Propylaea Japonica Research Articles

Interactive Effects of Elevated CO<SUB>2</SUB> and Cotton Cultivar on Tri-Trophic Interaction of <I>Gossypium hirsutum, Aphis gossyppii</I>, and <I>Propylaea japonica</I>

Information on the effects of enriched CO2 on both the chemical composition of plants and the consequences of such changes for performance of a herbivore and its predator is an important first step in understanding the responses of plants and insects to global environmental change. We examined interactions across three trophic levels, cotton, Gossypium hirsutum, an aphid herbivore, Aphis gossypii Glover, and a coccinellid predator, Propylaea japonica (Thunberg), as affected by elevated CO2 concentrations and crop cultivars. Plant carbon:nitrogen (C:N) ratios, condensed tannin, and gossypol content were significantly higher, and nitrogen content was significantly lower in plants exposed to elevated CO2 levels compared with that in plants exposed to ambient CO2. Cotton aphid survivorship significantly increased and free fatty acid content decreased with increased CO2 concentrations. No significant differences in survival and lifetime fecundity of P. japonica were observed between cultivars and CO2 concentration treatments. However, stage-specific larval durations of the lady beetle were significantly longer when fed aphids from elevated CO2 concentrations. Our results indicate that high gossypol in the cotton host plant had an antibiotic effect on A. gossypii and produced a positive effect on growth and development of P. japonica at the third trophic level. However, elevated CO2 concentrations showed a negative effect on P. japonica. We speculate that A. gossypii may become a more serious pest under an environment with elevated CO2 concentrations because of increased survivorship of aphid and longer development time of lady beetle.

１１月のマルバツユクサＣｏｍｍｅｌｉｎａ ｂｅｎｇｈａｌｅｎｓｉｓ Ｌ．上における捕食性昆虫の種構成（予報）

To develop an augmentative biological control with resident natural enemies in vegetable greenhouses, a common agricultural weed, Commelina benghalensis L. was investigated with respect to the occurrence of predacious natural enemies in Miyazaki City and Kiyotake Town, Miyazaki Prefecture in mid to late November. A total of 9 species in 3 families were collected from 18 sites. In the agricultural lands near the foot of a small mountain, the mean number of natural enemies per site was 18.8±8.04(±SD), and Propylaea japonica (Thunberg) was predominant species, followed by Orius spp. In the agricultural flatlands, the mean number of natural enemies per site was 27.9±35.46, and Orius spp. were predominant, followed by P. japonica (Thunberg). In the agricultural lands and vacant areas near the seaside, the mean number of natural enemies per site was 52.7±41.02, and P. japonica (Thunberg) was predominant, followed by Pilophorus typicus (Distant). The diapause rate of collected Orius spp. was approximately 50% . These results suggested that C. benghalensis L. is a reservoir of these beneficial natural enemies.

Naturally occurring populations of Bemisia tabaci, biotype B and associated natural enemies in agro-ecosystem in northern China

The sweet potato whitefly, Bemisia tabaci (Gennadius) biotype B was first found in southern China in 1994 and has since then become a pest of increasing importance throughout the nation. The population dynamics of this invasive species and the effect of natural enemies on its population dynamics were studied in commercial cotton fields during the summers of 2003 through 2005 in Langfang, Hebei (northern China). The abundance of Bemisia tabaci was found to increase rapidly in late July, and reached its first peak in mid-August, then followed by the second peak in early September. Whitefly populations subsequently declined slowly to attain a plateau after mid-September. A total of 13 natural enemy species were discovered in association with B. tabaci in cotton fields, including dominant species such as Chrysopa sinica Tjeder, Leis axyridis Pallas, Propylaea japonica Thunberg, Orius similis Zheng, and Eretmocerus sp. Caged experiments on velvetleaf, Abutilon theophrasti Medic, one of the preferred host plants of the insect, indicated higher B. tabaci population densities in small-mesh cages with exclusion of all natural enemies versus those in medium- and large-mesh cages, and the uncaged plants retained the lowest population densities of B. tabaci. While no natural enemies were observed in the small-mesh cages, natural enemies like Misumenopos tricuspiaata, Eretmocerus sp., Encarsia formosa Orius similis, Deraeocoris punctulatus and Scolothrips takahashii were found in medium- and/or large-mesh cages. Findings from this study suggest that under open-field conditions, various indigenous natural enemies of different sizes may act in concert in the suppression of B. tabaci populations.

