Janine E. Powell

Extracts of Flourensia cernua (L): volatile constituents and antifungal, antialgal, and antitermite bioactivities.

The chemical components of tarbush (Flourensia cernua) leaves were fractionated by extracting successively with hexanes, diethyl ether, and ethanol. Volatile profiles of each fraction were identified by using GC-MS. The hexanes fraction contained mostly monoterpenoids, while the ethanol fraction volatiles were primarily sesquiterpenoids. Crude fractions were tested for activity against fungi, algae, and termites. Application of as little as 1 μg of the essential oil from the hexanes fraction was sufficient to provide visible antifungal activity in bioautography assays. The diethyl ether fraction showed selective activity against the cyanobacterium responsible for the 2-methylisoborneol-induced off-flavor sometimes associated with catfish farming operations. All three fractions exhibited a high degree of antitermite activity.

Laboratory Evaluations of Four Entomopathogenic Nematodes for Control of Subterranean Termites (Isoptera: Rhinotermitidae)

Abstract The infectivity of four species of entomopathogenic nematodes, Steinernema carpocapsae (Weiser) [Breton strain], Steinernema riobrave Cabanillas, Poinar & Raulston [Weslaco strain], Heterorhabditis bacteriophora Poinar [HP88 strain], and Heterorhabditis indica Poinar, Karunakar & David [Coimbatore strain] was examined in the laboratory against two subterranean termites: Reticulitermes flavipes (Kollar) and Coptotermes formosanus Shiraki. In petri dish tests, they were all effective against C. formosanus at ≥400 nematodes per termite. Steinernema riobrave had no detectable effect against R. flavipes even at a rate of 2,000 nematodes per termite. The virulence of the nematodes for R. flavipes was H. indica > H. bacteriophora > S. carpocapsae > S. riobrave. The virulence of the nematodes for C. formosanus was H. indica and H. bacteriophora > S. carpocapsae and S. riobrave at α = 0.10 level. The LD50 of H. indica against R. flavipes in petri dishes and in containers with vermiculite/sand medium were 296 (95% FL: 231–353) and 264 (95% FL: 176–344) nematodes per termite, respectively. The LD50 of H. bacteriophora against R. flavipes in petri dishes was 494 (95% FL: 357–625) nematodes per termite. Heterorhabditis indica repelled termites at high concentrations in sand and vermiculite medium. The length of repellency varied with the nematode concentration. Nematodes were able to reproduce from R. flavipes and C. formosanus. The possibility of using nematodes to control termites is discussed.

MITES AND NEMATODES ASSOCIATED WITH THREE SUBTERRANEAN TERMITE SPECIES (ISOPTERA: RHINOTERMITIDAE)

Abstract Mites and nematodes associated with three subterranean termite species, Reticulitermes flavipes (Kollar), Reticulitermes virginicus (Banks), and Coptotermes formosanus Shiraki were studied. Mites belonging to 8 families were found associated with the three termite species. Australhypopus sp. (Acari: Acaridae) was the most common mite on R. flavipes and R. virginicus. Histiostoma formosana Phillipsen and Coppel (Acari: Acaridae) was the dominant mite species living on C. formosanus. Nematode, Rhabditis sp. (Rhabditida: Rhabditidae) was found in the three termite species examined. Nematodes did not cause termite mortality or abnormal behavior. Percentages of R. flavipes, R. virginicus, and C. formosanus parasitized by nematodes were 67.9, 38.8, and 3.3%, respectively. The nematodes were found mainly in the termite heads (85.8% in R. flavipes and R. virginicus). The abundance of mites varied with colonies and termite species. Australhypopus sp. occurred in large numbers when injured or dead termites are present, or when moisture of the rearing medium is low in R. flavipes and R. virginicus colonies. Histiostoma formosana and Cosmoglyphus absoloniSam i ák occurred in large numbers in C. formosanus colonies. Australhypopus sp. was tested against R. flavipes in the laboratory. It did not cause significant termite mortality at a rate of 10 mites/termite. From a biological point of view, mites investigated were not good candidates for controlling termites.

Survey of Termites in the Delta Experimental Forest of Mississippi

Termites were surveyed in the Delta Experimental Forest in west central Mississippi in 1998. Logs, branches, and stumps along three 200-m long, 6-m wide transects were investigated at each of the three study plots. Two subterranean termite species in the family Rhinotermitidae, viz., Reticulitermes flavipes (Kollar) and Reticulitermes virginicus (Banks), were recorded. Reticulitermes flavipes was the common species and constituted 81.3% of the termite occurrences. Of the 685 pieces of wood surveyed, 16.5% had termites. The percentage of the two termite species varied among plots. The percentage of wood materials with signs of termite activity or foraging termites present was positively correlated with the diameter of the wood materials (R = 0.85). The chances of a log, branch, or stump being attacked by these termites increases by 1.3% as the diameter of the wood material increases 1 cm. The percentage of dead wood with sign of termite activity ranged from 11.6% to 67.2% among the sampled plots. Termites were significantly less abundant at Plot 3, which might correspond to a lower elevation and a higher soil moisture.

