Armored Scales and Their Parasitoids on Commercial Avocados Grown in California or Imported from Mexico.

Levels of armored scales (Hemiptera: Diaspididae) on Mexican Hass avocados imported into California over May 2008-June 2009 were monitored on 135 trucks entering the state via the Blythe border station, the entry point receiving the highest volume of fruit. Levels of live sessile scales were 3.9-fold higher than indicated in a previous survey (September 2007-April 2008) although levels of live eggs and crawlers were similar to previous levels. A survey of avocado fruit in California infested with armored scales detected four species known to be endemic but failed to find any of the seven exotic Diaspididae entering the state on Mexican fruit. Monitoring of Mexican armored scales on imported avocados from September 2007 to December 2010 recovered 10 species of parasitoids predominated by two species of Signiphora Ashmead (Hymenoptera: Signiphoridae). One of these species, Signiphora flavopalliata Ashmead, comprised 36% of all collected Mexican parasitoids and is a known hyperparasitoid. A survey of armored scale parasitoids present on commercial California avocados detected 17 genetic signatures, with only four of these in common with those detected on imported Mexican fruit. The implications of these findings are discussed.

Biology of Pseudoligosita plebeia (Hymenoptera: Trichogrammatidae), an egg parasitoid of Homalodisca spp. (Hemiptera: Cicadellidae) collected from northwestern Mexico as a potential biocontrol agent of H. Vitripennis in California.

Pseudoligosita plebeia (Perkins) (Hymenoptera: Trichogrammatidae) is a candidate biological control agent targeting the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Little is known about the biology of P. plebeia. Here we report the results of laboratory studies describing the longevity of P. plebeia adults provided alternative food resources, their ability to parasitize H. vitripennis eggs of different ages, lifetime offspring production when provided steady access to excess host eggs, and levels of mature ovarian eggs present when wasps were held without access to hosts. P. plebeia is a gregarious parasitoid, with up to six adults emerging from a single H. vitripennis egg. When provided with honey and water, water alone, or no food or water, P. plebeia adult females lived an average of 64.1, 2.3, and 2.0 d, respectively. P. plebeia were able to successfully parasitize all ages of H. vitripennis eggs (1-8 d old), with higher parasitism in younger host eggs (1-3 d old) than in older host eggs (5-7 d old). An increasing trend in offspring production was seen for P. plebeia from adult age 2-26 d followed by a decreasing trend with offspring produced up to age 75 d. P. plebeia females are at least partially synovigenic, as they contained fewer mature eggs at younger ages (1 and 3 d old) than at older ages (5, 11, 15, and 31 d old). Our results provide foundational information regarding the biology of P. plebeia useful for its further evaluation as a potential biological control agent in California.

Phoretic dispersal of armored scale crawlers (Hemiptera: Diaspididae).

Dispersal and colonization of new areas by armored scale insects (Hemiptera: Diaspididae) is achieved by mobile first-instar nymphs, called crawlers. Few studies have considered the actual mechanisms by which crawlers disperse, and although crawlers are capable of actively wandering over short distances (generally < 1 m), their dispersal over longer distances has been thought to be wind-mediated. Here, we present evidence of a potentially more important means of dispersal over longer distances (> 1 m). We first confirmed that crawlers of four species of Diaspididae [Abgrallaspis aguacatae Evans, Watson & Miller; Hemiberlesia lataniae (Signoret); Aspidiotus nerii Bouché; and Diaspidiotus perniciosus (Comstock)] have four hairs on the end of each of their legs and that each of these hairs ends in a suction cup-like structure, reminiscent of the attachment structures possessed by phoretic mites. In a controlled environment, using crawlers of A. nerii, we then showed that the crawlers use these structures to attach themselves to three different insect species [Musca domestica L., Cryptolaemus montrouzieri Mulsant and Linepithema humile (Mayr)] and can effectively be moved phoretically by these insects. Crawlers can remain attached to flying insects for considerable periods of time, suggesting that this may be an important means of dispersal for armored scale insects. The importance of phoresy for diaspidid dispersal in the field remains to be determined.

