Dominica Larvae Research Articles

Insecticidal activity of essential oils derived from lavender, laurel and peppermint against lesser grain borer, Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae)

Fumigant effects of the essential oils from Laurus nobilis L., 1753 (Laurales: Lauraceae), Mentha piperita L., 1753 and Lavandula x intermedia Emeric ex Loisel, 1828 (Lamiales: Lamiaceae) were determined using the lesser grain borer [Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrychidae)], an important pest species of stored grains. The experiments were conducted in the 2021 in the Department of Crop Protection, Faculty of Agriculture, Malatya Turgut Özal University. The experiments were conducted in a controlled-climate chamber at 27 ± 1°C, 50 ± 10% RH and in the dark. The fumigant effects of essential oils were determined at five concentrations (1, 5, 20, 50 and 200 μl/L air) with larva, pupa and adult stages of R. dominica. The highest fumigant effect was with R. dominica larvae was complete mortality with 200 μl/L L. nobilis essential oil and for the adults, 200μl/L of either L. nobilis and M. piperita essential oil also caused complete mortality. However, the complete mortality of pupal stage was not obtained and the highest mortality was 49% with L. nobilis. As a result, it is considered that both L. nobilis and M. piperita essential oils have the potential to be used as effective biofumigants for stored product pests.

Effectiveness of the parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae) in the control of Sitophilus zeamais and Rhyzopertha dominica in paddy rice

Rice is an important cereal crop in Spain that is frequently attacked by pests that cause significant quantitative and qualitative losses. Among them, the maize weevil, Sitophilus zeamais, is the key pest, and the lesser grain borer, Rhyzopertha dominica, is a serious pest found later in the season. The cosmopolitan ectoparasitoid, Anisopteromalus calandrae, which attacks late-instar larvae of coleopterans that develop inside grain kernels, has been reported as an efficient natural enemy. In this study, we evaluated whether the control efficacy of this parasitoid on S. zeamais was affected by the presence of the alternative host, R. dominica. Our laboratory experiment demonstrated the parasitoid preference for S. zeamais larvae when mixed with R. dominica larvae at different proportions. This preference for the maize weevil larvae allowed us to maintain a similar control efficacy of S. zeamais when it was offered alone than when it was offered together with R. dominica larvae. In our second experiment, done in 500 kg bags of paddy rice, similar results were obtained, since the presence of R. dominica larvae did not alter the control efficacy of A. calandrae on S. zeamais larvae. Therefore, our results confirmed a good perspective for implementing the use of this natural enemy as a control tool in big bags of paddy rice.

Volatile Infochemicals from Rhyzopertha dominica Larvae and Larval Feces Involved in Theocolax elegans Host Habitat Location.

Simple SummaryFood protection is a key issue to guarantee food security. One of the major criticisms is related to insect pests, which can severely damage stored products. Control of stored product pests widely relies on synthetic pesticides, which are potentially harmful to human health and the environment. In this context, the application of chemicals during post-harvest should be limited, and natural enemies, like parasitoid wasps, might be useful for biologically based pest management programs. The effectiveness of this approach under field conditions is still uncertain, and more information about parasitoid biology and behavior can be valuable to improve mass rearing and control strategies. This study investigates the host habitat location behavior of Theocolax elegans, a generalist parasitoid attacking several stored product pests, including Rhyzopertha dominica, a key pest species of stored grains. Bioassays demonstrated that the parasitoid females were not attracted by intact kernels; indeed, the parasitoid females were strongly attracted by infested wheat and by the host feces, locating the suitable hosts through the characteristic volatile infochemicals emitted by these substrates. Results from the present research are encouraging and suggest that biological control agents might be used to reduce the amount of synthetic insecticides.The development of biologically based approaches for stored product pest control is needed to reduce chemical inputs. Bioassays were performed to investigate host habitat location in the trophic interaction durum wheat/Rhyzopertha dominica/Theocolax elegans. GC-MS analyses were carried out to identify some chemical compounds produced by the host-related substrates. Choice and no-choice experiments demonstrated that female parasitoids were poorly attracted to intact kernels with respect to the infested substrates. Furthermore, T. elegans females performed longer residence time on infested wheat, and they generally displayed a short-term like fidelity for this cue, remaining on it during the whole observation. Infested wheat emitted one chemical (fenchone), which is possibly linked to host larvae presence, while the feces produced by host larvae emitted some other characteristic compounds. Results demonstrated that the presence of host larvae is a key factor for T. elegans host habitat location, considering that the attractiveness of the undamaged wheat is irrelevant. Furthermore, parasitoid females tended to stay on attractive cues, limiting the risk of contamination of other commodities. Biological control tools may be useful to improve the efficiency of pest management programs, but their application should be carefully evaluated.

