Selectivity evaluation of insecticides used to control tomato pests to Trichogramma pretiosum

The effects of the insecticides abamectin, acetamiprid, cartap and chlorpyrifos on larvae, pupae (within the host egg) and adults of the egg parasitoid Trichogramma pretiosum Riley (Hym.: Trichogrammatidae) were evaluated under laboratory conditions, using three standard tests described by IOBC. When sprayed on the immature stages of this parasitoid, cartap and chlorpyrifos proved to be the most harmful insecticides, affecting both the emergence success and parasitism capacity of this parasitoid, whereas abamectin and acetamiprid were selective. Abamectin was harmful to adults (residue test on glass plates), slightly harmful to larvae, and moderately harmful to pupae (sprayed on the immature stages within host eggs Anagasta kuehniella (Zeller)); acetamiprid was moderately harmful to adults, harmless to larvae, and slightly harmful to pupae; cartap was harmful to adults, moderately harmful to larvae and harmful to pupae; chlorpyrifos to adults, harmless to larvae and harmful to pupae.     

Effects of wheat foliar fungicides on the aphid endoparasitoid Aphidius rhopalosiphi DeStefani-Perez (Hym., Aphidiidae) on glass plates and on plants

Abstract: The side-effects of several fungicides used in wheat to control disease at heading growth stage were assessed on the aphid parasitoid Aphidius rhopalosiphi by tests conducted in the laboratory on glass plates and in the greenhouse on young wheat plants. Very few formulations containing only one active ingredient (carbendazim, cyproconazole or epoxyconazole) or combinations of two (carbendazim + cyproconazole, carbendazim + hexaconazole) were harmless to A. rhopalosiphi in the glass-plate tests. There was no apparent synergism between fungicides tested in combinations. The parasitoid mortalities in tests carried out on plants were less and chlorothalonil, epoxyconazole, fenpropidin, fenpropimorph, flusilazole, flutriafol, prochloraz, tebuconazole, tridemorph and a number of combinations (carbendazim + flutriafol, chlorothalonil + cyproconazole, epoxyconazole + tridemorph, chlorothalonil + hexaconazole, chlorothalonil + flutriafol, cyproconazole + prochloraz, epoxyconazole + fenpropimorph, fenpropimorph + propiconazole, propiconazole + tridemorph, triadimenol + tridemorph) were harmless or only slightly harmful to the aphid parasitoid. Several combinations (carbendazim + epoxyconazole, carbendazim + fenpropimorph, carbendazim + flusilazole, carbendazim + tebuconazole, chlorothalonil + fenpropimorph, chlorothalonil + flusilazole, fenpropimorph + fenpropidin, fenpropimorph + prochloraz, fenpropidin + propiconazole, fenpropidin + tebuco nazole, tebuconazole + triadimenol) were toxic for wasps on plants. The parasitoid mortalities were less on plants than on glass plates but the wasps spent less time on treated leaves and in some cases parasitism of aphids was reduced to a large extent. These results suggest that in addition to study of the direct effects of pesticides on beneficial insects (mortalities, reduction of fertility) their effects on the behaviour of the insects should also be studied. Products that induced a repellent effect need further testing in field or semi-field conditions. However, many fungicide combinations that have little or no effect on A. rhopalosiphi can protect wheat against a wide range of diseases and the results obtained in this study indicate that an appropriate and effective protection of wheat at earing growth stage can be achieved with products that have no effects on aphid parasitoids.     

The side-effects of pesticides used in integrated production of peaches in Brazil on the egg parasitoid Trichogramma cacoeciae Marchal (Hym., Trichogrammatidae)

