3rd Instar Nymphs Research Articles

Levels of Salivary Enzymes of Apolygus Lucorum (Hemiptera: Miridae), From 1st Instar Nymph to Adult, and Their Potential Relation to Bug Feeding.

In recent years, Apolygus lucorum has caused increasing damage to cotton and fruit trees in China. The salivary enzymes secreted by A. lucorum when sucking on host plants induce a series of biochemical reactions in plants, and the pre-oral digestion benefits the bug feeding. In this study, the food intake of A. lucorum from 1st instar nymphs to adults was measured, and the corresponding salivary activity of pectinase, amylase, cellulase, protease, polyphenol oxidase and peroxidase was determined. Daily food intake varied with developmental stage, peaking in 3rd and 4th instar nymphs. Pectinase, amylase, cellulase and protease were detected in both nymphal and adult saliva of A. lucorum, while neither polyphenol oxidase nor peroxidase was detected. Protease activity varied with food intake peaking at the 3rd-4th instar, and then slightly decreasing at the 5th instar. Levels of pectinase, amylase and cellulase increased significantly with the daily feeding level until the 3rd instar, corresponding with increasing damage to host plants. The activity of both cellulase and protease had a significant linear relationship with the average daily food intake. The increasing activity of enzymes in saliva explain stage-specific impacts of A. lucorum on the host plants, and suggest that optimal management of A. lucorum would be confined to its control threshold prior to the peak of daily feeding in the 3rd instar.

Functional response of Coccinella septempunctata L. (Coleoptera: Coccinellidae) on Ommatissus lybicus (Homoptera: Tropiduchidae) Arif Shah

Dubas bug, Ommatissus lybicus (Homoptera: Tropiduchidae), is a major insect pest of date palm. Adult and nymph stages suck sap from all green parts and cause direct and indirect damage. Large number of predators feed on it; however, no information is available on their consumption rate and functional response using this prey. We aim to find out consumption rate of Coccinella septempunctata with an objective how adult female and fourth nymphal instars of C. septempunctata responds to 1st and 3rd instar nymphs of O. lybicus at various density levels under controlled condition. Both stages of C. septempunctata exhibited a type II functional response. Handling times and attack rates were significantly different between adult female and larval stage indicating that predator responds differentially to prey stage offered at same density. Estimated handling time of C. septempunctata adult female and fourth instar (in bracket) at 24 hours were 0.563(0.692) and 1.008(1.492) and estimated attack rate were 0.020 (0.014) and 0.003(0.002) on first and third instar nymphs of prey, respectively, which conclude that adult is more voracious stage than larva. However, further field studies on predator and prey stage specific in the presence of honeydew droplets on leaflets are still needed to quantify biocontrol efficiency of predator. Keywords: Bivoltine; Coccinella septempunctata; Dubas bug; Honeydew; Predation http://dx.doi.org/10.19045/bspab.2016.50069

Biology and feeding potential of Coccinella septempunctata (Linn.) against Lipaphis erysimi (Kalt) at different temperature regimes

Biology and feeding potential of Coccinella septempunctata (Linn.) were studied in laboratory on 3rd instar nymphs of mustard aphid (Lipaphis erysimi Kalt.) at two different temperature regimes. At 30± 20C, fecundity, oviposition period, hatchability of eggs, male and female longevity (232±70.46, 12.8±3.91, 82.87±6.66, 22.70 ± 2.21and 26.60 ± 4.45, respectively) were higher and incubation period, pre-oviposition period, total grub duration and pupal duration (2.6±0.51, 6.5±3.53, 8.7 ± 1.63 and 5.1 ± 1.10, respectively) were lesser in comparison to 25± 20C where fecundity, oviposition period, hatchability of eggs, male and female longevity, incubation period, preoviposition period, total grub duration and pupal duration were 169.8±61.12, 7.9±1.37, 71.68±4.08, 16.2 ± 1.31 and 21.50 ± 1.95, 2.9±0.73, 7.7±2.49, 11.1 ± 1.52 and 5.8 ± 0.918, respectively . At 27± 2 0C, total mustard aphid consumption by a grub of C. septempunctata during the whole life span, was 424.4±2.78 mustard aphids in comparison to 272.64±1.79 mustard aphid at 23± 20C. Similarly an adult male and female consumed 103.2±1.52 and 116.6 ±1.46 aphids per day respectively at 27± 2 0C in comparison to 65.6 ± 1.02 and 71.8 ± 1.60 at 23± 20C. Thus, at both temperatures aphid consumption increased gradually till 4th instar and 30±20C was found to be most suitable temperature as compared to 25±20C for the life history of C. septempunctata. Hence, it could be concluded that C. septempunctata might play a suitable role in biointensive Integrated Pest Management programme because of better longevity and high predatory potential against the mustard aphid.

