The application of insecticides to control Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is a principal component of the current management for citrus greening disease or Huanglongbing. It is recommended that growers apply systemic insecticides such as imidacloprid and thiamethoxam every 2 mo after seedling planting, but this practice renders the seedlings insecticide-free and vulnerable to psyllid infestation in the first 2 mo. We evaluated the risk of vector invasion during this period from field studies of the psyllid in five new king mandarin, Citrus nobilis Loureiro, orchards in the Mekong Delta region of Vietnam. The first psyllids were found after the first 2 wk, and 2 to 60% of the trees were finally infested by psyllids during the 2 mo. The risk of psyllid invasion could be significantly reduced if the insecticide were applied to seedlings before planting. Three systemics, imidacloprid, thiamethoxam, and clothianidin, were examined in both a net house and in the field to assess how quickly they could be effective after application and how long their efficacy could continue. High psyllid mortality >80% was attained in 10 d after application, and this level was maintained for 90 d in the net house and for 60 d in the field. Based on these results, we propose the effective use of neonicotinoids for protection of citrus seedlings against invasive psyllids during the first 2 mo after planting.

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International audienceIn social insects the discrimination process of non-nestmates is generally considered to be based on detection of cuticular hydrocarbons. The required quantity of the stimulus is fundamental but unknown. In laboratory conditions, we demonstrated that Aphaenogaster senilis ants are able to discriminate the presence of heterocolonial cuticular hydrocarbons on filter papers at concentrations of 0.05 ng/mm2, the equivalent of 10-4 worker. This result does not mean that workers are not able to recognize their own colony odour at lower concentrations, but that the discrimination response appears at very low levels

We compared the densities of the apple snail, Pomacea canaliculata, between fields that had been planted with soybean or rice in the previous summer. The densities of overwintered snails soon after irrigation at the beginning of rice planting were all very low in the fields after soybean. These values were much lower than the control threshold for the apple snail in direct seeding. Therefore, crop rotation with soybean seems to be a good economic measure to control the apple snail in direct seeding. The snail populations increased very rapidly in both types of fields, in particular, after soybean. Within two and a half summer months, the snail densities in the fields after soybean reached almost the same level as those in the fields after rice. This rapid population recovery in fields after soybean seems to be caused by density-dependent growth and reproduction in this species.