Evaluation of lignins and particle films as solar protectants for the granulovirus of the codling moth,Cydia pomonella

The identification of effective solar protectants for field application of the codling moth, Cydia pomonella (L.), granulovirus (CpGV) is of interest to improve its efficacy and commercial viability as a biological pesticide. We evaluated several materials as potential adjuvants to protect CpGV from ultraviolet degradation. In laboratory tests with a solar simulator (9.36×10⁶ J/m²), the addition of kaolin clay (Surround® WP at 3 and 6%, w/v), a paraffin wax-based emulsion (SPLAT? at 5%, v/v), and a bark extract trans-cinnamaldehyde combined with a film agent (both at 1%, v/v) did not significantly reduce larval entries or increase larval mortality in irradiated apples that were treated with a commercial CpGV product (Cyd-X). In semi-field tests in an apple orchard, a spray-dried lignin formulation containing CpGV (6.57×10¹² OBs/ha) and a lignin-based adjuvant used with Cyd-X (both applied at 4.7–5.6 kg lignin/ha) significantly improved residual activity of CpGV compared with Cyd-X alone applied at the same rate. However, the benefits were short lived and could not be detected after 7 days. In orchard tests, we evaluated two additional refined lignin-products (Lignosulfonate and Vanisperse? CB at 5.61 kg/ha) and two particle film materials (kaolin clay, ‘Cocoon?’, and calcium with boron ‘Eclipse?’) as adjuvants for UV protection of Cyd-X (6.57×10¹² OBs/ha) in tests against a dense codling moth infestation. Although all virus treatments were highly effective (causing ≥90% larval mortality), no significant effects of the adjuvant treatments could be detected. In these latter tests, the use of a silicone based wetting agent at 0.025% (v/v) may have been beneficial at increasing mortality among older larvae inside the fruit.     

The susceptibility of the pea moth, Cydia nigricana, to infection by the granulosis virus of the codling moth, Cydia pomonella

Laboratory studies demonstrated that neonate larvae of the pea moth, Cydia nigricana, are susceptible to infection with a granulosis virus (CpGV) isolated from the codling moth, Cydia pomonella. Comparative LC₅₀ values for C. nigricana and C. pomonella are 1.90 × 10⁵ and 1.54 × 10⁴ capsules/ml of diet, respectively. The virus extracted from CpGV-infected pea moth larvae is serologically related, and probably identical, to CpGV.     

New method for testing solar sensitivity of commercial formulations of the granulovirus of codling moth (Cydia pomonella, Tortricidae: Lepidoptera)

A method for screening codling moth granulovirus (CpGV) formulation sensitivity to sunlight using specially prepared half apples and a solar simulator is described. The half apple preparation allows an even coverage of virus over the surface of the fruit that would not be possible using whole apples. Leaves and artificial medium were not usable for extended periods of exposure in the solar simulator due to excess drying. Fruit was sprayed with 10⁻³ and 10⁻⁵ dilutions of three commercial formulations of CpGV (Carpovirusine, Cyd-X, and Virosoft) and infested with codling moth neonates. Half of the sprayed fruit was exposed to 650 W/m² for 4 h in an Atlas Suntest CPS solar simulator resulting in an accumulated radiant energy of 9.36 × 10⁶ J/m² before they were infested with neonate codling moth larvae. Spraying non-irradiated fruit with the 10⁻³ dilution of Cyd-X and Virosoft resulted in nearly 100% mortality of neonate larvae. Irradiation reduced viral activity by 71-98% at the 10⁻³ dilution and by up to 32% at the 10⁻⁵ dilution relative to non-irradiated fruit. The procedures utilized enabled good preservation of the fruit throughout the incubation period and minimized invasion of the fruit by plant pathogens and saprophytic organisms. This laboratory method for screening candidate formulations and potential UV protectants could conserve time and resources by eliminating adjuvants with less potential in laboratory tests and field testing only the most promising candidates. It also enables year-round testing.     