Rapid evolution of symbiotic bacteria populations in spirotetramat-resistant Aphis gossypii glover revealed by pyrosequencing

Aphis gossypii is one of the most economically important insect pests for agriculture worldwide. Aphids have developed symbiotic associations with bacterial species, which has led to morphological and molecular differences, such as body color and insecticide resistance. Adults and 3rd instar nymphs of a laboratory-selected spirotetramat-resistant strain of cotton aphid presented 579-fold and 15-fold higher resistance to spirotetramat, respectively, than a susceptible strain (Pan et al., 2015; Peng et al., 2016). In this study, we found that antibiotics, especially ampicillin and tetracycline, increased spirotetramat toxicity in resistant aphids. We also characterized all of the bacterial endosymbionts in these two clones by sequencing the 16S rRNA genes of the endosymbiont. The total reads could be clustered into 3534 operational taxonomic units (OTUs) that showed 97% similarity and belonged to six abundant phyla. Proteobacteria and Firmicutes dominated in the two strains, and the most abundant families were Enterobacteriaceae, Lactobacillaceae and Rhodobiaceae. The genera Arsenophonus, Anderseniella, Buchnera and Lactobacillus were most abundant in the susceptible strain, whereas a significant decrease in abundance of Anderseniella and a great increase in abundance of Arsenophonus and Lactobacillus were observed in the resistant strain. Certain identified species had low sequence similarity to the reported species, which indicates the possibility of novel taxa. The type and abundance of different bacterial groups varied significantly between the two strains. The insecticide selection pressure could be the reason for the observed shift in the bacteria groups. These results increase our understanding of the symbiotic relationships between bacteria and their hosts under insecticide stress and provide clues for the development of potential control techniques against this cotton aphid.

Parasitoid, <I>Aenasius arizonensis</I> (Girault) (Hymenoptera: Encyrtidae): its Biology, Morphometrics, Host Stage Preference and use in Biological Control

Aenasius arizonensis (Girault) ( = Aenasius bambawalei Hayat) (Hymenoptera: Encyrtidae), a solitary endoparasitoid of Phenacoccus solenopsis Tinsley, is a major invasive pest in several cotton growing countries around the globe. It has been recorded as an effective natural enemy of P. solenopsis . The biological characteristics of parasitoid were studied on P. solenopsis under laboratory conditions. The mean duration of development of A. arizonensis from oviposition to mummy formation was 5.9 ± 0.31 days for both male and female, while from mummy formation to adult emergence was 5.9 ± 0.31 and 7.3 ± 0.3 for male and female, respectively. The mean developmental period of male and female was 12.2 ± 0.33 and 14.2 ± 0.37 days, respectively. Males were short lived (16.3 ± 1.41 days) as compared to females (26.2 ± 1.72 days). Female started ovipositing on the day of emergence. The mean pre-oviposion, oviposition and post-oviposition periods were <1, 23.1 ± 1.66 and 3.1 ± 0.55 days, respectively. Mean daily and total fecundity in terms of number of parasitized host per female was 4.24 ± 0.2 and 100.5 ± 11.57, respectively. Sex ratio was skewed towards female and recorded as 1:2. Maximum percentage of parasitization occurred in adult host stage i.e. 90% followed by 3 rd , 2 nd , and 1 st instar nymph with 73.33%, 33.33% and 0 per cent, respectively. Among the three nymphal stages 3rd instar nymph was the most suitable stage for mass multiplication of parasitoid. Its successful utilization in mealybug management can be optimized by multiplying at this stage of host in the laboratory and thereafter inoculative release into the field. This report provides a detailed diagnostic description of A. arizonensis with illustration to facilitate easy identification & morphological differences between male & female along with the morphometric measurements of pupa & mummy.

