The effect of CME 134 onSpodoptera Littoralis Eggs and larvae

CME 134, a new benzoylphenyl urea chitin synthesis inhibitor, was less active than diflubenzuron and BAY SIR 8514, when tested againstSpodoptera littoralis eggs by a dipping method. AgainstS. littoralis larvae the compound was tested by feeding treated alfalfa, topical application and contact with crystalline residues on glass, followed by observation until the adult stage. With both 200–250 and 360–440-mg larvae 100% mortality was obtained by one-day feeding of alfalfa treated with 0.15 ppm a.i. Topical application to 100- and 200-mg larvae showed CME 134 to be about five and nine times more active than BAY SIR 8514 and diflubenzuron, respectively. These differences were even much greater in the contact tests. Cotton field plots were sprayed with either CME 134 or diflubenzuron formulations, leaves were collected at different intervals and fed for one day toS. littoralis larvae in the laboratory. 0.0009% a.i. CME 134 residues gave complete kill of 30–50-mg larvae after 5 and 20 days, and 86% kill after 28 days of aging. With 0.003 and 0.009% a.i., complete kill was obtained in 200–250-mg larvae until 50 days after spraying.     

The effect of diflubenzuron upon larvae of the geometrid Boarmia (Ascotis) selenaria on avocado leaves

Small (70 mg) Boarmia selenaria larvae fed for 4 days on avocado leaves or alfalfa dipped in aqueous diflubenzuron suspensions suffered from severe developmental disturbances. Similar results were obtained with leaves sprayed in an avocado orchard, with which, in addition, the considerable persistence of diflubenzuron under field conditions could be demonstrated. The substance was also active by topical application against large (500–600 mg) B. selenaria larvae, whereas by contact it was only moderately toxic. Some other non-conventional control agents, viz., the antifeedant AC-24055 and several juvenile hormone analogues, were of medium and negligible activity, respectively, against this insect.     

The effect of some benzoyl phenylureas on the larvae of earias insulana

Diflubenzuron, PH 60-38, PH 6043, penfluron (PH 60-44), PH 6045, triflumuron, chlorfuazuron (IKI-7899), teflubenzuron (CME 134), XRD473 and Dowco 439 were tested for their efficacy against the larvae of the spiny bollworm,Earias insulana (Boisd.), in laboratory experiments. The compounds were incorporated at different concentrations in an artificial diet and 5-day-old larvae were introduced and grown on the treated diets until pupation and adult emergence. Teflubenzuron was active at 0.1 ppm, chlorfuazuron at 0.75 ppm and PH 60-38 at 10 ppm; triflumuron and diflubenzuron were active only at 50 ppm; all the rest of the compounds were even less active. When cotton bolls were dipped in teflubenzuron and offered to 6-day-old larvae in the laboratory, only 4% and 10% of the larvae penetrated inside the bolls treated with 50 and 25 ppm a.i., respectively, whereas 68% penetrated inside untreated bolls.     

Diflubenzuron: Some aspects of its ovicidal and larvicidal mode of action and an evaluation of its practical possibilities

Diflubenzuron, 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)urea, possesses larvicidal and ovicidal activities. On larvae it acts mainly as a stomach poison, yet it sometimes exhibits important contact activity. Though all instars can be controlled, older instars are generally less susceptible than younger ones. Histological inspections of Leptinotarsa decemlineata larvae revealed that after ending exposure to the compound, distortions in newly deposited cuticular layers decreased gradually. Ovicidal effects resulted from direct contact of diflubenzuron with eggs or from contamination of females by contact or feeding. Electron microscopic observations of embryos of Leptinotarsa decemlineata, contaminated via the female, also showed disturbed cuticule formation, suggesting a similar activity of the compound in larvae and in eggs. Spraying the eggs of Leucoptera scitella shows the compound to be mainly ovidical at a rate of 100 mg litre^?1, whilst with lower concentrations (10 and 1 mg litre^?1) the young larval instar will be killed. The levels of cross-resistance to diflubenzuron as a larvicide are low and the compound can be used effectively in the field against populations that are highly resistant to conventional insecticides. Laboratory and field results, based on larvicidal and ovicidal activities of diflubenzuron, are discussed in respect of species belonging to the Diptera, Lepidoptera, Coleoptera, Acarina (Phyllocoptruta oleivora) and Hemiptera (Eurydema oleraceum and Psylla piri).     

