**Abstract**

The edible oil of *Elaeis guineensis* Jacq., oil palm, is crucial in filling the demand gap and meet the growing need for edible oil worldwide. Although all precautions have been taken to minimize the introduction of pest populations along with seed sprouts from importing countries, some pests are still found to invade crops and cause production losses. Most of these populations have been found to come from other Arecaceae palms such as coconut, palmyrah and betel nut that may be commonly found around oil palm fields. It has been estimated that the above pests reduced oil palm yield by 20–30%, persisted for several years after attack, depending on cultivation methods, and returned to previous yield levels within a few years of attack. The minor pests of coconut, palmyrah, and maize, psychid and slug caterpillar were discovered to be very invasive on oil palm, resulting in output losses of up to 50%. The presence of favorable conditions such as low temperature and high humidity within oil palm plantations may possibly be the reason for migration. The production losses caused by these migratory pests affect the sustainability of the produce and thus agriculture, so it is important to apply the good management practices.

**Keywords:** oil palm, pollinating weevil, rhinoceros beetle, caterpillars, integrated pest management

### **1. Introduction**

Oil palm (*Elaeis guineensis* Jacq.), is a rich source of edible oil and is a perennial crop cultivated in large areas to beat the edible oil shortage. Upon cultivation, a farmer can draw the yield for 25–30 years, stabilising his economy over its other oil seed crops. Oil palm is cultivated in tropical areas of Asia, Africa, and South America. The productivity of the crop is challenged by the availability of water and nutrient stress, abiotic stress like drought, biotic stresses like pests and diseases, etc. As oil palm requires nearly 300 litres of water per day, irrigation should be continuous at regular intervals, therefore, the micro-climate so formed with high humidity and cold makes pleasant conditions for the event of pests and diseases. The age of the palms will dictate the incidence of pests. The pest infestation from foreign sources may be due to the strict quarantine measures being followed at various ports important for seed sprouts. The sole chance for the pest outbreak is that the migration of pests from other crops grown in the nearby locations of the oil palm plantations is because of the availability of food material continuously. The perennial nature of palms and the monocropping system as practiced in many locations provide ample opportunities for the buildup of the pest. The spread of the problems is slow in new areas. Of the insect pests, the most important is the rhinoceros beetle and defoliators, causing heavy yield losses. The insect pests which are reported as minor and secondary pests on other crops got the pest status as the damage was noticed in both nursery and field palms of oil palm. Oil palm, as it is a perennial crop, is gorgeous to several pests such as the defoliators (leaf-eating caterpillars) such as bagworms, nettle, and hairy caterpillars feed on the palm fonds, causing damage by defoliating the oil palm tree thereby resulting in yield loss because of the reduction of photosynthetic activity and fruit production. High population levels can result in the whole skeletonization and death of the fronds. Damage of 50% will cause a yield decline of around 43% over the following 2 years. Even lower damage like 10–13% also can cause an analogous loss [1]. Natural enemies including predatory or parasitic insects and diseases caused by viruses and fungi, caterpillars are effectively kept below the economic damage threshold under normal conditions. Heavy pest attack is usually the results of a breakdown within the balance of nature. Generalist predators might not totally feed on the oil palm caterpillars and instead take advantage of other insects available within the ecosystem. In search of hosts, dust under dry conditions interferes with predators and parasites. The parasitoids number may be reduced which are commonly attacked by hyperparasitoids. Outbreaks of the caterpillars are sporadic and localised, thereby; parasites and predators do not fully control the caterpillar populations' altogether years and locations. A monitoring and closedcircuit television for oil palm is in practice for several years. By monitoring a pestilence, the world within which damage is happening is delineated [2]. Chemical intervention is merely used when populations reach threatening levels by injecting the trunk with a systemic insecticide that is translocated within the sap and carried into the leaf tissue. This implies that only the leaf-feeding caterpillars are killed, but not their natural enemies. Overall insecticide use is low, with no quite 5% of the whole area of oil palms receiving application in anyone year. Insecticide application averages about once in an exceedingly planting generation (around 25 years). In many instances, smallholders do not regularly manage the caterpillar populations with trunk injections and high uncontrolled outbreaks occur [3]. Chemical control typically takes place too late to prevent large production losses due to complex application techniques, subpar monitoring mechanisms, and therefore the challenging environment. Chemical application is also expensive and bad for the environment. There's enormous potential to boost the present pest management practices, and a number of other biological control agents may well be utilised in integrated pest management (IPM) systems [4]. Agronomic practices directed toward developing biodiversity within the oil palm cropping system, and improved pest monitoring and surveying could even be components of this IPM. The practice of Integrated Pest Management (IPM) against several pests and diseases (P&D) of oil palm includes holistic approaches designed for a P&D control program to cut back pest populations below the brink level with minimal environmental impact [5].

