|Authors: ||M.J. Raupp, I.H. Mars, G. d'Eustachio|
|Keywords: ||degree-day, host resistance, systemic insecticides|
The boxwood leafminer, Monarthropalpus flavus (Schrank), is a serious pest of boxwoods in landscapes and nurseries.
To aid in pest prediction, the life cycle of boxwood leafminer was described in relation to growing degree-days.
This information was used to time applications of three systemic insecticides: avermectin, imidacloprid, and acephate.
Avermectin and imidacloprid applied at adult flight provided excellent control.
Imidicloprid applied in the summer gave good control of larvae.
Avermectin and acephate were ineffective when applied in the summer.
While a pesticide application can provide control, the use of resistant plant material may provide a durable and environmentally superior strategy for dealing with this pest.
We examined the ability of boxwood cultivars to serve as hosts for the leafminer.
A field survey of nine cultivars revealed significant differences in levels of infestation by the boxwood leafminer.
An analysis of larval survival confirmed high levels of susceptibility in Buxus sempervirens ‘Myrtifolia’ and Buxus microphylla ‘National’ while B. sempervirens ‘Handsworthiensis’ and B. sempervirens ‘Vardar Valley’ exhibited high levels of resistance.
To rule out the possibility that differences in colonization were responsible for differences in levels of survivorship, we enclosed ovipositing flies on several cultivars and measured larval survival. Buxus sempervirens ‘Vardar Valley’ continued to demonstrate high levels of resistance to the leafminer and B. sempervirens ‘Myrtifolia’ was highly susceptible.
We also found evidence of resistance in the cultivar B. sempervirens ‘Memorial’. We tested the hypothesis that boxwood cultivars differed in leaf toughness, an attribute thought to be important to the egg-laying behavior of adult flies.
Differences in leaf toughness among cultivars existed.
However, no relationship was found between leaf toughness and the number of times leaves were attacked by ovipositing flies.
A mechanism other than leaf toughness may be responsible for differences in leafminer abundance on different varieties of boxwood.
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