Botanical insecticides for control of storage insect pests

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by Adelaida C. Quiniones

Chemical control of stored product insect pests has been the most efficient and effective means of protection of stored produce. However, with the increasing cost of inorganic chemicals and their known hazards to the environment an integrated means of control has been widely adopted. The search for botanical insecticides could supplement the expensive petroleum based chemicals. Botanical preparations have long been used for protection of stored produce by small scale farmers in oriental countries such as India where the neem tree has been used extensively. The success of these small farmers serve as the impetus for exploring the utilization of indigenous resources for small scale product protection and for possible industrial scale product protection. Several species of plants are now being screened for source of active ingredients against stored product insect pests (Table 1) commonly used are made of polyethylene or polyvinyl chloride film having a thickness of 0.1 mm (.004 inch) weighing 100 grams per square meter.

Table 1 List of plants studied for insecticidal activity on stored product insects

Table 1 List of plants studied for insecticidal activity on stored product insects - continue

After the completion of the fumigation it is necessary to collect the tablet residues or expended sachets. These materials can be disposed properly by swamping it in a soapy water until bubbling ceases (in open air) and then buried at least 30 cm below the soil surface. Under no circumstances should large quantities of expended residues be placed in a heap prior to being buried, because of the possible danger of ignition.

Formulation Available and dosage Rate

Phosphine (PH3) is commonly available in the form of tablets, pellets and sachets containing aluminum phosphide.

The following equivalents, based on commercial formulations containing aluminum phosphide as the phosphine source are given to simplify dosage calculations.

1 g phosphine = 1 tablet = 5 pellets = 1/11 sachet

Under Philippine conditions, the following rates of phosphine application are recommended.
15-45 tablets* 2-5 tablets per 15-20 tablets
per 100 cu. ft metric ton per 1000 cu ft
or or or
3-5 sachets ** 1 sachet per 2-3 sachet per
per 1000 cu ft 1-3 metric ton 1000 cu. ft.

* Recommended exposure time 3-5 day when tablet is used
** Recommended exposure time 3-6 days when sachet is used

Identification of Active Principles

Neem leaves and fruits

The constituents of the neem leaf powder were obtained by Tirimanna (1985) using two-dimensional thin layer chromatography. As a result of a strong saponification procedure, it is only the very stable compounds, which were observed on the chromatoplate. The compounds violaxanthin, butoin, 3carotene, zeaxanthin , ant heroxanth in, cryptoxanth in and neoxanthen were identified.

Seven epoxy compounds have also been isolated from fruits of Melia azedarach (Kraws et al., 1981). These compounds were rather stable and maybe of significance to scientists in search of a stable compound having insecticidal properties. This is relevant in view of the fact the neem leaf loses insect repellent property with age.

One sterol and 3 stable ketones were found, together with six very stable phenolic compounds. The occurrence of phenolic compounds in the neem plant is already well documented (Sengupta et al., 1960). Phenolic constituents are also recorded as antihelminthic factors (Taniguchi, 1960). The identification of quercetin in the neem leaf accounts for its antibacterial and antifungal properties and hence the curative properties of leaves in cases of sores and scabies (Basak and Chakraborty, 1968).

T. diversifolia (Wild Sunflower)

The active fraction D from this plant contains alpha - lactone with a hydroxyl group attached either to the lactone ring or to the alkyl substituent (Caring and Morallo-Rejesus, 1982). The unsaturation may be present in the ring itself or alpha to the carbon as indicated by the strong IR absorption at 1670 cm' and by the failure of the sample to decolorize bromine in carbon tetrachloride.

Studies of the characterization and identification of active insecticidal principles of the other plants listed in Table 1 are being continued at the University of the Philippines at Los Banos.

Insecticidal Activity

Black pepper (Piper nigrum) and red pepper (Capsium frutescens)

The insecticidal activity of these two species of plants against eight species of stored product insect pests listed in Table 1 was determined by Javier and Morallo-Rejesus (1968). They found the crude and semi-purified extracts of black pepper topically applied on the insects toxic. The admixture treatment of grains showed the ground black pepper (GBP) more toxic than the semi-purified and crude extract as residual contact and stomach poisons against the corn weevil (Javier and MoralloRejesus, 1982). It was also found resisually toxic for 2 months on the saw-toothed grain beetle, lesser grain borer and corn weevil.

