Stilbenes as enhancers for gypsy moth (Lepidoptera: Lymantriidae) nucleopolyhedrovirus

The stilbenes 4,4′-diaminostilbene-2,2′-disulfonic acid, 4-aminostilbene disulfonic acid, and dinitrostilbene-2,2′-disulfonic acid were tested as enhancers for the gypsy moth, Lymantria dispar (L.), nucleopolyhedrovirus (LdNPV). 4-Amino nitrostilbene disulfonic acid had no effect on the activity (LC50) of LdNPV, whereas both 4,4′-diaminostilbene-2,2′-disulfonic acid and 4-aminostilbene disulfonic acid were inhibitory. Diethylstilbestrol, a stilbene synthetic estrogen, and two synthetic estrogens (i.e., estradiol-17-acetate, estrone acetate) had no effects on viral activity. Two stilbene dyes (i.e., direct yellow 62, brilliant yellow 6) and a stilbene optical brightener (i.e., Tinopal LPW) significantly increased the activity of LdNPV. Activity was increased by approximately 230-fold by Tinopal LPW, 26-fold by direct yellow 62, and 36-fold by brilliant yellow 6. This study demonstrates that some stilbenes can act as enhancers, whereas others do not.

Enhancement in Activity of Homologous and Heterologous Baculoviruses Infectious to Fall Armyworm (Lepidoptera: Noctuidae) by Selected Optical Brighteners

The nuclear polyhedrosis virus (NPV) from Spodoptera frugiperda (J. E. Smith) (SfMNPV) was the most active virus tested against fall armyworm, larvae (LC50 = 8.1 PIB per mm2). No LC 50s could be obtained for the alfalfa looper, Autographa californica (Speyer), NPV (AcMNPV), the celery looper, Anagrapha falcifera (Kirby), NPV (AfMNPV), the wax moth, Galleria mellonella (L.), NPV (GmMNPV), or the bollworm, Helicoverpa armigera (Hübner), NPV (HaMNPV). The addition of an optical brightener, Tinopal LPW® (1%), (Sigma Co., St. Louis, MO) significantly enhanced the activities of all NPVs. The most activie NPV/Tinopal LPW combination was SfMNPV, followed by AcMNPVm HaMNPV, AfMNPV, and GmMNPV. In terms of speed of kill, SfMNPV was the most active virus tested. When Tinopal LPW was added, the LT50 was reduced by more than 35%. The addition of Tinopal LPW to the heterologous NPVs resulted in LC50 and LT50 values that were comparable to SfMNPV alone. Five of eight brighteners acted as activity enhancers for SfMNPV (i.e., Blankophor BBH, Blankophor HRS, Blankophor P167, Blankophor RKH, and Tinopal LPW), whereas Blankophor BSU, Blankophor DML, and Blankophor LPG did not enhance virus activity.

DIFFERENTIAL MORTALITY BETWEEN MALE AND FEMALE CHORISTONEURA OCCIDENTALIS (LEPIDOPTERA: TORTRICIDAE) LARVAE EXPOSED TO A BACULOVIRUS WITH OR WITHOUT OPTICAL BRIGHTENERS

Fifth-instar larval mortality was compared between male and female Choristoneura occidentalis Freeman exposed in the laboratory to sublethal doses of Choristoneura fumiferana (Clem.) multicapsid nuclear polyhedrosis virus (CfMNPV) with or without optical brighteners. More females than males died when the virus was used alone, but differences were not significant. When 1% brightener was added to CfMNPV suspension, differences in larval mortality between males and females were significant for three of the four brighteners tested. In addition, times at which 50% of the larvae died indicated that female larvae died 23 and 39% more quickly than male larvae, respectively, when brightener Blankophor HRS and Tinopal LPW were added to the virus, whereas at times at which 95% of the larvae died indicated that females died 33 and 54% faster than males. Alteration of sex ratio favoring male survival can play a significant role in the biological control of C. occidentalis by the virus.

Effects of a Nuclear Polyhedrosis Virus and a Fluorescent Brightener on Colonies of Spodoptera exigua (Hübner)

The beet armyworm, Spodoptera exigua (Hübner), is an important pest which is difficult to control because it is resistant to nearly all registered insecticides. A new commercial formulation of a nuclear polyhedrosis virus that is pathogenic to beet armyworm larvae, SPOD-X®, was tested with and without a fluorescent brightener, Tinopal LPW. The effects on larvae from six colonies of the beet armyworm which had recently been established from field collections in Georgia, Alabama and Mississippi were compared with a laboratory colony which had been maintained in the laboratory for 2 years. The LC50 was lower in all bioassays with SPOD-X in 0.25% Tinopal LPW than with SPOD-X in water, although in 3 of 12 bioassays the difference was not significant based on overlapping 95% confidence intervals. The mean LC50 for SPOD-X in water was 376 polyhedral occlusion bodies per cup (surface area 800 mm2). The mean LC50 for SPOD-X in 0.25% Tinopal LPW was 30 polyhedral occlusion bodies per cup. The LC50 for SPOD-X in water was not significantly different between the laboratory colony and 5 of 6 field-collected colonies when bioassayed concurrently. There was no significant difference in LC50 for SPOD-X in 0.25% Tinopal LPW between the laboratory colony and any of the field-collected colonies. Thus, Tinopal LPW enhanced the infectivity of SPOD-X for beet armyworm larvae in laboratory tests and reduced the variability of response of the beet armyworm colonies to the virus.

Prestalk cells in monolayer cultures exhibit two distinct modes of cellulose synthesis during stalk cell differentiation in Dictyostelium

Stalk formation in Dictyostelium discoideum involves the synthesis of a stalk tube by the prestalk cell population and stalk cell walls by the individual prestalk cells. Cellulose is a major structural component of the stalk tube and stalk cell walls. The DIF-deficient strain HM44 was used to study the events of stalk formation in monolayer cultures. The induction of cellulose synthase activity was shown to require both DIF and cAMP. Microscopical observations of monolayer cultures using the cellulose-indicating fluorochrome Tinopal LPW demonstrated the presence in these cultures of two cellulose-containing materials: the stalk cell walls and an intercellular material found between cells and around cell clumps. The synthesis of intercellular material precedes that of stalk cell walls in induced cultures. Cells committed to stalk cell formation were delayed in doing so if they were switched to medium containing cAMP but no DIF. During this delay the cells synthesized large quantities of the intercellular material. The intercellular material was shown to be microfibrillar, was sensitive to cellulase, and labelled with a colloidal gold-conjugated cellulase. The intercellular material may have the same mode of cellulose synthesis as that involved in stalk tube formation. If so, that mode would be favored by DIF and cAMP in combination, whereas the cellulose synthesis involved in stalk cell wall formation would be DIF-dependent but delayed or repressed by cAMP.