Plant extract contact toxicities to various developmental stages of Colorado potato beetles (Coleoptera: Chrysomelidae)

The contact toxicities of methanol extracts from the nine plant species Hedera helix, Artemisia vulgaris, Xanthium strumarium, Humulus lupulus, Sambucus nigra, Chenopodium album, Salvia officinalis, Lolium temulentum and Verbascum songaricum were tested on the developmental stages of Colorado potato beetle (CPB) (Leptinotarsa decemlineata). About 2 mL of plant extract, 40% (w/w), was applied to the first instar to fourth instar larvae and adult beetles using a Potter spray tower. Most of the tested plant extracts caused relatively low mortality in all the beetle instars. Among the plant extracts, H. lupulus extract was the most toxic to all stages of the insect, except for the adult beetles. Larval mortality ranged from 40% in the fourth instars to 84% in the third instars. In a second series of experiments, dose–response bioassays using H. lupulus extract produced lethal concentration 50 (LC₅₀) values ranging from 10%, 12%, 17% to 46% (w/w) active ingredient (plant material) for instars 1–4, respectively. This increasing mortality trend, however, did not extend to the adult stage where even the maximum dose of 40% plant material did not provide sufficient mortality to allow estimation of a LC₅₀. These results demonstrated that the extract from H. lupulus has potential as an active ingredient in biological pesticides developed to manage larval instars of the CPB. The potential uses of this plant extract may be in conventional and organic pest management or as part of a mixture of plant extracts or conventional insecticides. Before extracts can be considered as biological control agents, their impact on natural enemies should be assessed.     

Bio-efficacy of some leaf extracts on the inhibition of egg hatching and mortality of Meloidogyne incognita

Nematicidal activities of extracts from plants were assayed against Meloidogyne incognita in vitro. Leaves of six different plants were collected in and around Aligarh Muslim University Campus. Aqueous extracts of six plants were screened for egg hatchability and nematicidal activity against second stage juveniles of M. incognita in the plant pathology and nematology laboratory, AMU Aligarh. The nematode egg and juveniles were exposed 12, 24 and 48 h in (S, S/2, S/10, S/100) concentrations of plant extracts. The plant extracts of leaves of six plants species viz. Jatropha pandurifolia, Polyalthia longifolia, Wedelia chinensis, Nerium indicum, Duranta repens and Cassia fistula exhibited highly promising mortality of 99.00–72.00% after 48 h of exposure. Aqueous extracts of leaves of J. pandurifolia, P. longifolia, W. chinensis were recorded to be highly effective for inhibition of egg hatching and increasing juvenile mortality of M. incognita. There was a gradual decrease in egg hatching and increase in mortality rate of juveniles of M. incognita with increase in the concentration of leaf extract and exposure time.     

Insecticidal effect of plant extracts on common pistachio psylla,Agonoscena pistaciae Burckhardt and Lauterer (Hemiptera: Aphalaridae)

The common pistachio psylla, Agonoscena pistaciae (Hemiptera: Aphalaridae) is one of the most detrimental pests to pistachio trees. Nowadays various pesticides are used to control the common pistachio psylla, but extensive pesticide spraying against this pest over a period of several years has overpowered its natural enemies. The plant’s byproducts come as an alternative ecologically more compatible in substitution to the synthetic insecticides. This work aims to evaluate the insecticidal potential of herbal extracts of fruit peels of Citrus sinensis and Citrus reticulata, seeds of C. sinensis and Rubia tinctorum, and leaves of Lawsonia inermis against common pistachio psylla. Five concentration 40, 47, 56, 67 and 80 µl/ml, of these plant extracts were sprayed on the fifth instar nymphs of common pistachio psylla by Potter Spray Tower under laboratory conditions (26?±?2?°C, 60–70% RH and a photoperiod of 16L: 8D h). Results showed significant differences among the treatments of the plant extracts and between the concentrations. The LC₅₀ values of C. sinensis peels, C. reticulata peels, C. sinensis seeds, R. tinctorum seeds and L. inermis leaves were 62.04, 38.84, 43.60, 59.01 and 33.99 µl/ml, respectively. Also, all extracts showed the greatest mortality effect in 80 µl/ml concentration. According to these results, these plant extracts may use as herbal pesticides chemical control programme of common pistachio psylla.     