Abstract: The side‐effects of six pesticides used on peaches in Brazil were tested on the hymenopteran egg parasitoid Trichogramma cacoeciae using four laboratory tests: (a) adult parasitoid exposure to fresh pesticide residue on glass plates (worse case); (b) direct spray of host eggs enclosing the parasitoid egg, larvae or pupae (less‐exposed life stages); (c) exposure of adults to pesticide residues on plant leaves at different intervals after application (persistence); (d) Dose–response pesticide exposures of adults on glass plates. Two dose rates were used: (1) The highest recommended field dosage (FD) and (2) the predicted initial environmental concentrations (PIEC). The results showed that the preparations greatly differed in their initial toxicity and persistence. The insecticide Valient^® (methoxyphenozide) and the fungicide Venturol^® (dodine) were considered harmless to T. cacoeciae adults as they fell into the class 1 category according to the guidelines of the International Organization for Biological Control (IOBC) when parasitoids were directly exposed to chemical residues. The insecticide/acaricide Assist^® (mineral oil) was slightly harmful at the rate of PIEC 0.4 (40% of FD) and moderately harmful at FD. Pesticides in the categories harmless and moderately harmful can be considered for use in integrated pest management (IPM). The fungicide/acaricide Kumulus DF^® (sulphur) and the insecticides Dipterex^® 500 (triclorfon) and Lebaycid^® 500 (fenthion) were harmful at both concentrations. In the persistence test, Assist^® was short lived and therefore may in special cases (i.e. reduced direct contact) be considered for use in IPM, but Kumulus^® DF, Dipterex^® 500 and Lebaycid^® 500 constantly reduced parasitism between 77 and 100% and were rated as persistent (more than 30 days). The direct spray of parasitized host eggs at intervals after parasitism showed that Assist^® and Kumulus^® DF were harmless to the parasitoid egg, larvae and pupae within the host eggs. Dipterex^® 500 was slightly harmful when sprayed one day after parasitism (parasitoid egg) and moderately harmful to the other two stages (larvae and pupae). Lebaycid^® 500 was harmful to the parasitoid egg and larvae and moderately harmful to the pupae. The dose–response test showed that Kumulus^® DF and Dipterex^® 500 were toxic to T. cacoeciae. Kumulus^® DF was harmful from 1 PIEC 0.4 to 0.125 PIEC 0.4 dosages and was slightly harmful with 0.0625 PIEC 0.4 dosage. Dipterex^® 500 was harmful to T. cacoeciae in all the dosages tested.     

Selectivity of different biological products to the egg parasitoid Telenomus remus (Hymenoptera: Platygastridae)

The selectivity of five entomopathogens and a chemical insecticide (positive control) to pupae and adults of the egg parasitoid Telenomus remus (Nixon) was evaluated in the laboratory under controlled environmental conditions according to protocols established by the International Organization for Biological Control. Baculovirus anticarsia (Baculovirus AEE^®), Bacillus thuringiensis var. kurstaki (Thuricide^®), Bacillus thuringiensis var. aizawai (Agree^®), Beauveria bassiana (Boveril^®), Metarhizium anisopliae (Metarril^®) and Trichoderma harzianum (Trichodermil^®) are harmless to T. remus pupae, and adults. Thus, our results suggest that the insect control strategies applied here are compatible since entomopathogens were classified as harmless to T. remus in most examined cases and therefore facilitate a joint application to control different pests. Bacillus thuringiensis var. kurstaki (Dipel^®), despite being classified as slightly harmful in some of the evaluations, can still be considered compatible for use together with T. remus, especially when compared with chemical insecticides such as chlorpyrifos that might be considered harmful to the parasitoid survival.     

Susceptibility of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) adults to fungicides used to control apple diseases

This study evaluated the susceptibility under laboratory conditions of Trichogrammapretiosum Riley adults to fungicides recommended by the Integrated Production of Apple (IPA). The bioassays were carried out using the International Organization for Biological Control (IOBC), West Palearctic Regional Section (WPRS) standard protocols. Twelve selected fungicides were studied in the doses (g or ml active ingredient/100 L) captan 1 (0.115), captan 2 (0.120), kresoxim-methyl (0.010), sulphur 1 (AG) (0.480), sulphur 2 (0.480), folpet (0.105), mancozeb (0.160), pyraclostrobin (0.010), tebuconazole (0.010), tetraconazole (0.005), thiophanate-methyl (0.050) and triforine (0.024). Distilled water was used as the blank treatment and the insecticide triclorfon (0.150) as a positive control. The parasitoids were exposed to dry residues applied on glass plates. The reduction in the capacity of parasitism was used to measure the effect of the chemical in comparison to the blank treatment. Each treatment was replicated four times. The results allowed us to classify the fungicides tested in four categories: 1, harmless (< 30%); 2, slightly harmful (30-79%); 3, moderately harmful (80-99%); and 4, harmful (> 99%). 75% of the tested substances were classified as selective (classes 1 and 2) to the parasitoid. The fungicides captan 1, captan 2, kresoxim-methyl, folpet, pyraclostrobin, tebuconazole, thiophanate-methyl and triforine were harmless; mancozeb was slightly harmful; sulphur 1 (AG) and tetraconazole were moderately harmful and sulphur 2 was harmful. These findings should be taken into account when selecting fungicides to spray apple orchards against fungi diseases to preserve the egg parasitoid T. pretiosum.     

