Development of the red palm weevil, Rhynchophorus ferrugineus (Olivier), (Coleoptera, Curculionidae) on natural and synthetic diets

The development of the red palm weevil, Rhynchophorus ferrugineus (Olivier) was investigated on a newly developed semiartificial diet as compared with two natural diets namely sugarcane stem and banana fruit. The weevil was successfully maintained on these diets and duration of the life cycle for males and females, respectively were 164.97 and 194.61 days on the semiartificial diet, 192.5 and 186.5 days on banana, and 172.00 and 170.00 days on sugarcane. The average egg production per female was shown to be significantly higher on the semiartificial diet, being 184.00±18.68 eggs compared with an average of 125.00±11.97 and 133.00±15.21 eggs on banana and sugarcane, respectively. The fertility ranged between 94–100% in those eggs deposited by females previously reared on the tested diets. The developed semiartificial diet was shown to be suitable for maintaining laboratory colonies of the red palm weevil, and it can substitute natural diets.     

Development of the red palm weevil, Rhynchophorus ferrugineus (Olivier), (Coleoptera, Curculionidae) on natural and synthetic diets

The development of the red palm weevil, Rhynchophorus ferrugineus (Olivier) was investigated on a newly developed semiartificial diet as compared with two natural diets namely sugarcane stem and banana fruit. The weevil was successfully maintained on these diets and duration of the life cycle for males and females, respectively were 164.97 and 194.61 days on the semiartificial diet, 192.5 and 186.5 days on banana, and 172.00 and 170.00 days on sugarcane. The average egg production per female was shown to be significantly higher on the semiartificial diet, being 184.00±18.68 eggs compared with an average of 125.00±11.97 and 133.00±15.21 eggs on banana and sugarcane, respectively. The fertility ranged between 94–100% in those eggs deposited by females previously reared on the tested diets. The developed semiartificial diet was shown to be suitable for maintaining laboratory colonies of the red palm weevil, and it can substitute natural diets.     

Sucking rates of the white-backed planthopper Sogatella furcifera (Horv.) (Homoptera, Delphacidae) and yield loss of rice

The sap-sucking rates of the white-backed planthopper (WBPH) Sogatella furcifera (Horv.) (Homoptera, Delphacidae) were examined under a series of experimental conditions in the laboratory. The sucking rate increased with the age of the planthopper. The relative sucking rate of nymphs at the 1^st, 2^nd, 3^rd, 4^th, and 5^th instars and macropterous male adult was 0.19, 0.27, 0.37, 0.49, 0.59, 0.69, and 1 of that of macropterous female adult (set as standard insect [SI]), respectively. The SI sucked at a maximum rate from rice plants at tillering stage. In indica rice varieties, the SI had higher sucking rate than in japonica varieties. The effect of temperature on sucking rate could be described by an exponential quadratic equation. A power equation (W=0.0001S^1.8107) could be used to transfer the relative sucking rate in area (S, mm²) of honeydew excreted by WBPH into absolute dry mass weight (W, mg). The relationship between injury to rice by WBPH in cage and yield loss assessment showed that yield loss was mainly caused by decreased filling percentage of kernels and kernel weights rather than the number of panicles and spikelets per panicle. Finally, experimental results were integrated to a formula that links percentage of yield loss and sucking equivalence of WBPH.     

The development of mice and voles in an oak forest with a surplus of acorns

130kg of acorns of Common Oak (Quercus robur L.) were distributed on an area of 1.44ha in an oak forest near Zagreb (Croatia), where acorns were lacking. The influence of this surplus of food on the development of mice and voles was observed from September 1999 till February 2000 on the experimental plot and on an untreated control area before and after offering the acorns. The Redbacked Vole Clethrionomys glareolus was the most abundant and dominant species in both observed areas. After distribution of the acorns, all species of mice, e.g. the Yellownecked Fieldmouse Apodemus flavicollis, the Longtailed Fieldmouse A. sylvaticus, and the Striped Field Mouse A. agrarius, increased up to 4 times in number on the area treated with a surplus of acorns. On the same area, however, all species of voles, e.g. the Redbacked Vole C. glareolus, the Field Vole Microtus agrestis, and the Common Vole M. arvalis, decreased. The numbers of captured and recaptured rodents before and after offering acorns on the treated and the untreated control area were compared by statistical analysis (Chi²-test). The results show how food can influence the competitive relations between mice and voles.     

