The aggregation pheromone phenylacetonitrile: Joint action with the entomopathogenic fungus Metarhizium anisopliae var. acridum and physiological and transcriptomic effects on Schistocerca gregaria nymphs.

The combined use of entomopathogenic fungi and sublethal rate of chemical insecticides or other biological control agents have been proposed as an environmentally and sustainable strategy in the control of locust pests. In this paper, the quarter and the half of the recommended dose of Metarhizium anisopliae var. acridum (» and ½ Ma) and the aggregation pheromone (Phenylacetonitrile: PAN) were applied simultaneously and sequentially to Schistocerca gregaria fifth-instar nymphs. In addition, the physiological effects of PAN on locusts were assessed at the behavior, immune response, and biochemical level by evaluating for glutathione-S-transferase (GST), acetylcholinesterase inhibition (AChE), and malondialdehyde accumulation (MDA). Results showed that simultaneous application of PAN and the entomopathogenic fungus exhibited additive interaction. Synergistic interaction was also demonstrated when nymphs were exposed to PAN first, then treated with M. anisopliae var. acridum. Behavioral bioassay revealed that fifth-instar nymphs avoided the PAN odour and tended to remain away from the stimulus cup. In the choice assay, the pheromone significantly repelled the locusts at 2, 4, and 6 h of exposure which selected the PAN-free arena chamber. Moreover, treated nymphs become hyperactive and disoriented as evidenced by the cumulative distance travelled and the trajectory of locusts during the experiment. Immunological studies showed that PAN significantly decreased the differential haemocyte counts (prohemocytes and plasmatocytes) with a dose-response relationship. Data of biochemical analyzes showed that the PAN exposure reduced the activity of acetylcholinesterase and induced significantly the glutathione S-transferases and MDA concentration in the desert locust fifth-instar nymphs. Moreover, transcriptomic responses to the PAN exposure were evaluated using gene expression levels of CYP540 and GST. The transcript levels showed an up-regulation in GST expression level particularly in nymphs exposed for 4 and 6 h. A significant increase in CYP450 transcript level was also observed after 2 h of exposure, which decreased significantly after 4 and 6 h.

The Tunisian Artemisia Essential Oil for Reducing Contamination of Stored Cereals by Tribolium castaneum.

Essential oils of three species of Artemisia genus (A. absinthium L., A. campestris L. and A. herba-alba (Asso)) were analyzed by gas chromatography-mass spectrometry (GC-MS) and their potential insecticidal and repellent activities against the stored grain insect Tribolium castaneum (Herbst) was investigated. Fumigant and repellent activity bioassays were investigated in vitro. Chemical characterisation of essential oils showed that the bicyclic monoterpenes were predominant in all Artemisia essential oils, A. absinthium essential oil having the highest content of bicyclic monoterpenes, bicycloheptanes, naphthalenes and cycloalkenes. A. campestris had the highest content of sesquiterpenoids and acyclic monoterpenoids. A. herba-alba was characterised by the highest amounts of menthane monoterpenoids, oxanes, cumenes, oxolanes, ketones, benzenoids and monocyclic monoterpenes. Fumigant bioassay demonstrated that the three types of oil applied separately caused significant insect mortality. The lowest median lethal dose, LC50=142.8 µL/L, was observed with A. herba-alba. In repellency test, essential oil of A. absinthium was more potent with more rapid action than all other species. The mixture of Artemisia sp. essential oils showed an antagonistic effect in all the tested combinations. This study highlighted an important potential of Artemisia sp. especially A. herba-alba and A. absinthium in the control of the pests of stored products.

The role of egg pod foam and rearing conditions of the phase state of the Asian migratory locust Locusta migratoria migratoria (Orthoptera, Acrididae).

Coloration phase state, morphometrical ratios and the numbers of mature oocytes of Locusta migratoria migratoria were examined in a series of experiments to determine the means by which phase characteristics are passed to the next generation. Washing with distilled water of eggs from egg pods laid by gregarious crowd-reared females resulted in solitarization of the hatchlings after their isolation, indicating that a factor present in eggs encapsulated in foam is causal to gregarization. Such locusts showed a significant shift towards the typical solitarious body coloration, morphometry and number of mature oocytes as compared to locusts resulting from unwashed eggs. Gregarious coloration, morphometrical ratios and oocyte numbers could be partially restored when hatchlings from washed eggs were regrouped. When gregarious locusts were reared in isolation, they showed a solitary body color, whereas, morphometry and oocyte numbers were not affected by isolation.