Insecticidal activity of five Chinese medicinal plants against Plutella xylostella L. larvae

Twenty-five extracts of five Chinese medicinal plant species were screened for insecticidal activity against the diamondback moth, Plutella xylostella L., larvae by a leaf dipping bioassay method. The ethyl acetate, ethanol, and acetone extracts of Veratrum nigrum L. root and rhizome, the ethyl acetate extract of Phytolacca americana L. root, and the petroleum ether extract of Pseudolarix kaempferi Gord. root bark were effective against P. xylostella. Among them, the ethyl acetate extract of V. nigrum showed the strongest insecticidal activity against the second and third instar larvae of P. xylostella, with LC₅₀ values of 225 and 335 ppm, respectively. The other extracts gave little or no insecticidal activity against P. xylostella. These results indicated that V. nigrum may be a promising naturally occurring agent for P. xylostella larval control, and that the organic solvent used for plant extraction can affect its insecticidal activity.     

Host plant defenses of black (Solanum nigrum L.) and red nightshade (Solanum villosum Mill.) against specialist Solanaceae herbivore Leptinotarsa decemlineata (Say)

Black nightshade (Solanum nigrum, S. nigrum L.) and red nightshade ( Solanum villosum, S. villosum Mill.) are medicinal plants from the Solanaceae family that synthesize glycoalkaloids and other secondary metabolites. To recognize the potential insecticide activity of these compounds, leaf extracts (containing glycoalkaloid and methanol fractions) were tested for enzyme inhibition, antifeedant activity and toxicity. For in‐vitro glutathione S‐transferase (GST) inhibition activity, we used insecticide‐resistant Colorado potato beetle, Leptinotarsa decemlineata ( L. decemlineata; Say) midgut and fat‐body homogenate. In‐vivo toxicity and the antifeedant activity were performed using larval bioassays. The methanol extracts had greater GST inhibitory activity compared to the glycoalkaloids, as well as greater 2nd instar larvae mortality and antifeedant activity. Furthermore, the green leaf volatile compound, cis‐hex‐3‐enyl acetate, at the concentration of 5 ppm, caused 50% mortality of 2nd instar larvae. Our findings suggest the potential usefulness of S. nigrum and S. villosum extracts to control L. decemlineata.     

Larvicidal potentials of leaf and bark extracts of Eucalyptus camaldulensis (Schlect) and Eucalyptus citriodora (Hook) on Culex quinquefasciatus (Say) larvae

The larvicidal activity of leaf and bark extracts of Eucalyptus camaldulensis and Eucalyptus citriodora on juveniles of Culex quinquefasciatus was determined. Larvae were successfully bred in the laboratory to obtain a “pure” colony. One hundred and sixty‐two batches of 25 larvae each were treated with 3.90, 15.63, 62.50, 250 and 1000 mg/L of plant extract in three replicates, for 24 h to record mortality and for up to 96 h to record feeding and fecundity. There was an increase in percentage mortality with increase in concentration of the petroleum ether plant extracts. There was a statistically significant difference (P < 0.05) between extracts used in the bioassay and mortality of larvae, but there was no significant difference (P > 0.05) between the two plant species. Statistical analysis of average mortality figures using Probit analysis for the leaf extracts of E. citriodora and E. camaldulensis, respectively, had LC₅₀ of 245.47 (26.89 ± 10.13 [SE]) and 316.23 (22.89 ± 8.95) for the crude extracts; 97.72 (44.95 ± 12.89) and 223.87 (29.17 ± 9.56) for the petroleum ether extracts; and 162.18 (30.7 ± 11.16) and 257.04 (26.47 ± 9.28) for the methanol extracts. The bark extracts of E. citriodora and E. camaldulensis, respectively, had LC₅₀ of 251.19 (27.78 ± 8.39) and 398.11 (20.7 ± 7.17) for methanol; and 302.0 (21.56 ± 8.11) and 630.96 (13.56 ± 6.4) for hexane. Both plant species showed anti‐feeding properties against larvae of Culex quinquefasciatus.     

