to observe every plant within the field, so fields are sampled to estimate the level of infestation. The challenge of sampling is to balance the accuracy of estimates with the time and labor required to collect the samples. Although the reliability of estimates increases as sample size increases (up to a point), the collection of too large a sample is costly and inefficient and it wastes human resources.

Lesson 3.1.1: Scouting Forms

Some growers and IPM practitioners find it useful to use a form to record their observations. For more information on scouting, including a suggested scouting form, you should access the following article.

IRRI has also published a good scouting form for rice in its newly developed RiceDoctor tool.

We’ll be talking more about RiceDoctor later but if you want to check it out now just go to IRRI’s Rice Knowledge Bank site at – http://www.knowledgebank.irri.org/ and find and click on [Rice Doctor].

Lesson 3.2: Rice Growth Stages

An important skill in scouting and sampling, and later on in determining what to do about pests, is to be able to recognize the growth stage of the crop. Some pests are only dangerous at particular stages in a plant’s growth. Some management practices are only effective when done at a particular stage.

For rice, most people recognize 9 stages starting from the germination of the seed to a plant that has produced mature grain. The stages of growth and development of a rice plant are listed below:

Vegetative Stage

0. Germination

1. Seedling

2. Tillering

Reproductive Stage

3. Stem elongation

4. Panicle initiation to booting

5. Heading

6. Flowering

Mature grain stage

7. Milky grain stage

8. Dough grain stage

9. Mature grain

Lesson 3.3: Identification and Diagnosis

IPM practitioners are sometimes compared with medical doctors. Like them, a person practicing IPM must first diagnose health problems before deciding on the best treatment. Perhaps the most important skill in diagnosis is being able to identify the specific pest causing the problem. In IPM, an important part in pest identification is to also be able to identify beneficial organisms. Various studies have shown that many farmers (and also many agricultural professionals?) are not good at pest identification and know little about pest biology and behavior. In rice pest management, if farmers cannot distinguish between pests and friends, they will be likely to control anything, whether helpful or a genuine pest. As we discussed earlier, killing of beneficial organisms in the rice ecosystem can have disastrous results.

So how to make a correct identification? The traditional source of information is the local extension office which should have field identification guides for local common pests and diseases. Sometimes such guides are also available at universities or colleges and more and more this kind of information is available through the Internet.

In the following lessons you will find links that will take you to Websites that contain tips on how to identify the weeds, insects, diseases and nutrient deficiencies you may find through your scouting activities. Many of them also contain supplementary information on these organisms’ ecology and behavior.

Lesson 3.3.1: Identification of Weeds

Lesson 3.3.2: Identification of Insects

Pests

Other sources:

Lesson 3.3.3: Identification of Diseases

Lesson 3.3.4: Identification of Nutrient Deficiencies

Just an additional note on this. Diagnosing nutrient deficiencies is relatively more difficult that identifying pests as doing so involves looking primarily at symptoms and not at identifiable organisms. Farmers have traditionally relied on their ability to correlate various symptoms with probable causes. Leaf color is one of the key points they observe and some new tools are now available to strengthen this skill. A relatively expensive option is to use a SPAD (soil plant analysis development ) meter. This is a small handheld device that measures the greenness of leaves. The readings of color by this machine are highly correlated with relative chlorophyll content and nitrogen status. A simpler (and more affordable alternative) that provides similar information is the Leaf Color Chart (LCC).

Lesson 3.3.5: Identification of Rat, Bird and Snail Damage