Effects of abamectin on lesser grain borer, Rhyzopertha dominica F. (Coleoptera: Bostrichidae), infestation on some stored grains

BackgroundModern methods of stored wheat grain protection from insect pests strive towards optimizing the use of different techniques and methods within integrated pest management (IPM) programs. One of the methods of integral grain protection is the application of natural originating insecticides.Main bodyThe potential of the natural origin synthetic insecticide abamectin (a product of soil bacteria, Streptomyces avermitilis fermentation) on the grain borer, Rhyzopertha dominica F. (Coleoptera: Bostrichidae), in stored wheat, barley, ray, oats, and triticale was evaluated. The evaluation was conducted in 3 rates. The effects of its application on the infestation of R. dominica on certain physical and chemical traits of cereal grains were examined. The efficacy of abamectin after 7 days of exposure, in all applied dosages, was low (< 56.5% in wheat and < 30.5% in other grains). Abamectin efficacy was significantly increased after 14 days of exposure. R. dominica mortality was 99.0 and 100% after 21-day exposure at the abamectin rates of 0.5 and 1.0 mg kg−1, respectively. Ten weeks after grain treatment, the 3 examined rates prevented the emergence of progeny. The amount of the damaged grains and dockage, as a nus-product of feeding of R. dominica larvae and imago, compared to the untreated, infested sample was significantly smaller, which represents a positive aspect of abamectin application. The application did not change significantly the moisture, protein, and ash contents, in comparison to the control.ConclusionPositive aspects of the abamectin application on different grain species (wheat, barley, rye, oats, and triticale) caused the highest rates of R. dominica mortality after 21 days of exposure where a total prevention of progeny emergence and absence of changes on technological grain properties occurred.

Susceptibility of wheat, Triticum vulgare (Linn.) genotypes to the lesser grain bore, Rhizopertha dominica Fabricius (Coleoptera, Bostrichidae) larvae

The lesser grain borer, Rhyzopertha dominica Fabricius (Coleoptera: Bostrichidae) is a primary pest of stored wheat. Many authors studied its development on this cereal like (e.g. wheat, rice, sorghum, oats, pearl, millet, malt, barley chickpeas, peanuts and beans etc. The aim of performed laboratory experiments was to assess the feeding preferences for the different varieties of wheat viz; HI 7747, HD 1982, K 65, Kalyan Sona, TL 174 and UPT 72294 and to evaluate their susceptibility/resistance to progeny production of R. dominica particularly larvae. The experiments were conducted at 28°C and 60 ± 5% of relative humidity. The mean survival rate of R. dominica larval and dockage in various wheat were determined. The influence of the wheat genotypes on the larval development of R. dominica was significant.The highest number of Rhizopertha dominica larvae 23.00 were present in UPT 72294 which is observed the most preferred variety. This variety differs significantly from the others. The next variety in order to preference for food is TL 174 having 10 larvae followed by H.D. 1982 having 5.66 larvae, which do not differ significantly to each other but differ significantly from the rest of the varieties. The least preferred varieties are HI 7747 and K65 having only 1.33 larvae and these do not differ from Kalyan Sona and HD 1982.

