NOT E Phytoseiidae (Acari: Mesostigmata) from Cover Crops In
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NOT E Phytoseiidae (Acari: Mesostigmata) from Cover Crops in Western North Carolina1 Alex C. Mangini2 and Fred P. Hain USDA Forest Service, 2500 Shreveport Highway, Pineville, Louisiana 71360 and Department of Entomology, North Carolina State University, Raleigh, North Carolina 27695-7626 USA J. Entomol. Sci. 42(3): 415-420 (July 2007) Key Words Tetranychidae, Abies fraseri, soil microarthropods, ground cover, biological control ,The spruce spider mite, Oligonychus ununguis (Jacobi) (Acari: Prostigmata), is a pest of Fraser fir, Abies traseri (Pursh) Poi ret, grown in western North Carolina plan tations for the Christmas tree industry (Boyne and Hain 1983, Can. Entomol. 115: 93-105). The mites cause discoloration and necrosis of needles (Lehman 1982, Trans. Am. Entomol. Soc. 108: 181-286) and large populations can reduce the quality of the firs as Christmas trees. Mites in the family Phytoseiidae (Acari: Mesostigmata) are important predators of tetranychid mites (McMurtry et al. 1970, Hilgardia. 40: 331-390). This is also true of the spruce spider mite. The phytoseiid Neoseiulus tal/acis (Garman) limits population growth of 0. ununguis on Fraser fir seedlings; a significant decline in a field population of spruce spider mite on Fraser fir was associated with an increase in N. tal/acis numbers (Boyne and Hain 1983, Can. Entomol. 115: 1607-1614). Cover crops may be important in maintaining reservoir populations of N. tal/acis and other phytoseiid species in North Carolina Fraser fir plantations. Our objective was to sample for Phytoseiidae present in several cover crop spe- I cies that might be candidates for establishment in Fraser fir plantations. For com- I" parison, we also surveyed Phytoseiidae from a multiple-species feral ground cover in II a Fraser fir plantation. Knowledge of the phytoseiid mites present in these habitats will ', be va Iuable background .In formation . f'or Integrated pest management and b'looglcaI.I 1',1', control programs in North Carolina Fraser fir plantations. I We sampled six cover crop species that we believed would be compatible with 1,,'1' Fraser fir: Kentucky bluegrass, Poa pratensis L.; tall fescue ('KY31 '), Festuca arun- I dinacea Schreber', nimblewill, Muhlenbergia schreberi J.F. Gmelin; orchard grass, , Dactylis glomerata L.; subterranean clover, Trifolium subterraneum L.; and red sorrel, I Rumex acetosel/a L. The cover crop plots had been established for a separate study /11,:1' (Shribbs and Skroch 1986, J. Amer. Soc. Hort. Sci. 111: 525-528). Sixty 20 m 2 plots " 'Received 21 April 2006; accepted for publication 28 April 2007. 2Address Inquiries (email: [email protected]). 415 416 J. Entomol. Sci. Vol. 42, No.3 (2007) in a randomized complete block design with five blocks of twelve ground cover treat ments were laid out at the North Carolina State University (NCSU) Mountain Horti cultural Research Station, Fletcher, Henderson County, NC (elevation 730 m). Nim blewill plots were mowed 1-2 times per year and treated in spring with simazine and glyphosate to control weeds. Red sorrel plots were maintained with occasional ap plications of fluazifop or sethoxydim to control grasses. Treatment plots were sur rounded by a buffer of tall fescue ('KY31') (Shribbs and Skroch 1986, J. Amer. Soc. Hort. Sci. 111: 525-528). The six cover crop species were sampled on 18 October 1982, 17 April, 21 June, 20 July, 3 and 16 August, and 6 and 17 September 1983. Three of the five blocks were randomly selected at each date. One sample from each of the three blocks was collected. Within the block, the sample was taken randomly. Thus, 24 samples were obtained from each cover crop. The feral ground cover was located on an experimental Fraser fir plantation at the NCSU Mountain Research Station, Waynesville, Haywood County, NC (elevation 853 m). This cover crop was not cultivated other than an occasional mowing. No pesti cides or herbicides were applied. The Fraser fir trees were, at the time of the study, 180-610 cm (6-20 ft) in height. In many instances, the ground cover was shaded out directly under the trees and replaced by a carpet of dead needles. This untended ground cover consisted of: aster, Aster cU/1issiTorrey and Gray; Kentucky bluegrass, Poa pratensis L.; clover, Trifolium repens L. and T. pratense L.; fescue, Festuca arundinacea Schreber; giant chickweed, Stellaria pubera Michaux; nimblewill, Muhlenbergia schreberi J.F. Gmelin; orchard grass, Dactylis glomerata L.; thistle, Carduus lanceolatus L.; veronica, Veronica persica Poiret; and wild carrot, Daucus carota L. and several less common species. In 1982, four samples were taken from the cover crop in the alleys between the trees on 7 and 14 July and 20 August. Four samples from under the canopy of a randomly selected Fraser fir were taken on 4, 11, 18 and 25 September and 2 October. In 1983 samples were taken weekly from 30 May through 25 September for a total.of 17 sample dates. In 1983, at each sample date, a Fraser fir tree was randomly selected and five samples were taken, three from under the canopy of the tree and 2 from the cover crop in an adjacent alley. In total, 117 samples were collected, 46 from the alley between tree rows and 71 from under the Fraser fir canopies. Our sampling method was based on that of Metz and Farrier (1973, Environ. Entomol. 