Leaf surface preference in the cabbage worm,Pieris rapae crucivora,and parasitism by the gregarious parasitoid Cotesia glomerata

Leaf surface preference of the cabbage worm, Pieris rapae crucivora Boisduval (Lepidoptera: Pieridae), for cabbage, Brassica oleracea L. var. capitata (Brassicaceae), and parasitism by the parasitoid Cotesia glomerata (L.) (Hymenoptera: Braconidae) were investigated experimentally in the laboratory. Female butterflies did not discriminate between the adaxial and abaxial surfaces of cabbage leaves when laying eggs on a vertically placed leaf. Larvae also did not discriminate between the adaxial and abaxial surfaces throughout their larval life. However, second and third instars preferred the lower surface of horizontally placed leaves to the upper surface, irrespective of whether they had hatched on the upper or lower side; other instars showed no preference for the lower surface. Parasitism rates of first and second instars on the upper surface were higher than those of larvae on the lower surface. Egg distribution on leaf surfaces and the leaf surface preference by young larvae are discussed in terms of avoidance of parasitism by the parasitoid C. glomerata.     

Low Temperature Storage of <Emphasis Type="Italic">Telenomus remus</Emphasis> (Nixon) (Hymenoptera: Platygastridae) and its Factitious Host <Emphasis Type="Italic">Corcyra cephalonica</Emphasis> (Stainton) (Lepidoptera: Pyralidae)

We conducted three bioassays to evaluate the effect of low-temperature storage of eggs (host) and pupae and adults (parasitoid) on the biology and parasitism capacity of the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). Viable stored Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) eggs were parasitized to the same degree or even higher than fresh eggs when stored until 14 days at 5°C or until 21 days at 10°C. In contrast, the percentage of parasitized sterilized eggs was equal to the control only when stored for 7 and 14 days. Survival of T. remus pupae declined with storage time at both studied temperatures (5 and 10°C). However, after 7 days of storage, survival of pupae was still 86.3 and 64.9% at 10 and 5°C, respectively. The number of adult male survivors remained similar until the fourth storage day at both 5 and 10°C. In contrast, female survival did not differ until day 8 at 10°C or day 6 at 5°C. Parasitism capacity of stored adults was not altered by storage compared with the control. Therefore, we conclude that the maximal storage time at 10°C is 21 days for viable C. cephalonica eggs and 7 days for T. remus pupae, while parasitoid adults should not be stored for more than 4 days at either 5 or 10°C.     

Susceptibility of Various Stages of Trichogrammatoidea armigera Nagaraja to Some Pesticides and Effect of Residues on Survival and Parasitizing Ability

The toxicity, persistence and effect on parasitism of 10 insecticides, eight fungicides and one acaricide on Trichogrammatoidea armigera Nagaraja, an egg parasitoid of a Helicoverpa armigera (Hb), were investigated in the laboratory and under field conditions. At field recommended dosages, the fungicides oxycarboxin, copperoxychloride, streptomycin sulphate + tetracycline hydrochloride and 2‐bromo‐2‐nitropropane‐1,3‐diol and the acaricide dicofol were safe, while the insecticide phosalone and fungicide tridemorph were moderately toxic to adults. All other insecticides tested, namely dimethoate, fenitrothion, monocrotophos, phosphamidon, endosulfan, cypermethrin, decamethrin, fenvalerate and fluvalinate, and the fungicides carbendazim, methyl thiophenate and carboxin were toxic to adults. A high level of parasitism was recorded for all fungicide treatments and for dicofol and fluvalinate. The larval stage of the parasitoid was more tolerant than other stages. The residual toxicity of all fungicides, and dicofol, did not affect the ability of the parasitoid to parasitize its host, while the insecticides phosalone and fluvalinate were slightly persistent, favouring 44.7% and 49.3% parasitism after 15 days. Residues of dimethoate, decamethrin, cypermethrin, fenvalerate, monocrotophos and phosphanidon were moderately persistent, while fenitrothion and endosulfan were persistent.     

