Environmental Entomology (1998) 27, 373-381

Robert K.D. Peterson, Leon G. Higley, Fikru J. Haile and José A.F. Barrigossi (1998)
Mexican bean beetle (Coleoptera: Coccinellidae) injury affects photosynthesis of Glycine max and Phaseolus vulgaris

Environmental Entomology 27 (2), 373-381
Abstract: Based on previous photosynthesis studies, adult Mexican bean beetles, Epilachna varivestis Mulsant, produce a different physiological response to injury in soybean than other insect defoliators. In 1993 and 1994, we conducted experiments to determine the nature and extent of photosynthetic rate reductions in soybean, Glycine max (L.) Merrill, and dry bean, Phaseolus vulgaris L. We used a randomized complete block design for all experiments. In most experiments, treatments were an uncaged, uninjured leaflet; a caged, uninjured leaflet; and a caged, injured leaflet. Treatments were replicated >5 times. Experimental units were individual trifoliolate leaflets. Four to 8 larvae or adults were placed in each leaflet cage and allowed to feed for 6-18 h. After feeding, the insects and leaf cages were removed and gas exchange properties were determined. Both adults and larvae reduced photosynthetic rates of the remaining tissue of the injured leaflet on both soybean and dry bean. A significant linear relationship between photosynthetic rate and percentage injury was observed for both adult and larval injury. Injury reduced photosynthetic rates in all 6 soybean and dry bean cultivars used in the experiments. There was no recovery of photosynthetic rates after injury of an individual leaflet. Stomatal conductance rates were not consistently different between injured and uninjured leaflets. Intercellular CO₂ concentrations were similar or higher in injured leaflets. Consequently, reductions in photosynthesis do not seem to be attributable to stomatal limitations. Quantum efficiency was not affected by injury, indicating that light-harvesting structures were not perturbed. Therefore, our results suggest that the limitations to photosynthesis are attributable to the utilization of CO₂ or the supply or utilization of phosphate. Our findings suggest that the limitation is associated with RuBPcase, RuBP regeneration, or phosphate utilization.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Robert K.D. Peterson, José Alexandre F. Barrigossi

Research topic(s) for pests/diseases/weeds:
damage/losses/economics

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Epilachna varivestis	Soybean (Glycine max)
	Epilachna varivestis	Beans (Phaseolus)