Evaluation of Two Biotypes of Euseius scuta lis (Acari: Phytoseiidae) as Predators of Bemisia tabaci (Homoptera: Aleyrodidae) DALE E. MEYERDIRK AND DONALD L. COUDRIET Boyden Fruit and Vegetable Insects Research Unit, Agricultural Research Service, U.S. Department of Agriculture, University of California, Riverside, California 92521 Downloaded from https://academic.oup.com/jee/article/79/3/659/2214652 by guest on 01 October 2021 J. Econ. Entomol. 79: 659-663 (1986) ABSTRACT Two predaceous mite biotypes of Eusetus scutalts (Athias-Henriot) were eval- uated as biological control agents of Bemtsta tabact (Gennadius). One biotype was originally collected on citrus in Morocco; the other was collected on lantana in Jordan. Both biotypes survived well on ice plant pollen, but their survival varied when fed various stages of B. tabact. The Jordanian mite had longer survival when fed eggs or first or second instars of the whitefly. Eggs, followed by first instars, were the most suitable whitefly host stage fed to the mites; the least suitable stage was the second instar. Egg consumption by both mites showed preference for freshly laid eggs. Although the mean survival rate was 22.9 days, one Jordanian biotype survived 69 days when fed whitefly eggs. Oviposition periods did not extend beyond 16.6 days for either biotype. The Jordanian biotype showed higher fecundity, longer ovipositional period, and longer survival when fed various stages of B. tabact than the Moroccan biotype. Potential use of the Jordanian mite for biological control purposes appears promising for regulation of B. tabact in California. Euseius scutalis (Athias-Henriot) is a common the world (Costa 1976) and recently has become a phytoseiid mite with a cosmopolitan distribution serious vector of three virus disease agents (squash in the Middle East and North Africa on a variety leaf curl, lettuce infectious yellows, and cotton leaf of host plants including Citrus sp. (Porath & Swir- crumple viruses) in Southern California (Duffus & ski 1965), Vitis sp. (Daneshvar 1980), Hibiscus es- Flock 1982). Chemical control is limited because culentus L. and Gossypium sp. (Narayanan & Kaur of the whitefly's behavior-i.e., adult feeding, 1960), and Gossypium herbaceum L. (Swirski & mating, oviposition, and larval development oc- Amitai 1965). It is considered synonymous with curring on the underside of its host's leaves. Thus, Typhlodromous scutalis (Athias-Henriot 1958), canopy penetration of aerially applied pesticides Amblyseius rubini Swirski & Amitai, A. gossipi El- has not been effective (Johnson et al. 1982). Pes- badry, and A. delhiensis Narayanan & Kaur (Wy- ticide resistance to organophosphates and pyre- soki & Bolland 1983, Bounfour 1985) according to throids has also developed (Prabhaker et al. 1985). Bounfour (1985). The biology and ecology of E. This pesticide resistance plus the evidence of re- scutalis from Morocco was studied by Bounfour productive stimulation by pesticides (Dittrich et (1985). E. scutalis has been reported (as E. rubini) al. 1985) has prompted research on biological con- feeding not only on spider mites, but also on trol of B. tabaci. whiteflies (Aleyrodidae) and other foods (Swirski The purpose of our investigation was to evaluate et al. 1967a, Wysoki & Cohen 1983). This phe- two predaceous mite biotypes of E. scutalis from nomenon of phytoseiid mites feeding on whiteflies different geographical locations and different host is not uncommon. The sweet potato whitefly, Be- plants as predators of B. tabaci, and to determine misia tabaci (Gennadius), has been reported as prey if either could serve as a potential biological con- of Amblyseius swirski (Athias-Henriot) (Swirski et trol agent of this whitefly species. al. 1967a), E. scutalis (as E. rubini) (Teich 1966, Swirski et al. 1967a), Euseius aleyrodis (Elbadry) Materials and Methods (Elbadry 1967, 1968, Gameel1971), A. limonicus (Garman & McGregor) (Swirski & Dorzia 1968), One of the biotypes of E. scutalis was collected A. chilenensis Dosse and Eusieus hibisci (Chant) from citrus in Marrakech, Morocco, by James (Swirski et al. 1970, Meyerdirk & Coudriet 1985), McMurtry (Division of Biological Control, Uni- T. sudanicus Elbadry (Gameel1971), T. medani- versity of California, Riverside, Calif.). No obser- cus Elbadry (Elbadry 1967), T. athiasae (Swirski vations were made to determine associations with et al. 1967b), and T. occidentalis Nesbitt (Swirski whiteflies. The other biotype was collected from & Dorzia 1969). lantana in association with B. tabaci in the Jordan B. tabaci is reported to be the most economi- Valley of Jordan by D.E.M. cally important whitefly vector of plant viruses in