The ground red pepper (GRP) and GBP were residually toxic to the bean weevils for 2 and 6 months, respectively.

The effectiveness of red pepper on bag rice under warehouse condition (natural infestation) at average temperature of 25.70-27.90°C was further evaluated. The major stored product insect pests were corn weevil and red flour beetle. Three methods of applications were done: mixing powdered and whole fruit of RP with rice grain or in sachet with doses of 1200 ppm or 1800 ppm and spraying the bag with either 5, 10 or 20% of the extract. All methods of application and dose levels effectively protected the bagged rice from infestation for no longer than two months storage.

Neem (azadirachta indica A. Juss)

The repellent and antifeedant effect of seed powder and oil of neem on five species of stored product pests was investigated by Akou-Edi (1985). Laboratory trials in Togo using red corn treated with neem oil at concentrations of 1, 2, 4 & 8 ml/kg or with seed powder at 20, 40, 80 g/kg infested with confused flour beetles and corn weevils showed significant difference between the treated and untreated samples (Tables 2 & 3). As a rule, the effect of neem oil and need powder increased with higher concentrations but difference between concentrations was not significant on both test insects.

Atudy on the effect of neem seed kernel and leaf powder on the development of Callosobruchus maculatus (F.) on 3 bean seed species treated at the rate of 0.5, 0.1 and 2.0 parts per 100 parts of seeds showed reduced oviposition capacity, lengthened larval and pupal period, reduced percent adult emergence, longevity and growth index (Quiniones and Thawatsin, 1987). Among mungbean, bush bean and cowpea bean, the latter was found to be the most preferred food for the development because it supported normal development and enhanced population growth. Tables 4 and 5 showed reduced oviposition and percent egg hatched as an effect of neem leaf and seed kernel powder.

Studies on the effect on neem kernel extract (NSKE) on metamorphosis of Ephestia kuehniella (mill moth) and which established a concentration effect curve were undertaken by Maurer (1985). A methanolic extract of sundried neem seeds was applied at a concentration of 4 ppm on 4-5th instar larva. The stage of development that a larva had reached was determined by measuring the size of the head capsule. The average size of the head capsule at each larval stage was determined in a preliminary experiment on untreated larva under the same conditions (30°C, 82-86% RH). A 4 ppm concentration and less resulted in the insertion of an additional larval instar between the fourth and fifth larval stages. Hence, metamorphosis was prolonged after treatment with neem seed kernel extract. The mortality induced by concentrations of 4 ppm NSKE or higher, occurred first during the molting phase between different larval stages. No feeding deterency was observed.

Table 2. Repellant effect of neem oil on adults of two stored product insect species
INSECT SPECTES NEEM OIL CONCENTRATION
(ml/kg)

AVG. NUMBER ( + SD) OF INSECTS COUNTED AFTER 7 DAYS
    CONTROL TREATED P
Tribolium 1 17.25 ± 5.70 7.74 ± 2.12 0.01
confusum 2 18.25 ± 4.56 6.75 ± 2.82 0.0001
  4 17.75 ± 4.33 7.25 ± 2.32 0.0001
  8 23.37 ± 2.53 2.63 ± 1.85 0.0001
Sitophilus 1 15.37 ± 4.60 9.63 ± 1.92 0.01
zeamais 2 16.37 ± 3.20 8.63 ± 3.34 0.01
  4 15.25 ± 5.80 9.75 ± 2.57 0.05
  8 17.38 ± 3.42 7.62 ± 3.54 0.01

Table 3. Repellant effect of neem seed powder on two stored product insect species
INSECT SPECTES NEEM SEED POWDER
CONCENTRATION
(ml/kg)