Host acceptance and oviposition behaviour of solitary wasp, Anisopteromalus calandrae (Howard) (Hymenoptera : Pteromalidae), A parasitoid of stored grain pests

The host acceptance and oviposition behaviour of the ectoparasitoid, Anisopteromalus calandrae (Howard) (Hymenoptera : Pteromalidae) was observed on unexposed (hidden) and exposed host of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.) under laboratory conditions. The egg-laying behaviour was accomplished in eight phases in hidden hosts of S. oryzae i.e., inside wheat kernels but it was much shorter having five steps in those of exposed hosts. Average total time taken by a mated A. calandrae in unexposed host (inside wheat kernels) during different oviposition sequences was 55 minutes. On the other hand, average total time taken by a mated A. calandrae in exposed host of S. oryzae during oviposition sequences was 91.1 minutes. A. calandrae preferred fully developed S.oryzae grubs rather than half- grown pre-pupae and early pupae in exposed condition. Generally, eggs were laid on or near S. oryzae host larvae or pupae inside wheat kernel because of ectoparasitic nature of A. calandrae. More eggs are deposited in case of S. oryzae hosts at the abdominal region dorsally, sometimes eggs were laid on the meta-thoracic segment dorsally but rarely eggs were laid on late S. oryzae pupae prior to adult transformation. Oviposition by a mated A. calandrae female parasitoid was influenced by the host’s size and shape on exposed as well as unexposed (within seed kernel) conditions. Generally, the 3rd and the 4th instar larvae and pre-pupae of S. oryzae were preferred for egglaying in exposed condition. The parasite did not lay eggs on naked R. dominica larvae or pupae.&#x0D; Bangladesh J. Zool. 46(2): 205-216, 2018

Host-age preference of Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae), a larval parasitoid of the lesser grain borer, Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) and the cowpea weevil, Callosobruchus maculatus

The pteromalids (Hymenoptera: Pteromalidae) Anisopteromalus calandrae (Howard), Dinarmus basalis (Rondani), Lariophagus distinguendus (Forster), Pteromalus cerealellae (Ashmead) and Theocolax elegans (Westwood) are solitary larval ectoparasitoids used to suppress several species of stored-product insects that infest storage grains. We investigated host-age preference of T. elegans using no-choice laboratory experiments. Lesser grain borer, Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) larvae (9, 11, 13, 15, 17, 19, 21 and 23 days-old) in wheat grain kernel and cowpea weevil, Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae) larvae (5–19 days-old) in cowpea beans were exposed to neonate T. elegans mated females to lay their eggs for two days. Our results showed that the highest number of parasitoids emerged from 23 days-old R. dominica larvae. The numbers of parasitoids emerged from 19, 21 and 23 days-old R. dominica larvae were statistically significantly different in experiments (F-test, 0.05). Progeny of T. elegans reared from R. dominica and C. maculatus larvae were either fully-winged (macropterous), short-winged (brachypterous) or wingless (apterous). Female T. elegans were rarely host-feeding on C. maculatus larvae. Theocolax elegans progeny were emerging from 14 days-old C. maculatus larvae only. We discussed insectary mass production of T. elegans for biological control.

Improved high-throughput bioassay for Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

As we gain more information through functional genomic studies of Rhyzopertha dominica (F.), we need a high-throughput bioassay system to screen potential biopesticides. Rhyzopertha dominica is an internal feeder during immature stages and presents unique challenges with traditional bioassay methods. Our primary goal was to develop a fast method to evaluate larval development on small amounts of material incorporated homogenously in an artificial diet. Herein we describe a new method that incorporates an artificial diet composed of egg yolk, brewer's yeast, and amylopectin for evaluating the effect of potential biopesticides on the development of R. dominica larvae. Evaluation is accomplished through visual inspection of digital X-ray images, or weighing containers of infested larvae on diet treatments. We demonstrate the method with aprotinin and Bacillus thuringiensis Cry3Aa protoxin, test materials that retard the development of R. dominica larvae. Different bioassay containers were evaluated, including a single larva assay with pipette tips or 8-strip tubes, or a group bioassay in black 16-well trays. In addition to improvements in time and manual manipulations, larvae can now be obtained for biochemical studies by gently washing away the diet. Discrimination of the effect of test materials by weighing the infested containers at specific timepoints was the most simplified approach to rapidly screen test compounds.

