Effect of injury by the pea midge, Contarinia pisi (Winn.), on yield and quality of vining peas
1989
Joensson, B.G. (Nordreco AB, Bjuv (Sweden))
The effect of injury by the pea midge, Contarinia pisi (Winn.), was studied in commercial vining pea fields in Southern Sweden. The study included two pea cultivars with potential to set 2 and 3 pods/node, respectively. The proportion of infested flower buds increased progressively from the first fertile node on the pea plant to the highest yield-contributing node in the pea fields studied, which had been selected because they were highly infested. Each field provided different levels of infestation as the intensity typically declined from the border towards the centre of the field. When expressed as percentage of infested buds on the yield-contributing nodes, there was a strong negative correlation between injury level and yield. There was no indication of a difference in yield response to injury by C.pisi between the two cultivars. An increase in injury level resulted in a reduced number of fully developed pods/plant, an increase in the number of peas/pod as well as in maturity level and a decreased proportion of small peas. Small peas of a low maturity are regarded as high quality peas. The yield from a pea crop that had lost pods owing to injury by C. pisi was higher than that obtained from a crop that had lost an equal number of pods owing to other factors. The decrease in yield as a result of injury by C. pisi, expressed as percentage of infested buds, was relatively slight. The reasons for this are discussed, taking into account the distribution of infested flower buds on the plant, compensation by the plant and normal flower and pod abscission caused by factors other than C. pisi. This shedding averaged 43% on the tripodded cultivar and 25% on the dipodded one.
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