A laboratory evaluation of the effectiveness of diflubenzuron against Dermestes maculatus De Geer and other storage insect pests

The chitin synthesis inhibitor diflubenzuron, applied as a wettable powder spray to woven polypropylene at 100–500 mg m^?2, was effective against Dermestes maculatus De Geer for at least 12 weeks. D. maculatus was unable to develop on ox hide dipped in a suspension of diflubenzuron (125 mg litre^?1), or on fishmeal dusted at 1–10 mg of active ingredient kg^?1. Diflubenzuron prevented the development of infestations of Callosobruchus maculatus (L.) on peas and of Acanthoscelides obtectus (Say) on beans dusted at 1–5 mg kg^?1. The compound was also very effective against early instar larvae of Trogoderma granarium Everts on wheat. The persistence and activity of diflubenzuron at low dosage rates against D. maculatus appear to justify larger scale trials.     

Ph 70–23: A new acaricide and insecticide interfering with chitin deposition

PH 70–23 is a new benzoylphenylurea interfering with chitin deposition. In larvae of Spodoptera littoralis, incorporation of N-acetyl-glucosamine into chitin was equally inhibited by PH 70–23 and diflubenzuron, the first commercially available benzoylphenylurea. In contrast to diflubenzuron, which is active only against insects and eriophyid mites, PH 70–23 has the advantage of also being highly active on spider mites. The latter activity might be partly due to leaf penetration of PH 70–23. Laboratory experiments indicate PH 70–23 to have a better ovo-larvicidal activity than the commercial acaricides tested (cyhexatin, dicofol, fenbutatin oxide and tetradifon) against Tetranychus cinnabarinus, T. turkestani, T. urticae and Panonychus ulmi. A method in which eggs were deposited on residues of cyhexatin or fenbutatin oxide resulted in much lower activities than application of the spray liquid after egg deposition. Activities of PH 70–23, dicofol and tetradifon were hardly influenced by this difference in the test method. The direct contact activity of PH 70–23 on eggs of mites is influenced by the relative humidity and the age of the eggs. The total ovolarvicidal activity of PH 70–23 is only slightly positively influenced by the relative humidity, however. Ovicidal activity of PH 70–23 is also achieved by transovarial transmission. The compound does not influence the fertility of the mites. Comparison of a strain of T. urticae, resistant to dicofol, parathion and tetradifon, with a susceptible strain indicated absence of cross-resistance to PH 70–23. Compared to diflubenzuron, PH 70–23 shows an interesting shift in the spectrum of insecticidal activity.     

The effect of BAY SIR 8514 onspodoptera littoralis (Boisduval) eggs and larvae

The chitin biosynthesis inhibitor diflubenzuron and its analog BAY SIR 8514 are equitoxic for eggs ofSpodoptera littoralis. BAY SIR 8514 residues on alfalfa fed toSpodoptera larvae were more toxic than diflubenzuron residues, whereas BAY SIR 8514 topically applied to these larvae was consistently twice as toxic as diflubenzuron, according to different criteria.     

Effects of temperature and yeast supplementation on the development ofTribolium castaneum (Herbst) in wholemeal and polished flour derived from four cereals in Maiduguri, Nigeria

The effects of temperature, yeast and polishing (removal of bran) on the development ofTribolium castaneurn (Herbst) in flour derived from millet, sorghum, maize and wheat were investigated for one generation in Maiduguri, Nigeria. Significantly moreT. castaneurn adults and larvae developed in flour stored at 35 °C than in flour stored at 30 °C or 40 °C; mortality of adult beetles in flour stored at 40 °C was 95 % in sorghum and maize and 100 % in millet and wheat. Addition of three levels (2.5, 5.0 and 10.0 %, w/w) of yeast to cereal flour, on average, significantly increased the population of adult and larval progenies relative to the population in yeast-free flour. Considerably higher number of adult beetles developed in wholemeal than in polished flour derived from millet.     