Release ofTelenomus remus [Hym. scelionidae] againstSpodoptera frugiperda [Lep.: Noctuidae] in Florida,U.S.A.

Telenomus remus Nixon, a scelionid egg parasite of Lepidoptera, was released against fall armyworm,Spodoptera frugiperda (J. E. Smith), near Homestead, Florida U.S.A. from May 1975 — May 1977. A small percentage (4.5) of the egg masses collected were parasitized byT. remus, however no recoveries were made in the months following the final release. An egglarval parasite,Chelonus insularis (=texanus) (Cresson), was reared from 50% of the larvae from eggs collected.T. remus apparently was not established in Florida.

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Résumé Telenomus remus Nixon, scelionide parasite des œufs de lépidoptères, a été laché contreSpodoptera frugiperda (J. E. Smith) près de Homestead en Floride, de mai 1975 à mai 1977. Un faible pourcentage des pontes récoltées (4,5%) se révélèrent parasitée parT. remus, cependant aucun parasite ne fut retrouvé dans les mois qui suivirent le dernier lacher. Un parasite ovo-larvaire,Chelonus insularis (=texanus) (Cresson) a été obtenu à partir de 50% des larves issues des œufs récoltés. ApparemmentT. remus n'a pas été établi en Floride.

     

Characterization of NADP<Superscript>+</Superscript>-specific <Emphasis Type="SmallCaps">l</Emphasis>-rhamnose dehydrogenase from the thermoacidophilic Archaeon <Emphasis Type="Italic">Thermoplasma acidophilum</Emphasis>

Thermoplasma acidophilum utilizes l-rhamnose as a sole carbon source. To determine the metabolic pathway of l-rhamnose in Archaea, we identified and characterized l-rhamnose dehydrogenase (RhaD) in T. acidophilum. Ta0747P gene, which encodes the putative T. acidophilum RhaD (Ta_RhaD) enzyme belonging to the short-chain dehydrogenase/reductase family, was expressed in E. coli as an active enzyme catalyzing the oxidation of l-rhamnose to l-rhamnono-1,4-lactone. Analysis of catalytic properties revealed that Ta_RhaD oxidized l-rhamnose, l-lyxose, and l-mannose using only NADP⁺ as a cofactor, which is different from NAD⁺/NADP⁺-specific bacterial RhaDs and NAD⁺-specific eukaryal RhaDs. Ta_RhaD showed the highest activity toward l-rhamnose at 60 °C and pH 7. The K _m and k _cat values were 0.46 mM, 1,341.3 min⁻¹ for l-rhamnose and 0.1 mM, 1,027.2 min⁻¹ for NADP⁺, respectively. Phylogenetic analysis indicated that branched lineages of archaeal RhaD are quite distinct from those of Bacteria and Eukarya. This is the first report on the identification and characterization of NADP⁺-specific RhaD.     

Morphological defense of the egg mass of Spodoptera frugiperda (Lepidoptera: Noctuidae) affects parasitic capacity and alters behaviors of egg parasitoid wasps

The fall armyworm, Spodoptera frugiperda, is a dangerous pest of cereals originating from the tropical and subtropical parts of the Americas. It has invaded over a hundred countries and is spreading rapidly throughout East Asia. Biological control programs are a “model strategy” for the control of invasive pests. Egg parasitoids Telenomus remus and Trichogramma pretiosum are viewed as candidates for the control of S. frugiperda. The aim of this study was to evaluate the behavioral patterns and parasitism efficacy of Te. remus, Tr. pretiosum, and Trichogramma dendrolimi on S. frugiperda egg masses with and without scales. The proportion of parasitism by Te. remus was significantly higher than that by Tr. dendrolimi and Tr. pretiosum. The proportion of parasitism by Tr. pretiosum and Tr. dendrolimi on egg masses with scales was significantly lower than that on egg masses without scales. However, Te. remus had a similar proportion of parasitism on egg masses with and without scales. Residence time, oviposition time, oviposition frequency, risk of host being found, and risk of parasitism by Te. remus were significantly higher than the corresponding parameters of Tr. pretiosum and Tr. dendrolimi. Tr. pretiosum females exhibited a higher residence time, oviposition time, oviposition frequency, risk of host being found, and risk of parasitism than those of Tr. dendrolimi females. In addition, Te. remus females often crept into the scale layer covering the egg masses, whereas Tr. dendrolimi and Tr. pretiosum females did not; they could only parasitize the eggs located on the periphery of the egg mass. Both Te. remus and Tr. pretiosum females had similar proportions of superparasitism, which were significantly higher than that of Tr. dendrolimi. Therefore, Te. remus is the dominant egg parasitoid of S. frugiperda and this has important implications for developing augmentative biological control strategies for S. frugiperda.     