Inorganic and organic UV filters: Their role and efficacy in sunscreens and suncare products

Minerals such as titanium dioxide, TiO₂, and zinc oxide, ZnO, are well known active semiconductor photocatalysts used extensively in heterogeneous photocatalysis to destroy environmental pollutants that are organic in nature. They are also extensively used in sunscreen lotions as active broadband sunscreens that screen both UVB (290-320 nm) and UVA (320-400 nm) sunlight radiation and as high SPF makers. When so photoactivated by UV light, however, these two particular metal oxides are known to generate highly oxidizing radicals (OH and ) and other reactive oxygen species (ROS) such as H₂O₂ and singlet oxygen, ¹O₂, which are known to be cytotoxic and/or genotoxic. Hydroxyl (OH) radicals photogenerated from photoactive TiO₂ specimens extracted from commercial sunscreen lotions [R. Dunford, A. Salinaro, L. Cai, N. Serpone, S. Horikoshi, H. Hidaka, J. Knowland, FEBS Lett. 418 (1997) 87] induce damage to DNA plasmids in vitro and to whole human skin cells in cultures. Accordingly, the titanium dioxide particle surface was modified to produce TiO₂ specimens of considerably reduced photoactivity. Deactivation of TiO₂ diminishes considerably, in some cases completely suppresses damage caused to DNA plasmids, to human cells, and to yeast cells compared to non-modified specimens exposed to UVB/UVA simulated solar radiation. The photostabilities of sunscreen organic active agents in neat polar and apolar solvents and in actual commercial formulations have been examined [N. Serpone, A. Salinaro, A.V. Emeline, S. Horikoshi, H. Hidaka, J. Zhao, Photochem. Photobiol. Sci. 1 (2002) 970]. With rare exceptions, the active ingredients undergo photochemical changes (in some cases form free radicals) and the sunscreen lotions lose considerable Sun protection efficacy only after a relatively short time when exposed to simulated sunlight UVB/UVA radiation, confirming the recent findings by Sayre et al. [R.M. Sayre, J.C. Dowdy, A.J. Gerwig, W.J. Shields, R.V. Lloyd, Photochem. Photobiol. 81 (2005) 452].     

The occurrence and distribution of resistance of codling moth to Cydia pomonella granulovirus in Europe

Thirty‐five codling moth (CM, Cydia pomonella L., Lepidoptera, Tortricidae) populations collected in different commercial orchards in six European countries were tested for their susceptibility to Cydia pomonella granulovirus (CpGV‐M). Including previously published data on CpGV‐M resistance, a total of 38 CM colonies showed considerably elevated LC₅₀ values, independent of the country origin. When only few test individuals are available, determination of mortality of neonate larvae at a discriminating concentration range of 10⁴ to 10⁶ OB/ml (>log4) as a direct measure of percentage susceptible individuals in a CM population is more advisable than calculation of LC₅₀ values. The >log4 mortality alone or in combination with the LC₅₀ value can be used for identification of resistance in a population. Results indicated a locally separated but widely spread occurrence of CM populations with low susceptibility to CpGV‐M. The most plausible hypothesis for the emergence of CpGV‐M resistance is its selection by repeated use of CpGV products.     

Development of a direct test of baculovirus resistance in wild codling moth populations

The occurrence of resistance of codling moth (CM, Cydia pomonella L.) to Cydia pomonella granulovirus (CpGV) used as biological control agent revealed the need for fast and reliable resistance monitoring methods. Here, we describe the development of a laboratory resistance test that is directly performed on larvae extracted from infested apples. This test is based on a 14‐day bioassay at a discriminative CpGV concentration of 2 × 10⁵ occlusion bodies/ml diet and can be applied to L1–L4 larvae. Information on virus resistance can be obtained within <4 weeks. In a survey, CM larvae were isolated and tested from 6698 apples from 10 different orchards in Germany, Austria, Switzerland, Italy and the Netherlands. We identified seven CM populations resistant or partly resistant to CpGV isolates. Although some of the orchards were treated with commercial CpGV products, this method allowed us to obtain reliable information about the resistance status of the examined populations.     

The Role of Formulation Additives in Increasing the Potency of Cydia pomonella Granulovirus for Codling Moth Larvae,in Laboratory and Field Experiments