Immature development and adult eclosion of Ufens principalis Owen (Hymenoptera: Trichogrammatidae), an egg parasitoid of Homalodisca spp. (Hemiptera: Cicadellidae) in southern California.

The biology of the immature stages and adult eclosion of Ufens principalis Owen, an important parasitoid of Homalodisca eggs in southern California, were studied. The duration of the egg, larval and pupal stages at 26.7 degrees C were 0-1, 7 and 9 days, respectively. Sacciform larvae, which developed gregariously within host eggs, were motile until about five days of age, and then became sessile. Parasitized host eggs changed from whitish and soft when freshly-laid to yellow-orange and hard at five days and older. This change was accompanied by formation of septal walls separating the mature larvae and pupae. The rate of immature development had a strong positive linear relationship (R(2)=0.853, n=98) with temperatures in the range of 20.0-30.3 degrees C. The theoretical minimum threshold for immature development was 13.5 degrees C, and the required heat units were 241.0 degree-days. Adult eclosion from host eggs occurred mostly (85%) on the first two days of emergence. Although most females emerged during the morning hours (0600-1200 h), males tended to emerge earlier than females with equal emergence during the morning and late night hours (2400-0600 h). The rate of successful adult emergence was high (88%). The ratio of enclosed adults to the number of exit holes was 1.18, indicating that most adults tended to independently cut their exit holes. The number of exit holes had a strong negative relationship (R2=0.711, n=125) with exit hole size, suggesting that larger numbers of developing immatures per host egg result in an overall decrease in adult size.

High levels of exotic armored scales on imported avocados raise concerns regarding USDA-APHIS' phytosanitary risk assessment.

Between 1914 and 2007, a quarantine protected California avocado, Persea americana Mill., groves from pests that might be introduced into the state along with fresh, imported avocados. Soon after Mexican avocados were first allowed entry on 1 February 2007, live specimens of several species of armored scales (Hemiptera: Diaspididae) not believed to be present in California were detected on 'Hass' avocados entering the state from Mexico. Initially, the California Department of Food and Agriculture (CDFA) prevented avocados infested with these scales from entering the state or required that they be fumigated with an approved treatment such as methyl bromide. After a Science Advisory Panel meeting in May 2007, U.S. Department of Agriculture-Animal and Plant Health Inspection Service (USDA-APHIS) reaffirmed its position that armored scales on shipments of fruit for consumption (including avocados) pose a "low risk" for pest establishment. In compliance with APHIS protocols, as of 18 July 2007, CDFA altered its policy to allow shipments of scale-infested avocados into the state without treatment. Here, we report on sampling Mexican avocados over an 8-mo period, September 2007-April 2008. An estimated 67 million Mexican Hass avocados entered California over this period. Based on samples from 140 trucks containing approximately 15.6% of this volume of fruit, we estimate that approximately 47.6 million live, sessile armored scales and an additional 20.1 million live eggs and crawlers were imported. We found eight probable species of armored scales in the samples, seven of these are not believed to occur in California; 89.3% of the live scales were Abgrallaspis aguacatae Evans, Watson and Miller, a recently described species. In contrast to the USDA-APHIS opinion, we believe the volume of shipments and levels of live scales they contain present a significant risk to California's US$300 million avocado industry and to other crops that might become infested by one or more of these exotic species.

Toxicity of seven foliar insecticides to four insect parasitoids attacking citrus and cotton pests.

