Search

Six species of legume or cereal-feeding aphids, Acyrthosiphon pisum, Aphis craccivora, Megoura crassicauda, Rhopalosiphum maidis, Rhopalosiphum padi and Sitobion akebiae (Hemiptera: Aphididae), were tested as candidates for alternative hosts of Aphidius gifuensis (Hymenoptera: Braconidae), an indigenous natural enemy attacking vegetable pest aphids Aulacorthum solani and Myzus persicae (Hemiptera: Aphididae). A. pisum, R. maidis and S. akebiae were accepted by A. gifuensis. S. akebiae showed the most successful parasitism by A. gifuensis among the six aphid species tested, with a mummification rate of 71.7% and emergence rate of 96.7%. No parasitism was observed on R. padi, an alternative host available in the banker-plant system with an exotic parasitic wasp, Aphidius colemani (Hymenoptera: Braconidae). A. gifuensis females reared on S. akebiae had the same developmental period and body size as those reared on M. persicae, with no significant differences. They also demonstrated successful parasitic performance in A. solani and M. persicae. These results suggest that S. akebiae should be a promising alternative host for use in a banker-plant system with A. gifuensis.

Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) B- and Q-biotypes are exotic insects in Japan and are consequently regarded as insect pests in agricultural fields. Using B- and Q-biotypes, we investigated the hatching rate, survival rate during the larval stage and the total development period from egg to adult. Whiteflies were allowed to lay eggs on several host plants: cabbage, Brassica oleracea var. capitata; cucumber, Cucumis sativus L.; tomato, Solanum lycopersicum L.; eggplant, Solanum melongena L.; bell pepper, Capsicum annuum cv. grossum; and five cultivars of kidney bean, Phaseolus vulgaris (cvs. Kentucky101, Nagauzura, Morocco, Satsukimidori and Honkintoki), and the effects on the above traits were evaluated. Clear differences between the two biotypes were detected. A particularly important difference was that the B-biotype successfully developed to adults on only one of five cultivars of kidney bean, whereas the Q-biotype was able to utilize all the test plants as hosts regardless of the cultivar. This finding suggests that the determination of host plants in B. tabaci is greatly influenced by not only plant species but also by cultivar. In addition, there is a high possibility that the Q-biotype has the ability to adapt to a wider range of plant species and cultivars compared with the B-biotype.

The development, survivorship and reproduction of the whitefly Bemisia argentifolii Bellows et Perring (B. tabaci [Gennadius] B-biotype), raised on four commercial vegetables, were studied in the laboratory at 25°C. The development time of B. argentifolii was 21.8 d on eggplant, 22.4 d on cucumber, 22.7 d on sweet pepper and 25.6 d on tomato; the development time on tomato was significantly longer than that on the other vegetables. The survival of immature B. argentifolii raised on eggplant was significantly higher than on tomato. The mean lifetime fecundity of B. argentifolii on eggplant, cucumber, sweet pepper and tomato was 221.3, 167.6, 92.3 and 62.9 eggs, respectively; lifetime fecundity on eggplant was significantly greater than that on the other plants. The intrinsic rate of natural increase (rm), net reproductive rate (R0) and mean generation time (T) was 0.168, 185.1 and 31.2 d on eggplant; 0.153, 130.7 and 31.8 d on cucumber; 0.143, 73.1 and 30.0 d on sweet pepper; and 0.110, 36.1 and 32.7 d on tomato, respectively. Based on population growth parameters, we conclude that eggplant is the most suitable and tomato the least suitable host plant for B. argentifolii.

An acarid bait trap constructed from moistened, folded filter paper containing a small quantity of dry yeast was used to monitor the number of Tyrophagus similis and Rhizoglyphus robini in agricultural soils. In laboratory-based evaluations, the trap captured, on average, 88% (capture rate=no. of captured/no. of released×100 (%)) of the T. similis and 65% of the R. robini adults by 3 d after application of the trap, though the capture rate was lower for the immature stages of both species. Field trials were carried out to monitor T. similis numbers in a spinach greenhouse soil and R. robini numbers in a Welsh onion field soil using both the bait trap and the Tullgren funnel. Population trends for T. similis were similar in both trials, but T. similis numbers were consistently and significantly higher in the bait trap than in the Tullgren funnel. Numbers of R. robini obtained from the soil did not differ significantly between the two methods. These results suggest that efficient monitoring of acarids in the genera Tyrophagus and Rhizoglyphus is possible using the acarid bait trap.