AVG. NUMBER (I.S.D.) OF INSECTS
COUNTED AFTER 7 DAYS
    CONTROL TREATED P
T. confusum 20 18.50 ± 3.89 6.50 ± 2.78 0.0001
  40 21.87 ± 4.79 3.13 ± 3.09 0.0001
  80 21.87 ± 6.11 2.75 ± 2.55 0.0001
Sitophilus 20 14.87 ± 4.94 10.13 ± 5.67 n.s.
zeamais 40 16.62 ± 2.62 8.38 ± 3.38 0.01
  80 17.62 ± 7.23 7.38 ± 4.53 0.01

Table 4. Mean eggs of C. maculatus on three varieties of bean seeds treated with neem powder
TREATMENT

BEAN SEED VARIETY

 MEAN
  MUNGBEAN BUSH BEAN COWPEA  
Control 32.78 33.67 37.60 34.74a
Leaf powder, 0.5% 21.17 21.57 24.40 22.38b
Leaf powder, 1.0% 15.67 16.13 18.27 16.69c
Leaf powder, 2.0% 14.97 15.30 17.37 15.88c
Seed kernel powder, 0.5% 15.63 16.03 18.18 16.61c
Seed kernel powder, 1.0% 7.37 7.63 8.33 7.78d
Seed kernel powder, 2.0% 6.60 6.83 7.50 6 97d
SEED MEAN 16.31b 16.77b 18.80a  

Mean with the same letter superscript is not significantly different at 1% level (DMRT).

Table 4a. Analysis of variance on mean eggs of C. maculatus
SV Df SS MS Fc
Seed type(A) 2 74.24 37.12 43.087**
Neem application (B) 6 4772.06 795.34 923.203**
A x B 12 18.62 1.551 1.800ns
Error 42 36.185 0.8615  
TOTAL 62 4901.011    

**highly significant
nsnot significant
CV = 5.36%

Table 5. Percent hatching in three varieties of bean seeds treated with neem in days
TREATMENT

BEAN SEED VARIETY

 MEAN
  MUNGBEAN BUSH BEAN COWPEA  
Control 100.00 100.00 100.00 100.00a
Leaf powder, 0.5% 79.31 81.51 84.41 81.74b
Leaf powder, 1.0% 69.68 69.37 73.22 70.75c
Leaf powder, 2.0% 66.29 67.35 71.12 68.25c
Seed kernel powder, 0.5% 71.75 71.44 75.26 72.82c
Seed kernel powder, 1.0% 48.87 49.42 51.09 49 79d
Seed kernel powder, 2.0% 45.55 46.36 48.36 46.76d
SEED MEAN 68.78b 69.35b 71.92a  

Mean with the same letter superscript is not significantly different at 1% level (DMRT).

Table 5a. Analysis of variance on percent hatching
SV Df SS MS Fc
Seed type(A) 2 117.687 58.843 4.047*
Neem application (B) 6 17,980.10 2,996.68 206.138**
A x B 12 35.156 2.929 0.201ns
Error 42 610.562 14.537  
TOTAL 62 18,743.50    

*highly significant
CV = 5.44%
nsnot significant

According to Zehrer (1985) one of the traditional preservatives in Togo for protecting cowpea (Vigna unguiculata) from Callosobruchus maculatus infestation in storage is neem oil. Cowpea is Togo's most important pulse crop. It is already infested in the field by bruchids, especially C. maculatus, hence, signs of natural infestation can already be seen before storage. A study to compare efficiency of other traditional preservatives with that of neem oil was conducted. Cowpeas were treated with 0.5% V/V neem oil and peanut oil. Monthly observations on the insect and its damage on the stored produce were carried out. The untreated seeds retained only 60% of the original weight after 6 months and 30% of it after 10 months. The damage was caused by bruchids, mostly C. maculatus and T. confusum. On the other hand, neem oil protected the cowpeas throughout the storage period but their taste war slightly bitter. The use of neem oil would be feasible and appropriate for subsistence farmers since it is available throughout the country and no additional equipment is required for the production of neem oil.

