Evaluation of the potential of the Tasmanian brown lacewing, Micromus tasmaniae Walker [Neuroptera: Hemerobiidae], as a biocontrol agent of aphids on glasshouse capsicums

Abstract

Capsicums are one of the most important glasshouse vegetable crops in the world, on which aphids are the key pest group. In New Zealand, there are no commercially available biocontrol agents for glasshouse aphid pests. Due to the development of resistance to many organophosphate and carbamate pesticides especially by the aphid Myzus persicae Sulzer, broad-spectrum chemical control is becoming increasingly difficult in conventional and 'integrated' pest management programmes. Therefore, a need exists for a suitable biocontrol agent of aphids to be mass reared and released into glasshouses.

The Tasmanian brown lacewing, Micromus tasmaniae Walker, is an aphid predator that is found commonly throughout Australasia and has many characteristics that make it an excellent candidate for mass rearing and subsequent release in glasshouses.

A method for rearing M. tasmaniae was developed which significantly reduced the labour inputs and adult lacewing mortality rates, and increased the efficiency of egg production, compared with existing rearing methods. However, further potential exists for increased production efficiency and some recommendations are discussed.

Trials conducted in this study have demonstrated that inoculation of M. tasmaniae eggs on capsicum plants has potential for control of M. persicae under glasshouse conditions. M. tasmaniae larvae selectively consume young aphids on the upper buds and growing shoots of the plant. However, the populations of aphids remained relatively high, although the leaves are likely to contribute little to fruit growth.

The results of these trials suggest that cannibalism restricts the number of eggs which can be placed on plants. It is important in terms of pest control for the predator to establish control early in aphid population development, or the regulatory capacity of the larvae is exceeded. It has been suggested in these trials that there is a positive relationship between the number of healthy buds on a plant and the persistence of lacewing larvae on plants. Furthermore, there was likely to be a positive relationship between the number of healthy buds on a plant and predator density. There were some indications from these trials that temperatures around 28º C in Canterbury glasshouses during summer may impair larval performance.

Based on these trials, the potential for inoculation of M. tasmaniae eggs on plants to supplement the existing use of selective aphidicides (such as the carbamate pirimicarb) at low rates for aphid control in glasshouses has been demonstrated. Recommendations for future glasshouse trials of M. tasmaniae are discussed.