Studies were undertaken to improve the biological efficacy of the granulovirus (CpGV) of the codling moth, Cydia pomonella , by evaluating the performance of some formulation additives that might improve virus persistence and/or virus uptake by first instar larvae. Laboratory studies, using a leaf disc bioassay, demonstrated that 15% cane molasses incorporated within a formulation of purified CpGV dramatically reduced the median lethal exposure time (LET 50 ) to CpGV for neonate larvae at a CpGV dosage rate of 10 7 occlusion bodies (OBs) ml -1 . Screening of a range of other compounds showed that sucrose, fructose and sorbitol (at 10% concentrations) and extracts of apple flesh and skin also gave significant reductions in the LET 50 of CpGV formulations containing these ingredients. Pectin, malic acid and &#102 -farnesene did not significantly reduce the LET 50 . In a field trial, molasses included at 15% (v/v) in a CpGV formulation, containing a dosage rate of 10 12 OBs ha -1 , gave as good control of codling moth damage as virus formulations containing the 'sticker' 0.2% skimmed milk at higher dosage rates of 10 13 and 10 14 OBs ha -1 . Studies of CpGV persistence on foliage revealed no significant improvement of virus persistence on apple foliage using 10% or 15% molasses formulations. A second field trial demonstrated that 10% molasses, 10% sorbitol or 0.08% &#102 -farnesene significantly reduced codling moth deep damage to fruit when these ingredients were added to formulations of pure CpGV. Substantial sooty-mould growth ( Cladosporium spp.) was observed on apple foliage treated with formulations containing molasses, indicating that this formulation additive has secondary consequences that would need to be taken into account if molasses was to be used in commercial CpGV formulations. Nonetheless, these studies clearly demonstrate that major biological improvements in CpGV performance can be achieved by the incorporation of formulation additives, including molasses and several other compounds, that probably function as attractants and/or feeding stimulants for codling moth larvae.     

Comparative activity of baculoviruses against the codling moth Cydia pomonella and three other tortricid pests of tree fruit

The granulovirus of Cydia pomonella (L.) (CpGV) offers potential for selective control of codling moth. Two major limitations of CpGV are its narrow host range and lack of persistence in the orchard agroecosystem. The nucleopolyhedroviruses of the alfalfa looper Autographa californica (Speyer) (AcMNPV) and those of the celery looper Anagrapha falcifera (Kirby) (AfMNPV) have broad host ranges. Comparative assays of CpGV, AcMNPV, and AfMNPV against codling moth neonate larvae revealed a 54-93-fold greater susceptibility of codling moth to the granulovirus than to the two nucleopolyhedroviruses based on the LC(50) values for each virus. The LC(50)s for CpGV, AfMNPV, and AcMNPV were 32.7 capsules/mm(2), 1.77 x 10(3) occlusion bodies (OBs)/mm(2), and 3.05 x 10(3)OBs/mm(2), respectively. The LT(50) determined for AfMNPV using an approximate LC(95) of the virus against neonate larvae was 3.6 days. Histological examination of tissues in moribund codling moth larvae that had been treated with AfMNPV revealed the presence of nonoccluded and unenveloped virus rods in midgut tissue. Neither OBs nor signs of infection were detected in other tissues. The activity of AfMNPV was also evaluated in three other tortricid apple pests (obliquebanded leafroller, Choristoneura rosaceana (Harris); Pandemis leafroller, Pandemis pyrusana Kearfott; and the oriental fruit moth, Grapholitha molesta (Busck)). Codling and Oriental fruit moths were significantly more susceptible to AfMNPV than were the two leafroller species.     

A model of the effect of codling moth granulosis virus on Cydia pomonella

A model was developed based on an initial ingestion phase, followed by a period of virus multiplication and host death, to describe the effects of codling moth granulosis virus (CpGV) concentration and time from initial infection on the percentage of codling moth larvae (Cydia pornonella) dying from virus infection in the laboratory. With modification, this model also described the effect of CpGV concentration on the reduction of damage to fruit by C. pomonella larvae in the field. In both cases, the effect of CpGV increased with the l/10th power of virus concentration. LT₅₀ (time to death of 50% of larvae) was inversely related to virus concentration in the laboratory. The model predicts the threshold concentration for death of larvae, as well as LD₅₀(C₅₀ and LD₉₀(C ₉₀,) for all ages of larvae. The model also predicts that if the majority of larvae entered through the sides of apple fruits, rather than through the calyx or near the stalk (as they probably did in the field), then the efficacy of CpGV in reducing fruit damage would be lowered. This effect of site of entry is especially marked at low virus concentrations.     

Characterisation of Cydia pomonella granulovirus from codling moths in a laboratory colony and in orchards of British Columbia*

Sequence analyses indicate that a granulovirus isolated from a laboratory colony of codling moth in British Columbia, Canada is identical or very similar to the Mexican isolate of Cydia pomonella granulovirus (CpGV-M). In addition to codling moth, the vims was found to cause mortality of secondary leafroller pests of North American orchards, including the fruit tree leafroller and the obliquebanded leafroller. A survey in apple growing regions of British Columbia indicates that 23% of the wild population of codling moth larvae carry CpGV.     

