In this article we will discuss about:- 1. Definition of Integrated Control 2. Principle of Integrated Control 3. Strategy of Integrated Control 4. Feasibility of Integrated Control for Pests of Certain Crops.
Definition of Integrated Control:
Integrated control is defined as a pest management system that in the context of the associated environment and the population dynamics of the pest species, utilizes all suitable techniques and methods in as compatible a manner as possible and maintains the pest populations at levels below those causing economic injury. In its restricted sense, it refers to the management of single pest species on specific crops or in particular places.
In a more general sense, it applies to the co-ordinated management of all pest population in the agricultural or forest environment. It is not simply the juxtaposition or superimposition of 2 control techniques (such as chemical and biological controls) but the integration of all suitable management techniques with the natural regulating and limiting elements of the environment.
Principle of Integrated Control:
Integrated control derives its uniqueness of approach from its emphasis on the fullest practical utilization of the existing mortality and suppressive factors in the agro-ecosystem.
To achieve this goal crop protection must be guided by the following two principles:
1. Pest control should be developed and applied in the total environment. The pest populations are managed in such a manner that existing limiting and regulatory factors are exploited to the fullest extent possible and without disturbance to the regulation of other pests. This principle defines the underlying philosophical approach to integrated control.
2. Additional mortality or regulatory factors are introduced into the environment at appropriate times to maintain the pest population at levels below those causing economic injury. These levels should be determined in terms both of the foreseeable crop loss and of the economics of crop production and marketing. This principle defines the goal of the integrated control system.
Strategies for Integrated Control:
The strategy for an integrated approach should include efforts:
(a) To reduce the seriousness of the pest problem by evolving crop varieties as resistant to insect pests as possible,
(b) To reduce pest infestation by maneuvering the ecology of the crop including introduction of exotic parasites,
(c) To nip the infestation in the bud by such mechanical campaigns as collection of egg-masses, affected shoots, etc., and
(d) To resort to a suitable combination of chemical and biological methods of control including some of the modern sophisticated techniques.
In the past the practice has been to recommend control measures separately for each pest, which are as follows:
In the above table as many as 40 control measures are recommended against 26 pests of paddy. It is left to the farmer or to the local extension worker to select at the moment and on the spot one of the methods listed against the pest which happens to be doing more serious damage to the crop at the time. Although at first this appears to be quite a rational thing to do, there are some practical disadvantages in this kind of approach.
First, the general tendency is to select the handiest out of the most effectively advertized methods leaving out the most rational one for which there happens to be no provision in advance. The result is that some methods which would have proved more effective and cheaper are not tried, and pest control is reduced to the application of an insecticide, the distributing or manufacturing firm for which has the most effective propaganda organization in the region.
The second major disadvantage of the existing practice is that for each pest there are several recommendations and the result is that the farmer and the local extension worker are faced with an unmanageably large number of pest control recommendations for each crop. Neither can they make advance provision for each of the long list of pesticides, nor are they able to make a judicious selection. The result is confusion leading to a sense of frustration and helplessness, which in turn leads to drift and escapism, allowing the pests to have their full share and to be regarded as unavoidable evils to be tolerated.
The obvious remedy is to attempt a kind of rational synthesis of the diverse recommendations against the diverse pests of each crop so as to evolve rational integrated control schedules for growing pest-free crops of each important commodity. Of course, this schedule should not be too rigid, and it should have a reasonable amount of built-in flexibility for necessary modifications from year to year and from place to place.
Feasibility of Integrated Control for Pests of Certain Crops:
1. San Jose Scale in Kashmir:
In recent years highly effective insecticides have come into the market for the control of this cosmopolitan pest; but in Kashmir the problem continues to cause serious concern, and the pest attacks such a large variety of fruit and forest trees that it is not possible to carry out chemical control on all.
The result is that chemical control proves to be only a temporary palliative; for the infestation is very heavy and, therefore, the good effect of chemical control is soon lost, so that the orchards have to be treated again and again during the same season.
In order to overcome this difficulty it is highly advisable and feasible to integrate chemical and biological control for keeping this pest economically under control. It is advisable to treat the orchards of valuable fruits like apple with suitable insecticides and to follow it up with intensive biological control.
In areas like Kashmir it is quite feasible to rear parasites like Prospaltella in very large numbers throughout the winter season in specially heated rooms wherein the parasite population can be rapidly multiplied 10 to 20 times during each generation of about 4 weeks, and then to flood the areas infested with the comparatively small overwintering population of San Jose scale on uneconomic plants around the fruit orchards.