Bioactivity of Piper guineense Schum. & Thonn seed and Moringa oleifera Lam. leaf powder against Trogoderma granarium Everts (Coleoptera: Dermestidae)

Laboratory studies were carried out to investigate bioactivity of Piper guineense seeds and Moringa oleifera leaf powders applied singly or in a mixture against larvae and adult Trogoderma granarium Everts in airtight containers. Three levels (0.0 g, 0.5 g, and 1.0 g/20 g groundnut seeds) of the plant powders were used and pirimiphos-methyl was applied at 0.01 g/20 g seeds (recommended dose). Another control consisting of untreated seeds with aerated lids was included in the bioassay. Both larvae and adults were not killed in control with aerated lids throughout the experimental period and larvae were also tolerant to airtight storage conditions. Adults were more susceptible to plant powders than larvae and adult mortality recorded in P. guineense at 1.0 g, 0.5 g and M. oleifera at 1.0 g/20 g seeds were not significantly different from the mortality observed with the recommended dose of Pirimiphos methyl at five days after treatment (DAT). Larval mortality observed in a mixture of both plants (1:1; w/w) caused significantly higher mortality (77.5%) than other treatments at 5 DAT. All treatments (P. guineense and M. oleifera applied singly or in a mixture) were repellant to larvae T. granarium with 60% repellency recorded in the mixture of plants, 50% repellency in P. guineense and 30% repellency in M. oleifera slurry. The water absorption capacity of treated seeds was not affected by treatment with plant powders and ranged from 31.98% to 37.59%.     

Feeding deterrence,larvicidal and haemolymph protein profiles of an Indian traditional medicinal plant Alangium salviifolium (L.F.) Wangerin on cluster caterpillar,Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

Different organic solvent crude extracts from the leaves of Alangium salviifolium (L.F.) Wangerin, were tested for their feeding deterrence, larvicidal activity and protein concentrations on the fourth instar larvae of Spodoptera litura L. under laboratory conditions. Treatments were given through two different host plant leaves such as brinjal and castor. The bioassay was carried out at different concentrations viz., 0.625, 1.25, 2.5 and 5%. The maximum antifeedant activity in brinjal (52.0%) and castor (29.97%) leaf discs was recorded in ethyl acetate extract as compared with hexane and chloroform extracts at 5% concentration. The result of larvicidal activity revealed that the maximum larval mortality was registered in brinjal leaves (65.81%) and castor with (57.48%) in ethyl acetate extract as compared to hexane and chloroform extracts at 5% concentration. The ethyl acetate extract of A. salviifolium contained alkaloids, diterpenoids, and saponins. The treatment also reduced haemolymph protein concentration after 48 h.     

Laboratory assessment of acaricidal activity of Cymbopogon winterianus,Vitex negundo and Withania somnifera extracts against deltamethrin resistant Hyalomma anatolicum

Larval packet test was used for detection of resistance levels against cypermethrin and deltamethrin, the most commonly used synthetic pyrethroids, in the multi-host tick Hyalomma anatolicum collected from district Moga, Punjab (India). Results indicated the presence of level I resistance against deltamethrin (RF = 2.81), whereas the tick isolate was susceptible to cypermethrin (RF = 0.2). The aqueous and ethanolic extracts of leaves of Cymbopogon winterianus, Vitex negundo and Withania somnifera along with roots of Vitex negundo were assessed for their acaricidal activity against the larvae of deltamethrin resistant H. anatolicum. The efficacy was assessed by measuring per cent larval mortality and determination of LC₅₀ values. The various ethanolic extracts produced a concentration dependent increase in larval tick mortality, whereas the aqueous extracts exhibited a much lower mortality. The highest mortality (93.7 ± 0.66 %) was observed at the 5.0 % concentration of ethanolic extract of leaves of C. winterianus and the lowest LC₅₀ value (0.011 %) was recorded for ethanolic extracts of leaves of V. negundo. The results indicated that these plant extracts have potential to be developed as herbal acaricides.     

