Entomopathogenic Fungi Tested in Planta on Pepper and in Field on Sorghum, to Control Commercially Important Species of Aphids

Given the aphids high reproductive capacity, assessing their biocontrol by using entomopathogenic fungi is crucial; to determine their potential, fungi were tested in planta and in field conditions. Significant decrease of Myzus persicae (Sulzer) population was observed in planta after applying Beauveria bassiana (strain 7R), Trichoderma gamsii (strain Z) or Metarhizium brunneum (strain Meta Br1) at 1 × 107 or 1 × 108 conidia/mL on pepper plants. Significant differences of aphids’ populations were detected between fungus concentration and control (F = 68.743, df = 6.980, P <0.001), where M. brunneum at 1 × 108 conidia/mL reduced aphids population close to zero. At 20 °C, dead aphids’ mycosis by B. bassiana and T. gamsii was 78% and 84%; at 25 °C was 83% and 88%; and at 30 °C was 75% and 79%, respectively. Mexican PTG4 and commercial GHA B. bassiana strains were tested in field (treating seeds with 1 × 106 conidia/mL) against the Melanaphis sacchari (Zehntner) aphid populations, on naturally infested sorghum plants. Results showed that plant germination and emergence were not affected, whereas yield (grams of sugar/plant) was significantly higher among treated compared with untreated plants. The aphid population decreased in plants from PTG4 treated seeds; indeed, this treatment had a significant positive effect on the flowering index, whereas the stem fresh weight and juice volume was significantly increased among plants from GHA treated seeds. Taken together, tested strains can be used as a tool to control aphids’ population on several crops such as pepper and even increase the yield in sorghum.

Elevated CO2 Alleviates the Effects of Drought on Wheat - Aphid Interaction

Due to rising concentration of atmospheric CO2, climate change is predicted to intensify episodes of drought, however, our understanding of how combined environmental conditions will influence crop-insect interactions is limited. The direct effects of elevated CO2 and drought stress on wheat (Triticum aestivum L.) nutritional quality, insect resistance and their indirect effects on the grain aphid (Sitobion avenae) performance are reported here. Elevated CO2 was able to alleviate low water content in wheat caused by drought stress. Both elevated CO2 and drought promoted soluble sugar accumulation in wheat. However, elevated CO2 decreased and drought increased the amino acid content in wheat. Elevated CO2 induced the down-regulation of jasmonic acid (JA) -dependent defense, but up-regulated the salicylic acid-dependent defense. Drought enhanced abscisic acid accumulation that promoted the JA-dependent defense in wheat. Aphid-induced phytohormone resistance in wheat was not influenced by elevated CO2 and drought. The negative effects of drought on the performance of the aphid population was offset by positive effect of elevated CO2. In conclusion, elevated CO2 can alleviate the effects of drought stress on wheat nutritional quality and resistance, which results in unchanged damage to wheat from aphid populations under future elevated CO2 and drier conditions.

Identifying aphid resistance in the ancestral wheat Triticum monococcum under field conditions

Wheat is an economically, socially, and nutritionally important crop, however, aphid infestation can often reduce wheat yield through feeding and virus transmission. Through field phenotyping, we investigated aphid resistance in ancestral wheat Triticum monococcum (L.). Aphid (Rhopalosiphum padi (L.), Sitobion avenae (F.) and Metopolophium dirhodum (Wlk.)) populations and natural enemy presence (parasitised mummified aphids, ladybird adults and larvae and lacewing eggs and larvae) on two naturally susceptible wheat varieties, Triticum aestivum (L.) var. Solstice and T. monococcum MDR037, and three potentially resistant genotypes T. monococcum MDR657, MDR045 and MDR049 were monitored across three years of field trials. Triticum monococcum MDR045 and MDR049 had smaller aphid populations, whereas MDR657 showed no resistance. Overall, natural enemy presence was positively correlated with aphid populations; however, MDR049 had similar natural enemy presence to MDR037 which is susceptible to aphid infestation. It is hypothesised that alongside reducing aphid population growth, MDR049 also confers indirect resistance by attracting natural enemies. The observed resistance to aphids in MDR045 and MDR049 has strong potential for introgression into commercial wheat varieties, which could have an important role in Integrated Pest Management strategies to reduce aphid populations and virus transmission.