In this way the infestation from outside the orchards can be effectively checked, and fewer insecticidal applications resulting in reduced number of operations will be required in the orchard itself. This is a very fertile field for an effective and fruitful integration of chemical and biological control applied simultaneously in time but separately in space.
2. Maize and Millet Crops:
Considering the vast variety of potential dangers from insect pests to millet crops, the policy of millet growers should be to evolve a cooperative routine schedule of control operations somewhat on the following lines:
(i) After harvesting, the stalks of millet plants should be used up as soon as possible and in any case before the end of the winter season. The stalks harbour various stages of borer pests.
(ii) For the same reason, stubble should be dug out and destroyed. It is advisable to plough the fields just before the beginning of summer to uproot the stubble, which should be collected and used as fuel or burnt, and to disturb and expose the egg-masses of grasshopper pests and pupae of caterpillar pests to the sun and to predators. The bunds of the field and the ground around trees and fences, which specially harbour these pest stages, should be scrapped, ploughed or hoed. Grasses on the bunds should be used up or destroyed along with the pest stages.
(iii) For seed, a pest-resistant variety should be selected.
(iv) Sowing should be at a high seed rate so as to enable uprooting of pest-infested plants without decreasing the plant population below the optimum level.
(v) The crop should be inspected from the earliest stages for the appearance of- (a) dead-hearts due to borers of any kind, (b) moths emerging from pupae which have been under diapause and so have escaped operation (ii), (c) egg-masses laid by these pests, and (d) other external feeders. In the same round of operations the dead-hearts, the egg-masses and the sluggish moths should be collected and destroyed.
(vi) Chemical control operations should be carried out according to the nature and intensity of the pest. In the case of sucking insects a strong contact insecticide should be used; but if there is also an infestation of leaf-eaters, such as caterpillars and grasshoppers, then a more persistent insecticide should be used. Grasshoppers and cutworms can also be controlled by poison baiting.
(vii) The precautionary operation (i) to (v), if carried out properly on a large enough scale and on a co-operative basis should prevent the borer population being built up beyond tolerable limits. If, however, for some reason these precautionary measures are not practicable and intensive chemical operations are yet feasible, a suitable persistent insecticide should be applied to poison the newly hatched larvae of the borers during the few minutes when they are crawling on the surface of the plant before boring into its tissue.
For this purpose insecticide sprays or granules should be used just before the peak period of hatching determined by means of a biometer for the species which it is most necessary to control.
3. Sugarcane Pests:
The main characteristics of some of the serious pests to be considered in devising measures for their control are as follows:
(i) The top borer and Pyrilla lay eggs in large prominent masses, which can be easily located from a distance against the green background of the leaf-surface. This makes these pests quite amenable to mechanical control, i.e., collection and destruction of egg-masses. This is quite a feasible proposition under Indian conditions where batches of boys and girls can easily clean up large areas. Supervision by visual survey is also easy.
(ii) All 3 types of borers, viz., top-borer, stem-borer, and the root- borer, cause characteristic dead-hearts in the early season of the crop. Collection of such affected shoots along with the associated insects can be combined with the campaign mentioned under (i) above. The top borer attack can be easily detected in all stages of the crop.
(iii) Both Pyrilla and borer pests are often heavily parasitized in their different stages.
(iv) All types of borers lay eggs on plant surface, and their larvae crawl on the surface for a few minutes before getting into the tissue out of reach of insecticidal chemicals.
The different operations of the control schedule have to be precisely timed, as follows:
(a) Sugarcane planters should be made fully conscious of the fact that sugarcane is a graminaceous crop and that wild graminaceous plants growing in the vicinity and on the bunds can serve as alternate hosts for sugarcane pests. Hence, keeping the area clean of such plants as well as stubble of the previous season’s crop is a prerequisite for successful sugarcane cultivation. This is a precautionary measure which should not wait for the appearance of any pest or even for sowing of the crop.
(b) For seed, a pest-resistant variety should be selected, if available.
(c) The next precautionary measure to be adopted at the time of sowing is against termites and root borers, especially in areas where they cause troubles year after year. This measure consists of chemical treatment of the furrows in which the sets are to be sown, so that termites and young larvae of root-borer trying to approach sugarcane plants may get a lethal dose of insecticide.
