Synergism of pyrethroid — organophosphorus insecticide mixtures in insects and their toxicity againstspodoptera littoralis larvae

Synergism of mixtures of pyrethroids with organophosphorus (OP) compounds in insects is reviewed, and the toxicity of such combinations againstSpodoptera littoralis (Boisd.) larvae is reported. Mixtures of one of the pyrethroids cypermethrin, fenvalerate or deltamethrin with one of the OP compounds monocrotophos, profenofos, azinphos-methyl or acephate were assayed at different ratios as 24-h-old dipping residues on alfalfa, which was fed toS. littoralis larvae for 48 h. With most of the binary mixtures containing various OP concentrations in excess of those of the pyrethroids, synergism was demonstrated. In the pairs fenvalerate — azinphos-methyl, deltamethrin — azinphos-methyl and deltamethrin — profenofos, however, no synergism was found. In a detailed investigation with pyrethroid concentrations causing 20% mortality and OP concentrations giving a kill of no higher than ;10%, the above findings on synergism were amply confirmed. A cypermethrinmonocrotophos mixture showed synergism also on cotton leaves sprayed in the field. Synergism could not be demonstrated by topical application of pyrethroid — OP mixtures.     

Pyrethroid synergism and prevention of emergence inTribolium castaneum andMusca domestica vicina by the insect growth regulator RO 13-5223

Ethyl [2-(4-phenoxyphenoxy)ethyl] carbamate (RO 13-5223) at a dietary concentration of 100 mg kg^-1 synergized the toxicity of thetrans- andcis-isomers of permethrin and cypermethrin in inhibiting the growth (measured as gain in larval weight) ofTribolium castaneum andMusca domestica vicina. With both species the synergism factor forcis-cypermethrin with 100 mg kg^-1 synergist was 1.5- to twofold for RO 13-5223 and about fourfold for piperonyl butoxide. Synergism was more pronounced with first instar than with fourth instarT. castaneum larvae. Methoprene was not a pyrethroid synergist withT. castaneum larvae, so the synergistic effect of RO 13-5223 appears to depend on its structural features and not its insect-growth-regulator activity. Joint application of RO 13-5223 and pyrethroids resulted in a dual effect on bothT. castaneum andM. domestica: increased inhibition of larval growth due to pyrethroid synergism, and progeny suppression — expressed by larval and pupal mortality — due to RO 13-5223 juvenilizing activity.     

Susceptibility of the carob moth,Ectomyelois ceratoniae,toBacillus thuringiensis

A 1% concentration ofBacillus thuringiensis wettable power (containing 16,000 IU/mg), applied at a rate of 48,000 IU/cm², killed 95% of 4th-instar larvae of the carob moth,Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae), after 66 h and 100% after 85 h of exposure in laboratory tests. The mortality caused by a 0.5% concentration (24,000 IU/cm²) was significantly lower and presumably inadequate for practical application against this pest.     

Feeding deterrents forphilosamia ricini (samia cynthia subsp.Ricini) fromtithonia diversifolia

Tagitinin A and C and hispidulin isolated fromTithonia diversifolia (Hemsl.) Gray, were potent feeding deterrents, when evaluated against 4th instar caterpillars of the Eri-silkworm(Philosamia ricini Hutt.) (Lepidoptera: Saturniidae); tagitinin F was not.     

Impact of two synthetic pyrethroids and methomyl on management of the cabbage aphid,brevicoryne brassicae (L.) and its associated parasitoid,diaeretiella rapae (M'Intosh)

The effectiveness of two synthetic pyrethroids, cypermethrin and fenvalerate, and of methomyl applied to cabbage plants was tested against the cabbage aphid, Brevicoryne brassicae (L.), and its parasitoid, Diaeretiella rapae (M'Intosh). Dosage rates chosen were equivalent to the manufacturer's maximum and minimum recommendations. Methomyl was considerably more toxic to B. brassicae adults than the two synthetic pyrethroids used. Fenvalerate, at the lowest rate used (71 g ha^?1), showed satisfactory effectiveness in reducing aphid adult population on treated plants by c. 77% below that of the control. All insecticides and rates used significantly reduced the emergence of parasitoid adult D. rapae from mummified aphids compared to the control. Fenvalerate clearly had less impact on emergence than cypermethrin or methomyl at any dosage used, while methomyl has appeared to be the most toxic compound in this respect. Longevity of parasitoid adults was highly affected by insecticide application, particularly those adults emerging from mummified aphids exposed to methomyl or cypermethrin. However, only a slight difference in longevity was seen at the lower rate of 71 g ha^?1 of fenvalerate. At the lowest dosage rates used, methomyl and cypermethrin reduced the F₁-progeny of adult parasitoid females by 70.5% and 58.3%, respectively, of the control, whereas fenvalerate reduced the progeny by only 36.4%.     