Effects of Bt‐toxin Cry1Ac on Propylaea japonica Thunberg (Col., Coccinellidae) by feeding on Bt‐treated Bt‐resistant Helicoverpa armigera (Hübner) (Lep., Noctuidae) larvae

Abstract: Propylaea japonica is an important predatory insect of common cotton pests. To assess the ecological effects of transgenic Bt cotton, expressing Cry1Ac toxin, on this predator, we examined the life history parameters of P. japonica for two generations by feeding them with Bt‐resistant Helicoverpa armigera. After ingesting Bt‐treated Bt‐resistant H. armigera larvae in the third and fourth instar, the body mass and body length of adult P. japonica decreased, a combined effect of poor prey quality and Cry1Ac Bt‐toxin may account for these effects. However, larval survivorship and development in these two instars, pupal mortality, fecundity and adult longevity of P. japonica were not affected in both the generations. These results suggest that ingesting Bt‐toxin Cry1Ac‐treated pests in advanced larval stage might have no significant effect on the fitness of predator P. japonica.

Early instar response to plant-delivered Bt-toxin in a herbivore ( Spodoptera litura) and a predator ( Propylaea japonica)

Propylaea japonica is a significant predator in cotton fields in China. To assess the ecological effects of Bt-cotton cultivars (GK-12 and NuCOTN 33B, producing the fused Cry1Ab/Ac toxin and Cry1Ac toxin, respectively), the development of Spodoptera litura on transgenic Bt-cotton, the intake of Bt toxins, and the effects of Bt-cotton reared S. litura on young larvae of P. japonica were evaluated. Based on enzyme-linked immunosorbent assay (ELISA), the Bt-toxin concentrations in newly molted second-instar S. litura were 978.0 and 720.0 ng g −1 when fed on GK-12 and NuCOTN 33B cotton, respectively. The survival rate of S. litura was decreased, the time required to reach the second-instar was prolonged, and the body mass was lowered, when reared on NuCOTN 33B compared to those on DPL5415. However, there were no significant differences between GK-12 and Simian 3 (Parental non-Bt-transgenic for GK-12). After feeding on GK-12 or NuCOTN 33B -fed S. litura neonates for 72 h, young larvae of P. japonica contained more Bt-toxin than cotton leaf tissue, but less than respective Bt-cotton fed S. litura. A decrease ( P = 0.061 ) in body mass was observed when P. japonica young larvae were fed for 72 h with 24 h old NuCOTN 33B -reared S. litura larvae, compared to those fed with DPL5415 -reared S. litura; no significant differences were found when prey was fed with GK-12 vs. Simian 3 plants. Significantly fewer P. japonica larvae molted into second-instar when fed with S. litura reared on NuCOTN 33B, compared to ones fed prey from DPL5415 plants. No such effects were observed when feeding on GK-12 vs. Simian 3 -reared prey. These results suggested that the Cry1Ab/Ac fusion toxin had no direct effect on young larva of P. japonica, and a combined interaction of poor prey quality and Cry1Ac toxin may account for the negative effects observed on P. japonica development when fed NuCOTN 33B -reared S. litura.

給与アブラムシの相違がヒメカメノコテントウの生育ならびに栄養におよぼす影響

25℃の恒温下でヒメカメノコテントウ第3世代幼虫に10種のアブラムシを与え, 成虫にいたるまでの期間, 死亡率, 摂食量, 生体重, 羽化直後の頭巾などを調査すると同時に, アブラムシおよびテントウ両者の生体成分を分析し, つぎの結果をえた.1. マメアブラムシ, エンドウヒゲナガアブラムシ, タイワンヒゲナガアブラムシ, イバラヒゲナガアブラムシ, モモアカアブラムシおよびニガナノアブラムシを与えたテントウはおおむね順調に生育したが, Aphiscraccivora pseudoacaciae, ニワトコアブラムシ, ダイコンアブラムシおよびモモコフキアブラムシ給与の場合の死亡率は高く, 生存虫の生育は遅延した.2. 給与アブラムシの種類による全糖量およびタンパク質量の多少には一定の傾向がみられなかったが, 脂肪量ではテントウの生育に好影響を与えたアブラムシのそれがそうでないものよりも多く, 前者を摂食したテントウの脂肪量もまた増加した.3. テントウの生育に好影響を与えたアブラムシの遊離アミノ酸の種類および量はそうでないものよりも多く, 前者を摂食したテントウのそれにも並行的関係がみとめられた. またアミノ酸の場合ほどではないが, 糖の種類数においても上と類似の傾向がたしかめられた.