The cold hardiness of three aphid species, Acyrthosiphon pisum, Aulacorthum solani and Megoura crassicauda, was investigated using the active stages of holocyclic and anholocyclic clones. Although a progressive increase of supercooling points (SCPs) was exhibited with increasing age in the three aphid species, little variation in the SCPs was observed among the species at the same developmental stages. However, the survival rate at a prefreeze temperature of −10°C differed among the three aphid species. The survival rate of both nymphs and adults of M. crassicauda was the lowest and that of A. pisum the highest. At −10°C, the survival rate of fourth-stadium nymphs of A. pisum reared at 15°C under a short photoperiod (10L : 14D) was higher than that of the same stadium nymphs reared at 20°C under a long photoperiod (16L : 8D), but there was no significant difference in the survival rate between the holocyclic and anholocyclic clones reared under the same conditions. These results indicate that nymphs and adults of both holocyclic and anholocyclic clones have insufficient cold hardiness to survive the severe winter in the northern parts of Japan. Furthermore, the distribution of the two life cycle clones of M. crassicauda in Japan was estimated from the different levels of cold hardiness among the three aphid species.

A soybean variety ‘Adams’ is known to be resistant to soybean dwarf disease. The number of nymphs and survival rate of Aulacorthum solani decreases remarkably on ‘Adams’. To understand the resistant mechanism of ‘Adams’, we compared the feeding behavior of A. solani adults on resistant ‘Adams’ and susceptible ‘Suzukari’ soybean varieties using an electronic monitoring system (EMS). On ‘Adams’, two ingestion waveforms, the Irss and the Is waveform were observed. The Irss waveform was recorded just after the S waveform, suggesting ingestion from non-phloem. This waveform was not observed on ‘Suzukari’. A. solani on ‘Adams’ probed frequently and repeated short-term phloem ingestion, while A. solani on ‘Suzukari’ ingested from phloem continuously for a long period. Consequently, the total phloem ingestion time was shorter on ‘Adams’ than on ‘Suzukari’. These results suggest that a decrease of ingestion from phloem on ‘Adams’ causes a reduction of nutrient uptake in quality and quantity, and eventually a decrease in survival rate, reproduction and development of A. solani.

To evaluate the effects of soybean trap crops and maize barrier crops on the occurrence of and damage caused by pentatomid bugs and lepidopterous pod borers in soybean fields, the suitability of early maturing cultivars of soybean (Glycine max) and dent maize (Zea mays ssp. dentata) to protect medium- and medium-late-maturing cultivars of soybean were investigated in 1999 and 2000. Five species of Pentatomidae, Riptortus clavatus, Piezodorus hybneri, Halyomorpha mista, Plautia stali, and Nezara antennata, were observed in the soybean fields during August and September. The population of N. antennata was very small in both years. The numbers of R. clavatus, P. hybneri, and H. mista were relatively constant in both years, but the numbers of P. stali differed between years. R. clavatus and P. hybneri did not aggregate on the trap crops. In August 1999, P. stali were crowded on the trap crops and subsequently moved to the field crops. There was no difference in the damage caused by pentatomids between the soybean blocks separated by the barrier crop, except the damage at the early developmental stage of seeds in 1999. These results suggest that neither trap crops nor barrier crops are effective in controlling pentatomids, though they may be suitable for monitoring P. stali. On the other hand, the barrier crops had an effect on the damage caused by lepidopterous pod borers in both years. Especially in 1999, the soybean crops surrounded by the barrier crop showed as little damage as crops that had been sprayed twice with an insecticide (fenvalerate+fenitrothion). This result indicates a usefulness of barrier crops for control of lepidopterous pod borers. However, the effectiveness of the barrier crops must be investigated further.

北海道十勝支庁芽室町産のエンドウヒゲナガアブラムシ(十勝系統)の無翅成虫を15±1°C, 16L:8Dの室内条件下でしょ糖濃度とpHが異なる人工飼料上で育て,生存率,寿命,産子数を調査した.1) 生存率,寿命,産子数の値はいずれもしょ糖濃度45g/100ml, pH 8.3のとき最大値となった.飼料に移してから10日目の無翅成虫の生存率は75.0%,平均寿命は17.8±2.0日となり,ソラマメ芽出し上での生存率85.7%,寿命20.5±1.7日と有意差がなかった.平均産子数は32.0±2.4個体でソラマメ芽出し上での値の45.3%であった.2) 十勝系統ではAkey and Beck (1972)の示した値と異なるしょ糖濃度,pH値が生存率,寿命,産子数に関する最適値となり,アブラムシの系統間でこれらの最適値が異なることがわかった.