Laboratory studies were carried out to compare the toxicity of seven foliar insecticides to four species of adult beneficial insects representing two families of Hymenoptera: Aphelinidae (Aphytis melinus Debach, Eretmocerus eremicus Rose & Zolnerowich, and Encarsiaformosa Gahan) and Mymaridae (Gonatocerus ashmeadi Girault) that attack California red scale, Aonidiella aurantii (Maskell); sweetpotato whitefly, Bemisia tabaci (Gennadius) (both E. eremicus and E. formosa); and glassy-winged sharpshooter, Homalodisca vitripennis (Germar), respectively. Insecticides from four pesticide classes were evaluated using a petri dish bioassay technique across a range of concentrations to develop dosage-mortality regressions. Insecticides tested included acetamiprid (neonicotinoid); chlorpyrifos (organophosphate); bifenthrin, cyfluthrin, and fenpropathrin (pyrethroids); and buprofezin and pyriproxyfen (insect growth regulators [IGRs]). Chlorpyrifos was consistently the most toxic pesticide to all four species of beneficial insects tested based on LC50 values recorded 24 h posttreatment compared with 48-h LC50 values with the neonicotinoid and pyrethroids or 96 h with the IGRs. Among the three pyrethroids, fenpropathrin was usually less toxic (except similar toxicity to A. melinus) than was cyfluthrin, and it was normally less toxic (except similar toxicity with E. formosa) than was bifenthrin. Acetamiprid was generally less toxic than bifenthrin (except similar toxicity with G. ashmeadi). The IGRs buprofezin and pyriproxyfen were usually less toxic than the contact pesticides, but we did not test for possible impacts on female fecundity. For all seven pesticides tested, A. melinus was the most susceptible parasitoid of the four test species. The data presented here will provide pest managers with specific information on the compatibility of select insecticides with natural enemies attacking citrus and cotton, Gossypium hirsutum L., pests.

Description and behavioural biology of two Ufens species (Hymenoptera: Trichogrammatidae), egg parasitoids of Homalodisca species (Hemiptera: Cicadellidae) in southern California.

The morphology, distribution, and hosts of two egg parasitoids, Ufens principalis Owen sp. n. and U. ceratus Owen sp. n. (Hymenoptera: Trichogrammatidae), are described for the first time. These species are compared to U. niger (Ashmead), the only species of Ufens s. str. currently described from the Nearctic, and diagnostic differences are presented. The behavioural biology of U. principalis, and U. ceratus to a smaller extent, is also described for the first time. Ufens principalis exhibited a rapid and long-distance response in the form of directional flight toward freshly laid eggs of Homalodisca species, its primary hosts in southern California. Parasitism involved aggregations of female U. principalis on fresh Homalodisca egg masses, which remained attractive to U. principalis for a relatively short time. The level of oviposition by U. principalis females was low during most of the day and peaked before sunset in tandem with a peak in Homalodisca oviposition. Oviposition behaviour of U. principalis is described and the distribution of ovipositor probe durations showed that most probes were generally of very short duration. Mating of both Ufens species occurred on the egg mass, with males showing aggressive behaviour towards each other as they competed for emerging females. Ufens ceratus males displayed greater aggression towards other males than U. principalis males. By contrast, fights among U. principalis males involved more individuals and lasted longer than corresponding fights between U. ceratus males.

Evaluation of phloxine B as a possible control agent against citrus thrips (Thysanoptera: Thripidae).

We evaluated the toxicity of phloxine B photoactive dye combined with a cane molasses bait against citrus thrips, Scirtothrips citri (Moulton). Laboratory bioassays conducted under artificial light showed that thrips mortality followed a log-dose probit-response model with an estimated LC50 of 0.0079% dye. Diluted cane molasses plus 0.01% phloxine B then was used as a standard for comparison of eight additional baits, including three formulations of concentrated citrus peel liquor (CCPL1-3). Citrus thrips mortality ranked highest to lowest with CCPL1 and CCPL3 > CCPL2, Mo-Bait and cane molasses > concentrated beet molasses, concentrated cane molasses, hemicellulose extract, and whey. Several commercial surfactants were tested to see if their addition to the standard increased efficacy. Hyper-Active, Kinetic, and Tween 60 at 1% and Cohort, Hyper-Active, Kinetic, and Silwet at 0.25% when added to the standard, reduced citrus thrips mortality, whereas Tween 60 and Dyne-Amic at 0.25% had no effect. Cane molasses with one or 5% phloxine B dye and CCPL1 with 1% dye were sprayed on citrus trees and allowed to weather in the field. Laboratory bioassays conducted after leaves had weathered for up to 8 d indicated that bait-dye toxicity was persistent. Possible use of the bait-dye mixture in commercial control of citrus thrips is discussed.