Detection of Rhyzopertha dominica larvae in stored wheat using ELISA: The impact of myosin degradation following fumigation

Hard red winter wheat kernels were infested with eggs of Rhyzopertha dominica. After 20 d, when the larvae reached the fourth instar, they were killed by exposing the infested kernels to phosphine gas for 24 h. The infested kernels were then divided into four portions and treated as follows: one portion was immediately frozen at −80 °C to avoid myosin degradation; the other three portions were kept at 32 °C and 65% relative humidity, and then frozen at −80 °C after 14, 28, and 56 d post-fumigation, respectively. Each treatment was replicated five times. Myosin was measured using a commercial enzyme linked immunosorbent assay (ELISA) method that specifically detects this protein (Biotect ®, Austin, TX). Myosin degradation was most rapid in the first 2 weeks after the larvae were killed, decreasing from 1.672 to 0.695 ng/well during this period (a 58.4% reduction). There were no significant differences in myosin degradation between samples that were 14, 28, and 56 d post-fumigation. Grain is often fumigated to control insects. Frequently, this occurs many weeks before the grain is milled and may be repeated during the storage period. Therefore, estimates using the ELISA test may underestimate internal insect infestation because of myosin degradation. Insect fragment estimates for previously fumigated grain could be underestimated by as much as 58%.

Effect of Anisopteromalus calandrae (Hymenoptera: Pteromalidae) in controlling residual populations of Rhyzopertha dominica (Coleoptera: Bostrichidae) in wheat stores

The parasitic wasp Anisopteromalus calandrae (Howard) was released at six (5, 10, 20, 30, 40 and 50 pairs) densities to evaluate the effects of different introduction rates in controlling residual populations of the lesser grain borer Rhyzopertha dominica (Fabricius) in wheat grain stored in bulk in 46m2 rooms. At the 50-pair density, the parasitoid suppressed 83% of R. dominica in June–July and 74% in August–September. At the 5-pair density, the numbers of F1 progeny per female were 44 and 51, during the first and second period, respectively while at the 50-pair release rate, only 6 and 7 individuals were recorded, respectively. In a second test, the effects of different materials used for storing were evaluated on both insects. Five hundred (500) grain-residing 20–22-day-old R. dominica larvae were mixed with 250 g fresh wheat stored separately in each of five types of bags, i.e. jute, calico (Americana cloth), polypropylene, polythene, nylon, then exposed to 50 pairs of A. calandrae. The parasitoid suppressed host populations in all types of bags, except in those made of polythene. The highest percentage (69 and 81%) suppression occurred in calico bags during the June–July and August–September periods, respectively. The lowest suppression of 51 and 57% was observed for polypropylene bags during the respective periods. The parasitoid-induced mortality was positively correlated with the parasitoid density.

Detection of internal wheat seed infestation by Rhyzopertha dominica using X-ray imaging

Standardization for grain grades has been established in most countries to maintain the quality of a crop until it reaches consumers. Different methods have been investigated for their potential to detect insect infestations in grain destined for domestic and export markets. The potential of detecting infestations caused by Rhyzopertha dominica in wheat kernels using a real-time soft X-ray method was determined in this study. Artificially infested wheat kernels were incubated at 30°C and 70% relative humidity and X-rayed sequentially for larval, pupal, and adult stages of R. dominica. Algorithms were used to extract histogram features, textural features, and histogram and shape moments from the X-ray images of wheat kernels. A backpropagation neural network (BPNN) and statistical classifiers were used to identify uninfested and infested kernels using the 57 extracted features. The BPNN correctly identified all uninfested and infested kernels and more than 99% of kernels infested by R. dominica larvae. The classification accuracies determined by the BPNN were higher using all 57 features than when using the histogram and textural features separately. The BPNN performed better than the parametric and non-parametric classifiers in the identification of uninfested and infested kernels by different stages of R. dominica.