The toxicity of endod extract to the early life stages of Dreissena bugensis

Toxicity bioassays were conducted on embryos and early larvae of quagga mussels, Dreissena bugensis, using a filtered aqueous extract and a lyophilized butanol extract of the soap berry plant Phytolacca dodecandra. Developmental stages exposed to each extract were embryos to trochophores (ca 3h‐17h), trochophores to D‐hinge larvae (ca 17h‐40h) and embryos to D‐hinge (3h‐ca 40). Over the whole embryo to D‐hinge exposure period, the aqueous extract resulted in a lowest observed effective concentration (LOEC) of 5mgl^‐1 although mortality did not exceed 50%. For the butanol extract, the LOEC was 2mgl^‐1 and the LC₅₀ was 2.1 mgl^‐1. For the aqueous extract, most of the endod toxicity was seen at the embryo stage, whereas for the butanol extract the toxicity was associated with the trochophore stage. Compared with other non‐oxidizing commercial molluscicides, endod has only moderate toxicity to early dreissenid life stages.     

Control of storage rot of cassava tuber caused by Rhizopus oryzae using some plant extracts

Abstract

The potency of Piper nigrum seed and leaf, Aframomum meleguata seed and Ageratum conyzoides leaf extracts in the control of cassava tuber rot caused by Rhizopus oryzae was investigated. Water, ethanol and petroleum ether were used as extracting solvents. These extracts were fungitoxic both in vitro and in vivo against the test pathogen. P. nigrum seed extracts were the best followed by those of A. meleguata seed, A. conyzoides leaf and then P. nigrum leaf. The extracts were more effective in controlling rot development in unwounded than wounded tubers especially when they were applied before inoculation with the test pathogen. Ethanol extracts gave the highest growth inhibition in vivo followed by water and the petroleum ether extract whereas water extracts showed marked superiority over the extracting solvents in checking rot development in cassava tuber. Water and ethanol extracts of P. nigrum seed and leaf, A. meleguata seed and A. conyzoides leaf could be used as pesticide of plant origin in the control of R. oryzae causing cassava tuber rot in storage.     

Insecticidal activities of Ginkgo biloba seed coat extracts against Spodoptera exigua (Lepidoptera: Noctuidae)

The present study relates to a methanol extract of the seed coat of Ginkgo biloba, and tested particularly on the third instar larvae of Spodoptera exigua. The extract was found to have an inhibitory effect on the growth of the larvae besides bringing a change in the nutrient reserves in the body of the insect. Topical application of five different doses of the methanol extract resulted in a mortal effect to third instar larvae of S. exigua that is very much dependent on the dose as well as duration of exposure. Lower doses revealed lower mortality after 24 h of application. At doses of 1.00, 2.00, 4.00, 8.00 and 16.00 ng/larva, mortalities were 9.25, 26.07, 50.32, 56.28 and 92.44%, respectively. The dose for 50% mortality (LD₅₀) of methanol extracts by applied by a topical method with 1 µL of acetone solution was 1.92 ng/larva. Nutrient reserves like protein, glycogen and lipid are known to regulate pupation and adult emergence. These reserves have been found to be lower in treated larvae, indicating the insecticidal role of methanol extracts from G. biloba against third instar larvae of S. exigua.     