Effect of ZnO and TiO2 nanoparticles preilluminated with UVA and UVB light on Escherichia coli and Bacillus subtilis

We evaluated the effects of zinc oxide (ZnO) and titanium dioxide (TiO₂) nanoparticles (NPs) preilluminated with ultraviolet light on Escherichia coli and Bacillus subtilis. The experiments were conducted using three different types of light: visible, Ultraviolet A (UVA, 315–400 nm), and Ultraviolet B (UVB, 280–315 nm). The bacteria were exposed to NPs, either as liquid suspensions for growth inhibition assays or on agar plates for colony forming unit (CFU) assays. We found that the ZnO NPs were more toxic when preilluminated with UVA or UVB light than with visible light in both growth inhibition and CFU assays. TiO₂ NPs were not toxic to the bacteria under UVA or UVB preillumination conditions. The photo-dissolution of ZnO NPs increased with UV preillumination, which could explain the observed toxicity of ZnO NPs. We detected oxidative stress elicited by photoactive nanoparticles by measuring superoxide dismutase activity. The results of this study show that the toxicity of photoactive nanoparticles can be increased by UV preillumination by dissolution of toxic ions, which suggests the potential for preillumination-dependent toxicity of nanoparticles on soil environments in low light or darkness.     

Cydia pomonella granulovirus Genotypes Overcome Virus Resistance in the Codling Moth and Improve Virus Efficiency by Selection against Resistant Hosts

Cydia pomonella granulovirus (CpGV) has been used for 15 years as a bioinsecticide in codling moth (Cydia pomonella) control. In 2004, some insect populations with low susceptibility to the virus were detected for the first time in southeast France. RGV, a laboratory colony of codling moths resistant to the CpGV-M isolate used in the field, was established with collection of resistant insects in the field followed by an introgression of the resistant trait into a susceptible colony (Sv). The resistance level (based on the 50% lethal concentrations [LC₅₀s]) of the RGV colony to the CpGV-M isolate, the active ingredient in all commercial virus formulations in Europe, appeared to be over 60,000-fold compared to the Sv colony. The efficiency of CpGV isolates from various other regions was tested on RGV. Among them, two isolates (I12 and NPP-R1) presented an increased pathogenicity on RGV. I12 had already been identified as effective against a resistant C. pomonella colony in Germany and was observed to partially overcome the resistance in the RGV colony. The recently identified isolate NPP-R1 showed an even higher pathogenicity on RGV than other isolates, with an LC₅₀ of 166 occlusion bodies (OBs)/μl, compared to 1.36 × 10⁶ OBs/μl for CpGV-M. Genetic characterization showed that NPP-R1 is a mixture of at least two genotypes, one of which is similar to CpGV-M. The 2016-r4 isolate obtained from four successive passages of NPP-R1 in RGV larvae had a sharply reduced proportion of the CpGV-M-like genotype and an increased pathogenicity against insects from the RGV colony.     

Evaluation of spray-dried lignin-based formulations and adjuvants as solar protectants for the granulovirus of the codling moth, Cydia pomonella (L)

Commercial formulations of the codling moth, Cydia pomonella L., granulovirus (CpGV) are limited by their short residual activity under orchard conditions in the Pacific Northwest. We evaluated spray-dried lignin-encapsulated formulations of CpGV for improved solar stability based on laboratory bioassays with a solar simulator and in field tests in an infested apple orchard. In laboratory tests, aqueous lignin formulations containing a high dosage of 3 x 10(10) occlusion bodies (OB)/L, with and without the additives titanium dioxide (TiO(2)) and sugar, provided significant solar protection of virus, i.e., mortality of codling moth exposed to lignin formulations that had been irradiated with 9.36 x 10(6) joules/m(2) was 92-94%, compared with 66-67% from a glycerin-stabilized product (Cyd-X) or suspension of pure unformulated virus at the same rates. By comparison, a lower dosage of the lignin formulation (3 x 10(8)OB/L) did not provide significant solar protection. Equivalent dosage-dependent patterns in solar protection were observed in further tests with the lignin formulation, when an intermediate (3 x 10(9)OB/L) as well as the low dosage provided no solar protection. Equivalent rates of a blank lignin formulation (containing no virus) did not affect larval mortality, suggesting a protective effect of the lignin on the virus at the high rate. The use of several spray adjuvants, 'NuFilm-17' and 'Organic Biolink' (sticker-spreaders at 0.06% v/v), 'Raynox' (sunburn protectant at 5% v/v), and 'Trilogy'(neem oil at 1% v/v) did not provide solar protection of a commercial CpGV preparation in laboratory tests. In season long orchard tests (Golden Delicious), the lignin formulation of CpGV applied at 6.57 x 10(12)OB/ha did not significantly improve control of codling moth or protection of fruit compared with Cyd-X at equivalent rates. Our studies show that lignin-based CpGV formulations provided solar protection at relatively high virus dosages. The testing of lignin formulations containing reduced virus concentrations may allow virus solar protection to be achieved at more economical rates.     

