Abstract
New techniques are presented on the use of
15
N
to mark insects.
15
N
, a stable isotope of nitrogen, was enriched above natural abundance in plant and insect tissues. Two laboratory studies ...demonstrated that enriched
15
N
‐concentrations could be tracked from plant to insect using mass spectrometry. In the first study, adult
Cotesia plutellae
(Kurdjimov) (Hymenoptera: Braconidae) and
Hippodamia convergens
Guérin‐Méneville (Coleoptera: Coccinellidae) were allowed to feed at the flowers of rapid‐cycling Chinese cabbage plants that had been fertilized with
15
N
‐enriched potassium nitrate (
KNO
3
‐
15
NO
3
). Both insect groups were found to have significantly elevated
15
N
levels after visiting the flowers of the
15
N
‐enriched plants for 48 hours. In the second study,
15
N
‐enriched bean plant (
Phaseolus vulgaris
L.) tissue was incorporated into an insect diet and fed to navel orangeworms,
Amyelois transitella
(Walker) (Lepidoptera: Pyralidae). When the navel orangeworm larvae were 4th instars, they were removed from the diet and exposed to the parasitoid,
Goniozus legneri
Gordh (Hymenoptera: Bethylidae). Results indicated that the enriched
15
N
‐concentration of the bean plants was transferred to the navel orangeworms and, subsequently, to the parasitoids. This work may provide useful techniques to help establish whether agriculturally important entomophaga visiting
15
N
‐enriched flowers or parasitizing enriched sentinel larvae in the field can be effectively marked with
15
N
.
The encyrtid parasitoid Psyllaephagus bliteus Riek was introduced to California in 2000 to control the red gum lerp psyllid, Glycaspis brimblecombei Moore. Field experiments were conducted to ...determine the effect of regional summer climate (California coastal vs. interior valleys) on P. bliteus performance. Measurements of parasitoid performance, including reproduction and longevity, showed that P. bliteus was adversely affected by the extreme summer heat in the interior valley sites. The results suggest that regional climatic differences can contribute to the lower parasitism rates observed in California's warmer interior valleys. The results are discussed with respect to biological control of G. brimblecombei and the potential limitations of the parasitoid P. bliteus, as well as the possible impact of climate and intraguild predation as alternative hypotheses for the observed variable geographic performance of P. bliteus.
Economic losses resulting from vineyard mealybug infestations have increased dramatically during the past decade. In response, there has been a cosmopolitan effort to improve control strategies and ...better understand mealybug biology and ecology, as well as their role as vectors of plant pathogens. Mealybugs are named for the powdery secretions covering their bodies. The most important vineyard mealybugs belong to the subfamily Pseudococcinae (Hardy et al. 2008). Although numerous mealybug species are found in vineyards, this chapter will cover only those that have risen to the level of primary pest. These are the grape mealybug, Pseudococcus maritimus (Ehrhorn), obscure mealybug, Pseudococcus viburni (Signoret), long-tailed mealybug, Pseudococcus longispinus (Targioni Tozzetti), citrophilus mealybug, Pseudococcus calceolariae (Maskell), vine mealybug, Planococcus ficus (Signoret), citrus mealybug, Planococcus citri (Risso), pink hibiscus mealybug, Maconellicoccus hirsutus (Green), and the newly identified Gills mealybug, Ferrisia gilli Gullan. Meanwhile in Brazil and India, Dysmicoccus brevipes (Cockerell) and Xenococcus annandalei Silvestri respectively, feed on vine roots. Collectively, these species will be referred to as the vineyard mealybugs, although their host range is diverse and many are pests of other agricultural crops and ornamental plants (McKenzie 1967; Ben-Dov 1995).
A survey for natural enemies of Planococcus ficus was conducted in Fars Province, Iran. Seven primary, two primary/secondary, three secondary parasitoid species, two coccinellids, primary ...parasitoids, and four predator species were associated with P. ficus. The eulophids Aprostocetus trjapitzini and Baryscapus sugonjaevi are new records for Iran. A key to the females of all parasitoids species is given. The survey provides a description of P. ficus natural enemies in Iran.
Psyllaephagus bliteus was imported from Australia in 1999 and released in California in 2000 as part of a classical biological control program targeting the red-gum lerp psyllid, Glycaspis ...brimblecombei, which in California feeds mainly on red gum, Eucalyptus camaldulensis Dehnh. Psyllaephagus bliteus is an internal parasitoid that delays development until the psyllid host reaches the late fourth or fifth instar. It pupates within the remains of the host, enclosed in three distinct layers. First, parasitised G. brimblecombei produce lerps with basal walls that are significantly thicker than those of unparasitised psyllids. Second, the parasitised psyllid mummifies soon after P. bliteus begins to pupate. Third, a highly melanised pupal sheath is produced that completely envelops the pupal P. bliteus. Photographs are provided and observations on the pupal sheath, which has seldom been described for any parasitoid, are compared with earlier descriptions. We discuss the function of each of the three layers with respect to the protection of the immobile P. bliteus pupa from the environment or natural enemies.
The effectiveness of a dormant-season oil spray with or without an organophosphate insecticide for control of the peach twig borer, Anarsia lineatella Zeller, was investigated. Results from ...experimental field plots indicated that an application of a dormant oil alone resulted in poor control of peach twig borer inside the hibernaculum. Limb crotches containing live peach twig borer in hibernacula were field-collected and treated in the laboratory with either organophosphate (diazinon) and oil insecticides or varying concentrations of a dormant oil alone. Significantly greater larval mortality was found in the organophosphate treatment, whereas mortality in the oil treatments was not significantly different from the control. Overwintering larvae from an insectary colony that were exposed to two rates of an oil had significantly greater mortality than larvae in a control sprayed with water, indicating that peach twig borer inside the hibernaculum may be protected from the insecticidal activity of the oil. To determine the effect of dormant sprays on parasite species composition and numbers, peach twig borer were field-collected and reared through to adult moths or parasitoids. Parasitoid activity was low, with only 0.79% of peach twig borer parasitized (n = 3,032). Macrocentrus ancylivorus Rowher, Spilochalcis n. sp. aff torvina (Cresson), Paralitomastix pyralidis (Ashmead), Erynnia tortricis (Coquillett), Euderus cushmani Crawford, and an unidentified braconid species were reared from 2,528 peach twig borer collected in orchards that did not receive an organophosphate insecticide. A single parasitoid, M. ancylivorus, was reared from 504 peach twig borer collected in orchards treated with an organophosphate insecticide. The virtual absence of peach twig borer parasitoids in fields treated with an organophosphate may be a reflection of the low number of moth pests collected at those sites.
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