Janet M. Smilanick’s research while affiliated with University of California, Davis and other places

Effects of methamidophos residue on adults and immatures of the pentatomid egg parasitoidsTrissolcus basalis(Wollaston) andT. utahensis(Ashmead) were assessed in the field and laboratory. Survival of adult females of both species exposed to field-treated tomato foliage was significantly reduced (ca. 50%) in the presence of 2- and 4-day old residues. Residues of as much as 16 days significantly reduced survival inT. basalisbut not inT. utahensis.Emergence ofT. basalisfrom egg masses ofNezara viridula(L.) exposed to the same field treatment was not significantly reduced, but survival of emergent adults was significantly reduced. Adult emergence of eitherT. basalisorT. utahensisfrom eggs ofEuschistus conspersusUhler and treated as pupae was not significantly affected, but survival of emergent females and males was significantly reduced for both species. When the parasitoids were treated as larvae, emergence rate was significantly reduced forT. basalisbut not forT. utahensis,and survival of emergent males and females was significantly reduced for both species. Reproductive capacity of emergent females was not significantly reduced in either species, but sex ratio of the progeny was male-biased for each species. Because postemergence survival of adults was greatly reduced by methamidophos treatment, percentage emergence of parasitoids from treated eggs is not an adequate measure of ecological selectivity of this insecticide.

Ovipositional behavior of the scelionid egg parasitoidsTrissolcus basalis(Wollaston),Psix tunetanus(Mineo & Szabo), and two color forms ofTrissolcus utahensis(Ashmead) was observed in laboratory experiments that employed a common host, the pentatomidEuschistus conspersusUhler. Brood sex ratios were female biased and less than 0.20;P. tunetanusdeposited a precise sequence of male and female offspring compared to the other species. In host discrimination experiments in which individual females were presented with an egg mass partially parasitized by a conspecific female,T. utahensisshowed considerable ovipositional restraint toward parasitized eggs. When presented with an egg mass partially parasitized by a female of another species—eitherT. basalisorP. tunetanus—T. utahensisdisplayed little discrimination and oviposited in most of the parasitized eggs that it contacted. When the experiment was reversed—T. basalisandP. tunetanusfemales presented individually with an egg mass partially parasitized byT. utahensis—both species showed little discrimination and oviposited in most of the parasitized eggs that they contacted. For eggs in which multiparasitism involved the combination ofT. utahensisandP. tunetanus,the latter emerged from over 70%, regardless of whether it was the first or second ovipositing female. When super- or multiparasitism involved the combination of the twoT. utahensiscolor forms or the combination ofT. utahensisandT. basalis,offspring of the first ovipositing female emerged from over 70% of the eggs. These results are consistent with the view that interspecific host discrimination in parasitoids is less common than conspecific host discrimination and provide some support for the hypothesis that brood sex ratio and competitive ability are inversely related in guilds of quasi-gregarious egg parasitoids. Implications for the selection of parasitoid species for classical and augmentative biological control are discussed.

Transgenic tobacco plants expressing Bacillus thuringiensis var. kurstaki HD-73 delta-endotoxin or cowpea, Vigna Unguiculata, trypsin inhibitor (CpTI) were eval- uated for efficacy against artificial infestations of Helicouerpa zea (Boddie) under field conditions. Mortality of H. zea larvae was significantly higher and leaf damage significantly lower for the genotype containing Bacillus thuringiensis gene compared with nontrans- genic control. Few H. zea larvae survived beyond first instar on the Bacillus thuringiensis genotype. Larval mortality was also higher and leaf damage lower on the CpTI genotype than its corresponding control, but the effect was less consistent and less pronounced than that produced by the Bacillus thuringiensis genotype. Neither transgenic genotype had a significant effect on natural infestations of the other phytophagous or predacious insects that were monitored.

In greenhouse studies, four nitrogen (N) rates were applied to potted grape plants. Foliar N increased significantly as applied N increased, and there were significant differences in N content between leaves taken from lower, middle, and upper node locations on the vines. In leaf cages, Tetranychus pacificus (McGregor) responded to increasing foliar N with significantly (P < 0.05) increased fecundity and shorter immature developmental time only during the second year of the study. There appeared to be no relationship between foliar N and immature survivorship, ovipositional duration, or female longevity.

Tetranychus spp. and peach silver mite, Aculus cornutus, are distributed randomly within the foliage of almond trees. Both, however, have extremely clumped patterns of distribution on a per leaf sample unit. The pattern of distribution for Tetranychus spp. was additionally affected by the phytoseiid mite, Metaseiulus occidentalis, the pattern being less clumped with the predator present. M. occidentalis was considerably less clumped than observed for the other mites. Additional analyses indicate that, except at low Tetranychus spp. densities, approximately one M. occidentalis per ten Tetranychus is sufficient to reduce the prey density 2 weeks hence. The distribution relationships in this paper provide a framework for development of a quantitative Tetranychus spp. monitoring program, presented in the following paper.

Bioassays using adult male Metaseiulus (= Typhlodromus) occidentalis (Nesbitt) demonstrated that deutonymphal, adult virgin, and mated, gravid females produce a sex pheromone(s). Evidence is presented which suggests some protonymph females also produce a sex pheromone(s). Males responded to the pheromone as if it were an arrestant once the male encountered the female. Males exhibited a distinctive “hovering” behavior with deutonymphs and some protonymphs. This is only the second species of phytoseiid mite demonstrated to have a sex pheromone and the first time phytoseiid deutonymphs have been shown to produce a sex pheromone. EIN VON UNREIFEN UND ADULTEN WEIBCHEN DER RAUBMILBE, METASEIULUS OCCIDENTALIS PRODUZIERTES SEXUALPHEROMON Biotests mit adulten Männchen und Weibchen von Metaseiulus (= Typhlodromus) occidentalis (Nesbitt) zeigten, dass weibliche Deutonymphen, virginelle Weibchen, und gravide, gepaarte Weibchen ein Sexualpheromon abgeben. Männchen reagieren auf zurückgehaltene weibliche Deutonymphen, indem sie ihre Taster und ihre Beine I und II über diese hielten und zwar im Kontakt mit dem Rücken des Weibchens. Die Männchen sprachen auch auf zurückgehaltene virginelle Weibchen oder auf Aetherextrakte von zerdrückten virginellen und graviden Weibchen an, indem sie mit den Extrakten länger in Kontakt blieben als mit Kontrollsubstanzen. Die Männchen reagierten auch auf weibliche Protonymphen der Mutterkolonien, allerdings weniger häufig als auf Deutonymphen. Männchen und Weibchen reagierten nicht auf Extrakte von Männchen. Die Männchen sprachen auch nicht an auf zurückgehaltene Männchen, ferner nicht auf Weibchen und Weibchenextrakte von T. urticae. Dies zeigt, dass die Reaktion keine blosse Erkennung der eigenen Art oder von Beutetieren darstellt. Die Männchen besuchten Weibchenextrakte oder zurückgehaltene Weibchen ebenso häufig wie Kontrollsubstanzen, demnach fand keine Distanzreaktion auf ein Pheromon statt. Wir vermuten, dass das Sexualpheromon von M. occidentalis‐Weibchen und − Deutonymphen vor allem als Männchen‐Arrestans wirkt, wenn das Männchen einem Weibchen begegnet. Die Bedeutung dieses Verhaltens auf die Biologie von M. occidentalis wird diskutiert. Dies ist die zweite Phytoseidenart, bei der ein Pheromon (oder Pheromone) nachgewiesen wird. Über die Pheromonabgabe durch Deutonymphen wird erstmals berichtet. 1979 The Netherlands Entomological Society