Parasitoid, &lt;I&gt;Aenasius arizonensis&lt;/I&gt; (Girault) (Hymenoptera: Encyrtidae): its Biology, Morphometrics, Host Stage Preference and use in Biological Control

&lt;em&gt;Aenasius arizonensis&lt;/em&gt; (Girault) ( = &lt;em&gt;Aenasius bambawalei&lt;/em&gt; Hayat) (Hymenoptera: Encyrtidae), a solitary endoparasitoid of &lt;em&gt;Phenacoccus solenopsis&lt;/em&gt; Tinsley, is a major invasive pest in several cotton growing countries around the globe. It has been recorded as an effective natural enemy of &lt;em&gt;P. solenopsis&lt;/em&gt;. The biological characteristics of parasitoid were studied on &lt;em&gt;P. solenopsis&lt;/em&gt; under laboratory conditions. The mean duration of development of &lt;em&gt;A. arizonensis&lt;/em&gt; from oviposition to mummy formation was 5.9 ± 0.31 days for both male and female, while from mummy formation to adult emergence was 5.9 ± 0.31 and 7.3 ± 0.3 for male and female, respectively. The mean developmental period of male and female was 12.2 ± 0.33 and 14.2 ± 0.37 days, respectively. Males were short lived (16.3 ± 1.41 days) as compared to females (26.2 ± 1.72 days). Female started ovipositing on the day of emergence. The mean pre-oviposion, oviposition and post-oviposition periods were &amp;lt;1, 23.1 ± 1.66 and 3.1 ± 0.55 days, respectively. Mean daily and total fecundity in terms of number of parasitized host per female was 4.24 ± 0.2 and 100.5 ± 11.57, respectively. Sex ratio was skewed towards female and recorded as 1:2. Maximum percentage of parasitization occurred in adult host stage i.e. 90% followed by 3&lt;sup&gt;rd&lt;/sup&gt;, 2&lt;sup&gt;nd&lt;/sup&gt;, and 1&lt;sup&gt;st&lt;/sup&gt; instar nymph with 73.33%, 33.33% and 0 per cent, respectively. Among the three nymphal stages 3rd instar nymph was the most suitable stage for mass multiplication of parasitoid. Its successful utilization in mealybug management can be optimized by multiplying at this stage of host in the laboratory and thereafter inoculative release into the field. This report provides a detailed diagnostic description of &lt;em&gt;A. arizonensis&lt;/em&gt; with illustration to facilitate easy identification &amp;amp; morphological differences between male &amp;amp; female along with the morphometric measurements of pupa &amp;amp; mummy.

The fitness of the cotton mealybug Phenacoccus solenopsis (Tinsley) is reduced after feeding on virus-infected Hibiscus rosa-sinensis

The cotton mealybug Phenacoccus solenopsis (Tinsley) and Cotton leaf curl Multan virus (CLCuMV), serious threats to economic crops and garden plants, have invaded southern China and widely infected Hibiscus rosa-sinensis. Whether an inter-species connection has facilitated the invasion process is unclear. In this study the interaction between P. solenopsis and H. rosa-sinensis infected with CLCuMV was investigated in the laboratory. We observed that 1st and 2nd instar nymphs of P. solenopsis preferred to feed on healthy H. rosa-sinensis leaves, whereas 3rd instar nymphs and female adults had no preference between healthy and virus-infected H. rosa-sinensis leaves. The developmental time of each P. solenopsis developmental stage increased significantly after feeding on infected H. rosa-sinensis leaves (p < 0.05). In particular, the development time for 2nd instar female and male nymphs and 3rd instar female nymphs increased by approximately twofold. The generation time of female mealybugs increased from 25.84 d on healthy H. rosa-sinensis to 32.12 d when feeding on CLCuMV-infected H. rosa-sinensis, and the survival rate decreased from 71.04 % on healthy H. rosa-sinensis to 5.80 % on infected plants. Nymph survival was most affected by feeding on infected plants. Additionally, the fecundity of female mealybugs feeding on infected H. rosa-sinensis decreased by 47.8 %. Thus, feeding on CLCuMV-infected H. rosa-sinensis significantly decreased the biological fitness and invading and colonizing abilities of P. solenopsis.