Insecticide control of a white grub,Maladera matrida,on sweet potato

In an effort to control the damage caused by the beetleMaladera matrida Argaman (Coleoptera: Scarabaeidae) to sweet potatoes,Ipomoea batatas (L.) Lam., experiments comparing heptachlor with other insecticides were conducted in the Besor region in the southern part of Israel in 1987. Taking the percentage of clean tubers at the final harvest as the criterion of insecticidal efficacy, the best results were achieved with heptachlor (97.3% clean tubers) and with the synthetic pyrethroid Talstar (biphenthrin) (91.1% clean tubers), while the percentage of clean tubers obtained in two untreated control plots was 52.5% and 65.9%. The effect of heptachlor and Talstar was not significantly different from that of Oftanol (isofenphos) plus Becis (decamethrin), but was significantly better than that of Dizictol (diazinon), Becis, Dizictol plus Becis, Oftanol, and the untreated controls. The average tuber weights from the treatments with heptachlor, Talstar and Becis were significantly higher than those of the untreated control plots and from the treatments with Dizictol, Oftanol, and Oftanol plus Becis.     

A list of arthropod pests of avocado and pecan trees in Israel

Lists are given of arthropod pests of avocado and pecan trees in Israel. These include ten new pests of avocado and three of pecan. The pests of economic importance on avocado includeBoarmia (Ascotis) selenaria (Schiff.) (Geometridae, Lepidoptera) andHeliothrips haemorrhoidalis (Bouché) (Thrypidae, Thysanoptera). The pests of importance on pecans includeEmpoasca decedens (Paoli) (Jassidae, Homoptera),Zeuzera pyrina L. (Cossidae, Lepidoptera), andMonellia costalis (Fitch) (Aphididae, Homoptera).     

Binary mixtures of pyrethroids produce differential effects on Ca influx and glutamate release at isolated presynaptic nerve terminals from rat brain

Isolated rat brain synaptosomes were used to evaluate the action of pyrethroid mixtures on Ca²⁺ influx and subsequent glutamate release under depolarizing conditions. In equipotent binary mixtures at their respective and/or estimated EC₅₀s with deltamethrin always as one of the two components, cismethrin, λ-cyhalothrin, cypermethrin, esfenvalerate and permethrin were additive and S-bioallethrin, fenpropathrin and tefluthrin were less-than-additive on Ca²⁺ influx. In binary mixtures with deltamethrin always as one of the two components, esfenvalerate, permethrin and tefluthrin were additive and λ-cyhalothrin was less-than-additive on glutamate release. Binary mixture of S-bioallethrin and cismethrin was additive for both Ca²⁺ influx and glutamate release. Only a subset of pyrethroids (S-bioallethrin, cismethrin, cypermethrin, and fenpropathrin) in binary mixtures with deltamethrin caused a more-than-additive effect on glutamate release. These binary mixtures were, however, only additive (cismethrin and cypermethrin) or less-than-additive (S-bioallethrin and fenpropathrin) on Ca²⁺ influx. Therefore, increased glutamate release evoked by this subset of pyrethroids in binary mixture with deltamethrin is not entirely occurring by Ca²⁺-dependent mechanisms via their action at voltage-sensitive calcium channels. These results suggest that pyrethroids do not share a common mode of toxicity at presynaptic nerve terminals from rat brain and appear to affect multiple target sites, including voltage-sensitive calcium, chloride and sodium channels.     

Residues of synthetic pyrethroid insecticides on horticultural crops

Foliar applications of synthetic pyrethroids were made to several crops to determine residue levels at various intervals after application. On onions, residues of cypermethrin, permethrin and fenvalerate were negligible > 0.1 mg kg^?1, 7 days after application. On lettuce, residues of fenvalerate and permethrin were 0.8 mg kg^?1. On celery, residues of fenvalerate did not decline and ranged from 0.12 to 0.25 mg kg^?1 during the 14-day period. On green bush-beans, residues of permethrin and cypermethrin did not decline during the 14-day period and ranged from 0.1 to 0.6 mg kg^?1. By day 7, residues of cyfluthrin, cypermethrin, deltamethrin, fenvalerate and permethrin on strawberries were less than the acceptable maximum tolerance of 0.1 mg kg^?1 with the exception of cypermethrin, applied at the rate of 0.14 kg a.i. ha^?1 which gave a residue of 0.14 mg kg^?1.     