Sucking rates of the white-backed planthopper Sogatella furcifera (Horv.) (Homoptera, Delphacidae) and yield loss of rice

The sap-sucking rates of the white-backed planthopper (WBPH) Sogatella furcifera (Horv.) (Homoptera, Delphacidae) were examined under a series of experimental conditions in the laboratory. The sucking rate increased with the age of the planthopper. The relative sucking rate of nymphs at the 1^st, 2^nd, 3^rd, 4^th, and 5^th instars and macropterous male adult was 0.19, 0.27, 0.37, 0.49, 0.59, 0.69, and 1 of that of macropterous female adult (set as standard insect [SI]), respectively. The SI sucked at a maximum rate from rice plants at tillering stage. In indica rice varieties, the SI had higher sucking rate than in japonica varieties. The effect of temperature on sucking rate could be described by an exponential quadratic equation. A power equation (W=0.0001S^1.8107) could be used to transfer the relative sucking rate in area (S, mm²) of honeydew excreted by WBPH into absolute dry mass weight (W, mg). The relationship between injury to rice by WBPH in cage and yield loss assessment showed that yield loss was mainly caused by decreased filling percentage of kernels and kernel weights rather than the number of panicles and spikelets per panicle. Finally, experimental results were integrated to a formula that links percentage of yield loss and sucking equivalence of WBPH.     

Adult morphology and life cycle under constant temperatures of the predator Rhyzobius lophanthae Blaisdell (Col., Coccinellidae)

The external and internal morphological characteristics of the predator Rhyzobius lophanthae Blaisdell (Coleoptera, Coccinellidae) were studied. The head, antenna, thorax elytra, hind wings, legs and abdomen are described. The adult has an average length of about 2.5mm and width of 1.8mm. The flagellum of the antenna consists of 9 segments. The whole surface of thorax and elytra is covered by setae. The tarsus of the 3 legs is 3-segmented. An external morphological difference between male and female is the outline of the 5^th sternite. The alimentary canal, the central nervous system, and the reproductive system of both male and female are also described. The testes consist of 10 follicles and the ovaries of 10 ovarioles. The life cycle of R. lophanthae was studied by rearing the predator on the diaspidid Chrysomphalus aonidum (Linnaeus). The duration of the development of the embryo, 1^st, 2^nd, 3^rd, 4^th larval instars, pupa and preoviposition period of adults were measured at 15, 20, 25 and 30°C.     

Entomophthoralean fungi associated with the common nettle aphid (Microlophium carnosum Buckton) and the potential role of nettle patches as reservoirs for the pathogens in landscape

Populations of the common nettle aphid, Microlophium carnosum Buckton, inhabiting nettle patches in an agricultural landscape were surveyed for entomophthoralean infection during 1998, 1999 and 2001. Five pathogenic species were identified from the aphid in the course of the survey. Erynia neoaphidis Remaudière & Hennebert, Neozygites fresenii (Nowakowski) Remaudière & Keller, and Neozygites microlophii Keller affected aphid colonies every year. Two minor pathogens, Entomophthora planchoniana Cornu and Conidiobolus obscurus (Hall & Dunn) Remaudière & Keller, were observed only in 2001.An artificial transmission of the three main fungi was carried out to prove horizontal transmission of infection between the common nettle aphid and different aphid species co-occurring in landscape. N. microlophii, probably monophagous pathogen, did not infect any of the six recipient aphid species in the experiment. Transmissions of E. neoaphidis and N. fresenii conidia were successful with five and four aphid species, respectively. The average mortality of tested aphids after transmission ranged from 0 to 33.33% for E.neoaphidis and from 0 to 15% for N. fresenii.     