Sex linkage of CpGV resistance in a heterogeneous field strain of the codling moth Cydia pomonella (L.)

The occurrence of codling moth populations in European apple orchards that were not controlled by Cydia pomonella granulovirus (CpGV) is the first reported case of field resistance against a baculovirus control agent. A monogenic dominant sex-linked mode of inheritance was previously demonstrated in single-pair crosses between a homogeneous resistant (CpRR1) and a susceptible (CpS) laboratory strain of codling moth. However, resistant field populations (CpR) are more heterogeneous in their levels of resistance, and the possibility that they could harbor different resistance genes to CpRR1 had not been directly addressed. Here we report single pair crossing experiments using a resistant codling moth strain collected from an apple orchard in the southwest of Germany. Single-pair crosses within the field strain revealed a genetic basis to the heterogeneity of CpR concerning CpGV resistance. Hybrid crosses to a susceptible laboratory strain and backcrosses of the F1 generation to the resistant CpR strain confirmed that the homogeneous CpRR1 and the heterogeneous field strain CpR share the same mode of inheritance. Thus the variable levels of CpGV resistance in field populations is likely due to frequency differences of the same resistance-conferring gene, rather than different genes, which will facilitate future efforts to monitor and manage resistance.     

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO₂-Ag nanowires with a diameter of 200 nm and a length of 6-20 µm were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO₂ phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO₂-Ag nanowires, a TiO₂ gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO₂ gel resulted in the formation of crystalline TiO₂ nanotubes. A subsequent Ag electrodeposition step inside the TiO₂ nanotubes resulted in formation of coaxial TiO₂-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO₂) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H₂ gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min of illumination, approximately 0.2 vol% H₂ gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution.     

Overcoming the resistance of codling moth against conventional Cydia pomonella granulovirus (CpGV-M) by a new isolate CpGV-I12

Recently, codling moth (CM, Cydia pomonella L.) populations with a significantly reduced susceptibility to C. pomonella granulovirus (CpGV) products have been observed in Germany. A novel CpGV isolate, designated CpGV-I12, is able to overcome the CpGV resistance. CpGV-I12 originated from Iran and showed superior efficacy in laboratory bioassays against a resistant CM strain (CpR), which has a 100-fold reduced susceptibility to commercially used isolate CpGV-M. Determination of the median lethal concentration (LC₅₀) indicated that CpGV-I12 is nearly as efficient in resistant CpR as CpGV-M in a susceptible CM strain (CpS). Beyond, CpGV-I12 caused superior mortality in CpS. Infection experiments showed that the resistance breaking effect can be observed in all instars of CpR. CpGV-I12 is a promising alternative control agent of CM in orchards where conventional CpGV products fail. In addition, we demonstrate in bioassays with recombinant expressed Cry1Ab that cross-resistance to CpGV and Bacillus thuringiensis products is not likely.     

Incidence and transmission of a granulovirus in a large codling moth [Cydia pomonella L. (Lepidoptera: Tortricidae)] rearing facility

Incidences of potential per os Cydia pomonella granulovirus (CpGV) transmission within a large codling moth colony were identified. CpGV was detected in the water which is used to wash egg sheets. When pre-neonates were extracted from eggs prior to emergence and tested for the presence of CpGV, 40% were found to carry amounts of CpGV detectable by a polymerase chain reaction (PCR) assay, suggesting possible transovarial transmission of the virus. Although symptoms typical of virus infection and larval death were found infrequently within communal rearing trays, the frequency with which CpGV DNA was detected by PCR assays increased from a mean of 31% of 10-day-old larvae to 94% of 25-day-old larvae. CpGV in codling moth cadavers remained virulent after being held at 60 degrees C for 3 days under conditions similar to the treatment of spent diet at the rearing facility before its disposal. PCR tests of surface samples taken from air filters and rearing rooms of the rearing facility were found to contain CpGV. Bioassays of surface samples from the diet trash bin and a filter through which outside air is passed before entering the rearing chambers resulted in significant codling moth neonate mortality. The virulence of CpGV in dust from the spent diet and the original inadvertent positioning of the diet trash bin directly below one of the air intake ducts are suggested as a possible additional source of CpGV contamination within the facility.     