Cannibalism of parasitoid‐attacked conspecifics in a non‐carnivorous caterpillar

Cannibalism, the killing and consumption of conspecifics, can even occur in insect species typically considered to be non‐carnivorous. Of particular interest is the cannibalism of parasitoid‐attacked conspecifics, which could reduce parasitism levels in subsequent generations for that conspecific population. This study reports on the occurrence and some of the consequences of cannibalism in parasitoid‐attacked obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). We show that larvae of C. rosaceana, which is considered to be an herbivorous caterpillar species, did not prey upon live conspecifics, but readily consumed conspecifics attacked by Habrobracon gelechiae Ashmead (Hymenoptera: Braconidae). Further examination found that C. rosaceana larvae feeding on parasitoid‐attacked conspecifics, since their fourth instar, suffered a higher mortality and reduction in body size than those fed on plant material only. The cannibalism of attacked conspecifics did not appear to offer any nutrient benefits for the cannibal. To our best knowledge, this is the first empirical example of the occurrence and some of the consequences of cannibalism by a non‐carnivorous insect on its parasitoid‐attacked conspecifics. We discuss the adaptive significance of such cannibalism on parasitoid‐attacked conspecifics with respect to a trans‐generational fitness gain for the population through the killing of the parasitoids, thereby reducing parasitism in subsequent generations.     

Interactions between the Parasitoid Rhopus nigroclavatus (Ashmead) (Hymenoptera: Encyrtidae) and its Mealybug Hosts Tridiscus sporoboli (Cockerell) and Trionymus sp. (Homoptera: Pseudococcidae)

This research investigated age-class-specific parasitism rates of the buffalograss mealybugs Tridiscus sporoboli (Cockerell) and Trionymus sp. by Rhopus nigroclavatus (Ashmead) (Hymenoptera; Encyrtidae), size class preference of this parasitoid, and mealybug–parasitoid interactions through choice and no-choice studies. In the no-choice studies, the mean rates of parasitism by R. nigroclavatus were 45, 20, 0, and 0%, respectively, for mealybugs adult female, third and fourth instars, first and second instars, and eggs. Choice studies indicated that rate of parasitism increased with host size. The mean rates of parasitism on mealybugs in the choice studies were 100% for adult females, 24% for third and fourth instars, 0% for first and second instars, and 0% for eggs. A second set of choice studies investigating mealybug/parasitoid behavior revealed that R. nigroclavatus oviposits in all post-egg mealybug age classes, but first and second instars were less often parasitized than older mealybugs.     

The side-effects of plant extracts and metabolites of Reynoutria sachalinensis (F. Schmidt) Nakai and conventional fungicides on the beneficial organism Trichogramma cacoeciae Marchal (Hym., Trichogrammatidae)

The aim of this study was to investigate the side-effects of plant extracts (plant strengthener with resistance inducing properties) and conventional fungicides on the egg parasitoid Trichogramma cacoeciae Marchal. Two plant extracts and one metabolite from Reynoutria sachalinensis (F. Schmidt) Nakai (crude water extract (Rey-crude^&reg;), which is used for the control of powdery mildew and other diseases, a methanolic fraction of this extract (Rey-meth^&reg;) and the anthraquinone plant constituent (Physcion^&reg;), as well as four fungicides (Thiram^&reg;, Dithane^&reg; M45, Euparen M^&reg; and Kumulus^&reg;) were tested. Adults of T. cacoeciae of uniform age were exposed to fresh dry film of the compounds and the percentage reduction in parasitism compared with water-treated controls was calculated. The results of experiments using the highest recommended concentrations sprayed on glass plates showed that the preparations greatly differed in their effect on the parasitoid. All of the conventional fungicides tested were found to be harmful. In contrast, Rey-crude and Physcion were harmless to T. cacoeciae , whereas the fraction Rey-meth was slightly harmful. In further experiments the side-effects of the plant protection agents on T. cacoeciae were compared when sprayed at different concentrations either on glass plates or on vine leaves. The results confirmed the findings of the first trials but showed that side-effects of the compounds Dithane M45 and Euparen M were less toxic when applied to vine leaves.     