Enhancing of Phytoremediation Efficiency Using Indole-3-Acetic Acid (IAA)

In this study, a pot experiment using Solanum nigrum L. grown in cadmium-contaminated soil was conducted in a greenhouse. Indole-3-acetic acid (IAA) was applied at three different concentrations (1 mg L^?1, 10 mg L^?1, and 100 mg L^?1) to examine the effects on phytoremediation efficiency. According to the experimental results, IAA increased the shoot biomass of S. nigrum significantly, by 124% at the highest concentration used, and increased the Cd concentration in the shoot of S. nigrum by 16%. The Cd extraction amount from a single plant was increased by up to 158%, demonstrating potential practical application for remediation practice.     

Euphorbia cotinifolia (Euphorbiaceae): a promising alternative for leaf cutting ant Atta cephalotes (Hymenoptera: Formicidae) control

Field observations indicate that Euphorbia cotinifolia escapes attack by leaf cutting ants, which are the largest generalist herbivores of the Neotropics. We used controlled bioassays to evaluate the effect of E. cotinifolia on the foraging of the Atta cephalotes ant. In a free-choice trial, to five colonies were offered Mangifera indica leaves with a 10% aqueous E. cotinifolia extract, leaves with distilled water and untreated leaves. The carrying time and leaf area consumed were determined over a five-hour period. The effect of E. cotinifolia on the development of the symbiotic fungus on three sets of five colonies fed the leaves of this plant were compared to the controls fed M. indica and oat flakes, and the effect of the addition of extracts on the culture medium used for the symbiotic fungus isolation was evaluated. Euphorbia leaf consumption was lower than that of the other diets; its consumption as the exclusive foraging resource significantly affected the symbiotic fungus, resulting in changes in colour and texture and an 83.57% decrease in volume that occasionally caused 100% mortality. Although the aqueous extract of E. cotinifolia is not a phagodeterrent for foraging workers, it is evident that E. cotinifolia is not a preferred resource for A. cephalotes due to the negative effect on the growth and viability of the symbiotic fungus.     

Impact of herbivory on performance of <Emphasis Type="Italic">Vincetoxicum</Emphasis> spp., invasive weeds in North America

The alien invasive vines Vincetoxicum rossicum and Vincetoxicum nigrum (swallow-wort) are of major concern in eastern North America, where both species invade forested landscapes and threaten faunal and plant diversity. Among the few native natural enemies reported in Eurasia, the specialist chrysomelid, Chrysochus (Eumolpus) asclepiadeus (Coleoptera; Chrysomelidae), feeds on Vincetoxicum both above ground (as adults) and below ground (as larvae). The goal of our study was to assess the potential for using this beetle to manage invasive Vincetoxicum spp. in North America by quantifying the impact of herbivory by C. asclepiadeus on Vincetoxicum and determining whether this effect was influenced by plant density (“Allee effect”). Experimental work was carried out using a split plot design in the field in southern France. Pots of V. nigrum and V. hirundinaria, a substitute for V. rossicum, were planted at high (255 plants/m²), medium (127 plants/m²), and low (32 plants/m²) plant densities, and received treatments of 0 (control), 2 or 4 C. asclepiadeus adult beetles/pot. Leaf damage, root and shoot biomass, and quantity of seeds were measured after 4 weeks of adult feeding. Densities of 2 and 4 beetles/pot caused similar damage, with significant reductions in plant biomass at low plant density. While V. hirundinaria increased allocation of resources to roots in response to herbivory, V. nigrum did not. Seed production was greatest for both species grown at low plant densities, but only V. nigrum produced fewer seeds in response to herbivory. Our results, based on the effects of herbivory by C. asclepiadeus adults, suggest that if this beetle were to be introduced into North America for the management of Vincetoxicum spp. such as V. rossicum, reductions in plant biomass and spread would be greatest if beetles were released on edges or in newly-established satellite populations at low plant densities. In the case of V. nigrum, beetles could be released irrespective of plant density as reproductive output and seed dispersal would be reduced similarly.     