The development of mice and voles in an oak forest with a surplus of acorns

130kg of acorns of Common Oak (Quercus robur L.) were distributed on an area of 1.44ha in an oak forest near Zagreb (Croatia), where acorns were lacking. The influence of this surplus of food on the development of mice and voles was observed from September 1999 till February 2000 on the experimental plot and on an untreated control area before and after offering the acorns. The Redbacked Vole Clethrionomys glareolus was the most abundant and dominant species in both observed areas. After distribution of the acorns, all species of mice, e.g. the Yellownecked Fieldmouse Apodemus flavicollis, the Longtailed Fieldmouse A. sylvaticus, and the Striped Field Mouse A. agrarius, increased up to 4 times in number on the area treated with a surplus of acorns. On the same area, however, all species of voles, e.g. the Redbacked Vole C. glareolus, the Field Vole Microtus agrestis, and the Common Vole M. arvalis, decreased. The numbers of captured and recaptured rodents before and after offering acorns on the treated and the untreated control area were compared by statistical analysis (Chi²-test). The results show how food can influence the competitive relations between mice and voles.     

Winter mortality in sub-corticolous populations of Ips typographus (Coleoptera, Scolytidae) and its parasitoids in the south-eastern Alps

A study concerning the winter mortality of a sub-corticolous population of Ips typographus and its parasitoids has been carried out in the south-eastern Alps (Italy) during the winter 1997/98. Three attacked spruce trees were sampled three times (November, February and April) by collecting infested bark disks (1dm² each). All insects that emerged from the bark or died in the samples before emergence were counted. The mean number of living Ips typographus occurring under the bark decreases by 49% from November to April. Winter mortality mainly affects larval stages and young adults. The same trend was observed for the parasitoids Coeloides bostrychorum (48.5%) and Roptrocerus xylophagorum (47.5%).     

Efficiency of the mixed biocide GCSC-BtA against vegetable pests of different arthropod orders in the south-eastern China

The present paper deals with the efficiency of the mixed biocide GCSC-BtA against vegetable pests of five orders of arthropod insects in the south-eastern China, i.e., diamondback moth, Plutella xylostella (L.); green peach aphid, Myzus persicae (Sulzer); yellow-fanded flea beetle, Phyllotreta vittata Fabricius; vegetable leaf miner, Phytomyza nigricornis Macquart; and vegetable spider mite, Tetranychus neocaledonicus Andre. The results show that the mixed biocide GCSC-BtA has a higher efficacy of control against all of the five pests than the commercial biocide B.t. and insecticide Diazinon. GCSC-BtA gave a higher mortality value of 92.18% against P. xylostella as compared to the biocide B.t. with a value of 64.70% and Diazinon with a value of 50.00%. Similar mortalities were obtained with the other four pests regarding the efficacy of the three products tested against them.The concentration-mortality regression equations were calculated by the probit analysis, from which the average mortalities were calculated. The values calculated for GCSC-BtA were 81.13% for P. xylostella, 75% for M. persicae and T. neocaledonicus, 69.23% for P. vittata, and 61.03% for P. nigricornis as compared to those caused by Diazinon: 33.33%, 27.42%, 66.31%, 44.54%, 19.65% for P. xylostella, M. persicae, P. vittata, P. nigricornis, and T. neocaledonicus, respectively. Based on LC₅₀, P. xylostella was most susceptible to GCSC-BtA with a LC₅₀ value of 0.3445, followed by B.t. with a value of 0.8404 and Diazinon with a value of 1.3160. The LC₅₀ value of GCSC-BtA for M. persicae was 0.4660 which was about three times less than that of Diazinon. LC₅₀ value of GCSC-BtA for P. vittata was 0.3954 which was about the same as that of Diazinon. P. nigricornis and T. neocaledonicus were also much more susceptible to GCSC-BtA than to B.t. and Diazinon. It is concluded that GCSC-BtA kills more target pests than B.t. and is more effective than Diazinon in controlling the vegetable pests.     

