Experiments testing the effects on leafless peas of aldicarb, triazophos and a mixture of benomyl with zineb, were made on clay-with-flints soil at Rothamsted and on sandy loam at Woburn in 1977 and 1978.
The crop was shown to be susceptible to a wide range of pests and pathogens including the pea and bean weevil Sitona lineatus, the migratory nematode genera Pratylenchus, Tylenchorhynchus and Tylenchus, the pea moth Cydia nigricana, the aphids Acyrihosiphon pisum and Macrosiphum euphorbiae, the bean leaf roll and pea enation mosaic viruses and the powdery mildew fungus Erysiphe polygoni.
The mean yield of the four experiments when none of the treatments was applied was 3·6 t grain/ha, increased to 4·3 t/ha when all were applied. Aldicarb had the largest effect and increased mean yield at Rothamsted by 0·3 t/ha, attributed mainly to control of S. lineatus, and by 0·8 t/ha at Woburn attributed to control of S. lineatus and perhaps also to migratory nematodes, particularly Tylenchorhynchus. Triazophos and benomyl plus zineb did not individually increase yield but at Woburn when both aldicarb and triazophos were applied benomyl plus zineb increased mean yield by 0·7 t/ha.
All crops lodged severely, irrespective of treatment but perhaps because of experimental conditions. We suggest that susceptibility to lodging under field-scale conditions requires further study.