(d) If the termite attack is becoming serious despite the above-mentioned precaution or because that precaution has not been taken, then charging the irrigation water with a repellent or a suitable insecticide has to be resorted to. This operation need not form a regular item of the control schedule.
(e) Full preparation and all arrangements should be made to organize campaigns on as large a scale as possible to nip in the bud the attack of borers and of Pyrilla as soon as egg-masses and dead-hearts begin to appear in the young crop. These should be collected and destroyed.
This step is the most crucial operation for success against sugarcane pests. Depending on the experience of the past years, one or the other pest species may be expected to make its appearance every year. Hence this operation should form one of the routine items of sugarcane cultivation and should be continued as long as necessary.
(f) Egg-masses of both Pyrilla and top borer are at times heavily parasitized. Therefore, arrangements should be made to conserve the parasites by keeping the egg-masses in wire gauze cages from which only the minute parasites can fly out but the Pyrilla nymphs and borer larvae arc either trapped in the cage or made to fall in a pail of kerosinized water.
(g) If the foregoing operation has been carried out effectively and on a sufficiently large scale so that its beneficial effect is not upset by migration of insect pests from neighbouring areas, then the problem should be significantly reduced in magnitude in the main part of the crop season. All the same, the farmer has to keep vigil and adopt control measures as and when required.
It may be necessary to collect and destroy the egg-masses of top borer and Pyrilla and the tillers affected by borers in the main season also, but generally chemical control operations will have to be resorted to Pyrilla can be controlled by a number of contact insecticides, but it is advisable to time these operations with the help of biometer so that they coincide with the peak hatching of borer larvae and before they bore into the cane.
To this end it would be well to use a contact insecticide of suitable duration of persistence; thereafter effort should be made to integrate this chemical control with biological control. In case mite infestation also appears, it would be desirable to use a chemical which controls both insects and mites instead of a specific chemical like sulphur which kills only the mites.
4. Pests of Paddy:
There are 3 major characteristics which should be kept in view in evolving a rational integrated control schedule. The first 2 are rather disadvantageous. First, as many as 3 crops a year are taken from the same field, and this unbroken continuity creates ideal conditions for the development of paddy pests. Secondly, there is continuity in space also because the land used for paddy is in many places not fit for other crops. In other words, paddy cultivation is continuous both in time and space, and this is very conducive to pest multiplication.
The third characteristic is very helpful. Often the paddy seed is first sown in nurseries and later the seedlings are transplanted. Since the acreage of this nursery stage is much smaller than that of the transplanted crop, the control measures are bound to be less costly and more effective in the nursery stage.
Further, at the transplanting time practically each seedling is individually handled, and with a little extra care it should be possible to eliminate the affected seedlings, clip the prominent egg-masses of certain pests, and treat the seedlings against certain other pests.
Lastly, a number of paddy pests are multivoltine and consequently the flying adult stage comes again and again in the same season. Univoltine species such as grasshoppers are capable of migration. It is, therefore, necessary that farmers are made fully aware of the fact that control measures carried out in a few fields will not yield the desired results unless all the farmers pool their resources and carry out the control operations on co-operative basis.
(a) Regular Items of the Schedule:
The following items should be included in the regular agricultural operations for successfully growing the paddy crop:
(i) As a number of rice pests, e.g., Spodoptera, gall fly, gundhy bug, Hispa, breed on grasses during the off-season, it should be a definite policy of rice growers to keep their area free from wild grasses.
(ii) As preparatory operations for rice cultivation, proper ploughing and destruction of stubble are necessary to destroy pupae and caterpillars of stem-borers, pupae of swarming caterpillars, and eggs of grasshoppers. In areas where grasshopper trouble is likely to be serious the scrapping of the bunds should also be attended to as a routine.
(iii) For seed, a pest-resistant variety should be selected, if available.
(iv) Light-traps should be set up right from the beginning not only to attract and destroy the moths but also as indicators of the activity of these pests in the field so that timely control operations can be carried out. It should, however, be borne in mind that sometimes the area in the immediate vicinity of light-traps gets more severe infestation because the moths that evade the trap can cause severe damage round about the light- trap. To prevent this, such areas should be specially treated with suitable persistent contact insecticides.
(v) Right from the early stage, the fields should be inspected regularly for the appearance of prominent egg-masses of stem borer and swarming caterpillar, and as soon as they appear they should be collected and destroyed. It should be noted that destruction of egg-masses is the surest way of controlling these pests, particularly the stem-borer, the later stages of which are much more difficult to destroy.