Investigations on side-effects of the mixed biocide GCSC-BtA on different predators of Plutella xylostella (L.) (Lep., Plutellidae) in southeastern China

The present paper deals with laboratory studies on side-effects of the mixed biocide GCSC-BtA on Plutella xylostella (L.) (Lep., Plutellidae) and its predators, e.g. Amblyseius longispinosus (Evans) (Acari, Phytoseiidae), Erigonidium graminicola (Sundvall) (Araneae, Linyphiidae), Orius similis Zheng (Het., Anthocoridae) and Coccinella septempunctata L.(Col., Coccinellidae), in comparison to the commercial insecticides, e.g. Abamectin, Tebufenozide, Dichlorvos, Cartap and Lambda-cyhalothrin.The results showed that GCSC-BtA was highly toxic to the 3^rd instar of P. xylostella with 91.18% mortality, followed by Cartap with 84.38%, Abamectin with 78.00%, Tebufenozide with 75.57%, Lambda-cyhalothrin with 63.75% and Dichlorvos with 50.86% mortality. On the other hand, GCSC-BtA was found to be comparatively less toxic to the predators, causing 31.11%, 13.33%, 11.54% and 6.00% mortalities in A. longispinosus, E. graminicola, O. similis and C. septempunctata, respectively. For comparison, the mortalities recorded for Abamectin, Tebufenozide, Dichlorvos, Cartap, Lambda-cyhalothrin were 72.94%, 55.55%, 70.00%, 53.26% and 98.85% in A. longispinosus, 46.51%, 55.10%, 60.00%, 46.00% and 73.68% in E. graminicola, 22.00%, 16.00%, 35.71%, 26.78% and 81.03% in O. similis, 15.55%, 19.64%, 28.00%, 16.66% and 41.79% in C. septempunctata, respectively.Cluster analysis was introduced to group the mortalities caused by the treatments into three toxicity groups with the distance of D=4.1. The 1^st group consisted of GCSC-BtA characterized with low toxicity to all the predators tested with 15.49% mortality on average (highest 31.11% and lowest 6.00%). The 2^nd group consisted of Abamectin, Tebufenozide, Dichlorvos and Cartap with moderate toxicity to the predators with 39.96% mortality on average. The 3^rd group included Lambda-cyhalothrin with high toxicity to the predators with 73.83% mortality on average (highest 98.85% and lowest 41.70%). The susceptibility of the pest and its predators to GCSC-BtA and the insecticides is discussed. GCSC-BtA as a biological control agent is recommended for use in the integrated pests control programs in the vegetable fields.     

Conjugation of δ-endotoxin from Bacillus thuringiensis with abamectin of Streptomyces avermitilis as a new type of biocide, GCSC-BtA, for control of agricultural insect pests

Conjugation of -endotoxin from Bacillus thuringiensis with abamectin, a toxin of Streptomyces avermitilis, was carried out to form a new type of biocide, GCSC-BtA based on Germany-China Scientific Cooperation research, for the control of agricultural insect pests. The strategy for biochemical linkage was designed by conjugating an amino group in B.t. protoxin with a carboxyl group in carboxylated abamectin under the treatment of conjugator EDC [1-Ethyl-3-(3-dimethylaminopropyl carbodiimide Hydrochloride)]. The formation of B.t. protoxin was processed by solubilizing B.t. crystal in 25mM dithiothreitol (DTT) at 37°C for 2h. The carboxylated abamectin was formed by carboxylating the NaH-activated abamectin with 10mg/ml butyric anhydride at 111°C in a water-circumfluent condensation device for 2h. The conjugating reaction, consisting of 5mg/ml B.t. protoxin, 10mg/ml carboxylated abamectin and 19.17mg/ml EDC, was successfully conducted at room temperature for 24h. Significant differences were found between pure abamectin, carboxylated abamectin and the conjugated BtA by means of UV-photo absorptions recorded at wavelengths 354, 438, 518, 600nm (P<0.01). LT₅₀ of the conjugated GCSC-BtA to the 3^rd instar larvae of Plutella xylostella (L.) (Lep., Plutellidae) was 35.27 g a.i./ml, about 62% and 76% of that caused by the B.t. protoxin and the caxboxylated abamectin, respectively. The conjugated GCSC-BtA caused 87.14% mortalities in larvae of P. xylostella, 93.75% in adult Myzus persicae (Sulzer) (Hom., Aphididae) and 89.33% in adult Phyllotreta vittata Fabricius (Col., Chrysomelidae) as compared to 48.33% by the B.t. crystal only in P. xylostella. The symptoms caused by conjugated GCSC-BtA in the 3^rd instar of P. xylostella were black color in the head part and white-yellow in the abdomen of dead larvae, which differed from the black color or the white-yellow all along the body caused by either the B.t. crystal or the abamectin, respectively. It was concluded that the conjugated GCSC-BtA biocide had a broader host spectrum and a faster killing speed than either the B.t. crystal or abamectin alone for the control of agricultural pests.     

