|Insects on a head of pak choi|
|Dorsal view of the pollen beetle (approx 2.5mm long excluding appendages)|
|Pronotum (to the right) showing the side rim, plus punctures no more than two diameters apart.|
|Teeth on the front tibia|
|Dorsal view of a beetle larva from pak choi, noting brown sclerotised (hardened) head and legs (and first segment to a lesser extent) and overall 'rice grain' shape.|
|A closer view showing the segmentation of the antennae (towards the outside) and palps, with curved mandibles towards the centre.|
Having determined the species of the most numerous beetle, I moved onto the flea beetle - again a group often considered to contain a number of pest species.
|A flea beetle collected from pak choi|
|Hind leg of P. nigripes showing the position of the apical spur (at the 'knee').|
So, moving onto the last of the three species I collected - a thrips - the smallest at no more than 2mm in length.
|Not the best photo I have ever produced, but the long wings with black and white banding is indicative of the genus Aeolothrips. Despite their tiny size, this banding is visible with the naked eye.|
So, what can be concluded here? My thoughts can be summarised as follows:
- A large population of potential pests (mainly M. aeneus) are present and breeding on crops at the community farm, but these do not appear to be affecting yields.
- One reason for this lack of impact is that the stages being cropped are not those primarily affected (i.e. leaves are being cropped and there is no requirement for the crops to set seed - something that may actually be undesirable). It is clear from the literature that commercial oilseed crops may be impacted.
- It is possible that the wildlife-friendly ethos of the farm is helping as the field margins are allowed (indeed encouraged) to support a wide range of 'weed' species. Observations may confirm this suggestion, but it is possible that these 'weeds' act as 'companion plants' providing alternative food sources for potential crop pests. In a monoculture, this would not be the case.
- Alongside these species are what appear to be a healthy population of at least one small invertebrate predator which has been suggested as a natural (and native) control of potential agricultural pests. It is likely that this would be impacted by attempts to chemically control M. aeneus even if chemicals were chosen to avoid impacts on other key groups such as bees. Fortunately the farm project is chemical-free.
Balachowsky, A.S. (ed.) (1963). Entomologie Appliquee a L'Agriculture. Tome 1. Coleopteres (second volume). Masson, Paris.
Conti, B. (2009). Notes on the presence of Aeolothrips intermedius in northwestern Tuscany and on its development under laboratory conditions Bulletin of Insectology, 62 (1), 107-112 Other: 20093173454
Cox, M.L. (2007). Atlas of the Seed and Leaf Beetles of Britain and Ireland. Pisces, Newbury.
Heeger, E. (1855). Beitrage zur Naturgeschichte der Insekten. Sitzungsberichte der Akademie der Wissenschaften. Mathematisch - Naturwissenschaftliche Classe. Wien. 14: 273-281.
Hubble, D. (2010). Keys to the Adults of Seed and Leaf Beetles of the British Isles (Coleoptera: Bruchidae, Orsodacnidae, Megalopodidae & Chrysomelidae). Test Version 2010. Field Studies Council, Shrewsbury.
Kirk, W.D.J. (1996). Thrips. Richmond, Slough.
Kirk-Spriggs, A.H. (1996). Pollen Beetles. Coleoptera: Kateretidae and Nitidulidae: Meligethinae. Handbooks for the Identification of British Insects 5(6a). Royal Entomological Society, London.