Evaluation of an endosulfan tolerant strain of <Emphasis Type="Italic">Trichogramma chilonis</Emphasis> on cotton

The performance of an endosulfan tolerant strain of Trichogramma chilonis Ishii was evaluated against Helicoverpa armigera (Hübner) eggs on cotton plants in a net house. Under pesticide pressure, the tolerant strain could provide significantly higher parasitism in comparison to the susceptible strain. The parasitoid adult emergence was also significantly higher in the treatment with the tolerant strain in comparison to the susceptible strain, when parasitoids were released within 3 days of endosulfan spraying. Release of the tolerant strain of T. chilonis in conjunction with endosulfan spray application resulted in significantly higher pest mortality in comparison to the endosulfan treatment or release of T. chilonis alone. It could be inferred from the results that T. chilonis should be released only 3 days after endosulfan spray application as during the first 3 days after the spraying, endosulfan provided the required protection and adversely affected the performance of the parasitoid.     

Temperature influences the performance and effectiveness of field and laboratory strains of the ichneumonid parasitoid, <Emphasis Type="Italic">Campoletis chlorideae</Emphasis>

To understand the influence of temperature on host–parasitoid interactions as a consequence of climatic change, we studied development, survival, and fecundity of field and laboratory strains of the Helicoverpa armigera larval endoparasitoid, Campoletis chlorideae at five different temperatures under laboratory conditions. Post-embryonic development period and degree-days required for completing the life cycle by both the strains decreased by 2.5 and 1.5 folds at 27°C compared to 18°C. Post embryonic development period showed a negative (r = −0.99, P < 0.001) and the development rate a positive (r = 0.99, P < 0.001) association with an increase in temperature. However, no parasitoid larvae survived in H. armigera larvae reared at 12 and 35°C after parasitization, suggesting that temperatures ≥35°C as a result of global warming will be lethal for development and survival of immature stages of C. chlorideae. Adult longevity was negatively associated (r = −0.91 to −0.96, P < 0.001) with temperatures between 12 and 35°C. The parasitoid adults stored at 12°C survived for longer period and exhibited higher fecundity than those kept at 27°C, but the efficiency of parasitism and adult emergence were quite low. Sex ratio of the progeny at 12°C was highly male-biased than the insects kept at 27°C. Laboratory strain of the parasitoid exhibited better survival, and the adults lived longer than the field strain at 18°C than at 27°C. Therefore, C. chlorideae adults stored at 18°C could be used for parasitism, while the immature stages should be reared at 27°C for mass production of the parasitoid for biological control of H. armigera.     

Acceptability and suitability of Spodoptera exigua (Hübner) for Cotesia icipe Fernandez‐Triana & Fiaboe on amaranth

The beet armyworm Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) is a polyphagous insect that is distributed worldwide and was recently reported as an important pest on African indigenous vegetables. Cotesia icipe Fernandez‐Triana & Fiaboe (Hymenoptera: Braconidae) is a recently described parasitoid, reported from various Afrotropical countries. This work investigated the performance of C. icipe on S. exigua infesting Amaranthus dubius Mart. ex Thell. under laboratory conditions. Cotesia icipe was aggressive on the host and successfully oviposited on S. exigua with 70% of parasitoid females ovipositing after 2 hr of exposure. Parasitoid densities significantly affected the parasitism rate and the nonreproductive larval mortality. Parasitism rate was 9.7 ± 0.8% and 59.5 ± 3.1% for a single and cohort of five females released, respectively, when offered 50 host larvae. The cohort female release resulted in significantly higher larval nonreproductive mortality than the single release. However, there was no significant difference between parasitoid release densities in regard to pupal nonreproductive mortality. The larval and pupal mortalities in the presence of C. icipe were significantly higher than the natural mortalities at both parasitoid release densities. The parasitoid sex ratio was female‐biased for the cohort females but balanced when a single female was released. The hind tibia and forewing lengths were not affected by the density of female parasitoids but there were variations according to sex. The implication of these findings on the potential use of C. icipe for biological control of S. exigua in amaranth production systems is discussed.     