Biological characteristics and life tables of Neoseiulus umbraticusChant (Acari, Phytoseiidae) at three constant temperatures

The development time, survival and fecundity of the generalist predatory mite, Neoseiulus umbraticusChant, were determined at 20, 25, and 30°C and 65±10% RH. N. umbraticus females completed development in 9.7, 8.0 and 5.9 days, respectively, using a diet of all life stages of Tetranychus cinnabarinus Boisduval. Total developmental times of males were relatively shorter at 25 and 30°C than at 20°C. In general, preoviposition, oviposition, and postoviposition periods of N. umbraticus shortened as temperature increased. The longest survival rate of N. umbraticus of 80.5 days occurred at 20°C, followed by 67.0 and 57.6 days at 25 and 30°C, respectively. Mated females laid an average 0.9, 1.3 and 1.4 eggs per female per day and 33.1, 44.0 and 43.6 eggs over their entire lives at 20, 25 and 30°C, respectively. The sex ratios of this species were 0.57, 0.57 and 0.54 female (female+male) at 20, 25 and 30°C, respectively. The intrinsic rate of increase (r_m) became greater with rising temperatures from 0.123 at 20°C to 0.180 at 30°C. The net reproduction rate (R_o) was highest at 25°C (25.0 females/female) and lowest at 20°C (18.8 females/female), while T_o decreased with increasing temperatures, from 23.8 days at 20°C to 17.5 days at 30°C.     

A Review on Options for Management of Cowpea Pests: Experiences From Uganda

More than 100 field pests of cowpea (Vigna unguiculata L. Walp.) can be found in most of the crop production agroecologies in Africa, but four of these – aphids (Aphis craccivora Koch), flower thrips (Megalurothrips sjostedti Trybom), the legume pod borer (Maruca vitrata Fab. Syn. Maruca testulalis Geyer) and pod sucking bugs – are commonly encountered and are of economic importance in Uganda. The diverse cowpea pest complex dictates that a single control strategy is unlikely to produce satisfactory control.Earlier field studies done in eastern and northern parts of Uganda demonstrated that close spacing (30 × 20cm) effectively reduces aphid infestation (early season pest) but seems to promote thrips, legume pod borers and pod bugs infestation. The other option for management of early season pests and nematodes is seed dressing, especially with carbofuran (Furadan 5G). Late season pests are more effectively controlled by the use of foliar sprays, the type of pesticide depending on the pest profile. Intercropping also offers remedial control, but the crop combination must consider the pest profile, cowpea/sorghum intercrop being effective against aphids and thrips, and cowpea/greengram against legume pod borers and pod sucking bugs. Selected combinations of agronomic, chemical and cultural control measures (Integrated Pest Management), especially when combined with early planting, offer better management options than the use of sole treatments. The success of these packages is highly dependent on the degree and level of farmer involvement and to what extent they are tailored to meet his/her production goals.     

