Long-term changes in numbers of cereal invertebrates assessed by monitoring.

Abstract

For the past twenty years, The Game Conservancy has monitored abundances of cereal invertebrates in over 100 fields in Sussex in late June. The total number of invertebrates (excluding Acari, Collembola and Thysanoptera) recorded per sample has dropped by almost half in the course of the study, corresponding to a quarter of what was present in pre-pesticide times. This overall change was the result of widespread declines in Araneae and Opiliones, Lepidoptera, Aphididae (Hemiptera), Parasitica and Symphyta (Hymenoptera), Staphylinidae, Cryptophagidae and Lathridiidae (all Coleoptera) and Lonchopteridae (Diptera); these groups constituted 72%, on average, of the total by number . Taking Staphylinidae as an example, the decline occurred equally across all farms, in Tachyporus and non-Tachyporus spp. alike and, within Tachyporus, across age classes and species. The staphylinid decline could not be attributed to weather, to hedgerow removal or to changes in proportions of spring and winter cereals. A possible cause was a drop in the availability of fungal food, as the level of mildew and rusts infecting crops dropped in line with the increasing use of foliar fungicides.