SCIENTIFIC NOTES EFFECT OF INSECTICIDE RESIDUES ON SURVIVAL OF MICROPLITIS CROCEIPES ADULTS (HYMENOPTERA: BRACONIDAE) IN COTTON

A field test was conducted in August 1984 to determine the effects of thiodicarb (Larvin?), fenvalerate (Pydrin?), and flucythrinate (Pay-offs) residues on adult survival of Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), a common parasitoid of Heliothis spp. (Lepidoptera: Noctuidae) larvae. Preliminary topical tests demonstrated that these three insecticides were relatively non-toxic to adult M. croceipes. In the study presented here, five male and five female parasitoids (ages 1-4 d) were placed in each of 32 cylindrical cardboard cages (480 ml) constructed with organdy fabric at the ends, similar to those used by Scott and Lloyd (1975). Honey was provided as a food source. Three 2.0 ha plots of cotton within a 28.3 ha field were each treated with either thiodicarb (672.8 g AI/ha), fenvalerate (112.1 g AI/ha), or flucythrinate (44.9 g Al/ha), and one 2.0 ha plot remained untreated. Applications in a total volume of 37.3 1/ha were made using ground machinery. Immediately after treatment, eight cages each were placed at typical sites within each plot. Cages were attached to the terminal growth of a cotton plant such that wasps were allowed contact with the foliage. Four cages were removed from each plot 24 and 48 h after treatment and survival and mortality were recorded. Moribund wasps were recorded as dead, and wasps that escaped were not included in the calculation. A least squares two-way analysis of variance procedure was used to analyze the data. Across all treatments, significant differences (P<0.05) in survival did not occur between wasps observed at 24 and 48 h. Thus, the effects of any insecticide residues on survival were no greater at 48 h than at 24 h. High rates of survival (Table 1) indicated that M. croceipes tolerated residues of each of the insecticides tested. Survival was not significantly affected when flucythrinate residues were present on cotton. While residues of thiodicarb and fenvalerate induced only low levels of mortality in caged M. croceipes (Table 1), survival was significantly greater than that for the check. Apparently, M. croceipes was less tolerant of residues of thiodicarb and fenvalerate. Although fenvalerate was associated with the lowest rate of survival, this level would be

Scientific Notes: Development of Heliothis Virescens (Lepidoptera: Noctuidae) Larvae after Parasitization by Microplitis Croceipes and Microplitis Demolitor (Hymenoptera: Braconidae)

Microplitis croceipes (Cresson) is an important parasitoid of Heliothis spp. in the U.S.; M. demolitor Wilkinson was imported into the U.S. from Australia (Shepard et al. 1983). The following study was conducted primarily to determine how many times Heliothis virescens (F.) larvae molt after being parasitized by Microplitis spp. Heliothis virescens larvae were reared in plastic cups (25-ml) on an artificial insect diet (King & Hartley, 1985). Adult parasitoids were held in wooden cages (0.14 cu m) with Plexiglas? tops and ventilated in the back with organdy fabric. Undiluted honey was streaked on the top of the cage as a food source, and a water source was provided by means of soaked cotton balls held in plastic cups (25-ml). Rearing methods for the parasitoid colony are detailed by Powell & Hartley (1987). Host larvae were parasitized by exposing them singly on a small brush to several (15-20) female parasitoids (1-5 d-old) held in a plastic container (500-ml). Use of two to four such containers was rotated during manual exposure of hosts to wasps. This method improved the likelihood that each larva was parasitized because oviposition was observed. Multiple ovipositions in the same host were not allowed. Determining the occurrence of molting was facilitated by lightly powdering each hosts entire cuticle with Day-glo? fluorescent pigment (DAY-GLO Color Corp., 4515 St. Clair Ave., Cleveland, OH 44103); when larvae molted, the dye was cast with the exuviae. While in the first instar (ca. 24-h old), 36 host larvae were exposed for parasitization to M. croceipes and 36 were exposed to M. demolitor. The same number and procedure were used for three additional groups of larvae when they reached the early second, third, and fourth instars. In addition, 36 non-parasitized larvae for each instar group were held as controls and treated in the same manner as test larvae. Larvae were checked during morning hours to observe the occurrence of molting. When molting was observed, control and test larvae were re-powdered and developmental times (to the nearest day) between molts were recorded. Each larva was held individually in plastic cups containing diet (total of 36 control and 144 test larvae). Studies were conducted at 26 + 2?C, 60 + 10% RH, and a photoperiod of 15L:9D. Data were analyzed using a least squares analysis of variance procedure with an a priori significance level (ox) of 0.01. The percentage of H. virescens larvae developing to different instars after parasitization by M. croceipes and M. demolitor is illustrated in Fig. 1. When host larvae were in later instars at the time of parasitization by either Microplitis spp., they molted fewer times than larvae parasitized as earlier instars. For example, 94% of the hosts exposed to M. demolitor in the second instar molted twice more to develop to the fourth instar, while 93% of those exposed in the fourth instar molted only once more. The