Care should be taken to observe, collect and destroy the characteristic dead-hearts caused by stem borer, silver shoot caused by the gall fly, and the tunnels in leaves containing immature stages of rice Hispa. Thus, vigilant farmers working in co-operation can confidently hope to nip in the bud the infestation of these 5 important paddy pests.
(vi) The operations mentioned under (v) should also be carried out when the seedlings are collected together in convenient bundles before transplanting the seedlings. Also at this stage the seedlings can be thoroughly treated with a suitable persistent insecticidal dip for which Parathion emulsion for systemic action against stem-borer larvae has been suggested by some.
(vii) The swarming caterpillar and cutworms can also be checked from entering the field from outside by means of a trench around the field.
(b) Control Operations to be Carried Out as and when Necessary:
(i) The crop and bunds should be treated with a suitable insecticide (5% BHC dust) whenever any of the surface feeders like gundhy bug and grasshoppers increase in numbers beyond tolerable limits.
(ii) Cutworms and swarming caterpillar can also be destroyed by flooding the field. A little oil (6 litres/hectare) or better a suitable insecticidal solution may be mixed with the flood water. Even nymphs of gundhy bugs can be made to fall in this oily water by moving a bamboo lightly across the plants.
5. Pests of Pulse Crops:
Considering the different important pests of pulse crops it should be clear that farmers should keep themselves prepared for the following 4-pronged attack against insect pests:
(i) A thin top layer of the soil should be treated with a strong persistent soil insecticide, particularly in areas subject to cutworm attack year after year. This can be done just before or after sowing, or the insecticidal dust can be raked in eve at a later stage depending on the time when cutworm attack starts in the region. This treatment will not only poison the cutworms hiding in the soil during the day but also take care of certain other pests, such as gram pod borer and gujhia weevil, which are somewhat alike in this respect.
(ii) For seed, a pest-resistant variety should be selected, if available.
(iii) As far as possible, as soon as the pest attack starts, a common campaign may be organized for collection and destruction of such pests and infested material as can be easily spotted, e.g. leaves attacked with leaf miners, or even pea stem borers, twisted and deformed pods attacked by the red gram pod borer, and cutworms detectable by freshly cut shoots dragged into the soil.
(iv) If the trouble persists in spite of the first 3 operations or because they have not been carried out, then the crop should be treated with a penetrating formulation of a good persistent insecticide which acts both as a contact insecticide and as a stomach poison. This treatment should take care of almost all the pests.
It kills gram pod borers mainly by contact effect while they are eating the developing gram in the pod from outside, poisons cutworms when they feed on treated shoots, has a lethal effect on adults laying eggs in the crops, reaches leaf miners within their galleries, and controls pests like aphids. The main snag in this approach is that since leafy parts of leguminous crops are often used for both human and animal consumption, extreme care is needed to avoid residue toxicity hazards.
6. The Locust Problem:
In recent years the main emphasis has been on pesticides in dealing with problems of locust control. Studies at the IARI have resulted in 2 new approaches for dealing with the locust problem. One of these can be profitably and immediately integrated with the pesticide, and there is a prima facie case for integrating the other one also after some further studies. The first is the use of deterrent-cum- repellent material present in the kernel of neem (Azadirachta indica) seed. A 0.1% suspension of this seed kernel in water when sprayed keeps the crop safe from locust for 2 to 3 weeks.
Therefore, in a locust invasion the farmers can ensure the safety of their crops with the neem kernel while the government agencies take the usual action of wiping out the locust swarms by insecticidal chemicals. Theoretical studies have shown that locust outbreak is delimited both in time and space by biotic agencies, and we hope that after some further studies it may become possible to use these biotic agencies to nip the locust outbreak in the bud.
Thus, we can use the integrated approach- (a) for dealing with locust population explosion in the outbreak areas with the help of the enemies of locust, (b) if the locust outbreak does occur to ensure the safety of the crops with deterrent sprays of neem seed suspension, and (c) to wipe out the locust swarm by insecticidal chemicals.
7. The Phadka Grasshopper:
Chemical control of grasshoppers like phadka is well known and well established, but the chemicals are generally applied to the infested crop.