X‐ray Image Analysis to Detect Infestations Caused by Insects in Grain

ABSTRACTInsect infestations in stored wheat affect the chemical characteristics and baking qualities of wheat flour, and insect‐infested flours are unacceptable in the baking industry. The efficiency of the soft X‐ray method to detect infestations caused by Cryptolestes ferrugineus (Stephens), Tribolium castaneum (Herbst), Plodia interpunctella (Hübner), Sitophilus oryzae (L.), and Rhyzopertha dominica (F.) in wheat kernels was determined in this study. Wheat kernels infested by different insects were prepared by artificial implantation of insect eggs or by introducing adult insects in wheat samples. Kernels infested by different stages of the insects were X‐rayed until the adults emerged from the kernels. A total of 57 features using histogram groups, histogram and shape moments, and textural features were extracted from the X‐ray images and a linear‐function parametric classifier was used to identify the insect‐infested kernels. The parametric classifier identified more than 84% of infestations due to C. ferrugineus and T. castaneum larvae. The infestations by C. ferrugineus pupae‐adults and P. interpunctella larvae were identified with &gt;96% accuracy. Kernels infested by different stages of S. oryzae and R. dominica larvae were identified with &gt;98% accuracy. Using the Berlese funnel method, 67, 51, and 81% of first, second, and third instars of C. ferrugineus, respectively, were extracted in 6 hr. The same infested kernels were all categorized as infested by the parametric classifier. When kernels infested by different insects were pooled together, the parametric classifier correctly identified 74% of uninfested and 94% of infested kernels by the internal and external grain feeders. The 26% false positives identified from the independent test was caused by one sample infested by T. castaneum. When that sample was removed from the training set, the false positives were reduced to 16%, and 92.7% of infested kernels by different insects were correctly identified.

Susceptibility of the gelatinized wheat product bulgur to Sitophilus zeamais Motsch. and Rhyzopertha dominica (F.)

The development of Sitophilus zeamais and Rhyzopertha dominica was studied at relative humidities of 71, 58 and 43% in bulgur and wheat. Male and female adult weevils, introduced into 6 bulgur and 6 wheat media of different particle sizes, were allowed to oviposit for 7 days. Thirty R. dominica eggs were placed in each replicate of a similar set of bulgur and wheat media. S. zeamais produced more adult progeny in whole kernels of bulgur and of wheat and in the larger-sized particles, and a high percentage of R. dominica larvae developed into adults in these media. S. zeamais progeny produced and R. dominica larvae surviving were fewer, and developmental periods for both species longer, the smaller the particles and the lower the relative humidity. Males and females collected from bulgur and wheat media of the same particle size tended to weigh the same; but the smaller the particle size, the less the weights.

The Toxicity and Residual Effectiveness of Malathion and Diazinon Used for Protection of Stored Wheat1

The relative susceptibilities of 17 species of stored-product insects to malathion and diazinon deposits (ppm) on wheat sprayed with acetone solutions of each insecticide were determined from LC values obtained in a series of toxicity tests. Mature larvae of 4 species of Trogodema were used; all other test insects were adults. Diazinon was more effective than malathion against Cryptolestes pusillus (Schonherr), flat grain beetle; Latheticus oryzae Water-house; Rhyzopertha dominica (F.), lesser grain borer; Sitophilus oryzae (L.), rice weevil; S. zeamais Motschulsky; Sitotroga cerealella (Olivier), Angoumois grain moth; Tribolium brevicornis (LeConte); T. castaneum (Herbst), red flour beetle; T. confusum Jacquelin duVal, confused flour beetle; Trogoderma inclusum LeConte; T. parabile Beal, and T. simplex Jayne. Diazinon was less effective against Doliema plana (F.); Oryzaephilus menator (Fauvel), merchant grain beetle; O. surinamensis (L.), saw-toothed grain beetle; and Sitophilus granarius (L.), granary weevil. At the LC50, T. glabrum (Herbst) was more susceptible to diazinon than malathion, but not at the LC95. Results from residual protect ant tests designed to evaluate the relative effectiveness of various concentrations of insecticide residues (ppm) on wheat in preventing infestations of 6 species of stored-product insects showed diazinon to be slightly more effective than malathion when considering counts of all insects, but the most important differences observed were in the response of species to the treatments involved. Tolerance of “bran beetles” to malathion was in the order of Tribolium castaneum > C. pusillus > O. surinamensis , and tolerance to diazinon was ill the order of O. surinamensis > T. castaneum > C. pusillus . Good protection against R. dominica demonstrated by malathion treatments, as compared with S. oryzae , suggested that susceptibility of R. dominica larvae may be an important factor in the use of grain protect ants for prevention of infestations of this species. Infestations of S. oryzae were greater in malathion-than in diazinon-treated samples of wheat. One species, S. granarius , failed to compete favorably in the test complex.