Structure-related effects of pyrethroid insecticides on the lateral-line sense organ and on peripheral nerves of the clawed frog, Xenopus laevis

The effects of seven different pyrethroid insecticides on the lateral-line sense organ and on peripheral nerves of the clawed frog, Xenopus laevis, were investigated by means of electrophysiological methods. The results show that two classes of pyrethroid can be clearly distinguished. (i) Pyrethroids without an α-cyano group (permethrin, cismethrin, and bioresmethrin). These noncyano pyrethroids induce short trains of nerve impulses in the lateral-line sense organ. In peripheral nerve branches they induce a depolarizing afterpotential and repetitive firing. These effects are very similar to those previously reported for allethrin. (ii) Pyrethroids with an α-cyano-3-phenoxybenzyl alcohol (cypermethrin, fenpropathrin, deltamethrin, and fenvalerate). In the lateral-line sense organ these α-cyano pyrethroids induce very long trains of nerve impulses which may last for seconds and may contain hundreds or even thousands of impulses. The α-cyano compounds do not cause repetitive activity in peripheral nerves. Instead they induce a quickly reversible, stimulus frequency-dependent suppression of the action potential. Since the chemical structure of cypermethrin differs from that of permethrin only in the α-cyano group and because all four α-cyano compounds act in a very similar way, it is concluded that the α-cyano substituent is responsible for the large differences in neurotoxic effects. In the lateral-line sense organ the duration of nerve impulse trains induced by the noncyano as well as the α-cyano pyrethroids increases dramatically when the temperature is lowered. Further, in sensory fibers the effects of both classes of pyrethroid on the nerve action potential are more pronounced compared to their effects on motor fibers. It is argued that the different neurotoxic effects reported here originate from a common mechanism of action of pyrethroids, which is a prolongation of the transient increase of sodium permeability of the nerve membrane associated with excitation.It is concluded that the sodium channel in the nerve membrane is the major target site of noncyano and α-cyano pyrethroids.     

Alien scale insects (Hemiptera Coccoidea) in European and Mediterranean countries: the fate of new and old introductions

This contribution focuses on recent interceptions and introductions of alien scale insects and their current distribution in European and Mediterranean countries. Data and collections were gathered in markets, nurseries, and botanical gardens, mostly in Italy, either indoors or outdoors. New or recent records of the following alien species are presented: Exallomochlus hispidus (Morrison); Ferrisia virgata (Cockerell) (Pseudococcidae); Coccus viridis (Green); Milviscutulus mangiferae (Green) (Coccidae); Aonidiella orientalis (Newstead); Aspidiotus destructor Signoret; Aulacaspis tubercularis Newstead; Fiorinia fioriniae Targioni Tozzetti; Lepidosaphes pinnaeformis (Bouché); Pseudaulacaspis brimblecombei Williams (Diaspididae). New data and pest status of Phoenicococcus marlatti Cockerell (Phoenicococcidae) and Trabutina mannipara (Hemprich & Ehrenberg) (Pseudococcidae) are also reported. The possible repeated introductions of the latter from North Africa to south Italy by trans-Mediterranean winds, is hypothesized.     

Control of brown rot of citrus fruit by application of fungicides via sprinkler irrigation systems

Copper fungicides applied via low head sprinklers, reduced brown rot (caused byPhytophthora spp.) on oranges and grapefruit. The most effective fungicide was Bordeaux mixture, which reduced the disease rate to the same level as that obtained by standard spraying with this fungicide. Copper oxychloride was moderately effective and captan was ineffective. A field method for brown rot rating was devised.     

Persistence and safety evaluation of synthetic pyrethroids on sweet orange fruits

The residues of four synthetic pyrethroids from two spray concentrations per compound on sweet orange fruits dissipated at the respective half-life values of 2.45 and 3.15 days for 0.015 and 0.02% fenvalerate; 2.28 and 2.58 days for 0.015 and 0.02% permethrin; 1.73 and 2.12 days for 0.0075 and 0.01% cyper-methrin ; and 2.6 and 2.9 days for 0.0015 and 0.002% deltamethrin, respectively. However, the comparative persistence of synthetic pyrethroids on the rind of sweet orange fruits in the tropical belt in India was found to be in the order of fenvalerate = permethrin > cypermethrin > deltamethrin. No residues were detected in the fruit pulp.     