Field ecological studies at the IARI have shown that:
(a) The eggs of this species which have been hibernating during winter and summer hatch about 10 days after the first good monsoon showers,
(b) These eggs are found in appreciable numbers not in cultivated fields but on the sides of bunds and in uncultivated areas near about the cultivated fields, and
(c) The young ones of the grasshopper after hatching remain confined to the bunds and uncultivated areas for about 14 days before moving into cultivated fields.
Hence, we have made the recommendation that, instead of waiting for the crop to be infested and then treating it, insecticidal application should be made as soon as the first monsoon rainfall takes place not only on cultivated fields but, also on the bunds and the uncultivated areas in the neighbourhood.
In this way the pest can be controlled with much lees expenditure and before it inflicts any damage. This is a good example of integrating ecological and chemical approaches for the control of a pest, like phadka. It is likely that similar integration is possible in other species too.
8. Storage Pests of Grain:
Another example illustrating rather spectacular success of the integrated approach is the Pusa bin for grain storage. The efficiency of this structure in keeping stored grain safe from pest infestation and deterioration is based on the integration of measures against different pests.
The study at the IARI of the requirements, habits and idiosyncrasies of different pests has shown that:
(a) Certain species, such as the weevil Sitophilus oryzae, are very susceptible to reduction in moisture content of the grain, so much so that it has become a common belief that if the grain is kept reasonably dry its safety from pest infestation can be ensured — a belief embarrassingly belied by pests such as the khapra beetle which can breed in grain with very low moisture content;
(b) Certain species, e.g., khapra beetle, are very susceptible to reduction of oxygen tension and there is also a strong belief that the safety of the grain can be ensured by storing it under air-tight conditions — another belief belied by species like the grain weevil which can breed under very low oxygen tension;
(c) A number of complications arise from moisture migration within the grain mass, especially if the container is made of a good conductor of heat — so, for making a storage structure a poor conductor of heat should be selected. Owing to these different requirements of different pests, recommendations for safe storage of grain have been quite confusing and contradictory.
In devising the Pusa bin all these considerations were taken care of. Its walls are made of mud or unburnt brick, and there is embedded in them a film of polythene which is reasonably impervious to water vapour and gases. When grain like wheat is dried to less than about 10% moisture content and stored in the Pusa bin, it is unable to absorb atmospheric moisture during the monsoon, and the oxygen tension inside is reduced by respiration of grain and any insects present.
So neither pests like khapra nor those like grain weevil can breed in this bin. Internal moisture migration is reduced to the minimum by the wall being made of mud or unburnt brick. Thus, Pusa bin represents an excellent example of successful integrated approach in pest control.
9. The Giant African Snail:
Concern about this pest has been fast increasing. Studies at the IARI have provided some excellent leads to developing an integrated chemical-cum-biological control of this serious non-insect pest. The difficulty in integration of chemical and biological controls of insect pests has been that generally the pest as well as its enemy is an insect and by and large it has been quite a difficult job to find such selective chemicals that will kill the pest but not its enemy.
In the case of the giant African snail also the predators mostly talked about and recommended are 2 species of predatory snails, and the chemical and biological approaches to the control of this pest have been conflicting. But recently the effectiveness of 2 arthropod enemies of this molluscan pest has been spectacularly demonstrated. These arthropods, viz. several species of hermit crab of the genus Ceoenobita and a species of the millipede Orthomorpha, are not affected by the common molluscicide, the metaldehyde.
Hence, the path seems to have been well cleared for an effective and useful integration of chemical and biological controls in the case of this pest. This also opens up a vista for putting greater emphasis than before on exploring the use of biological control agents belonging to distant zoological groups. There seem to be enough reasons to believe that non-insect enemies of insect pests are much more effective under natural conditions than hitherto supposed.
Use of Stomach Poisons in Integrated Control:
Before the advent of DDT, insecticides used to be rather sharply divided into stomach poisons, contact poisons, and fumigants. This classification was obliterated with the discovery of a number of modern insecticides, many of which act both as contact poison and as stomach poison and some also as fumigant. At first this combination of these 2 or more types of action was quite welcome because it improved the effectiveness of the insecticide considerably.
Later on the same combination of actions began to prove irksome because the contact action was found to kill the parasite adults. Hence, efforts were made to avoid the contact action of DDT with some sort of coating on its particles during formulation.
At this stage it occurred to us that instead of trying to coat DDT particles it might be useful to try the older stomach poisons like basic lead arsenate which have no contact action. Consequently, some work has been in progress with promising results for integrating biological control with chemical control of the coconut leaf caterpillar with lead arsenate.