Role of sunscreen formulation and photostability to protect the biomechanical barrier function of skin

The impact of sunscreen formulations on the barrier properties of human skin are often overlooked leading to formulations with components whose effects on barrier mechanical integrity are poorly understood. The aim of this study is to demonstrate the relevance of carrier selection and sunscreen photostability when designing sunscreen formulations to protect the biomechanical barrier properties of human stratum corneum (SC) from solar ultraviolet (UV) damage. Biomechanical properties of SC samples were assayed after accelerated UVB damage through measurements of the SC's mechanical stress profile and corneocyte cohesion. A narrowband UVB (305–315 nm) lamp was used to expose SC samples to 5, 30, 125, and 265 J cm^?2 in order to magnify damage to the mechanical properties of the tissue and characterize the UV degradation dose response such that effects from smaller UV dosages can be extrapolated. Stresses in the SC decreased when treated with sunscreen components, highlighting their effect on the skin prior to UV exposure. Stresses increased with UVB exposure and in specimens treated with different sunscreens stresses varied dramatically at high UVB dosages. Specimens treated with sunscreen components without UVB exposure exhibited altered corneocyte cohesion. Both sunscreens studied prevented alteration of corneocyte cohesion by low UVB dosages, but differences in protection were observed at higher UVB dosages indicating UV degradation of one sunscreen. These results indicate the protection of individual sunscreen components vary over a range of UVB dosages, and components can even cause alteration of the biomechanical barrier properties of human SC before UV exposure. Therefore, detailed characterization of sunscreen formulation components is required to design robust protection from UV damage.     

Codling moth granulosis virus: effects of its use on some other orchard arthropods

In four field trials from 1978 to 1980, sprays of codling moth granulosis virus (CpGV) plus 1·0% skimmed milk powder did not significantly affect damage to fruit by leaf rollers (tortrix moths). In laboratory tests, survival of larvae of the leaf roller Archips podana fed on leaves sprayed with CpGV plus milk was unaffected and they grew faster than on unsprayed leaves, because of the milk deposits. This might increase damage by A. podana if CpGV plus milk were applied during the feeding period of this species. In one field trial an unusual infestation of fruit by larvae of pith moth Blastodacna atra was not affected by CpGV. Azinphos-methyl significantly reduced damage by B. atru and, in one field trial where sprays were correctly timed, that by leaf rollers. CpGV had no consistently significant effects on numbers of fruit tree red spider mite Panonychus ulmi or its predators, whereas azinphos-methyl induced outbreaks of P. ulmi by killing its predators.     

Photostabilized titanium dioxide and a fluorescent brightener as adjuvants for a nucleopolyhedrovirus

Titanium dioxide (TiO₂)reflects ultraviolet light, and so could beexpected to protect the occlusion bodies (OBs)of nucleopolyhedroviruses (NPVs) fromdegradation by sunlight. However, in thepresence of sunlight and water, TiO₂catalyzes the formation of hydrogen peroxide,which can degrade OBs. We tested microfineTiO₂ that had been photostabilized(particles were coated to prevent catalyticactivity), as a UV protectant for the OBs ofthe NPV of Helicoverpa zea (Boddie). Inthe absence of UV, activity of the OBs wasreduced by nonphotostabilized TiO₂ but wasunaffected by photostabilized TiO₂ or byzinc oxide (ZnO). None of these materialsinfluenced larval feeding rates. Undersimulated sunlight, photostabilizedTiO₂ protected the OBs to a greater degreethan did ZnO. Photostabilized TiO₂ wascompatible with a viral enhancer, thefluorescent brightener Blankophor HRS. Undersimulated sunlight, both materials increasedactivity of the OBs, relative to OBs withneither material, in a largely additive manner. In bioassays of foliage collected from fieldplots of lima bean plants sprayed with OBs withor without one or both of these materials,TiO₂ increased persistence of the OBs, butBlankophor HRS had no significant effect.