Identification and species status of the mango biotype of Colletotrichum gloeosporioides in Ghana

Research work was carried out to identify and ascertain the species status of the mango biotype of Colletotrichum gloeosporioides infecting mangoes in Ghana. Forty five isolates of Colletotrichum species were collected from 12 districts in Ghana while five each were obtained from mango fruits from Florida, Mexico and Puerto Rico. The entire internal transcribed spacer region, partial beta-tubulin gene and partial glyceraldehyde-3-phosphate dehydrogenase gene of isolates were sequenced and used in phylogenetic studies. The results of the sequence analysis of the first ribosomal transcribed spacer (ITS 1) region showed that 35 % of the isolates from Ghana and all the five isolates from Mexico were the mango biotype of C. gloeosporioides, while the others were not. Phylogenetic studies showed that the mango biotype of the pathogen was Colletotrichum asianum but not C. gloeosporioides as previously thought. However, the other isolates that were not the mango biotype were identified as Colletotrichum siamense and Colletotrichum species which had probably cross-infected mango from other fruit crops in the field.     

Characterization of 11 commercial pyrethroids on the functional attributes of rat brain synaptosomes

The action of 11 commercial pyrethroids on Ca²⁺ influx and glutamate release was assessed using high-throughput functional assays with rat brain synaptosomes to better understand the mechanistic nature of pyrethroid-induced neurotoxicity and aid in the reassessment of pyrethroids in vivo. Concentration-dependent response curves for each of the non-cyano and α-cyano containing pyrethroids were determined and the data used in a cluster analysis. The previously characterized α-cyano pyrethroids that induce the CS-syndrome (cypermethrin, deltamethrin, and esfenvalerate) increased Ca²⁺ influx and glutamate release, and clustered with two other α-cyano pyrethroids (β-cyfluthrin and λ-cyhalothrin) that shared these same actions. Previously characterized T-syndrome pyrethroids (bioallethrin, cismethrin, and fenpropathrin) did not share these actions and clustered with two other non-cyano pyrethroids (tefluthrin and bifenthrin) that likewise did not elicit these actions. Our current findings indicate that pyrethroids that have an α-cyano group (with the exception of fenpropathrin) were more potent enhancers of Ca²⁺ influx and glutamate release under depolarizing conditions than pyrethroids that did not possess this functional group. The collective data set does not support the hypothesis that pyrethroids, as a class, act in a similar fashion at presynaptic nerve terminals.     

Integrative diagnosis and molecular phylogeny of dagger and needle nematodes of olives and grapevines in the island of Crete,Greece, with description of Xiphinema cretense n. sp. (Nematoda,Longidoridae)

The occurrence and geographic distribution of longidorid nematode species inhabiting the rhizosphere of cultivated and wild olive and grapevine in Crete Island were investigated. Morphological and morphometrical studies identified five Longidorus and six Xiphinema species, with frequencies of prevalence (for wild and cultivated olives and grapevines, respectively) as follows: Longidorus closelongatus (2.0–13.3 %), L. cretensis (1.0–6.7 %), L. moesicus (13.3 % only in grapevines), L. orientalis (3.3 % only in grapevines), L. pseudoelongatus (7.0 % only in olives), Xiphinema cretense n. sp. (3.0 % only in olives), X. index (3.0–23.3 %), X. israeliae (6.3 % only in olives), X. italiae (3.3–10.0 %), X. pachtaicum (26.7–42 %) and X. simile (3.3 % only in grapevines). Xiphinema cretense n. sp. is characterized by a body size 3,872–6,135 μm long, lip region anteriorly rounded, separated from the rest of the body by a depression, odontostyle and odontophore 140.6 and 80.3 μm long respectively, vulva position at 46.0–50.5 %, female tail 31.0–38.0 μm long, nearly hemispherical with curvature essentially dorsal and with a tip completely rounded or presenting a very short bulge, c ratio (119.1–186.9), c’ ratio (0.7–0.8). Molecular characterisation using D2-D3 expansion regions of 28S rRNA, 18S rRNA and ITS1-rRNA was carried out and maximum likelihood and Bayesian inference analysis were used to reconstruct phylogenetic relationships among these species and with other longidorids.     

Neem kernel as an ovipositional repellent forSpodoptera litura (F.) moths

Laboratory and nursery tests showed that a 2% neem (Melia azadirachta L.) seed kernel suspension in water was effective as a repellent and ovipositional deterrent for moths of the tobacco caterpillar,Spodoptera litura (F.). The mean number of eggs laid on treated tobacco seedlings was 37 3 as against 1715 on control seedlings. As a consequence of the moths being repelled from the treated plants, they laid more eggs on the cloth and the glass surface in glass jar experiments. Repellency was even more pronounced when the moths were released in treated and untreated nylon-netting-caged nursery beds; the mean number of eggs laid on treated seedlings was then only 749 as against 19,713 in control beds.     