Occurrence of pathogens in associated living bark beetles (Col., Scolytidae) from different spruce stands in Austria

Pathogen occurrence was studied in 16099 adult specimens of 10 different bark beetle species, which live associated on Norway spruce (Picea abies (L.) Karst.). Beetles (mainly Ips typographus L. and Pityogenes chalcographus L.) were collected from 6 different localities in Austria (4 secondary spruce stands and 2 natural forest type stands, 9 sampling plots in total) in elevations between 400m and 1600m. Various viral, protozoan, and fungal pathogens could be diagnosed with a light microscope in the examined beetles. Numerous pathogen species were known from former studies, some pathogens were totally new or could be found in a new host species beside their type host. The most dominant pathogen species were Protozoa, Gregarina cf. typographi, Malamoeba cf. scolyti, and Chytridiopsis cf. typographi. Over the whole investigation period, the highest pathogen diversity with eight pathogen species was found in I. typographus. Differences were observed in the pathogen complex of each beetle species from the different collection sites and in different years of investigation. Several species showed an overlapping in their host range and infected various bark beetle species. Furthermore, pathogen occurrence and prevalence differed in bark beetles from 4 different sampling plots in an area (one locality) within a distance of a few kilometres.     

The effect of Alsystin (triflumuron) on larvae of the migratory locustLocusta migratoria migratorioides Investigations carried out in the semi-desert area of Sudan's Red Sea Province

The effects of Alsystin were tested onLocusta migratoria migratorioides larvae in stages 2–4 in field cage-trials carried out in the semi-desert area of the Red Sea Province of Sudan. The mortality rates achieved (between 60% and 90%) increased with the dosage used (between 10 and 80 g a. i./ha). However, these values were only reached 18 days after treatment. The most frequently observed defect in the dead larvae was a soft, incompletely hardened cuticle, often ruptured at the intersegmental membranes. Application of Alsystin caused no detectable reduction in the locusts' feeding activity. Consequently, the crop plants in the cages (Pennisetum) were completely consumed during the 20-day experimental period.In Freiland-Käfig-Versuchen wurde in der Rote-Meer-Provinz des Sudan die Wirkung von Alsystin aufLocusta migratoria migratorioides-Larven der Stadien L₂–L₄ getestet. Dabei wurden dosisabhängig (die Aufwandsmengen lagen zwischen 10 und 80 g a. i./ha) Mortalitätsraten zwischen 60 und 90% erzielt. Jedoch wurden diese Werte erst 18 Tage nach Applikation erreicht. Bei den gestorbenen Larven traten als häufigste Schädigungen eine nicht ausgehärtete bzw. geplatzte Cuticula auf. Die Applikation von Alsystin bewirkte keine Verringerung der Fraßaktivität. Als Folge hiervon wurden die in den Käfigen vorhandenen Kulturpflanzen (Pennisetum) während der 20tägigen Versuchsdauer vollständig aufgefressen.

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With 4 figures     

Zur Sch?dlingsvertilgung einiger Singvogelarten in einem Schwarzkiefern/Eichen-Mischbestand im Beynamer Wald bei Ankara

Analysis of nestling food in four species of Parus and one species of Ficedula using the 'Halsringmethode' showed a high quota of adults and caterpillars of the important forest pests: Tortrix viridana, Euproctis chrysorrhoea, Diprion pini, and Lymantria dispar. These four major pest species amounted in the nestling food of Parus major to 50%, P. coeruleus to 52.6%, P. ater to 40.9%, and Ficedula hypoleuca to 30.2%.     

Influences of host age, sex ratio, population density, and photoperiod on parasitism by Trichogramma evanescens Westw. (Hym., Trichogrammatidae)

Moth species Ephestia kuehniella and Sitotroga cerealella are serious pests in cereal-based food processing facilities and stores in Turkey. Control of these pests is undertaken by regular space treatment of infested areas with pesticides. An alternative control method could be the release of parasitic wasps of the genus Trichogramma. In laboratory tests, we use T. evanescens as a parasitic wasp reared on the eggs of Ephestia kuehniella. Adult wasps emerging from the host were maintained in glass tubes at 27±1° C, 60–70±5% r.h and L14:D10 and fed on honey solution. Adults of T. evanescens in vials without food enclosed from host eggs and all died within 1.8days; in comparison, in vials with honey, live adults were evident for 15.2days. Fresh (6–48h) and old (72–96h) host eggs were offered to T. evanescens and fresh eggs were more accepted than old. Host acceptance of females with males in vials was better than without males. The number of females in the vials also influenced the parasitization rate and single female parasitized more eggs. Adults living in light regime (L14:D10 and L6:D18) parasitized more eggs than in total darkness. Results are discussed with relation to enhancing parasitoid effectiveness in biological control in processing facilities and mills.     

