Field Monitoring and Efficacy of Entomopathogenic Nematodes Against Chamomile Stem Weevil Microplontus rugulosus and Chamomile Smooth Beetle Olibrus aeneus Under Greenhouse Conditions

Abstract

Chamomile Matricaria recutita (L.) is an ancient healing plant; it is used for a sore stomach, a mild laxative, anti-inflammatory and a gentle sleep aid. Chamomile plants are infested by chamomile stem-weevil Microplontus rugulosus (Col., Curculionidae) and chamomile smooth beetle Olibrus aeneus (Col., Phalacridae), and can lead to a high reduction in chamomile yield. This work aimed to survey M. rugulosus and O. aeneus by different monitoring methods as well as to manage them by using entomopathogenic nematodes. Sweep nets, water traps, and dissecting the chamomile stems and flowers were used to monitor for M. rugulosus and O. aeneus. Chamomile insects were collected from naturally infested plants moved from the field to the greenhouse. Management of chamomile insects was conducted using three strains of entomopathogenic nematodes; while the control plants were sprayed only with water. Each strain was replicated three times and each replicate included 50 chamomile plants (combined total was 150 for each strain). Three treatment dates were carried out in May, June and July; the first one was mainly for controlling stem weevil, while the other two dates were for smooth beetle. The results showed that 70–80 % of stems had damage and symptoms of stem weevils. Thirty percents from the investigated plants were larvae free of smooth beetle; whiles 70 % was infested with different classifications (e. g. 1, 2, 3, 4 or more than 4 larvae/blooms). The results confirm that smooth beetle infestation and larval numbers were higher in May and June than July. Steinernema carpocapsae had more efficiency than S. feltiae and Heterorhabditis bacteriophora in controlling both insects. Entomopathogenic nematodes could be one of the effective management strategies to control these insects in the chamomile fields.