Effects of temperature and yeast supplementation on the development ofTribolium castaneum (Herbst) in wholemeal and polished flour derived from four cereals in Maiduguri, Nigeria

The effects of temperature, yeast and polishing (removal of bran) on the development ofTribolium castaneurn (Herbst) in flour derived from millet, sorghum, maize and wheat were investigated for one generation in Maiduguri, Nigeria. Significantly moreT. castaneurn adults and larvae developed in flour stored at 35 °C than in flour stored at 30 °C or 40 °C; mortality of adult beetles in flour stored at 40 °C was 95 % in sorghum and maize and 100 % in millet and wheat. Addition of three levels (2.5, 5.0 and 10.0 %, w/w) of yeast to cereal flour, on average, significantly increased the population of adult and larval progenies relative to the population in yeast-free flour. Considerably higher number of adult beetles developed in wholemeal than in polished flour derived from millet.     

A study of 1,2-dibromoethane residues in wheat and milled products

A method is described for determining residues of 1,2-dibromoethane (EDB) in milled wheat products. The residues are first extracted with benzene, then recovered azeotropically for reaction with alkali and subsequent determination of liberated bromide ion by a Volhard titration. Freshly milled flours from wheat fumigated with 65.0 and 325 mg EDB/litre at 37°C were found to contain 10.6 to 39.4 mg EDB/kg and the bran contained from 51.4 to 153 mg EDB/kg.     

Acute and sublethal toxicity of novaluron, a novel chitin synthesis inhibitor, to Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

The acute and sublethal toxicities of novaluron, a novel chitin synthesis inhibitor, to a laboratory-reared insecticide-susceptible strain of Colorado potato beetle, Leptinotarsa decemlineata (Say), were determined. Novaluron exhibited excellent residual (120 h LC(50) = 0.42 mg litre(-1)) and good direct contact (120 h LC(50) = 27 mg litre(-1)) activity against second-instar larvae (L2). Hatch of eggs exposed by direct contact to novaluron solutions > or =100 mg litre(-1) was significantly reduced, as was the ability of emerged first-instar larvae to moult. L2 from eggs exposed to > or =100 mg litre(-1) novaluron weighed significantly less (P < 0.0001) than those from untreated eggs. However, L2 from eggs treated with 1 mg litre(-1) novaluron weighed significantly more (P < or = 0.05) than those from untreated eggs, suggesting novaluron can have a hormetic effect on L decemlineata larval development. Leptinotarsa decemlineata mating pairs fed foliage treated with novaluron at 25 or 75 g AI ha(-1) produced approximately 25% fewer egg masses and eggs per mass. Hatch of eggs on treated foliage was almost completely suppressed, and longevity of male beetles was reduced by approximately 50% when fed foliage treated with novaluron at 75 g AI ha(-1).     

Feeding behaviour as a limiting step in insecticide absorption for the wireworm Agriotes sp. (Coleoptera: Elateridae)

The fipronil control of wireworms field populations (larval Agriotes sp., Coleoptera: Elateridae) is difficult because of the low integumental penetration rates of this insecticide into the target larval body. The main way of insecticide absorption being associated with food, analysis of the larval feeding behaviour is of key importance for designing a strategy of dietary chemical control of those subterranean pests. In this purpose, a standard method for assessing the long-term survival of field specimens in the laboratory was developed together with experimental designs for investigating food searching and choosing by larvae. Larval biological performances under those laboratory conditions were checked monthly. Three criteria were taken into account for measures: the duration of individual survival, the gain in average body weight, and the moulting rhythm. Experimentation revealed that seed flour was highly desired by larvae and that larval feeding choice was affected over short distances only. This suggests the involvement of dietary preference rather than attractivity in the larval feeding behaviour. This implies that, at the operational step, insecticide had better be associated to food, either as a coating on the seeds, or inside preferred baits.     