꽈리허리노린재(Acanthocoris sordidus, Coreidae, Hemiptera)에 대한 몇 가지 살충제와 친환경농자재의 활성평가

꽈리허리노린재(Acanthocoris sordidus)는 흡즙성 해충으로서 가지과 작물을 주로 가해하며, 국내에서는 일부 고추농가에 피해를 주고 있다. 이러한 꽈리허리노린재를 방제하기 위하여 유기합성 살충제 20 종류와 7 종류의 친환경유기농자재를 이용하여 살충력을 알아보았다. 그 결과, 꽈리허리노린재 성충의 경우에는 약제처리 72시간이 경과한 후에 유기인계 살충제인 펜티온이 100%의 살충율을 나타내었고, 페니트로티온과 펜토에이트는 95% 이상의 살충률을 나타내었다. 3령 약충의 경우에는 펜티온과 페니트로티온, 펜토에이트가 72시간이 경과한 후에 100%의 살충력을 나타내었다. 반면에 친환경유기농자재의 경우에는 고삼추출물이 80% 함유된 약제를 처리한 결과 성충이 약제처리 72시간 후 53.3%의 살충력을 나타내었을 뿐 다른 약제들은 대부분 살충력이 없거나 저조하였다. The winter cherry bug (Acanthocoris sordidus Thunberg, Coreidae, Hemiptera) is a insect pest that have a piercing sucking type mouthpart, and it is injured to solanaceous plants including pepper plant. For the control of the winter cherry bug, 20 organic synthetic insecticides and 7 environmental friendly agricultural materials (EFAMs) were selected with single formulation. Fenitrothion, fenthion and phenthoate were significantly higher mortality to adults and 3rd instar nymphs of winter cherry bug as over 95 and 100 % after 72 hours with treatment. Otherwise, in case of EFAMs, there is no significantly higher effective materials to adults and 3rd instar nymphs of winter cherry bug. Eighty percentage of Sophora flavescens was showed only around 50% mortality with the high variation after 72 hours with treatment against adult of the winter cherry bug.

Pengujian kekhususan inang parasitoid Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae) pada empat spesies kutu putih yang berasosiasi dengan tanaman singkong

A parasitoid, Anagyrus lopezi (De Santis) (Hymenoptera: Encyrtidae) was introduced from Thailand into Indonesia in early 2014 to control the cassava mealybug Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae). To determine its potential uses and effect on non-target species, behavioural observation of the parasitoids were made on four species of mealybugs, i.e. P. manihoti, Paracoccus marginatus Williams-Granara de Willink, Pseudococcus jackbeardsleyi Gimpel-Miller, and Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae). For that purposes, a set of tests were conducted which includes host susceptability, preference, and suitability. Tests were conducted by exposing a female parasitoid to 3rd instar nymphs of each mealybug species in a petri dish. For susceptability test, parasitoid A. lopezi encounterend P. manihoti more often (13.70 ± 7.18 visits per 30 minutes) as compared to P. marginatus (985 ± 10.24), P. jackbeardsleyi (6.60 ± 3.62), and F. virgata (5.75 ± 4.09). So did ovipositor probing occurred more on P. manihoti (8.20 ± 5.68 probes per 30 minutes) than on P. marginatus (0.70 ± 1.84), P. jackbeardsleyi (0.35 ± 0.68), and F. virgata (0.10 ± 0.45). For preference test, host encounter and ovipositor probing by the parasitoid were more common on P. manihoti as opposed to other mealybug species. Out of four mealybug species tested, P. manihoti was the only suitable host for parasitoid development, with the number of progenies emerged 7.40 ± 2.17 individuals per 3 female parasitoids exposed in 24 hour. Host specifity exhibited by parasitoid A. lopezi may prevent adverse effect to other mealybug species inhabiting cassava fields.

Suitability of two exotic mealybug species as prey to indigenous lacewing species