The soybean aphid, AphisgijcinesMATsuMuRA, is distributedin tropical and subtropical regions such as SoutheastAsia and partsof Africaas wcll as temperate zones such as nomhern China andJapzn CWANG et al., 1962; KoBAyAsHI et al., 1972; SINGH and van EMDEN, 1979; HILL, 1987; HIRANo and Ftull,1993), A. glycinesisan important pestof the soybean plant CWANGct al., 1962; KoGAN und TuRN]?sEEn, 1987), causing not only dircctdamagc by feeding but also indircctdamage from itsheavy secretion of honcydew on the plants,which scrvcs as a growing medium forsoety mold fungus.A. glyct'nes isalso an important vector ot' viraldiseasesCIwAKI,1979;TAKAHAsHI et aL, 1980). Although A.glycineshaslongbcenknown as a soybean pest,fewstudics have beencarried out on the mechanism involvedinitspopulation flu¢ tuations. It isncccssary to clarify thc demographicparameters and ecological characteristics ofA. gipcines as a first step toward undcrstanding the populationdynamics of thisspecies. The presentrcport fbcuseson the dcvclopmental thresholds and ratcs, intrinsicrates of incrcasc,and other pertinentdemographic parametcrs forA.glycines

In the previous reports, the authors have studied the stabilization of organophosphorus insecticides and have reported that the surface acidity ofmineral carriers effects the stability of methyl parathion dust formulation with stabilizers, such as polyoxyethylene alkyl ether (PAE), polyoxyethylene dialkyl ether etc. The crop field tests and laboratory experiments were made in order to observe the effect of stabilizers on the insecticidal activity in methy parathion dust formulations. In the laboratory experiment, Callosobruchus chinensis LINNE and Allantus luctifer SMITH were used as test insects. In the crop field test, the first and second broods of the rice stem borer, Chilo suppressalis WALKER were used as test insects. Methyl parathion dust formulations with clay, clay plus talc (1:1), clay plus talc (3:1) and stabilizers were used as test insecticides (Tables 1, 2). Stabilizers used were PAE, alkyl naphthalene sulfonic acid salt (ANS), #0 fatty acid, and cuttlefish oil.The results of biological assay were shown in Tables 2, 4, 7 and 8, and these values, when transfered into probit unite and plotted against the time on logarithmic scale, revealed linear regressions in the condition under which the experiment was carried out (Tables 3, 5, 6). In the case of methyl parathion dust formulations with stabilizer, the effect on the insecticidal activity depends upon the sort of mineral carriers and stabilizers. When clay only was used as a diluent, PAE 0.5% as a stabilizer increased rather than obstructed the insecticidal activity of methyl parathion dust formulations.When clay plus talc (1:1) was used as a diluent, cuttle fish oil as a stabilizer obstructed the insecticidal activity and it was inferior to methyl parathion dust formulation without stabilizer. ANS had no connection with any sort of mineral carrier and rarely obstructed the insecticidal activity. Methyl parathion dust formulations with clay plus talc (3:1) were scarcely influenced by stabilizers and the result obtained by Bliss probit method is insignificant.But perhaps, the influence of talc brings about the tendency that dust formulations with PAE are slightly inferior to that with #0 fatty acid on ANS in the insecticidal activity.When talc is used as a diluent, stabilizing effect by compounds of PAE series is not remarkable, as the authors have explained in the previous reports. Though we could not ascertain the relationship between the quantity of stabilizer and insecticidal activity in this test, the result obtained by the crop field test shows, evidently that the insecticidal activity of dust formulations with 0.5% stabilizer is superior to that of dust formulations with 2.0% stabilizer and a proper quantity of stabilizer is approximately 0.5-0.7%.Consequently, in the search of a stabilizer for methyl parathion dust formulation use, we should carry out the biological assay in company with the chemical test of stability, sufficiently to determine the proper quantity of stabilizer, stabilizing effect, and the degree of obstructive action.

Fifteen to thirty three percent of the adults of Dolycoris baccarum LINNAEUS were parasitized by Cylindromyia brassicaria (FABR.), which were collected at Morioka, Iwate Pref. from June to August, 1983. Only one parasitoid larva emerged from one host insect and the parasitism was found in both sexes of the host. Adults of C. brassicaria emerged from the end of July to August both in the laboratory and in the field. On the other hand, no parasitoid larvae emerged from D. baccarum adults collected in September before the winter.