Par­a­sites and dis­ease

Element - - Cover Story -

The pin­head-sized var­roa bee mite is prob­a­bly bee en­emy num­ber one in New Zealand, and seems to be a ma­jor threat in many other ar­eas of the world too. This par­a­site at­tacks both de­vel­op­ing bee lar­vae and adult bees, caus­ing de­for­mi­ties, weak­ness and vul­ner­a­bil­ity to viruses that ul­ti­mately kill the hive.

Since ar­riv­ing in New Zealand in April 2000, var­roa has spread through­out all man­aged hives in the North Is­land, over half in the South Is­land. At one point more than a third of all New Zealand bee­keep­ers had given up in the wake of the dis­ease, and the rest have been forced to use chem­i­cal treat­ments to keep their hives alive. Some are now con­cerned that the use of these chem­i­cals to con­trol the mite might, iron­i­cally, also be a con­tribut­ing fac­tor to the po­ten­tial for colony col­lapse, as it in­creases the bees’ vul­ner­a­bil­ity to other dis­eases.

Dr Mark Good­win, an­other sci­en­tist with Plant and Food Re­search, said: “Var­roa is the largest threat but sev­eral new dis­eases have been iden­ti­fied in bees re­cently. These have jumped species as var­roa did 60 years ago. The most no­table is Nosema cer­anae, a stom­ach par­a­site, and Is­raelite Acute Paral­y­sis virus. This lat­ter is the prob­a­bly the cause of the colony col­lapse dis­or­der seen in the USA.”

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