Effect of elevated CO2 and temperature on thermal constants and lower threshold temperatures of maize aphid, Rhopalosiphum maidis (Fitch.) (Aphididae:Hemiptera) on maize, Zea mays (Linn.)

The objective of this study was to examine the development of corn leaf aphid,Rhopalosiphum maidis Fitch (Aphididae: Hemiptera) on maize Zea mays Linnaeus at elevated and ambient concentrations of CO2 (550 and 380ppm ± 25 ppm, respectively) at six temperatures (20, 25, 27, 30, 33 and 35°C) and to estimate thermal constants and lower temperature thresholds for the forecasting models based on heat accumulation units which could be developed for use in forecasting. The duration of different growth stages of R.maidis were reduced with an increase of temperature from 20°C to 35°C under both ambient and elevated CO2 conditions. The lower development threshold for first nymphal instar,second nymphal instar, third nymphal instar, fourth nymphal instar, adult duration and total development period required 10.1, 5.04, 13.42, 26.96, 10.9, 23.22 and 20.20°C under eCO2 whereas it was 13.32, 9.41, 19.13, 30.48, 16.38, 22.88 and 20.89°C under aCO2 conditions,respectively. The mean lower temperature threshold for nymph was slightly higher (16.38°C) at aCO2 compared to that of eCO2 (10.90°C) whereas for adult the mean lower temperature threshold was slightly higher (23.22°C) at eCO2 compared to that of aCO2 (22.88°C). The thermal requirement of R. maidis from first nymphal instar to adult (total development period) was found to be 100.00 degree days (DD) under eCO2 conditions as against 111.11degree days under aCO2 conditions. These estimated temperature thresholds and thermal constant can predict the pest scenarios and population dynamics of R. maidis.

Assessing the effects of Bt maize on the non-target pest Rhopalosiphum maidis by demographic and life-history measurement endpoints

The most commercialized Bt maize plants in Europe were transformed with genes which express a truncated form of the insecticidal delta-endotoxin (Cry1Ab) from the soil bacterium Bacillus thuringiensis (Bt) specifically against Lepidoptera. Studies on the effect of transgenic maize on non-target arthropods have mainly converged on beneficial insects. However, considering the worldwide extensive cultivation of Bt maize, an increased availability of information on their possible impact on non-target pests is also required. In this study, the impact of Bt-maize on the non-target corn leaf aphid, Rhopalosiphum maidis, was examined by comparing biological traits and demographic parameters of two generations of aphids reared on transgenic maize with those on untransformed near-isogenic plants. Furthermore, free and bound phenolics content on transgenic and near-isogenic plants were measured. Here we show an increased performance of the second generation of R. maidis on Bt-maize that could be attributable to indirect effects, such as the reduction of defense against pests due to unintended changes in plant characteristics caused by the insertion of the transgene. Indeed, the comparison of Bt-maize with its corresponding near-isogenic line strongly suggests that the transformation could have induced adverse effects on the biosynthesis and accumulation of free phenolic compounds. In conclusion, even though there is adequate evidence that aphids performed better on Bt-maize than on non-Bt plants, aphid economic damage has not been reported in commercial Bt corn fields in comparison to non-Bt corn fields. Nevertheless, Bt-maize plants can be more easily exploited by R. maidis, possibly due to a lower level of secondary metabolites present in their leaves. The recognition of this mechanism increases our knowledge concerning how insect-resistant genetically modified plants impact on non-target arthropods communities, including tritrophic web interactions, and can help support a sustainable use of genetically modified crops.

Seasonal abundance of the most important insect pests of maize and their natural enemies in Egypt

The experiment was conducted to study the seasonal abundance of the most important insect pests of maize and its relation with natural enemies and weather factors in Assiut governorate during 2019 and 2020 seasons.The samples were examined from June to September to determine the population of Limothrips cerealium (Haliday, 1836), Rhopalosiphum maidis (Fitch, 1856) and Sesamia cretica Lederer, 1857 and its the associated predators. The population of L. cerealium recorded a peak in the 4th week of July 2019 and the 1st week of August 2020. The highest population of R. maidis occurred in 1st week of September at both seasons. The simple correlation and regression between L. cerealium population and three weather factors were insignificant in both seasons while S. cretica population were found to be significant with R.H%. The population of R. maidis in the 1st season was insignificant negative with temperatures but was significant in the 2nd season. The plant age was more effective than the weather factors on the population of the three insect pests. The common predators were Orius albidipennis (Reuter, 1884) and Scymnus interruptus (Goeze, 1777)which were highly significant with all three insect pests.

Rhopalosiphum maidis (green corn aphid).

R. maidis is probably the most important pest of cereals in tropical and warm temperate climates. It causes direct feeding damage by the removal of plant sap from young leaves and growing points, and indirect damage via honeydew secretions and its ability to spread virus diseases. It causes particularly heavy economic losses in maize, sorghum, and barley. However, although it attacks wheat, oats, rye and other many cereals, significant economic losses on these crops are less common.