Mealybugs (Hemiptera: Pseudococcidae) have spread throughout subtropical and tropical regions, causing severe losses to crop production that have prompted much interest in discovering effective biological agents against these pests. The Brazilian indigenous lacewing (Neuroptera: Chrysopidae) species Chrysoperla externa (Hagen) and Ceraeochrysa everes (Banks) were studied against two exotic mealybug species, Ferrisia dasylirii (Cockerell) and Pseudococcus jackbeardsleyi Gimpel & Miller. To assess the relative potential of these lacewing species as control agents against these two pests, we confined 1st-, 2nd-, and 3rd-instar lacewing larvae with 2nd- and 3rd-instar nymphs and adult female mealybugs to evaluate development, survival, reproduction and predation rate. Lacewing larvae at 2nd- and 3rd-instar preyed successfully on mealybugs of all ages, and second instar mealybug nymphs supported successful development of lacewing larvae irrespective of the predators’ age. However, 1st-instar lacewing larvae either failed to complete development or showed lower performance when fed only 3rd-instar or adult female of mealybugs of either species. Comparing the lacewing species, Ce. everes tended to produce more eggs, but showed delayed development and lower egg viability as compared to Ch. externa. Furthermore, in every case in which a significant difference in predation rate was detected, it was always superior for Ch. externa. Further studies to assess the establishment of these species and other lacewing species associated with these introduced mealybugs are reasonable to provide sustainable biological control.

Effects of temperature and host stage on the parasitization rate and offspring sex ratio of Aenasius bambawalei Hayat in Phenacoccus solenopsis Tinsley.

Temperature and host stage are important factors that determine the successful development of parasitoids. Aenasius bambawalei Hayat (Hymenoptera: Encyrtidae) is a primary parasitoid of the newly invasive mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae). The effects of temperature on the parasitic characteristics of A. bambawalei have seldom been investigated. In the study, we explored the effects of temperature, exposure time, and host stage on the parasitization rate and offspring sex ratio (female to male) of A. bambawalei under laboratory conditions. The laboratory results showed that the successful parasitization rate of A. bambawalei increased with higher temperatures and older host stages. When the parasitoids were exposed to 36 °C for 24 h, the parasitization rate of female adults (52%) was nearly two times that of 3rd instar nymphs. Additionally, heat stress duration and host stage resulted in an increase in the offspring sex ratio of A. bambawalei. When A. bambawalei was exposed to 36 °C for 24 h, the offspring sex ratio increased dramatically to 81.78% compared with those exposed for 12 h, and it increased to 45.34% compared with those exposed for 16 h. The offspring sex ratio was clearly higher when the host stage was an adult female mealybug Our findings provide important guidance for the mass rearing and field releases of A. bambawalei for the management of P. solenopsis in the future.

Toxicity of an Acetogenin-Based Bioinsecticide AgainstDiaphorina citri(Hemiptera: Liviidae) and its ParasitoidTamarixia radiata(Hymenoptera: Eulophidae)

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is currently the most important insect pest affecting citrus worldwide due to its relation (as insect vector) with huanglongbing (greening) disease. To determine an alternative tool for D. citri control, this study evaluated the insecticidal activity of ethanolic extract from Annona mucosa Jacq. (Magnoliales: Annonaceae) seeds (ESAM), which has the acetogenin rolliniastatin-1 as its major compound, against D. citri. ESAM caused high mortality in both 3rd instar nymphs (LC50 = 429.43, 247.95, 148.16, 96.89, and 57.76 mg/L after 24, 48, 72, 96, and 120 h of exposure, respectively) and adults (LC 50 = 5,359.00, 2,464.00, 1,507.00, and 795.51 mg/L after 48, 72, 96, and 120 h of exposure, respectively), showing higher effectiveness than Azamax® 1.2 EC (azadirachtin + 3-tigloylazadirachtol, positive control) at the recommended concentration, which showed insecticidal effects only on nymphs. At a sublethal concentration (LC 25), ESAM caused significant reductions in feeding and oviposition of D. citri adults. However, the adult emergence of the ectoparasitoid Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) was reduced when exposed (by contact) to ESAM in its larval stage. In a greenhouse trial (seedlings cultivated in vases), the insecticidal activity of formulated ESAM was superior to that of Azamax® 1.2 EC, showing a residual effect of approximately 6 d (effectiveness > 80%). The effectiveness of ESAM (> 99%) for D. citri control also was confirmed in a commercial sweet orange farm (field trial). In light of these results, ESAM can constitute a useful component in the framework of D. citri integrated pest management, mainly in domestic orchards and organic systems.

