JASP 3 -- 1985.pdf - International Herbage Seed Group

34 JOURNAL OF APPLIED SEED PRODUCTION, VOL. 3, 1985alfalfa and store it as a pollen-nectar ball in the reproductivecells they construct in nesting boards. The female bee lays anegg on the pollen-nectar ball before sealing the cell. Afteregg hatch, the bee larva consumes the pollen-nectar ball asfood. This study was initiated to determine if residues ofcommercially used insecticides applied to alfalfa grown forseed were present in the pollen and nectar collected by thebees, and if so, whether the levels were high enough to betoxic to the bee larvae.MATERIALS AND METHODS'Arc' alfalfa was planted August 17, 1977, to supplyindividual plots, 3.6 X 6.0 min size. Each plot consisted offour rows, 90 em apart and was managed for alfalfa seedproduction in 1978,1979, 1980and 1981. Aportionoftheseplots was utilized in 1978 and 1979 for pilot studies. In 1980,the study was expanded to include additional insecticidescurrently used by growers in seed production. A summary ofresidue data (George and Rincker, 1982) showing residuesfound in the pollen-nectar ball from the cell, and leaffrom thecell is presented in Table 3. In 1980 and 1981, commerciallyused insecticides were applied to individual plots of alfalfa atrecommended rates (kg a.i. ha-t) as follows: demeton, 0.28;dimethoate, 1.68; trichlorfon, 1.68; carbofuran, 1.12; and at1. 5 times these rates. Aldie arb (Temik®), a pesticide presentlyunregistered for commercial use on alfalfa, in the PacificNorthwest, was also used in the pilot study in 1978 and 1979at 3.36 and 5.04 kg a.i. ha-t. It was not applied in 1980 or1981 but continued observations were made to determine ifresidues carried over from year to year. Aldie arb was appliedto a new plot at the lower rate in 1980 only. Oxydemetonmethyl(0.56 and 0.84 kg a.i. ha-t) was applied in 1981instead of demeton. Aldicarb was applied as a granularsidedressing in mid-May. All other insecticides were appliedas foliar sprays. Carbofuran and dimethoate were appliedonce about mid-May, but the others were applied threetimes during bloom stage near June 3, June 24 and July 8,each year.The first spring-growth of alfalfa was clipped and removedthe last week of April each year. Before the alfalfa regrowthbegan flowering, about June 1 each year, each plot wascovered with a Saran screen cage of 18 X 14 mesh (6 X 6 X1.8 m in height) to prevent the bees from becoming contaminatedwith unknown insecticides from outside their testarea.Laminated wooden bee nesting boards were provided ininsulated shelters inside each cage. A fresh supply of loosecells from wild-trapped leafcutting bees were used in 1980.The loose cells were incubated in a laboratory incubator set at30 C and 60% R.H. Freshly emerged bees were counted,sanitized (quick dip in a 0.5% solution of sodium hypochlorite)to control chalkbrood (Ascosphaera aggregata),and released into each cage after the alfalfa began flower-ing.The bees were introduced into each cage in groups of 10 to 15over a period of about one month. Total bees/cage were 104in 1980 and 140 in 1981. Bee cells recovered from eachtreatment in 1980 were identified and retained for use in plotswith the same treatments in 1981 to determine if there wasany adverse accumulative treatment effect the following year.Bees from the 1980 demeton treatments were used with theoxydemeton-methyl treatments in 1981.Pollination activities of the bees were observed at leasttwice a week to determine if bee numbers were declining orpollination was not being achieved due to loss of bee vigor.Sampling procedures and results of residue analyses onTable 1. Number and status ofleafcutting bee cells recovered from alfalfa seed plots treated in 1980 and 1981 with variousinsecticides.Rate Total No. of Cells %of Total CellsConstructed With CocoonsInsecticide (kg a.i. ha-l) 1980 1981 19801981%of Cocoons With %of Total CellsLive Larvae With Pollen Balls1980 1981 1980 1981Control 680 602 74Demeton 0.28 870 82Demeton 0.42 816 70Aldicarb 3.36 609 78Trichlorfon 1.8 368 790 58Trichlorfon 2.52 848 567 73Dimethoate 0.56 653 471 79Dimethoate 0.84 558 421 77Carbofuran 1.12 452 654 81Carbofuran 1.68 366 492 80A1dicarb(NT) 1 566 384 64A1dicarb(NT)2 585 75Oxydemeton-methyl 0.56 565Oxydemeton-methyl 0.84 801!Treated in 1978 and 1979 @ 3.36 kg of a.i. ha-l, but not in 1980 and 1981.ZTreated in 1978 and 1979 @ 5.04 kg of a.i. ha-l, but not in 1980 and 1981.38T2- 129 128 723 693 - 09 08 065558524461465770696789 93 12 3093 890 1596 1187 90 19 32100 92 12 3984 90 9 4690 88 11 3090 95 9 4190 97 10 3693 97 15 2593 1195 2497 25