Phagodeterrent response of the bulb mite Rhizoglyphus robini to various pyrethroids and some of their cleavage products

Feeding-avoidance response of the bulb mite Rhizoglyphus robini to various insecticidal and acaricidal pyrethroids and some of their cleavage products was examined using a two-choice cellulose disc bioassay. The mites were able to detect extremely low quantities of certain pyrethroids, down to 1–5ng of pesticide applied to a cellulose disc weighing 200 mg. The phagodeterrent potency of the pyrethroids was found to be in the following decreasing order: fenvalerate > cypermethrin > deltamethrin > bioresmetnrin > pyrethrin > bifenthrin > cis-permethrin > trans-permethrin. Fenpropathrin, bioallethrin, flucythrinate and tetramethrin were stimulatory up to a level of 50 ng disc^?1. A 100-ng dose of fenpropathrin deterred the mites. Chemical and photochemical cleavage products of pyrethroids possessed phagodeterrent potencies comparable to those of the intact pesticides. 3-Phenoxybenzotc acid and cis-chrysanthemic acid were the most effective deterrents followed by dibromochrysanthemic acid and the cis and trans bifenthrin acid moiety. The probable relevance of the observed phagodeterrence by pyrethroid residues and their cleavage products, as related to induction of dispersal and eventual outbreaks of mites, is discussed.     

Relationships between disease and yield in cotton fields affected byAlternaria macrospora

Application of various fungicides to cotton plots (Gossypium barbadense cv. Pima) affected byAlternaria macrospora resulted in a yield increase from 3955 kg/ha in unsprayed plots to 5207 kg/ha in plots treated with fentin acetate. Pathogen, host and disease parameters were estimated by a key of grades in the field and by precise measurements of detached plants. Measurements included the number of spores present in the field and numbers and/or areas of healthy, lesioned and shed leaves and bolls. No significant differences were found between the number of healthy bolls on variously treated plants and the number of lesioned bolls on the same plants. Disease incidence was relatively low in treated plots, with no significant difference between treatments and no correlation with the size of the pathogen population or the yield level in variously treated plots. The low proportion of lesioned leaves resulted from their tendency to shed and from the emergence of new leaves, which masked the damage. Rate of shedding was correlated with the respective yield and with the size of the pathogen population in the same plot. Leaf shedding was induced by lesions occupying an average of 1 to 3% of the leaf area. Shedding was affected by leaf position on the plant, being most frequent for the lowest leaves despite their being the least lesioned, and least frequent for the upper leaves even though these were the most lesioned.     

Differential susceptibilities to pyrethroids in field populations of Chilo suppressalis (Lepidoptera: Pyralidae)

To assess the feasibility of pyrethroids for rice insect control, we examined susceptibilities of six field populations of rice stem borer Chilo suppressalis (Walker) to 10 pyrethroids using the topical application method in laboratory in 2004 and 2005. Our results showed that the seven pyrethroids with high fish-toxicity (i.e., β-cyfluthrin, λ-cyhalothrin, β-cypermethrin, deltamethrin, S-fenvalerate, α-cypermethrin, and fenpropathrin) were more effective against C. suppressalis than the three compounds with low fish-toxicity (i.e., cycloprothrin, etofenprox, and silafluofen). The results also showed that all 10 of the pyrethroids were much more effective than methamidophos and monosultap for C. suppressalis control. In addition, we found that susceptibilities of some field populations of C. suppressalis to some high fish-toxicity pyrethroids were significantly reduced, and our results indicated that a Ruian (RA) field population showed a year-to-year variation in susceptibility to most tested pyrethroids between 2004 and 2005. Our data indicated that the tolerance levels increased dramatically in RA population, especially to β-cyfluthrin and deltamethrin. This study provided the first assessment of resistance to pyrethroids in field populations of C. suppressalis. In addition, a close correlation between resistance ratios to the 10 compounds and differences of the structures of these compounds was established in the RA05 population, which was resistant to most of the pyrethroids tested while it was still very susceptible to fenvalerate with no cross resistance. Finally, the feasibility and precaution were discussed in selecting pyrethroids as alternatives to replace high toxicity organophosphates for C. suppressalis control and insecticide resistance management.