Integrated Soybean Pest Management in Micro River Basins in Brazil

A Soybean IPM system was deployed in large, continuous river basin areas. The system was designed to improve the productivity of the rural environment by restoring balance among pests and their natural enemies. The system was developed with the active participation of various governmental, industrial and academic institutions, and it was based on the main approaches utilized by the EMBRAPA soybean IPM program referred here as IPM-Soybean.The work of IPM-Soybean in microbasins is being implemented in five counties in Paraná state (Campo Mourão, Mamborê, Missal, Cambé and Toledo) in an area of approximately 18,020ha of soybean involving 343 producers at various stages of implementation. The results obtained in the Rio do Campo basin in Campo Mourão, after four years of IPM-Soybean, showed drastic changes in pest control practices. Mean number of insecticide applications per cropping year in the river basin fell from 2.8 (1993/94 season) to 1.23 four seasons later. Biological control of the velvetbean caterpillar, Anticarsia gemmatalis, by Baculovirus anticarsia increased 57%, from 205ha treated with this biological product in the 1993/94 season to 2730ha in 1998. A mean of about 300,000 Trissolcus basalis (Wollaston) adults were released per year to control soybean stink bugs. As a consequence of the parasitoid release and the use of more selective insecticides, the number of insecticide applications to control stink bugs was significantly reduced. After two soybean seasons with IPM-Soybean in the river basin, mean applications for stink bugs decreased from 0.81 before the program started to 0.09 in 1996. The mean number of applications in the region and the state respectively were 9.20 and 11.44 times greater. In 1997 and 1998, the results again showed very low population densities of stink bugs in the river basin area, with a consequent reduction in insecticide applications for the control of these pests. Furthermore there was a substantial improvement in the range of products used in this area for soybean pest control. Broad spectrum products, used in 97.5% of the applications before start of IPM-Soybean (1993/94), were replaced with more selective products, especially biologicals and growth regulators. The latter had rarely been used by the river basin producers before the study (0.6% of the applications), but they accounted for 35.8% of the applications after four seasons with IPM-Soybean. IPM-Soybean developed in river basins has resulted in a more stable control system that, in turn, provides greater long-term equilibrium between the pests and the natural enemies populations in these soybean producing areas.     

The effects of intercropping with cereals and minimal permethrin applications on insect pests of cowpea and their natural enemies in Nigeria

Abstract

Major insect pests and their natural enemies were sampled on cowpea in monocrop and cereal intercrop plots in southern and northern Nigeria. Populations of flower thrips, Megalurothrips sjostedti (Trybom), were reduced by 42% and predators, mostly Orius spp. (Anthocoridae), by 23% on cowpea in maize intercrop plots at Ofiki in the south. Infestation by pyralid pod borer, Maruca testulalis Geyer, was unaffected by cropping system. The results suggest that tasselling maize attracts flower‐eating beetles (Meloidae) to intercrop plots, and that pod‐sucking Hemiptera were increased by cereal intercrops at Yankara in the north. Three u.l.v. applications of permethrin at 150 g a.i./ha to monocrop cowpea reduced pest populations by 50 to 85% in the south and increased yield sevenfold. However, the sprayed crop in the north was lost due to a heavy infestation of pod‐sucking bug, Clavigralla tomentosicollis Stål, and outbreaks of Aphis craccivora Koch on sprayed plots in both localities suggested damage to natural enemies. It is concluded that the pest management potential of intercropping is variable and dependent on environmental factors, but it is recommended that intercropping be used in integrated pest management systems with the progressive decrease in insecticide use.