Repellent and toxic properties of plant oils and extracts on Cydalima perspectalis Walker (Lepidoptera: Crambidae)

Buxus plants in Europe become frequently infested by the Box tree moth, Cydalima perspectalis Walker (Lepidoptera: Crambidae) but applicable biological control methods are limited. To make a first step in preventing egg deposition on Buxus plants, seven essential oils (Carum carvi, Juniperus communis, Lavendula angustifolia, Melaleuca alternifolia, Pinus sylvestris, Rosmarinus officinalis and Thymus vulgaris), one seed oil (Sambucus nigra) and six plant extracts (Equisetum arvense, Juniperus communis, Quassia amara, Salvia officinalis, Tanacetum vulgare and Thymus vulgaris) were investigated on their potential to influence oviposition preference in the greenhouse. The four essential oils exhibiting the highest repellency values (RV = 0.61–0.94) were further assessed in laboratory leaf disc bioassays on larvae. Despite the strong repellent effect of S. nigra on female oviposition, no impact could be detected on the larvae. These were significantly susceptible to exposed leaf discs treated with T. vulgaris and M. alternifolia essential oils including feeding deterrence, survival and larval weight. T. vulgaris was the most effective oil considering both effects. The effective lethal concentration (LC₅₀) of T. vulgaris was calculated to be 1% at 72 h. Our results suggest the possibility of using essential oils to protect Buxus plants in order to reduce the overall risk for defoliation by larval feeding.     

Effects of Pseudomonas fluorescens strain UTPF5 on the mobility,mortality and hatching of root-knot nematode Meloidogyne javanica

The root-knot nematode Meloidogyne spp. includes important plant pathogens worldwide. This study has considered nematode Meloidogyne javanica second stage larvae activity in the extracts of Pseudomonas fluorescens strains UTPF5 and cytotoxic effect of the strain on the nematode. The movement of second stage larvae of nematodes in water agar medium at four concentrations of bacterial extracts and second stage larvae mortality rate of hatching nematode and bacterial strains in vitro were affected. Different concentrates of the strain UTPF5 effect nematode larvae movement and disposal of the same. Bacterial extraction kills almost 100% of the larvae hatching after 24?h and a complete ban on egg hatch of biocontrol nematodes and nematode indicated that root-knot nematode larvae movement on the right attract the bacteria P. fluorescens to extract in the first place.     

Evaluations of larvicidal activity of medicinal plant extracts to Aedes aegypti （Diptera： Culicidae） and other effects on a non target fish

A preliminary study was conducted to investigate the effects of the extracts of 112 medicinal plant species, collected from the southern part of Thailand, on Aedes aegypti. Studies on larvicidal properties of plant extracts against the fourth instar larvae revealed that extracts of 14 species showed evidence of larvicidal activity. Eight out of the 14 plant species showed 100% mosquito larvae mortality. The LC50 values were less than 100μg/mL （4.1μg/ mL-89.4μg/mL）. Six plant species were comparatively more effective against the fourth instar larvae at very low concentrations. These extracts demonstrated no or very low toxicity to guppy fish （Poecilia reticulata）, which was selected to represent most common non-target organism found in habitats ofAe. aegypti, at concentrations active to mosquito larvae. Three medicinal plants with promising larvicidal activity, having LC50 and LC50 values being 4.1 and 16.4 μg/mL for Mammea siamensis, 20.2 and 34.7 μg/mL forAnethum graveolens and 67.4 and 110.3μg/mL forAnnona muricata, respectively, were used to study the impact of the extracts on the life cycle ofAe. aegypti. These plants affected pupal and adult mortality and also affected the reproductive potential of surviving adults by reducing the number of eggs laid and the percentage of egg hatchability. When each larval stage was treated with successive extracts at the LC50 value, the first instar larvae were found to be very susceptible to A. muricata and the second instar larvae were found to be susceptible to A. graveolens, while the third and fourth instar larvae were found to be susceptible to M. siamensis. These extracts delayed larval development and inhibited adult emergence and had no adverse effects on P. reticulata at LC50 and LC50 values, except for the M. siamensis extract at its LC50 value.     

