Résumé :
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Studies on the harmfulness of entomofauna from the genera Lygus and Orthops were carried out on seed plantations of : onions in 1975-78 and again in 1981-85 ; beans in 1975-78 and 19884-85; carrots in 1968-70 and 1983-85 and cucumbers in 1975-78. From the collected heteropterofauna on the above crops 5 families were distinguished : Miridae, Pentomidae (except cucumbers), Lygaeidae, Nabidae and Anthocoridae, 12 heteropterous species being collected on onion, 21 - on beans, 32 - on carrots and 16 - on cucumbers. The most numerous on the studied crops were phytophagous Heteroptera constituting 95-99 % of all collected heteropterofauna, whereas predaceous Heteroptera constituted only 1-6 %. In the 1960's and 1970's on seed plantations of onions, beans and cucumbers the most prevalent was Lygus rugulipennis (67-79 %) and L. gemellatus (8-12 %), on carrots - Orthops campestris (61 %), O. Kalmi (13 %) and L. rugulipennis (15 %). An analysis of the collected heteropterofauna in the 1980's showed that on the seed plantations of onions and beans L. rugukipennis occured in 94-96 % suppressing L. gemellatus, which constituted hardly 0,3 % and only on onions. On seed carrots, L. rugulipennis dominated over species from the genus Orthops, characteristic for umbelliferous plants. All the seed crops under studi were invaded by Heteroptera during flowering of these plant, except cucumbers, where they occured before flowering of these plants, except cucumbers, where they occured before flowering, I.E. in the III decade of June and I decade of JUly, after which there generally developed two generations during the vegetation season. The harmfulness of tarnished plant bugs sucked up flower buds, pod buds and blans at the stage of milk maturity. That caused falling of flowers and pod, as well as scars on the seeds, and in effect - a decrease in the value and yield of seed beans. On carrots, tarnished plant bugs sucked up flowers and immature seeds, injuring seed embryos, thus decreasing the yield and germinating ability of seeds. On cucumbers, tarnished plant bugs injured heart-shaped and the youngest leaves, causing necrotic spots and holes leading to withering of leaves and even of the entire plant. On the basis of studies on the developmental cycle of the tarnished plant bugs, L.rugulipennis and O. campestris, and field observations it was attempted to determine theorical thresholds of harmfulness on : seed onions - 2-3 imagines/1 m of yielding onions during flowering; yielding beans - 10-20 imagines/100 net sweeps per plant during invasion ; carrots - 30 tarnished plant bugs/100 net sweeps cucumbers - 1 imago/1 plant during pest invasion. Two chemical treatments against tarnished plant bugs on seed plantations of onions and carrots appeared to be highly profitable. In the case of onions the yield increase of seeds ranged from 53 to 508 kg/ha, which gave the crop increase value from 33 thousands to 1,5 mln zlotys/ha. In case of beans the seed increase ranged from 44 to 296 kg/ha which gave the value increase from 96 th. to 1,2 mln zlotys/ha, and constituting only on beans from 4,6 to 5,7 %. In addition to that, the germination capacity of carrot seeds increased from 10 to 28 % and the number of injured bean seeds decreased by 50-84 %. The cost of onion and carrot seeds was so high (ranged from 2 to 6 th. zlotys/kg) and the costs of treatments were so low (on average 1200-1800 zlotys/ha), that each zloty paid for the protection of these crops was repaid averagely at 380-530 zlotys/ha. The following insecticides were used to control tarnished plant bugs in the mentioned above field crops: Ambusz 25 EC at the rate of 0,15 dmE3/ha, Decis, 2,5 EC at the rate of 0,4 dmE3/ha, Ripcord 10 EC at the rate of 0,3 dmE3/ha and Thionex 35 EC at the rate of 1,5 dmE3/ha, Thiodan 35, fluid was used as a comparative preparation at the rate of 1,5 dmE3/ha. All the insecticides, except Ambusz and Thiodan (their effectiveness differed in different years), displayed a high effectiveness in decreasing the population of tarnished plant bugs both 24 and 48 hours after treament and throughout the vegetation period which in consequence had a significant influence on the seed yield increase and on the germinating capacity of seeds, e.g. of carrots.LA Polish
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