The effect of chemical and biological treatment on root and crown rot disease caused by Phytophthora cryptogea Pethybr. & Lafferty in Gerbera

Phytophthora root and crown rot (Phytophthora cryptogea) on gerbera is difficult to manage because most gerbera cultivars are susceptible to P. cryptogea. This study was conducted in order to determine the in vivo (pot experiment) efficacy of some fungicides and biofungicides. In pot experiments, fungicides were applied 7 days after inoculation with P. cryptogea, while biofungicide was applied 7 days before inoculation. In this study, soil drenches of five fungicides were tested. “Ametoctradin+dimethomorph (100 ml/day),” “mandipropamid+difenoconazole (60 ml/day),” “propamocarb+fosetyl‐Al (200 ml/day),” “mancozeb+metalaxyl‐M (250 g/day)” and “azoxystrobin+difenoconazole (100 ml/day)” active substances were used. Similarly, one biofungicide Bacillus amyloliquefaciens syn. MBI 600 (50 g/100 L) was applied by soil drenching. Efficacy of treatments was assessed according to the percentage of the root system which was visibly rotten at the end of the experiment. Root and crown rot severity was rated on a scale of 0 = 0% root system necrotic, 1 = 1%‐25% necrotic, 2 = 26%‐50% necrotic, 3 = 51%‐75% necrotic and 4 = 76%‐100% necrotic from 12 to 21 days. In this experiment, “azoxystrobin 200 g/L + difenoconazole 125 g/L” exhibited the highest efficacy against P. cryptogea with a ratio of 43.75%. The other fungicides and biofungicides ametoctradin 300 g/L + dimethomorph 225 g/L, mandipropamid 250 g/L + difenoconazole 250 g/L, propamocarb 530 g/L + fosety‐Al 310 g/L, mancozeb 64%+metalaxyl‐M 4% and Bacillus amyloliquefaciens syn. MBI 600 11% were ineffective. Importance should be given to management strategies of P. cryptogea of and more experiments should be carried out for a better understanding of the use of registered fungicides and biofungicides.     

Landscape effects on the complex of <Emphasis Type="Italic">Bactrocera oleae</Emphasis> parasitoids and implications for conservation biological control

We studied the parasitoid complex of Bactrocera oleae Rossi (Diptera: Tephritidae) in order to analyse the parasitism response to landscape structure at different spatial extents. Olive fruits were sampled and incubated in the laboratory for insect emergence, thus allowing the calculation of parasitoid emergence rates. A landscape analysis was performed in five concentric buffers, ranging from 0.5 to 2 km diameter around the sampling points. Woodland was chosen as focal class. The percentage of landscape and the splitting index, a measure of fragmentation, were used to quantify landscape composition and configuration, respectively. Significant effects of landscape on parasitism rates were detected. In particular, the percent parasitoid emergence was negatively affected by the splitting index of woodland at a spatial extent ranging from 1 to 2 km. These findings suggest that landscape characteristics are likely to affect parasitoids in well-structured agroecosystems as well. In particular, connectivity at a large scale may favour B. oleae parasitoids more than the abundance of woodland. Potential implications for conservation biological control are discussed.     

<Emphasis Type="Italic">Fusarium verticillioides</Emphasis>: Evaluation of Fumonisin Production and Effect of Fungicides on In Vitro Inhibition of Mycelial Growth

The objectives of this study were to evaluate the fumonisin production by 16 F. verticillioides strains on corn cultures and the effect of quintozene and fludioxonil + metalaxyl-M fungicides on “in vitro” mycelial growth on agar. In addition, the effect of fludioxonil + metalaxyl-M on fumonisin production in defined liquid culture medium was analyzed. Fumonisin B₁ levels on corn cultures ranged from 2.41 to 3996.36 μg/g and the F. verticillioides 103F strain produced the highest level (3996.36 ± 390.49 μg/g, P < 0.05). F. verticillioides strains were inoculated in potato dextrose agar with the addition of quintozene (75 to 9,375 μg/ml) and fludioxonil + metalaxyl-M (1.5 + 0.6 to 187.5 + 75 μg/ml) in order to evaluate the effect of these fungicides on “in vitro” mycelial growth. The F. verticillioides strains showed great variability concerning ED₅₀ values, which were below the recommended application dose for quintozene, but above that for fludioxonil + metalaxyl-M. Moreover, fungicide addition to the culture medium increased mean FB₁ levels compared to the control, suggesting the importance of focusing on the effect of fungicides on mycotoxin production as well as on the phytopathogen control.