Acaricidal effects of cardiac glycosides, azadirachtin and neem oil against the camel tick, Hyalomma dromedarii (Acari: Ixodidae)

The cardiac glycoside, digitoxin, from Digitalis purpurea L (Scrophulariaceae), a cardiac glycosidal (cardenolide) extract from Calotropis procera (Ait) R Br (Asclepiadaceae), azadirachtin and neem oil from Azadirachta indica A Juss (Meliaceae) were tested for their effects against larvae and adult stages of the camel tick, Hyalomma dromedarii Koch (Acari: Ixodidae). The contact LC50 values of the first three materials against adults were 4.08, 9.63 and >40.7 microg cm(-2), respectively, whereas the dipping LC50 values of the four materials were 409.9, 1096, >5000 and >5000 mg litre(-1), respectively. Contact and dipping LC50 values of the extract and azadirachtin against larvae were 6.16, >20.3 microg cm(-2) and 587.7 and >2500 mg litre(-1), respectively. Azadirachtin had no effects on egg production or feeding of adults up to 5000 mg litre(-1); however at 2500 mg litre(-1), it caused significant reduction in feeding activity of larve, prolonged the period for moulting to nymphal stage, and caused 60% reduction in moultability. Results of the two cardiac glycoside materials are comparable with those of several commercial acaricides. The risks and benefits associated with the use of cardiac glycosides are considered.     

无患子皂苷对甜菜夜蛾的影响及其化学成分分析

为明确无患子皂苷对甜菜夜蛾的控制作用,本试验分别用添加无患子皂苷(0.25、0.5、1、2、4、8、16 mg/g)的混毒饲料喂养甜菜夜蛾2龄幼虫,测定甜菜夜蛾幼虫存活率、幼虫发育历期、蛹重、化蛹率、卵孵化率、性比等指标。采用液相色谱-质谱联用仪(HPLC-MS)分析无患子皂苷中的主要化学成分。结果表明,喂饲后72 h,取食4 mg/g混皂苷饲料的甜菜夜蛾幼虫开始死亡,其幼虫存活率随皂苷浓度的升高而降低;相比空白对照组,取食4 mg/g混皂苷饲料的幼虫,其幼虫期延长8.55 d(P<0.05),蛹重降低了41.13%(P<0.05),化蛹率下降46.43%(P<0.05)。取食0.5 mg/g以及2 mg/g混皂苷饲料的幼虫其卵孵化率分别比空白对照降低9.61%、16.12%;取食混有皂苷的饲料会扰乱甜菜夜蛾的性比,其中混入2 mg/g皂苷的处理对其性比影响最大,雌性比为25.00%。从无患子皂苷中鉴定出10种皂苷类化合物,共鉴别出6种常春藤型三萜皂苷,3种齐墩果酸型三萜皂苷,1种大戟烷型三萜皂苷。     

Effects of methoxyfenozide on Lobesia botrana Den & Schiff (Lepidoptera: Tortricidae) egg, larval and adult stages

The effect of the non-steroidal ecdysone agonist methoxyfenozide was evaluated against different developmental stages of the grape berry moth, Lobesia botrana Dennis & Schiffermuller (Lep, Tortricidae). Methoxyfenozide administered orally reduced the fecundity and fertility of adults treated with 1, 5 and 10 mg litre(-1); longevity was not affected. An LC(50) value of 4.5 mg litre(-1) was obtained when applied to eggs of less than 1 day old. Surface treatment was more effective than when applied by spraying. Administered into the diet, methoxyfenozide had a larvicidal effect; older larvae were more susceptible than younger larvae, with LC(50) values of 0.1 mg litre(-1) for L(1), 0.04 for L(3) and 0.02 for L(5). Larvae treated with sub-lethal doses throughout their lives did not emerge as adults at the highest doses (0.08, 0.04, 0.02 and 0.01 mg litre(-1)), with 65% and 40% emergence occurring for the lowest (0.005 and 0.0025 mg litre(-1)). Mortality occurred only in the larval stage.     