Lageundi (Vitex negundo)

The protectant effect of whole and powdered leaves of lagundi on stored corn against corn weevil was evaluated by Bhuijah (1988) for a period of 6 months. Two level of dosages were used (1 & 5%) for both whole and powdered leaves on 5 kg of corn. After 30 days of storage, the protectant effect of 5% lagundi leaf powder and 1% whole leaf was lost as shown by increased infestation of all lagundi treated samples (Table 6). Only neem seed oil treated corn seeds remained protected and had low percent infestation throughout the study. Apparently the insecticidal constituent of the lagundi leaves were not stable, hence the repellent property were readily lost.

Vegetable Oils Controlling Storage Insect Pests The practice of adding a little vegetable oil to stored rice or legumes for protection against stored-insect pests is well known and well established in oriental countries like China, India and Indonesia. Recently the practice of protecting stored produce with oil has spread and has been adopted in Africa and South America. Recently Van Rheenen (1983) pointed out the applicability of this method of protecting storage grains to supplement safe chemical formulations.

The mode of action, appropriate dosages and duration of efficacy of oils have been investigated by various workers on storage insect pests (de Oca et al., 1978, Pandey, et al, 1976, Sangappa, 1977 and Singh et al., 1978). Differences between crude and purified oil have been studied and crude oil has been found to be a better protectant (Van Schoonhoven, 1978) while the triglyceride oleic acid combination was found the most effective (Schoonhoven and Hill (1981).)

The amount of oil needed for the control of most storage pests vary from 2 cc/kg seed (Magoya et al., 1982) to 15 cc/kg seed (Cruz and Cardona, 1981) depending on the level of infestation. Table 7 & 8 list the various vegetable oils controlling corresponding pests and pests of crop species in storage.

Table 6. Percent infestation of treated corn grains at different storage periods at room temperature
TREATMENTS

DAYS
  30 60 90 120 150 180
Control 2.04a 10.60a 22.91a 61.97a 80.27a 88.51a
1% lagundi leaf powder 1.67a 11.24a 18.26a 58.51a 78.11a 90.22a
5% lagundi leaf powder 0.90b 6.79a 14.42a 65.73a 77.51a 90.15a
1% lagundi whole gried leaf 1.52ab 5.48ab 15.69a 62.20a 74.79a 38.58a
5% lagundi whole dried leaf 2.55a 10.80a 19.05a 57.12a 70.73a 88.81a
Actellic 0.38bc 0.33b 0.17b 5.45b 5.24b 14.19b
Neem seed oil 0.25c 0.06b 0.00b 1.30b 14.14b 31.75b

Means in a column followed by a common letter are not significantly different at the 1 % level by DMRT.

Table 7. Vegetable oils controlling storage pests
OIL STORAGE PEST AUTHOR (S)
Castor C. chinensis Sangappa, 1977
Coconut C. maculatus Varma and Pandey, 1978
Cotton seed C. chinensis Sangappa, 1977
  C. maculatus Pandey, et al., 1981
  S. oryzae de Oca et al., 1978
  S. granarius Yun-Tai Qi and Burkholder, 1981
Groundnut S. cerealella de Oca et al., 1978
  C. maculatus IITA, 1976
  S. granarius Varma and Pandey, 1978
    Yun-Tai Qi and Burkholder, 1981
Maize C. maculatus Akelo-Tsegah, 1976
    Singh, et al., 1978
  A. obtectus Magoya et al., 1982
    van Rheenenet al., in press
  C. chinensis Cruz and Cardona, 1981
  S. granarius Yun-Tai Qi and Burkholder, 1981
  S. oryzae de Oca et al., 1978
  S. cerealella de Oca et al., 1978
Mustard C. chinensis Sangappa, 1977
  C. maculatus Varma and Pandey, 1978
Neem C. chinensis Pandey et al., 1976
    Sangappa, 1977
Palm S. oryzae de Oca et al., 1978
  S. cerealella de Oca et al., 1978
Rice C. maculatus Pandey et al., 1981
Sunflower C. chinensis Sangappa, 1977
  C. maculatus Pandey et al., 1981
Sesame C. maculatus Varma and Pandey, 1978
Soybean C. chinensis Cruz and Cardona, 1981
  S. granarius Yun-Tai Qi and Burkbolder, 1981
  S. oryzae de Oca et al., 1978
  S cerealella de Oca et al., 1978
Sunflower A obtectus Magoya et al., 1982
    van Rheenen et al., in press
  C. chinensis Sangppa, 1977
  C maculatus Varma and Pandey, 1978
Paraffin C. maculatus Calderon, 1979

