Date of Award

Spring 1993

Project Type

Dissertation

Program or Major

Plant Science

Degree Name

Doctor of Philosophy

First Advisor

James E Pollard

Abstract

Experiments were designed to study the malformation of strawberries, Fragaria x ananassa (Duchesne) caused by the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois). In greenhouse experiments, duration of blossom exposure to tarnished plant bug affected the type of malformation observed. Exposure at anthesis for 48 hours was most likely to cause apical seediness, the malformation associated with tarnished plant bug. The number of nonviable achenes per fruit increased with longer feeding durations. Malformation was also affected by blossom stage. Prebloom feeding caused blossom death. Feeding at petal fall or achene separation resulted in malformations, including apical seediness. Feeding at later stages caused little damage.

Light and scanning electron microscopy were used to assess tarnished plant bug feeding on strawberries. During early fruit development stages, insects fed upon achenes. On further developed fruit, feeding sites changed to receptacle tissue. Achene injury during early fruit stages is the most likely cause of apical seediness. Feeding during later stages caused localized cellular damage, resulting in indentations on the receptacle.

Twenty strawberry cultivars grown in a matted row trial were evaluated for susceptibility to tarnished plant bug injury. A wide range of injury was observed. 'Honeoye', 'Sparkle', 'Veestar' and 'Canoga' had significantly less injury than other cultivars. 'Mic Mac', 'Scott', 'Blomidon' and 'Redchief' were most susceptible. Cultivars with the least injury tended to have the greatest marketable yields.

Six strawberry cultivars, observed to vary in damage from tarnished plant bug injury were grown under three insecticide regimes (three sprays, one spray and no spray) to determine how differences in vulnerability might affect conventional chemical controls. Cultivars most susceptible to damage harbored more nymphs than less susceptible cultivars. Differences among cultivars were greatest when no insecticide was applied. 'Honeoye' and 'Sparkle' had the least apical seediness, followed by 'Redchief', 'Guardian' and 'Kent'. 'Mic Mac' consistently had the highest level of injury. Reducing insecticide applications did not increase apical seediness for cultivars exhibiting low susceptibility.

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