1. A study of Carabidae of arable land with special reference to effects of soil applied pesticides by BRIAN R. CRITCHLEY, B.Sc.(Wales) Dip.Agric.Sci.(Cantab0 A thesis submitted in part fulfilment of the requirements for the Degree of Doctor of Philosophy in the University of London. Imperial College Field Station Sunninghill Ascot, Berkshire. May, 1968 2. ABSTRACT Carabidae in arable fields were studied at the Imperial College Field Station from November, 1964 to July, 1967 inclusive. Sampling was by pitfall trapping using modified plastic, plant pots. Within-trap predation was reduced by separating large from small species with a zinc gauze grid. Eighty-five species of Carabidae were recorded but only 15-25 species were caught in sufficient numbers (>1% of total catch per annum) to be considered as potent- ially valuable predators. Absolute numbers of Bembidion lampros were estimated using the mark and recapture method and were equivalent to two individuals per square foot of land in June during the summer peak of activity. Natural mortality factors were studied in carabid larvae with special emphasis on insect parasitism. The residual contact and fumigant toxicities of thion- azin in sandy loam soil to adult Carabidae were studied in different environmental conditions and with individuals of different species, size, sex, age, and physiological condition. The minimal effective dosage (the smallest amount to give >95% kill as an end point) at 15°C as determined by time/mortality studies with Bembidion lampros and Pterostichus vulgaris was 1-4 p.p.m. (2-8 lb.a.i./6" acre). The relative toxicities of four organophosphorus pesticides to B.lampros, P.vulgaris. and Agonum dorsale were phorate>thionazin>disulfoton>menazon. Menazon was non toxic at normal field dosages. 3. The effects on Carabidae of thionazin, ethylene dibromide, ehloropicrin and Dazomet applied to the soil for the control of Heterodera rostochiensis in potatoes were studied in field experiments during 1965-67. Thionazin broadcast at 10 and 40 lb/acre greatly reduced numbers of Carabidae in the summer as did Dazomet and ethylene dibromide at 400 and 800 lb/acre respectively. The ecological signif- icance of these results is considered. The persistence of thionazin residues in soil, water, and in adult Carabidae were analysed by gas chromatography. Downward leaching of thionazin by water in sandy loam soil was demonstrated in field and laboratory experiments, and thionazin was identified in the bodies of dead Carabidae. 4. CONTENTS Eau ABSTRACT 2 GENERAL INTRODUCTION .4 5 Part I Population Studies on Carabidae in Agricultural Land 8 Part II Factors Affecting the Toxicity and Persistence of Pesticides in Soil to Carabidae * 43 Fart III Field Studies bn the Action of Soil Applied Pesticides on Carabidae of Arable Land 119 Part IV Persistence of Thionazin Residues in Soil, Water and Carabids 188 GENERAL DISCUSSION 235 ACKNOWLEDGEMENTS * 238 REFERENCES 239 APPENDIX 257 5. GENERAL INTRODUCTION Since the Second World War synthetic organic pesti- cides have become increasingly important in the control of pests affecting health and food production throughout the world. The benefits from their use cannot be doubted but since Rachel Carson's (1963) publication of Silent Spring there has been much concern about their possible harmful effects from misuse. In the United States the production of all pesticides for 1960 was in the region of 900 million pounds (Hayes, 1964) and it is estimated that this amount will double by 1970• In Great Britain pest problems are not on the same scale but nevertheless about 150 pesticides are in use today (Ministry of Agriculture, Fisheries & Food, 1965) and most are used in agriculture. Carabids, because of their generalized predatory habits are not considered as important natural enemies as are specific ones such as coccinellids and some parasites. Many instances can, however, be quoted of carabids as bene- ficial predators and papers by Wishart, Doane & Maybee (1956), Hughes (1959), Skuhravy (1959), Wright, Hughes & Worrall (1960), Hughes & Mitchell (1960), Dobson (1961), and Coaker & Williams (1963) are especially significant because they relate to Carabidae in arable fields. There is still much to be learned of their feeding habits and of their effects as predators in arable fields; also required is a knowledge 6. of the effects on them of pesticides - and especially of the organophosphorus group which are now replacing many of the organo-chlorine pesticides formerly used as soil insecticides. Carabids are comparatively long lived as adults and have life cycles of one or more years Some species are omnivorous and some are primarily phytophagous and may be pests e.g. of strawberry fields. The great majority are predators and hence are potentially beneficial. Thus, the possibility that these insects may be seriously affected by pesticides must not be overlooked especially as, if killed, they are likely to take longer to recover than the pests against which the treatments are