Effectiveness of a naturally derived insecticide, spinosad, against the pine processionary moth Thaumetopoea wilkinsoni Tams (Lepidoptera: Thaumetopoeidae) under laboratory conditions

The pine processionary moth Thaumetopoea wilkinsoni Tams is a serious pest on pine trees in southwestern Turkey. The efficacy of a naturally derived insecticide, spinosad, on fourth-fifth instar larvae of T. wilkinsoni was studied under laboratory conditions. The product exhibited strong larvicidal activity and at doses above 5 mg litre(-1) caused > 90% mortality in the fourth-fifth larval stages of the species after 72 h. At 72 h the LD50 and LD90 values were 3.26 and 5.69 mg litre(-1) respectively. The results showed that spinosad is highly effective on T. wilkinsoni larvae.     

Induction of prolonged larval feeding stage by juvenile hormone analogues inTribolium Castaneum

Dietary ZR-512 and ZR-619 at concentrations of 10 — 1000 ppm induced prolongation of the larval feeding period up to tenfold, increasing larval weight up to double that of untreated larvae. A comparison study of four juvenoids, using 200 ppm of ZR-512, ZR-515, ZR-619 or ZR-777, showed that ZR-515 elicits the highest larval weight (6.2 mg) and ZR-777 the lowest (3.6 mg). In all cases a pronounced enhancement of larval weight — of 50 — 250% relative to untreated larvae (2.4 mg) — was obtained.Tr. castaneum larvae reared up to their 3rd instars on a diet containing 100 ppm of ZR-512, ZR-515, ZR-619 or ZR-777 and then transferred to a juvenile hormone-free diet, were not affected. The period between 4th instar larva and pupation should therefore be considered as critical for juvenile hormone effect. The induced prolongation of the larval stage after juvenile hormone treatment was followed by a pronounced enhancement of cuticle phenoloxidase activity, indicating an alteration of the larval biochemical processes. Although juvenile hormone treatment inhibitsTr. castaneum pupation and emergence, it markedly prolongs larval feeding stage and weight and thus accelerates damage.     

Contact activity of diflubenzuron against Spodoptera littoralis larvae

The effect of diflubenzuron as a residue on glass or applied topically to Spodoptera littoralis larvae was investigated. Diflubenzuron was active as a residue on glass against 100 and 200 mg larvae; the toxicity of residues was identical whether a dispersable formulation or a wettable powder or the technical substance were used. By topical application, diflubenzuron had an ED₅₀ for cumulative percentage mortality up to the adult stage of 004 and 0066 μg/larva for 100 and 200mg larvae respectively. Neither the site of the topical application nor whether the larvae were kept singly or in groups of ten after the treatment had an influence on toxicity. The data indicate that diflubenzuron has contact toxicity to at least one insect species as well as the known stomach poison action.     

The effect of IKI-7899, a new chitin synthesis inhibitor,on larvae ofTribolium castaneum andSpodoptera littoralis

The effect of IKI-7899 and diflubenzuron on larval development and emergence ofTribolium castaneum and ofSpodoptera littoralis was determined. The LC₅₀ of IKI-7899 at adult emergence ofT. castaneum larvae fed the compound in their diet and the ED₅₀ of S.littoralis larvae treated topically were approximately one-sixth those of diflubenzuron.     

Effect of diflubenzuron on growth and carbohydrate hydrolases ofTribolium castaneum

The potency of diflubenzuron is much greater in inhibiting growth and development of 1st instar larvae ofTribolium castaneum than of 4th instar larvae, as expressed by death at the apolytic stage and retardation of larval development. A dose-dependent decrease in the activity of trehalase, invertase and amylase was obtainedin vivo with the increase in diflubenzuron concentration. At 5 ppm dietary concentration, a reduction of 37 and 27% in invertase and trehalase activity, respectively, was obtained in 4th instar larvae fed for 3 days on treated diet. The amylase activity was affected to a lesser extent. The observed disturbances of trehalase activity might hamper the supply of glucose needed for chitin build-up and those of invertase and amylase activity might affect feeding. Diflubenzuron does not inhibit these enzymesin vitro; hence, thein vivo effect seems to result from general disturbances in carbohydrate metabolism.