Diversity of aphid pests on the crops in Kanchanpur district, Nepal

A survey was conducted to explore the aphid pests’ diversity in Kanchanpur district, far-western, Nepal from April 2018 to March 2019. A total of 15 aphid pests were collected and identified, viz. Acyrthosiphon pisum (Harris), Aphis craccivora (Koch), Aphis gossypii (Glover), Aphis fabae (Scopoli), Aphis nerii Boyer de Fonscolombe, Brevicoryne brassicae (Linnaeus), Lipaphis erysmi (Kaltenbach), Macrosiphum euphorbiae (Thomas), Macrosiphum rosae (Linnaeus), Myzus persicae (Sulzer), Rhopalosiphum maidis (Fitch), Rhopalosiphum padi (Linnaeus), Rhopalosiphum rufiadominale (Sasaki), Uroleucon compositae (Theobald), and the guava aphid. Exploration of aphid pests showed that they caused serious damages to agricultural crops by attacking different parts of plants.

IDENTIFIKASI HAMA KUTUDAUN (Hemiptera: Aphididae) PADA TANAMAN JAGUNG HIBRIDA (Zea mays L.) DI KABUPATEN SOLOK SUMATERA BARAT

Jagung (Zea mays L.) merupakan tanaman serealia penting sebagai sumber karbohidrat bagi jutaan penduduk di dunia. Kutudaun (Hemiptera: Aphididae) merupakan salah satu hama penting pada tanaman jagung. Namun informasi tentang jenis kutudaun yang menyerang tanaman jagung hibrida di Solok, Sumatera Barat masih sangat terbatas. Tujuan penelitian ini adalah mengetahui jenis spesies hama kutudaun yang menyerang tanaman jagung di Nagari Bukit Payo, Kecamatan Tanah Garam, Kabupaten Solok. Penelitian ini dilaksanakan dari bulan Januari hingga Juni 2019. Metode yang digunakan dalam penelitian ini adalah survei. Tanaman jagung yang dijadikan sampel dipilih secara acak (sampling). Pengambilan kutudaun tersebut dilakukan sebanyak 2x dengan waktu pengambilan selama musim tanam jagung hibrida. Kutudaun diperoleh dengan cara mengumpulkan koloni kutudaun yang terdapat pada bagian daun, batang dan tongkol dari tanaman jagung. Kemudian kutudaun langsung dimasukkan ke dalam tabung eppendorf yang telah berisi alkohol 96% menggunakan kuas, lalu diberi label lokasi dan tanggal pengambilan sampel. Selanjutnya kutudaun sampel dibawa ke Laboratorium Bioekologi Serangga, Departemen Proteksi Tanaman, Fakultas Pertanian, Universitas Andalas untuk mengetahui jenis dan jumlah individu kutudaun. Kutudaun diidentifikasi berdasarkan karakter morfologinya dengan menggunakan buku panduan Aphids on the World’s Trees, Aphids on the World Crops, Aphids on the World’s Herbaceous Plants and Shrubs. Hasil penelitian menunjukkan bahwa tanaman jagung hibrida di Kecataman Tanah Garam, Kabupaten Solok terserang hama kutudaun (Hemiptera: Aphididae), namun populasi kutudaun tergolong rendah yaitu 262 kutudaun. Kutudaun yang ditemukan pada tanaman jagung di Nagari Bukit Payo, Kec. Tanah Garam, Kab. Solok adalah sebanyak 2 spesies yaitu Rhopalosiphum maidis Fitch dan Myzus persicae. Rendahnya populasi kutudaun yang menyerang tanaman jagung hibrida tersebut disebabkan karena beberapa faktor, seperti varietas jagung, pola tanam, dan praktek budidaya yang dilakukan oleh petani setempat.Kata kunci: Populasi, Aphididae, Jagung, Identifikasi, Kutudaun

Biological and Ecological Characteristics of the Ladybird Beetle (Lemnia biplagiata Swartz, 1808) (Coccinellidae: Coleoptera)

This paper studies the ladybird beetle in the laboratory at two average temperature levels: 22.2 ± 0.02 and 30.7 ± 0.03oC with average humidities of 69.5 ± 0.05 and 86.8 ± 0.06%, respectively, using Rhopalosiphum maidis as prey to observe its biological characteristics. The study results show that the ladybird beetle completes its life cycle in a time range from 19.75 ± 5.75 days at 30.7 ± 0.03oC and 86.8 ± 0,06% RH to 25.75 ± 6.50 days at 22.2 ± 0.02˚C and 69.5 ± 0.05% RH. The survival rate of ladybird larvae and the percentage of larvae aged 4 into pupae at 22.2 ± 0.02˚C and 69.5 ± 0.05% RH were higher than those at 30.7 ± 0.03oC and 86.8±0.06% RH by 32.4% and 8.24%, respectively. Using Rhopalosiphum maidis as food, the ladybird beetle larvae’s food consumption increases from age 1 to age 4 and the adults consume more food than the fourth-stage larvae by 11.60 R.maidis/day at 22.2 ± 0.02˚C and 69.5 ± 0.05% RH. At 30.7 ± 0.03oC and 86.8 ± 0.06% RH, the ladybird beetle larvae’s R. maidis food consumption at all phases was about 2.5 times higher than at 22.2 ± 0.02˚C and 69.5 ± 0.05% RH.