Residual toxicity of bait formulations containing plant essential oils and commercial insecticides against the desert locust, Schestocerca gregaria (Forskäl)

Essential oils extracted from seven different plants belonging to five families, and four commercial insecticides representing different chemical classes were tested against the 3rd nymphal instars of the desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae) by bait application technique. The bait was prepared from wheat bran with molasses and fortified with different amounts of the studied toxicants, then introduced to the insect in cages. Methomyl, the most potent insecticide showed LC50 of 0.051μg/g. Fenvalerate, Fenitrothion, and Carbosulfan possessed potency accounted to 49.0%, 34.2%, and 9.0%, respectively, compared with Methomyl potency (100.0%). Cumin (Cuminum cyminum) oil was the highest toxic to the nymphs, while Parsley (Petroselinum sativum) was the lowest. Out of the eleven screened substances, 3 insecticides and 3 plant oils were subjected to detailed residual toxicity investigations at their corresponding LC90 values. The criteria of assessment included estimation of T50 and T20 values (time in days at which mortality declined to 50% and 20%, respectively), feeding activity, reproductive potential, and histopathological alterations in the rectal pads of the tested insect. For example, the T50 and T20 values for Methomyl equalled to 2.0 and 7.3 days, compared with 3.0 and 5.9 days, respectively, for Onion (Allium cepa) oil. Generally, Fenvalerate and Fenitrothion possessed T20 values higher than those obtained for Sweet Basil (Ocimum basilicum) and Cumin. Compared to control, Sweet Basil oil decreased severly consumption index (C.I.), efficiency of conversion of digested (E.C.D.) and ingested (E.C.I.) food. The growth rate was significanly declined by Fenitrothion, Fenvalerate, Sweet Basil, and Onion. Fenitrothion, Cumin, and Onion decreased approximate digestibility. The tested toxicants affected oviposition periods, number of egg pods and eggs laid per female and the total number of hatched eggs. The latter were found 305 eggs in control treatment, compared with 20, 74, 107, 120, 150, 117 eggs for Fenitrothion, Methomyl, Fenvalerate, Onion, Sweet Basil, and Cumin treatments, respectively. Except Cumin treatment, the other treatments caused anatomical alterations in the rectum of the adult S. gregaria represented by increasing length and width of rectal pads, as well as increase of epithelial cells. We may claim that the over all results of this study may be considered as novel findings in the course of searching for potent biopesticides against the locust, S. gregaria, and encourage further research under field conditions.

Over-expression of CYP6A2 is associated with spirotetramat resistance and cross-resistance in the resistant strain of Aphis gossypii Glover

A laboratory-selected spirotetramat-resistant strain (SR) of cotton aphid developed 579-fold and 15-fold resistance to spirotetramat in adult aphids and 3rd instar nymphs, respectively, compared with a susceptible strain (SS) [26]. The SR strain developed high-level cross-resistance to alpha-cypermethrin and bifenthrin and very low or no cross-resistance to the other tested insecticides. Synergist piperonyl butoxide (PBO) dramatically increased the toxicity of spirotetramat and alpha-cypermethrin in the resistant strain. RT-qPCR results demonstrated that the transcriptional levels of CYP6A2 increased significantly in the SR strain compared with the SS strain, which was consistent with the transcriptome results [30]. The depletion of CYP6A2 transcripts by RNAi also significantly increased the sensitivity of the resistant aphid to spirotetramat and alpha-cypermethrin. These results indicate the possible involvement of CYP6A2 in spirotetramat resistance and alpha-cypermethrin cross-resistance in the cotton aphid. These together with other cross-resistance results have implications for the successful implementation of resistance management strategies for Aphis gossypii.

Biology, morphology and DNA barcodes of Tessaratoma javanica (Thunberg) (Hemiptera: Tessaratomidae)

Tessaratoma javanica (Thunberg) (Hemiptera: Tessaratomidae) an important sucking pest of litchi is studied for supplementing information on its biology, morphometrics of life stages and mtCOI (DNA barcodes). More details generated on the study add to the description of stages namely egg, 1st to 5th nymphal instars and adults. The evaluation of morphometrics of the life stages reveal that the progression of growth is more during 2nd to 3rd nymphal stages, and these are critical as far as the growth and development is concerned. The life cycle takes about 141.7±4.25 days; eggs last for 12.81±1.4 days with 97.14±2.86% hatchability; and duration of 1st , 2nd, 3rd, 4th and 5th nymphal instars were 11.69±0.58, 7.23±0.2, 8.63±0.55, 13.04±0.55 and 26.31±0.97 days, respectively. In addition mtCOI analyses have been done employing standard 658 bp barcode fragments facilitating molecular diagnostics of the adults and other life stages and the phylogenetic tree with available sequence in the GenBank.

