Myiopardalis pardalina in Afghanistan

The Baluchistan melon fly, Myiopardalis pardalina (Bigot), is a serious and worsening problem in Central Asia. As it survives snowy and subzero temperatures as an over wintering pupa, it constitutes a quarantine risk to temperate countries where melons are grown, including in North America and Southern Europe. It is spreading rapidly in Turkmenistan and Uzbekistan as well as Afghanistan, and present from Turkey to India. Losses without control mount as high as 80%. In spite of this, the control of the fly has been little studied, and published recommendations are largely for cover applications of chemicals. It responds to no known lures, and reports of bait responses, though mixed, indicate poor responsivity. This study addressed these problems with a crash program of research in the melon season of 2006, in Mazar-i-Sharif, Afghanistan, with the following findings. (1) Although absence of proof of response is not proof of absence of response, adult flies responded to none of a wide suite of food baits in the field or laboratory. (2) Females laid viable eggs, with offspring completing their life cycle, having received no food as adults, adding suggestive support to a conclusion that adults may not be attracted to food baits. (3) When leaves were coated with sugar, however, flies which were on them were stimulated to remain, indicating that the addition of sugar to cover sprays (as opposed to spot sprays which might have attracted flies from a distance) may enhance their effectiveness and persistence. (4) Pupae experimentally buried to different depths led to teneral adult emergence from 50cm of soil, and thus fruit disposal by burial may need to be deeper than this. (5) Pupae in soil fully flooded for 48 hours suffered no reduction in survival, and thus field flooding for control may need to be longer than this. (6) A study of pupation found that: up to ten prepupal larvae may leave a melon through the same hole; unlike those of Bactrocera, larvae do not jump about; as a result, immediately around and below an exit-holed melon large numbers of pupae may be found in the soil. As infested melons are identified by exit-holes, if these are removed by the farmer a large number of potentially-reinfesting adults are still present in the field but tightly grouped and thus easily located. (7) Postpupal adults emerging from the soil were killed by surface spot applications of carbaryl dust, even if applied days earlier: such applications, to the precise sites where infested melons were removed, may reduce the risk of adult reinfestation. As a result, recommendations were developed for in-field, in-season control by cover sprays with added sugar and the removal of infested melons with spot treatment of their resting places. A need remains, however, for research into attacking the life cycle at its putatively most vulnerable point the over wintering pupae in melon fields which, in Afghanistan, are traditionally planted with winter wheat. Winter suppression, ideally cooperatively on an area-wide basis, seems to offer the best hope for sustainable control if the best way to do this can be discovered. (author)