Laboratory rearing techniques described by 659 660 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 79, no. 3 plant pollen, Malephora crocea Jacques, and fresh eggs of Pacific spider mite, Tetranychus pacificus McGregor, were used as the main food source in the stock culture and were added every 3 or 4 days. The experimental arenas consisted of one set of cotton-leaf disks free of B. tabaci and others con- taining either freshly laid eggs (<24 h old) or first > or second instars of the whitefly. Whitefly host ma- I- ...J terial was changed every 3 days. M. crocea pollen c( I- was added every 3 days to whitefly-free cotton a: disks. Disks were also placed with the upper leaf o ::E surface down on the water-saturated polyurethane Downloaded from https://academic.oup.com/jee/article/79/3/659/2214652 by guest on 01 October 2021 I- MOROCCO pads and labeled. A disk (6 mm diam) of dark ~ 100 green blotter paper, placed on each cotton leaf u a: disk, served as the ovipositional site for E. scutalis. ~ 80 E. scutalis adult females from each biotype were individually isolated and held for mating with one 60 or two males for 24 h without a food source. One E. scutalis female of each biotype was then iso- 40 Food Supply lated on each of 25 cotton leaf disks with either 8 Pollen b ~lllllW Eggs pollen, eggs, or first or second instars of B. tabaci, 20 c !i.l..iL.b..A&.l 1 sl inst8r or no food. An abundant supply of host material d ~tabaci 2nd inslsr e No Food was available to each adult mite for a 3-day pe- a riod. Laboratory observations were made every 24 5 10 15 20 25 30 35 40 h; number of eggs laid per female mite and mor- DAYS AFTER MATING tality were recorded. When mites were fed only Fig. 1. Accumulative mortality curves of adult fe- on whitefly eggs, the number of eggs consumed males of two E. scutalis biotypes fed different host ma- per day was recorded. When pollen or first or sec- terial. ond instars of the whitefly were provided as food material, only the total number of eggs laid by each biotype of E. scutalis plus mortality were Tanigoshi et al. (1981) were used. Excised cotton recorded. E. scuta/is eggs were randomly collected leaf disks (2 cm diam) were placed with upper from each feeding group and monitored to deter- leaf surfaces down on a water-saturated polyure- mine their viability. thane pad in a stainless steel pan (20 cm square E. scutalis survival rates were determined by by 2.5 cm deep). A cellucotton barrier (ca. 1.25 transferring 25-50 protonymphs (1 day old) pre- cm wide) saturated with water was placed along viously fed pollen to cotton leaf disks (five nymphs the periphery of each leaf to prevent escape of per disk) containing either eggs or first or second mites from the leaf arena. Ovipositional sites for instars of B. tabaci or pollen. Leaf disks and food the stock culture consisted of several cotton fiber sources were changed every 3 or 4 days until the strands beneath a plastic coverslip (22 mm). Ice mites died. Those mites that wandered off the sub- UJ 26 ...J « 24 :::l: ~ 22 JORDAN I , 20 MOROCCO 0 Cl Morocco strain UJ 18 :::l: discontinued :J Ul 16 Z 0 14 U Ul 12 CJ CJ 10 UJ 0 8 z 6 z « UJ ::!" Fig. 2. B. tabaci egg consumption by adult females of two E. scutalis biotypes. June 1986 MEYERDIRK & COUDRIET: E. scutalis PREDATION ON B. tabaci 661 Table 1. Oviposition period and fecundity of two biotypes of E. scutalis when fed different host materials f no. of days Parameter Biotype B. tabacl Pollen No food Eggs 1st instar 2nd instar Oviposition period (days) Jordan 14.5a 15.6a 12.4a 2.7a 0.3a Morocco 16.6a 9.2b 4.0b 2.0a 0.5a % eggs laid ~14 days Jordan 84.1a 87.8a 9l.6a 100a l00a Morocco 80.2a 97.9b 98.0a 100a l00a Total no. eggs laid/9 Jordan 15.0a 16.8a 9.5a l.6a 0.3a Morocco 35.7b 12.4b 5.9b 2.3a 0.8a No. eggs/9/day Jordan l.Oa Ua 0.6a 0.5a 0.3a Morocco 2.2b l.3a l.3b l.Oa 0.2a Downloaded from https://academic.oup.com/jee/article/79/3/659/2214652 by guest on 01 October 2021 Means within a column and parameter followed by the same letter are not significantly different (P < 0.01; Duncan's [1951] multiple range test). strate and could not be found were not included extended periods of time, which may be attributed in calculating the percentage of survival. to its association with this whitefly species on lan- B. tabaci used in these studies were collected as tana. Both biotypes were short-lived when no food adults from Lantana camara L. in the Imperial source was offered. The whitefly second instar was Valley, Calif., in 1982 and subsequently reared on not readily fed upon by either biotype, as denoted cotton in a greenhouse at Riverside, Calif. Seasonal by the high mortality early in the test.