Population dynamics of Megaselia halterata (Diptera: Phoridae) in Spanish mushroom crops

Abstract

Diptera, phorids and sciarids, are some of the most serious pest affecting mushroom crops. Phorids have traditionally been considered a minor pest throughout the world. However, phorid populations have also markedly increased from minor to major pest status in India, UK and USA, with yield losses ranging between 10 and 40%. This paper summarizes the information regarding the phorid Megaselia halterata populations over a period of 18 months at three Spanish mushroom farms, with eighteen crop cycles monitored, three per each of the six seasons in the survey. The phorid populations peaked in spring and autumn, with an strong dip in winter. The accumulated rainfall registered in a season is strongly correlated with the number of adults trapped inside the mushroom farms. The phorid adults mainly went into the facilities at casing. During harvesting, the number of adults trapped increased, corresponding to the first generation of phorids that had developed inside the growing substrates and coming from eggs laid during the casing period. This new generation of flies could invade adjacent mushroom farms. So, preventing from flies entering the facilities, shorting the harvesting period and steaming-off of the substrates before they are thrown out is strongly advised.