### **2. Pollinating Weevil,** *Elaedobius kamerunicus*

2The pollinating weevil, *Elaedobius kamerunicus* (Coleoptera: Curculionidae) has been known to be the foremost efficient insect pollinator of oil palm and has successfully

#### *Integrated Pest Management (IPM) in Oil Palm,* Elaeis guineensis *Jacq. DOI: http://dx.doi.org/10.5772/intechopen.108580*

improved the pollination and increased the yield. Its introduction has greatly reduced the requirement for assisted pollination. *Elaeidobius kamerunicus* was introduced into Malaysia during the late 1980s to spice up the assembly of oil palm fruit bunches. Almost 40 years since the introduction of *E. kamerunicus*, significant improvements are witnessed within the increase of yield of oil palm. Nevertheless, the present concern within the oil palm sector is regarding the decreasing of fruit sets that will be plugged by *E. kamerunicus* [6]. Through their subsequent visits to the female inflorescences, when the stigmas are receptive, the female flower emits short pulses of an analogous but sharper and more penetrating odour that attracts Elaeidobius species apart from the male flowers and the pollen grains. The weevils chew the anther filaments of opened male flowers, during anthesis when a robust aniseed-like scent is emitted; they crawl or move about on the spikelets [7]. When the weevils crawl over the male inflorescences an outsized number of pollen grains are dispersed which are carried by wind [8]. The weevils enter the female inflorescence but quickly leave after finding no food there, returning to the male flowers. When *Elaeidobius* species crawl around the female inflorescence, pollen is discharged, which causes them to become covered in it. Over 5000 beetles are thought to visit each female inflorescence during receptivity, and each one can carry up to 600 pollen grains. The development of the larvae occurs on tissue that has served its role and has no utility for the palm because oviposition occurs after anthesis, hence *Elaeidobius* species do not significantly harm the palm [9]. The most ideal insect for introduction into Malaysia and other regions with poor oil palm pollination is *E. kamerunicus*. *E. kamerunicus*, one of the many species of this genus investigated in Cameroon, was the most prevalent in the country's coastal regions throughout both the wet and dry seasons, transported more pollen than other species, and had a respectable ability to search (**Figure 1**) [10].

The weevils are quite useful, and man has introduced them to palm farms to use them for pollinating those trees. In regions where palms and weevils were not native, hand pollination was used, which was exceedingly expensive for the growers. The inadequate pollination has been a significant issue in these nations. In addition to the slow pace of fruit establishment, inadequate pollination can occasionally cause bunch failure [11].

The Tenera palm variety demonstrated larger yield improvement as a result of *E. kamerunicus* introduction to Malaysia than the Dura variety. Larger, heavier, and more compact bunches were assembled as a result of weevil pollination, which also increased the oil to bunch ratio from under 19 to 23–25%, especially on trees that were 4–10 years old. *Thrips hawaiiensis*, an older, less effective pollinator, was not ostensibly replaced by *E. kamerunicus*. In terms of pollinating oil palms, the weevil population is crucial. Weevil populations have been found to be reduced by a number of