Stylet penetration activities of Diaphorina citri associated with transmission of Candidatus Liberibacter asiaticus

Author(s): Ferreira, C.; Okuma, D. M.; Lopes, J. R.S. | Abstract: The electrical penetration graph (EPG) technique was used to determine Diaphorina citri stylet penetration activities associated with Candidatus Liberibacter asiaticus (Las) acquisition and inoculation in citrus. In a first experiment, healthy D. citri adults were connected to the EPG system and placed on Las-infected plants. Probes were artificially terminated after the following stylet penetration periods and waveforms: I) 20 min in waveform C (pathway phase through epidermis and parenchyma); II) C + 30 s in D (first contact with phloem tissue); III) C+D + 70 s in E1 (penetration and possibly salivation/ingestion in the phloem sieve elements); and IV) C+D+E1+ 1 h in E2 (phloem sap ingestion). The insects were tested for Las infectivity by real-time PCR 3 wks later. In a second experiment, 3rd-instar nymphs were first submitted to an acquisition access period of 2 wks on Las-infected plants and then connected to the EPG system on healthy citrus seedlings during the same stylet penetration periods of the first experiment. D. citri acquired the pathogen only after penetration in the phloem sieve elements and mostly during waveform E2 (27 infective insects of 54 tested). Only 2 of 52 insects exposed to infected plants until waveform E1 (treatment III) were positive. In the second experiment, transmission (by 9 of 50 insects tested) was observed only by psyllids allowed to perform E2 on healthy seedlings. Overall, the data show that both acquisition and inoculation occur during the phloem phase, primarily during sustained sap ingestion (E2). This information is important for designing efficient control tactics aimed at preventing Las transmission by D. citri. Financial support: Citrus Research and Development Foundation, CNPq and Fundecitrus

Toxicity of essential plant oils, in comparison with conventional insecticides, against the desert locust, Schistocerca gregaria (Forskål)

Essential oils extracted from ten different plants belonging to five families were tested against the 3rd nymphal instars of the desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae) by topical application technique. Also, the toxicity of four chemical insecticides, as well as the joint action resulted from mixing botanicals and insecticides were evaluated. Either at LD50 or LD90 values, the Allium cepa-oil proved to be the most toxic where the above mentioned values equaled to 1.11 and 1.42ppm, respectively followed by the Petroselinum sativum (1.34 and 1.61ppm, respectively). The LD50 and LD90 values for the oils of Pelargonium radula, Cuminum cyminum, Ocimum basilicum, Origanum vulgare and Matricaria chamomilla ranged between 1.54–1.59ppm and between 1.84–1.91ppm, respectively. GC/MS analyses revealed the presence of known biologically active compounds such as p-Cymene, Linalool, Thymol, Caryophyllene and Carvacrol in some of the analyzed oils. Fenitrothion was the most toxic (LD50=0.33ppm), while fenvalerate was the least (LD50=1.48ppm). The other 2 insecticides possessed intermediate and nearly equitoxic values (LD50=1.2ppm). Surprisingly, the A. cepa oil was more toxic than methomyl, and the other plant oils possessed toxicity accounted to 74–80% and 83–98% of methomyl toxicity when comparisons were made at the LD50 and LD90 levels, respectively. Combining plant oils with insecticides resulted in different types of interaction (e.g., synergism, additive and antagonism). Such results may be considered as novel findings in the course of searching for potent botanical insecticides against the locust, S. gregaria, and magnify the industrial value of such plant oils in the era of biopesticides.

Diapause induction and termination in the small brown planthopper, Laodelphax striatellus (Hemiptera: Delphacidae).