Protection of cowpea,Vigna unguiculata L. (Walp.) with Newbouldia laevis (Seem.) extracts against infestation by Callosobruchus maculatus (Fabricius)

Evaluation of protectant ability of Newbouldia laevis (Seem.) extracts against infestation by Callosobruchus maculatus in cowpea, Vigna unguiculata L. (Walp.) was carried out in the laboratory at ambient temperature of 28?±?2?°C and 70?±?5% relative humidity. Extracts from wood ash, leaf, stem and root bark were tested at different concentrations of 0, 1, 2, 3, 4 and 5%. One hundred per cent mortality of adult beetles was achieved at all concentrations within 72?h of treatment with extracts except in wood ash at 1% concentration, but they were significantly different (p?<?0.05) from the controls. All the extracts were still able to cause high beetle mortality after one, two and three months of cowpea storage at high concentrations (4 and 5%) except wood ash, although there was a slight decrease in mortality during the period of storage. All the extracts significantly (p?<?0.05) reduced oviposition and adult emergence of C. maculatus when compared with the controls although the reduction was higher at 5% concentration than others. Adult beetle emergence was completely prevented at higher concentrations (4 and 5%) except in wood ash. Both oviposition and adult emergence increased during the months of storage probably because of the slight reduction in the effectiveness of the extracts. The root bark extract was much more effective in reducing oviposition and adult emergence than others throughout the period of storage. The plant extracts of N. laevis was able to protect the cowpea seeds from damage and prevent weight loss. Cowpea seed damage and weight loss was significantly more (p?<?0.05) in the controls than other for the three-month duration probably because of the more adult emergence. The extracts from N. laevis did not adversely affect the germination of the protected seeds and seed germination ranged from 86.7 to 100%. It has been shown in this study that the extracts of N. laevis were effective against C. maculatus in cowpea although the root bark extract seemed to be the most effective while the wood ash extract was least effective. Their effectiveness, however, slightly decreased during the period of storage. N. laevis could be incorporated into pest management of stored cowpeas since the products are ecologically safe.     

Compatibility and efficacy of the lady beetle <Emphasis Type="Italic">Thalassa montezumae</Emphasis> and the entomopathogenic fungus <Emphasis Type="Italic">Isaria fumosorosea</Emphasis> for biological control of the green croton scale: laboratory and greenhouse investigations

The lady beetle Thalassa montezumae and the entomopathogenic fungus Isaria fumosorosea (Ifr) were assessed alone and in combination to suppress green croton scale, Phalacrococcus howertoni, populations on croton plants using laboratory bioassays and greenhouse cage studies. The acquisition of Ifr blastospores by beetle larvae (3rd instar) and adults during contamination in well plates was used to simulate exposure to direct spraying and subsequent possible fungal infection was assessed. Spore dispersal by the insects was determined after the blastospore-contaminated T. montezumae life stages roamed on agar plates for 24 h by counting the number of colony-forming units (CFUs) produced in the plates. There were no significant differences in survival times at 14 days post-treatment between beetle larvae and adults exposed to Ifr and those exposed to water only. Mean survival time of larvae exposed to Ifr was 14 days and water 12 days, whereas for adults it was 13 days compared to 13 days, respectively. Plates with Ifr blastospore-contaminated T. montezumae adults roaming on the agar surface displayed significantly more fungal trails as CFUs compared to plates with larvae. In greenhouse cage studies, the mean mortality rates of the scale exposed to beetle larvae, either alone (80.8%) or in combination with Ifr (89.1%), were not significantly different. Scale mortality rates in the fungus-only (60.5%) and beetle larvae-only treatments were statistically similar. The treatment with both biocontrol agents had a significantly higher scale mortality rate compared to the treatment with Ifr only. Therefore, spraying Ifr prior to releasing T. montezumae is an effective and compatible biological control strategy for management of the green croton scale on croton plants.