Within-season dynamics of red palm mite (Raoiella indica) and phytoseiid predators on two host palm species in south-west India

Abstract

Field surveys were conducted monthly between December 2008 and July 2009 in Kerala, south-west India to compare the population dynamics of the red palm mite Raoiella indica (RPM) on two host plants Areca catechu and Cocos nucifera during one non-monsoon season when, in general, RPM populations increase. The aim was to examine the effects of host plant, host plant locality and the impact of climatic factors on RPM and related phytoseiid predators. There were significantly higher RPM densities on areca in peak season (May/June) compared to coconut; although significantly more coconut sites were infested with RPM than areca. Although no one climatic factor was significantly related to RPM numbers, interactions were found between temperature, humidity and rainfall and the partitioning of host plant locality showed that where conditions were warmer and drier, RPM densities were significantly higher. Specifically on coconut, there was a significant relation between RPM densities and the combined interaction between site temperature, site humidity and phytoseiid densities. There was a marked difference in the density of phytoseiids collected between areca and coconut palms, with significantly more on the latter, in several months. Amblyseius largoensis was the most commonly collected phytoseiid in association with RPM, although Amblyseius tamatavensis species group and Amblyseius largoensis species group were collected in association with RPM also. There was also evidence of a weak numerical response of the combined phytoseiid complex in relation to RPM density the previous month on coconut but this was not observed on areca.