Table 8. Storage pests controlled by vegetable oils
OIL STORAGE PEST AUTHOR (S)
Cajanus cajan Callosobruchus chinensis (L.) Sangappa, 1977
Cicer arietinum C. chinensis (L.) Pandey et al., 1976
  C. maculatus (F.) Calderon, 1979
Phaseolus vulgaris A. obtectus (Say) Magoya et al., 1982
    van Theenen et al., in press
  Zabrotes subfasciatus (Boh.) Hill and van Schooven, 1981
    van Schooven, 1978
Sorghum vu/gare Sitotroga cerealella (Ol.) de Oca et al., 1978
  S. oryzae (L.) de Oca et al., 1978
Triticum vu/gare S. cerealella de Oca et al., 1978
  S. granarius (1.) Yun-Tai Qi and Burkholder, 1981
Vigna radiate S. oryzae (L.) de Oca et al., 1978
  C. maculatus (F.) Pandey et al., 1981
    Varma and Pandey, 1978
Vigna unguiculata C. chinensis (L.) Cruz and Cardona, 1981
  C. maculatus (F.) Akelo-Tsegah, 1976
    IITA, 1976
    Singh et al., 1978
Zea mays S. cerealella (Ol.) de Oca et al., 1978
  S. oryzae (L.) de Oca et al 1978

 

Prospects of Insecticides from Plants

Acceptance of botanical insecticides for the control of storage insect pests by smal scale farmers is influenced by the following parameters: availability, safety, quality and cost. Application of the control methods is simple and does not need sophisticated equipment add to the desirability of the method. The search for more plant species with insecticidal properties is being pursued by scientists from all over the world. However, a systematic evaluation and identification of chemical and physical characteristics of active constituents should be accelerated. It is on this basis where knowledge on their efficacy in time, various levels of dosages and knowledge on toxicity on target pests will be valuable in field application.

REFERENCES

AKOU-EDI, E. 1985. Effects of neem seed powder and oil on Tribolium confusum and Sitophilus zeamais Natural Pesticides from the neem tree (Azadirachta indica A. Juss) and other tropical plants. Proceed. 2nd Int. Neem Conference, Ravischholzhaueen, Federal Republic of Germany 25-28 May, 1983. pp. 445-451.

BHUIYAH, I. MIAH. 1988. Use of Lagundi, Vitex negundo L. as shelled corn Protecant against corn weevil, Sitophilus zeamais Motsch. MS Thesis, CLSU, Munoz, Nueva Ecija. 90 pp. CALDERON, M.1979. Mixing chickpeas with paraffin oil to prevent Callosobruchus maculatus (F.) infestation. pp. 23-31. In Spec. Publ. Div. Sci. Publ. Bet Dagan, Israel No. 140.

CARINO, Ma. F.A. 1981. Insecticidal screening of crude extracts from nine Composite species and the isolation and characterization of the insecticidal fraction from Tethonic diversifolia (A. Gray) MS Thesis, Univ. of the Philippines at Los Banos, College, Laguns.

CARINO, F.A. and B. MORALLO-REJESUS. 1982. Isolation and characterization of the insecticidal fraction from Tithonia diversifolia (A. Gray) leaves. Ann. Trop. Agric. 4:1-11.

DE OCA. G.M., F. GARCIA and A. VAN SCHOONHOVEN. 1978 Effect of four vegetable oils on Sitophilus oryzae and Sitotroga cerealella in stored maize, sorghum and wheat. Rev. Colomb. Entom. 4:45-49.

JAVIER, P.A. 1981. Isolation and bioassay of insecticidal principles from red pepper (Capsicum annum L.) and black peper (Piper nigrum L.) against several insect species. MS Thesis, Univ. Philippines at Los Banos, College, Laguna. 50 pp.