2: 433-440). For each sample, a 15 cm 2 sample of vegetation was clipped and placed in a plastic bag. The litter (L, F, and H horizons) (Coleman et al. 2004, Fundamentals of soil ecology. 2nd ed. Elsevier Academic Press. Burlington, MA. 386 p.) in the resulting exposed 15 cm 2 area was gathered by hand and placed in the bag. 2 A metal cylinder (3 cm high and with an inside area of 20 cm ) cut from standard pipe was pushed 3 cm into the soil at the center of the 15 cm 2 area. The resulting plug of soil (A horizon) was also placed in the bag. Thus, a combined sample included those parts of the ground cover containing most of the soil mesofauna (Coleman et al. 2004, Fundamentals of soil ecology. 2nd ed. Elsevier Academic Press. Burlington, MA. 386 p.; Metz and Farrier 1973, Environ. Entomol. 2: 433-440) as well as plant-inhabiting mites on the vegetation. No attempt was made to standardize the samples by weight. Each soil/litter/vegetation sample was placed individually on a Tullgren funnel equipped with a 40 W incandescent bulb for drying and the sample was kept on the funnel for one week. Microarthropods were collected into a 120 ml cup under each funnel. Each cup contained a solution of 95% ethanol and a few drops of glycerol. Arthropods in each cup were sorted using a stereoscopic microscope (10-50X). Phy- MANGINI AND HAIN: Phytoseiidae from Cover Crops 417 toseiid mites were sorted into immatures, males and females; and females were further sorted into "morphs." Sorted specimens were stored in glass vials filled with 70% ethanol and a few drops of glycerol and capped with "polyseal" caps to prevent evaporation. Female phytoseiid mite specimens were mounted on glass microscope slides in Hoyer's Medium (Krantz 1978, A manual of acarology. 2nd ed. Oregon State Univer sity Bookstores. Corvallis, OR. 509 p.), one mite per slide, and each was secured with a 12 mm diameter glass cover slip. To clear the mites and dry the medium, the slides were placed for 48 h in a drying oven set at 50°C. After drying, the cover slip on each slide was ringed with Glyptal® (Glyptal Inc., Chelsea, MA) to prevent rehydration (Krantz 1978, A manual of acarology. 2nd ed. Oregon State University Bookstores. Corvallis, OR. 509 p.). Provisional species determination of the adult female phyto seiid mites was made by the senior author with the assistance of Dr. Maurice H. Farrier (NCSU, Department of Entomology). Samples of each provisionally-identified species were sent to Mr. Harold A. Denmark, a phytoseiid systematist with the Florida Department of Agriculture and Consumer Services, for confirmation. Male and im mature phytoseiid mite specimens were not determined because they were difficult to identify accurately. Arthropods collected from the cover crop plots at Fletcher included Acari (Meso stigmata, Prostigmata and Oribatida), Chilopoda, Collembola, Diptera (larvae), Ho moptera and Thysanoptera. Mesostigmata included the families Ascidae, Parasitidae and Rhodacaridae; Scutacaridae was the predominant family of Prostigmata. Sub terranean clover growth was meager and much bare ground occurred in its blocks. Consequently, few arthropods were collected from this crop. At Waynesville, the mesofauna from the feral ground cover was similar to that in the cover crop plots at Fletcher. Additionally, Protura were found in the fir needle litter at Waynesville. Nine phytoseiid species in four genera were collected in the cover crops at Fletcher (Table 1). The predominant species were Proprioseiopsis asetus (Chant), Neoseiulus setulus (Fox) and P. clausae (Muma). Fifteen phytoseiid species in eight genera were collected from the feral ground cover in the Fraser fir plantation at Waynesville (Table 2) including two new species of Phytoseiidae (one Proprioseiopsis species and one Typhlodromips species) (HA Denmark, personal communication). The most abundant species were Neoseiulus cucumeris (Oudemans), Typhlodromips sessor (Deleon) and N. tal/acis (Garman). Phytoseiid diversity and abundance appeared to be similar among the six cover crops at Fletcher. Although the feral ground cover at Waynesville was sampled more intensely and for a longer period of time, it produced fewer total specimens than the crops at Fletcher. It did, however, have a greater species diversity than the individual crops at Fletcher, both individually and collectively. Finally, for the Waynesville col lections, there was little difference between the number of specimens collected from samples taken from under the canopy of the Fraser fir trees and the those samples collected between the tree rows (49% versus 51% of total specimens, respectively).