Agricultural implications of pesticide-induced hormesis of insects and mites.

Resurgence of pest insects and mites and secondary pest outbreaks are commonly observed following pesticide applications on agricultural commodities. Reduction of natural enemy populations is the major factor blamed for these phenomena but insect or mite hormesis is a second, often overlooked factor which may be partially responsible. A major impact of hormesis is that it often leads to the need for additional pesticide treatments and can result in a spiralling increase in the use of pesticides, a term labelled in entomological literature as the 'pesticide syndrome'.

Sex ratios in field populations of two parasitoids (Hymenoptera: Chalcidoidea) of Coccus hesperidum L. (Homoptera: Coccidae).

We tested several assumptions and predictions of host-quality-dependent sex allocation theory (Charnov et al. 1981) with data obtained for the parasitoid Metaphycus stanleyi Compere on its host, brown soft scale (Coccus hesperidum L.), in a California citrus grove and in the laboratory. Scales ceased growing after parasitization by M. stanleyi. Thus, M. stanleyi may gauge host quality (=size) at oviposition. Host size positively influenced adult parasitoid size, and parasitoid size in turn influenced adult longevity of M. stanleyi. However, parasitoid fitness gains with host size and adult size were similar in males versus females. Sex allocation to individual hosts by M. stanleyi depended on host size; females consistently emerged from larger hosts than males. Host size was important in a relative sense; the mean host sizes of females versus males, and of solitary versus gregarious parasitoids varied with the available host size distribution. The offspring sex ratio of M. stanleyi reflected the available host size distribution; the sex ratio of emerging parasitoids varied with the available host size distribution. We did not detect a "critical host size" below which males emerged, and above which females emerged; rather, only females emerged from hosts in the upper size range, and a variable ratio of males and females emerged from hosts in the lower size range. We conclude that the sex ratio of field populations of M. stanleyi is driven largely by the available size distribution of C. hesperidum. In addition, we tested predictions resulting from theoretical analyses of sex allocation in autoparasitoids with data obtained on Coccophagus semicircularis (Förster) parasitizing brown soft scale in the field. The sex ratio of C. semicircularis was consistently and strongly female biased (ca. 90% females). Based on available theoretical analyses, we suggest that this sex ratio pattern may have resulted from a very low encounter rate of secondary hosts coupled with a strong time limitation in C. semicircularis females. This explanation was the most plausible given constraints stemming from the detection of secondary hosts, their variable location within primary hosts, and their handling times. Finally, the size of hosts which yielded single versus multiple parasitoids, and the sizes of these parasitoids, were compared. These comparisons suggested that: (1) M. stanleyi females gauge host sizes precisely, and in terms of female offspring; thus a fitness penalty is not incurred by females which share a host, while males benefit from sharing a host, and; (2) instances where multiple C. semicircularis emerged from a single host were probably the result of parasitism by different females, or during different encounters by a single female.

Radon-222 and 222Rn progeny concentrations measured in an energy-efficient house equipped with a heat exchanger.

Radon-222 and 222Rn progeny concentrations, barometric pressure and pressure differentials between inside and outside were measured continuously in the basement of a recently constructed energy-efficient house in metropolitan Denver, CO. Although the monitoring equipment was developed primarily for underground mines, it proved to be applicable for house monitoring. Results indicate that for tightly sealed houses, forced-flow transport does not significantly contribute to the 222Rn present even when the pressure within the house is less than the outside pressure by 0.8 Pa (.006 mm Hg). Calculations of 222Rn levels using diffusion as the primary transport mechanism are in agreement with observed data. The diffusion coefficient of 222Rn in the walls and floor surrounding the basement is higher than values previously reported. Ventilation by means of a heat exchanger reduces the 222Rn levels in accordance with measured air exchange rates, regardless of the pressure differential between inside and outside.