JAVIER, P.A. and B. MORALLO-REJESUS. 1986. Insecticidal activity of black pepper (Piper nigrum L.) extracts. Phil. Ent. 6(5):517-525.

MAURER, G. 1985. Effect of a methanolic extract of neem seed kernels on the metamorphosis of Ephestia kuehniella. Pesticides from the neem tree (Azarlirachta indica A. Juss) and other tropical plants. Proceed. Second Int. Neem Conference Rauschholzhausen, Federal Republic of Germany 25-28 May, 1983. 365376.

MORALLO-REJESUS, B. 1987. Botanical pest control research in the Philippines. Philipp. Ent. 7(1):130.

 

Entomopathogens for the control of storage pests

by Adelaida C Quiniones

Several disease pathogens from insect pests of stored products have been studied. These diseases are caused by pathogenic bacteria, viruses, fungi, nematodes and protozoa and are frequently fatal to these pests especially during the larval stage. The young larvae are the most sensitive to the pathogens.

Insect pathogens can be isolated from infected insects and then cultured in the laboratory except for the viruses and protozoa which can only be cultured in living insects. Dust preparations or aqueous suspension of these pathogens can be applied to stored products in bulk in much the same way as conventional insecticides.

Another way of application of the pathogens is through food baiting with peromone or other attractants. The baited food may be placed close to the stored products. This method was effective for dissemination of pathogenic protozoa to kill beetles (Burkholder and Shapes, 1979) and also viral and bacterial pathogens of moths. Shapes et al., (1977) suggested, however, that to be very effective, the contaminated insects must leave the source of attractant and spread the pathogen within the pest population. This could be achieved by using a pheromone that fades out quickly and where there is little or no shelter so that the infected pesta are inclined to move out after feeding.

In this method, transmission of the pathogens may occur in one of these ways: 1) larval eating on cadavers on infected larvae or adults, 2) consumption of infected stored food, 3) contamination during mating, and 4) infection from the female during oviposition to its progeny.

General considerations:

In the considering the potential use of microbial insecticides, it may be generalized that the mode of infection or mode of action of entomogahhogens or their toxic by-products may be divided into two groups; according to their natural port of entry into their hosts.

The first group includes bacteria, protozoa and viruses. These pathogens must be ingested in order to cause infection and later on mortality. Viruses are quite specific in their sites of development and multiply only in certain tissues within the body of their host. Bacteria may multiply throughout the tissues and body fluids of the host causing septecemia. The crystalliferous bacteria (Bacillus thuringiensis) may kill their hosts purely on the basis of the activity of their associated toxins.

The second group includes the fungi and nematodes which enter their host through their integument. These microorganisms are more subject to regulations by the environment. If the environment favors them, they multiply tremendously and easily colonize their hosts. Physical factors like temperature and humidity affect their survival and/or ability to cause infection. These will also affect the progress of infection and the susceptibility or resustance of the host.

Bacteria:

Bacillus thuringiensis Berliner, the most common bacteria used for the control of stored insect pests, was isolated from diseased larvae of the Mediterranean flour moth, Ephestia knehniella Zeller in 1911. It has been tested on a wide range of storage moths: Plodia interpunctella Hubner, E. elutella, E. cautella, S. cerealeela (Oliver) and Corcyra cephalonica (Stainton). It was effective against all the above species except S. cerealella. In this species the larva spends its life cycle within the single grain and hence probably does not have sufficient contact with the pathogen when applied on the surfaces (McGaughey, 1976).

In bulk wheat and corn infested by P. interpunctella and E. cautella, it has been demonstrated by McGaughey (1976, 1978) that good control (at least 92%), may be obtained if only the surface layers of the bulk are treated with dust or aqueous suspension of B. thuringiensis. The recommended depth of treatment was 100 mm at least and the pathogen had to be well-mixed to ensure an even treatment within this layer. The recommended dose rate for this particular preparation was 125 mg/kg.

Admixture to surface layers of bulk grain during grain transfer and after the silo have been filled were found eaually effective. Viability of B. thuringiensis is slightly reduced after one year storage (Kisinger and McGaughey, 1976).

