Field studies on occurrence, alternate hosts and mortality factors of Date Palm Mite, Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae)

Abstract

The occurrence of date palm mite (DPM), Oligonychus afrasiaticus, its association with other mite species and alternate host plants were studied in nine provinces of Saudi Arabia during eight consecutive years (2011–2018). In addition, different mortality factors of DPM during the fruiting season were assessed in Riyadh city. The results showed that all DPM developmental stages were recorded on date palm young-aged fronds as well as grasses growing underneath the trees during off-fruit periods, even in severe winters. Interestingly, DPM was found only on narrow leaf alternate host plant species belonging to the families Arecaceae and Poaceae. Moreover, Hyphaene thebaica, Phoenix canariensis, Cenchrus ciliaris, Dichanthium annulatum, Hilaria sp., Hyparrhenia hirta, Pennisetum ciliarae, P. divisum, Pennisetum sp. and Aeluropus littoralis were reported for the first time as alternate host plants of the DPM. Two phytophagous mites, Eutetranychus orientalis and E. palmatus (Tetranychidae), and the predatory mite Spinibdella cronini (Bdellidae) were found associated with DPM on date fruits. However, the phytoseiid mite Cydnoseius negevi was found on the grasses growing under the trees. Amongst mortality factors, pathogens followed by predators were responsible of deaths in different DPM stages. However, the unknown environmental factors caused maximum mortality of all DPM stages than any other factor. Based on the obtained data, it is suggested that young-aged fronds should be sampled prior to fruit setting for early detection of DPM and consequently should be chemically treated during the off-season. In addition, the alternate host plants as well as date palm trees growing along the roadside should be chemically treated as they may be a source of DPM. Also, more attention should be given to search and conserve indigenous predators which can be used efficiently against DPM. It is anticipated that such data can provide valuable information to improve IPM program for controlling DPM in other regions of Saudi Arabia.