Transgenic Expression of dsRNA Targeting the Pentalonia nigronervosa acetylcholinesterase Gene in Banana and Plantain Reduces Aphid Populations

The banana aphid, Pentalonia nigronervosa, is the sole insect vector of banana bunchy top virus (BBTV), the causal agent of banana bunchy top disease. The aphid acquires and transmits BBTV while feeding on infected banana plants. RNA interference (RNAi) enables the generation of pest and disease-resistant crops; however, its effectiveness relies on the identification of pivotal gene sequences to target and silence. Acetylcholinesterase (AChE) is an essential enzyme responsible for the hydrolytic metabolism of the neurotransmitter acetylcholine in animals. In this study, the AChE gene of the banana aphid was targeted for silencing by RNAi through transgenic expression of AChE dsRNA in banana and plantain plants. The efficacy of dsRNA was first assessed using an artificial feeding assay. In vitro aphid feeding on a diet containing 7.5% sucrose, and sulfate complexes of trace metals supported aphid growth and reproduction. When AChE dsRNA was included in the diet, a dose of 500 ng/μL was lethal to the aphids. Transgenic banana cv. Cavendish Williams and plantain cvs. Gonja Manjaya and Orishele expressing AChE dsRNA were regenerated and assessed for transgene integration and copy number. When aphids were maintained on elite transgenic events, there was a 67.8%, 46.7%, and 75.6% reduction in aphid populations growing on Cavendish Williams, Gonja Manjaya, and Orishele cultivars, respectively, compared to those raised on nontransgenic control plants. These results suggest that RNAi targeting an essential aphid gene could be a useful means of reducing both aphid infestation and potentially the spread of the disease they transmit.

Impact of indoxacarb and sulphur formulation on aphid and three specific predators in Okra fields

Background For the sake of environmental safety, many new insecticide generations developed. Sulphur formulations and other botanicals or formulated synthetic insecticides were recommended in many integrated pest management programs to protect, particularly, edible vegetables and fruit trees from insect and mite pests as well as plant pathogenic diseases. Such formulations, at the recommended application rates, proved to be safer for mammals. Regarding their safety to beneficial arthropods, diversified results were reported. This study was designed to investigate and evaluate the impact of indoxacarb and sulphur formulation against some natural enemies naturally prevailing in some vegetable crops. Results Application of indoxacarb and sulphur formulation in Okra fields to control aphid was carried out. The adverse effects of these applications against some important predators were investigated. The obtained results revealed that indoxacarb was more effective than sulphur application in all treatments. At the end of the experiment, the percentages of population reductions of Coccinella indoxacarb treatment reached ≈ 92 and 76% for larvae and adults, respectively. The corresponding figures for Chrysoperla were ≈ 79 and 82% for larvae and adults, respectively. Indoxacarb-induced reduction in the Paederus population reached about 80%, while sulphur formulation had negative effects. Both indoxacarb and sulphur formulations were harmful to the aphid, inducing about 97 and 26% reduction, respectively, for the mean number of aphid populations. Conclusion It could be concluded that indoxacarb is more hazardous towards different natural enemies prevailing naturally in open fields at anywhere season round the year, and care must be in consideration when we choose and select some insecticides to kill or to eradicate pests and simultaneously conserve the natural enemies.

Defoliation and dieback of Sitka spruce in Reykjavík, Iceland

The green spruce aphid Elatobium abietinum is an important defoliating pest of Sitka spruce (Picea sitchensis) in Iceland. A comparison of two urban Sitka stands in Reykjavík, from 2013-2017, reveals a distinct defoliation difference between trees located near a main road (94% defoliated) and several hundred meters away from heavy traffic (47%). Chemical analyses of the spruce needles demonstrate substantially higher nitrogen ratios in trees near traffic. Furthermore, the recently warming winter temperatures promoted larger overwintering aphid populations since 2003, as well as a shift of mass outbreaks from autumn to spring, accompanied by distinct growth suppressions one year after an aphid population spike in the post-2003 tree-ring data. The results of this study indicate that the mechanisms triggering Sitka spruce dieback in Reykjavík include a combination of increasing winter temperatures, more frequent and severe green spruce aphid outbreaks, as well as elevated N values in the needles of urban trees.