applied. This thesis is divided into four parts. Each is complete in itself but the four together are meant to give an overall picture of the relative abundance of Carabidae in certain arable fields and of the possible effects on them of soil applied pesticides, especially the organo-phosphate thionazin. Part I describes a study of Carabidae in arable fields not treated with pesticides. The relative abundance of the more common species was determined by pitfall trapping. Absolute numbers, movement and dispersal were assessed for one species i.e. Bembidion lampros. Some natural mortality factors affecting carabid larvae were also studied. Part II describes laboratory evaulations of the susceptibilities of adult Carabidae to various pesticides, particularly thionazin 7. (0,0-diethyl 0-2-pyrazinyl phosphorothioate). The toxicity and persistence of the pesticides were determined in differ- ent controlled conditions and for species of different size, age, physiological condition, and behaviour. Part III describes the results of three years field experiments to study the immediate and longer term side effects of soil applied pesticides used for the Control of the potato cyst nematode, Heterodera rostochiensis. Spring applications of granular thionazin applied in-the-furrow at two rates were compared with broadcast treatments also at two rates. The immediate and longer term effects of three soil fumigants, ethylene dibromide chioropicrin and Dazomet (3,5 dimethyl tetrahydro 1, 3, 5, 2H-thiadiazine-2-thione) applied in autumn were also compared. Finally, in Part IV the persist- ence of thionazin in a sandy loam soil was determined in laboratory and field experiments using gas chromatography. The leaching of thionazin in soil was determined and residues in drainage water were analysed. Residues of thionazin in adult Carabidae exposed to treated soils were analysed by gas and thin layer chromatography to determine amounts of pesticide picked-up and possible hazards to organisms higher up in food chains. 8. PART Population Studies on Carabidae in Agricultural Land CONTENTS ?taw. INTRODUCTION .4. • 4 • • 66666•• • • 9 MATERIALS AND METHODS • 10 1. Pitfall Traps 10 2. Sites 10 RESULTS 13 1. Carabidae Recorded 13 2. Relative Abundance of Common Species 13 3. Comparison of Carabidae from Different Sites • 16 4. Absolute Population Estimates of Bembidion. lampros • 24 5. Foraging Range and Rate of Dispersal of B.lampros 27 6. Choice of Habitat 29 7. Effects of Predators and Parasites on Numbers of Carabid Larvae 30 DISCUSSION 35 SUMMARY AND CONCLUSIONS 41 9. INTRODUCTION Before studying possible side effects of pesticides on Carabidae in a particular area it is necessary to deter- mine the species* their abundance and distribution within and around the crop habitat. The common "key" species must be defined and their edblogical abundance determined. The ability of species to disperse to or from areas affected by pesticides should also be assessedo Most adults and the larvae of a few species of Carabidae are very active on the soil surface and one of the best ways of sampling them is by pitfall traps. However, owing to their predatory habits within - trap predation must be minimised and hence an improvement was made on the standard jam jar method. Adult and larva Carabidae were trapped continuously throughout the year in either bare soil or in a crop in three arable fields at Silwood Park. An absolute population estimate of Bembidion lampros* the most commonly occurring carabid species in arable fields at Silwood Park* was made during peak activity in the summer using a mark and recapture method. Natural mortality factors* especially insect parasitism of carabid larvae, were also investigated. 10. MATERIALS & METHODS 1. Pitfall Traps Surface active carabid adults and larvae were trapped live in the field in pitfall traps. These consisted of plastic plant pots 3i in. deep, 31 in. wide and mottled grey in colour. Holes at the bottom of the traps were covered with fine mesh nylon gauze and permitted the exit of rainwater but not of trapped carabids. A removable zinc gauze platform with 2 mm. diameter holes rested on the inwardly sloping sides of the pot about 1 in. from the bottom. The top of the trap was level with the surface of the soil and immediately below the trap was a 3-6 in. deep pit to allow rapid drainage. One inch above the trap was a transparent (or coloured) 4 in. wide plastic cover supported by a curved piece of zinc coated wire (Fig.1). Soil within 12 in. of the traps was kept free from weeds and organic debris. The traps were emptied at least once a week. 2. Sites Carabids were collected from three arable fields at Silwood Park: Four Acre Field, Church Field and Hill Bottom. The beetles were sampled in pesticide treated and untreated potato plots in experimental areas of Four Acre Field and Church Field, in an untreated area of Four Acre Field kept fallow and cultivated at regular intervals, and on one edge of the field bordering a mixed sycanore.beech^sweet chestnut wood.