Viruses:

A nuclear polyhedrosis and a granulosis viruses have been isolated from E. cautella. Both severely infect P. interpunctella; whereas granulosis virus from P. interpunctella does not cross-infect E cautella (Hunter, 1973). Another nuclear polyhedrosis virus has been isolated from C. cephalonica (Rabindra and Subranabian, 1973) but it is not known whether it will cross-infect other moths. In all cases the young larvae are the most susceptible stage.

Granulosis virus controlled effectively moth on bulk wheat and corn when surface layer of bulk was treated with aqueous suspension or dust of the virus to a depth of at least 100 mm. The suspension or dust both contained 3.2 x 103 virus capsules/mg and the grain was treated at a rate of approximately 1.9 mg/kg.

The application of an aqueous suspension of the granulosis virus of P. interpunctella has also been found to be an effective protectant for stored in-shell almonds (Hunter, et al, 1973), and stored raisins (Hunter et al, 1979). High storage temperature, however, reduces the viability of the virus and hence lowers the efficiency of this method of control. At 27°C, the control, after 5 & 6 months, remained high at 93% and 77%, respectively. In contrast, at 32°C, control after four months was 87% but this dropped to 34% and then 16% after 5 & 6 months.

Protozoa:

Several protozoa are known to be severe pathogens of the Coleopteran. The following protozoans were tested: Nosema whitei for Tribolium castaneum (Herbs") and T. confusum J. du Val (Burges et al, 1971), N. whitei and N. oryzaephili for Oryzaephilus surinamensis (Linn) (Burgess et al, 1971) and Mattesia trogoderma for Trogoderma spp. (Schwalbe et al, 1974). Another species, Nosema plodiae Kellen and Lindegreem, has been isolated from the moth Q interpunctella and its mode of transmission investigated (Keller and Lindegren, 1971). Its use in control has not been studied.

The admixture of protozoa spores in particular, N. whitei to stored grain has been discussed by Burges (1973). He suggests that it would be necessary to admix a pathogen cocktail to control the range of Coleoptera that might be encountered in a particular storage situation.

Fungi:

There are many fungi (hyphomycetous species) which grow on insects. Some are saprophytic while others are parasitic. Those most widely encountered are members of the genera Beauveria, Metarhizium and Isaria, and to a lesser extent Aspergillus, Cephalosporium, Sorosporella, and Hirsutella.

The commonest species is Metarhizium anisopliae (Metch) (Sor., the cause of the green muscardine disease of river' insects). This fungus has been seen to penetrate the integuments of several insects. In a recent study by Quiniones (1986) on the control of stored pests of copra, particularly the copra beetle, diluted spores of M. anisopliae up to 4.8 x 10-6 when topically brushed on the surface of stored copra, was effective to control this beetle.

Table 1. Microbial pathogens of some stored pest product insects
INSECT SPECIES PATHOGEN REFERENCE
Ephestia cautella Hubner B. thuringiensis Berliner Burger & Hurst 1977
Plodia interpunctella Hubner    
E. elutella (Hubner)    
Sitotroga cerealella (Oliver)    
P. interpunctella Hubner Granulosis virus (GV) Hunter et al 1975
P. interpunctella Hubner Nuclear polyhedrosis virus (NPV) Hunter et al 1975
E. cautella (Huhner)    
E. cautella (Hubner) NPV Rabindia & Subranabiam 1973
Tribolium castaneum (Herbs") Nosema whitei Burges et al 1971
T. confusum J du Val    
Oryzaephilus surinamensis L Nosema oryzaephili Burges et al 1971
Trogoderma spp Mattesia trogodermae Schwalbe et al 1974
T. glabrum (Herbs")   Shapes et al 1974
P. interpunctella Nosema plodiae Kellen and Lindegren, 1971
Tribolium castaneum Metarhizium anisopliae (Metch) Sor. Quiniones, In press
Necrobia rufipes De Geer    
Oryzaephilus surinamensis L.    
Tenebrio molitor Beauveria bassiana Vuill. Masera, 1936
  Serratia marcescens Bizio  

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