The small brown planthopper, Laodelphax striatellus (Fallén) enters the photoperiodic induction of diapause as 3rd or 4th instar nymphs. The photoperiodic response curves in this planthopper showed a typical long-day response type with a critical daylength of approximately 11 h at 25°C, 12 h at 22 and 20°C and 12.5 h at 18°C, and diapause induction was almost abrogated at 28°C. The third stage was the most sensitive stage to photoperiod. The photoperiodic response curve at 20°C showed a gradual decline in diapause incidence in ultra-long nights, and continuous darkness resulted in 100% development. The required number of days for a 50% response was distinctly different between the short- and long-night cycles, showing that the effect of one short night was equivalent to the effect of three long nights at 18°C. The rearing day length of 12 h evoked a weaker intensity of diapause than did 10 and 11 h. The duration of diapause was significantly longer under the short daylength of 11 h than it was under the long daylength of 15 h. The optimal temperature for diapause termination was 26 and 28°C. Chilling at 5°C for different times did not shorten the duration of diapause but significantly lengthened it when chilling period was included. In autumn, 50% of the nymphs that hatched from late September to mid-October entered diapause in response to temperatures below 20°C. The critical daylength in the field was between 12 h 10 min and 12 h 32 min (including twilight), which was nearly identical to the critical daylength of 12.5 h at 18°C. In spring, overwintering nymphs began to emerge in early March-late March when the mean daily temperature rose to 10°C or higher.

Pathogenicity of three entomopathogenic fungi to Matsucoccus matsumurae.

Matsucoccus matsumurae (Kuwana) (Hemiptera: Coccoidea: Matsucoccidae) is an invasive alien species and a destructive pest of two native Chinese pines, Pinus tabulaeformis Carr. and P. massoniana Lamb., throughout the eastern regions of China. The pathogenicity of three entomopathogenic fungi, Lecanicillium lecanii strain V3.4504 and V3.4505, Fusarium incarnatum-equiseti strain HEB01 and Lecanicillium fungicola strain HEB02, against M. matsumurae was tested in four instars, to evaluate their potential as a biological control agent. The results showed that the four strains caused disease and death of the scale insect, among which the L. lecanii strains V3.4504 and V3.4505 displayed stronger virulence than the F. incarnatum-equiseti strains HEB01 and L. fungicola strain HEB02 to M. matsumurae in the 2nd-instar nymphs and the adult females. Furthermore, L. lecanii V3.4505 was most virulent to M. matsumurae. The adult females and the male 3rd-instar nymphs of M. matsumurae were susceptible to L. lecanii V3.4505; the adult females were more susceptible at LT50 = 1.96 than the 3rd-instar nymphs at LT50 = 5.67. The body surface structure, cuticle thickness and wax secretions of M. matsumurae impacted the fungal infection. L. lecanii is a promising biocontrol agent, and newly emerged male 3rd-instar nymphs and adult females are a crucial period of the insect’s life cycle for M. matsumurae biocontrol.

Dispersal Capacity and Behavior of Nymphal Stages of Halyomorpha halys (Hemiptera: Pentatomidae) Evaluated Under Laboratory and Field Conditions

The invasive brown marmorated stink bug, Halyomorpha halys (Stal) (Hemiptera: Pentatomidae), is a highly polyphagous and mobile pest causing crop damage aggregated at the perimeters of crop fields. Understanding the dispersal biology of H. halys is critical for the development of reliable monitoring and management strategies. In this study, dispersal ecology of H. halys nymphs was studied under laboratory and field conditions. In the laboratory, horizontal and vertical walking capacity was quantified for mobile nymphal stages (i.e., 2nd through 5th instars) and compared with adults. There was a significant difference in the horizontal distance moved by H. halys among the life stages tested. Third instars exhibited significantly greater walking distances compared with adults; horizontal walking distances by other nymphal stages were not significantly different from adults. A similar pattern was observed from vertical climbing tests of H. halys. Third and 4th instars climbed significantly greater distances compared with 2nd instars and adults, while distances climbed by 5th instars were intermediate. In the field, the walking distance of 3rd and 5th instar nymphs on mowed grass was quantified based on direct observation of individuals for 30 min. Under these conditions, 5th instars moved nearly two-fold greater distances compared with 3rd instars, but surface temperature affected both nymphal stages similarly. Shorter bouts of movement were common at surface temperatures below 25 °C, whereas individuals showed longer walking distances above 25 °C. In mark-release-recapture studies, 4th and 5th instars were released and recaptured in traps baited with attractive pheromonal-based stimuli to estimate dispersal rates under field conditions. When insects were released 5 m from traps, both instars were first recaptured within 2 h after release, with the recapture rates of 54 and 69 % for 4th and 5th instars over 24 h, respectively. When insects were released 20 m from traps, 4th and 5th instars were first recaptured in less than 5 h, with the recapture rates of 27 and 51 %, respectively. The results of this study indicate that H. halys nymphs have strong dispersal capacity with which populations can easily move among host plants and other attractive stimuli at farmscape levels.