#### **Figure 1.**

*Pollinating Weevil,* Elaeidobius kamerunicus. *(A) Female inflorescence, (B) male inflorescence, (C) pollinating Weevil,* Elaeidobius kamerunicus*, (D) pollinating weevils on male inflorescence, (E) weevil at a spiklet of oil palm male flower.*

factors, including climate, pesticides, interactions with other insects in the area, and male inflorescence [12]. The pollinator force of the weevil was sustained at a spread between 3095.2 and 19126.1 weevils per ha. The mean of weevils per spikelet shows that the range of weevils was between 13.51 and 54.06 per spikelet. There was no correlation between rainfall and population density of EK. However, a correlation was obtained between weevil density and therefore the number of anthesis female inflorescence of oil palm (r = 0.938, p < 0.05). Results of the t-test show that the 6-yearold oil palm stands had a significantly different population density than that of an 8-year-old oil palm stand. The data of this study should be useful as baseline data to analyse why there's such a large range of weevils per ha or spikelet [13].

The natural enemies of the pollinating weevil, *E. kamerunicus* are the parasitoid nematodes *Aphelenchoides bicaudatus* and *Cylindrocorpus inevectus* attacking during pupal stage [14]. The pupae were found to be severely infested with *A. bicaudatus* then were treated until nematode-free before being released [15]. The nematode *Elaeolenchus parthenonema* is harmful to the weevil [16], but the *Bacillus thuringiensis* products Lepcon-1, Bafog-1 (S), and Ecobac-1 (EC) are proven innocuous to the weevil [17].

In order to search out the impact of bio-agents together with chemical insecticides on the expansion and survival of the pollinating weevils of oil palm, the study was distributed. Newly emerging inflorescences in 24 palms were selected and tagged for applying pesticides and bio-agents. Conventional insecticides quinalphos (0.05%), monocrotophos (0.072%), lambda cyahalothrin (0.02%), and microbial agents namely *Metarhizium anisopliae* (6.4 <sup>10</sup><sup>5</sup> spores/ml) and *Beauveria bassiana* (3.5 10<sup>5</sup> spores/ml) at normal concentrations were tested as treatments by applying on the inflorescence as a liquid spray. The concentrations of these selected chemical insecticides were proved lethal to the target pests of oil palm. The population count of the weevils (egg to adult stages) was recorded employing a sampling technique. Daily weather data was also recorded during the observation period to correlate the population fluctuation if any with the abiotic factors. Observations recorded on the weevil population showed significant results. Analysis of the obtained data was met out using the chi-square test. The chi-square test results clearly indicate that the difference within the weevil population in untreated and insecticide-treated palms is very significant and contrarywise in untreated and microbial agents viz. *Metarhizium anisopliae* and *Beauveria bassiana*. The chemical pesticide quinalphos had a major impact in reducing the weevil population whereas the microbial agents did not cause a major reduction. However, *Metarhizium anisopliae*, which may be a good microbial agent against many coleopteran pests, was observed to cause less impact on the pollinating weevils which are coleopterans. This means that the microbial agents are safer for pollinating weevils compared to the standard pesticide and hence, can safely be included within the oil palm pest management practices [18].

### **3. Pests of oil palm**

Prior to field planting, oil palm is usually passed through single or double stage nursery system. Oil palm seedlings are maintained for 12–14 months in nursery and culled and planted within the field. Preventive measures such as insecticide application at frequent intervals protect the nurseries and are almost free from pest incidence. However, when within the neglected conditions, few pests are observed causing damage to the seedlings. A number of them are listed below (**Tables 1** and **2**). *Integrated Pest Management (IPM) in Oil Palm,* Elaeis guineensis *Jacq. DOI: http://dx.doi.org/10.5772/intechopen.108580*


#### **Table 1.**

*Pests of oil palm nursery.*


#### **Table 2.**

*Pests of oil palm plantations.*

### **4. Insect pests**

Insect pests are the most limiting factor for crop production in tropical Asia, among which Lepidopteran pests cause a major amount of injury. Oil yielding and vegetables are the foremost profitable crops and farmers everywhere feel the requirement to shield such high value crops from any style of damage caused by insect pests.
