Second-instar Caterpillars Research Articles

D-limonene-based formulations for the management of Diaphania hyalinata, Plutella xylostella and Spodoptera eridania in a greenhouse

Diaphania hyalinata, Plutella xylostella and Spodoptera eridania are considered important pests in vegetable crops, causing significant production losses. The most common method for managing these pests is the use of synthetic insecticides that cause chain damage, from human health to the environment. A less aggressive alternative is the use of botanical insecticides, such as essential oils, which present themselves as potential for the composition of bioinsecticides. In the present study, the efficiency of formulations based on d-limonene (major compound of the orange peel oil - Citrus sinensis) on the mortality of D. hyalinata, P. xylostella and S. eridania was evaluated. For this purpose, formulations containing d-limonene (2.0%), Tween 80 (0.05%) and water were prepared, combined with different encapsulating agents (xanthan gum, guar gum and maltodextrin) diluted to 2% (v /v). The formulations were sprayed on plants using a sprayer and five second-instar caterpillars were distributed on each plant. The mortality of caterpillars was evaluated 72 h after the application of the formulas. Formulation based on the compound d-limonene with the encapsulating agent guar gum had an effect on the mortality of P. xylostella and S. eridania and formulation with the encapsulating agent maltodextrin had an effect on the mortality of S. eridania.

Inhibitory effects of Serjania erecta on the development of Chrysodeixis includens

The soybean looper, Chrysodeixis includens, is a primary soybean pest that reduces crop productivity. This work examined control of C. includens populations with methanolic extract of Serjania erecta, a native Cerrado plant, while minimizing risks to pollinators, natural enemies and the environment. Serjania erecta specimens were collected, identified, and subjected to methanol extraction. Bioassays were performed using newly hatched and second-instar caterpillars and different extract concentrations on the diet surface to obtain IC50 values. Two replicates, containing 10 caterpillars, were established in triplicate. The IC50 values were 4.15 and 6.24 mg of extract mL−1 for first-instar and second-instar caterpillars, respectively. These growth inhibition results informed the extract concentrations assessed in subsequent development inhibition assays, in which the pupal weight was higher under the control than under the treatments. Extract treatments increased the duration of the larval, pupal and total development. The potential of different concentrations of S. erecta extract to inhibit the enzymes carboxylesterases was also evaluated. Carboxylesterases activity decreased by 41.96 and 43.43% at 7.8 and 15.6 μg mL−1 extract, respectively. At 31.3 μg mL−1 extract, enzymatic activity was not detected. Overall, S. erecta leaf methanolic extract showed inhibitory potential against carboxylesterases.

Secondary Metabolites of Asclepias curassavica (Apocynaceae) and its Effects on Food Preference and Mortality of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Asclepias curassavica L. plant is toxic for vertebrates, and little is known about its effects on invertebrates, as well as whether its secondary metabolites have an influence on food preference and survival of insects. Thus, a study was conducted to verify the action of A. curassavica on Spodoptera frugiperda J.E.Smith. The plants were collected, dried and ground to compose a crude ethanolic extract. Food tests were carried out with and without opportunity of choice, using corn leaf discs immersed in the extract at concentrations of 1%, 2% and 4%, for assessment of food consumption (g) and preference index. Later, the extract was topically applied on second- and fifth-instar caterpillars, at concentrations of 1%, 2%, 4% and 6%, in order to observe its effect on survival. In parallel, analysis was conducted to verify the presence and measure the amount of total polyphenols and flavonoids in the extract. There was contact action between the extract and second-instar caterpillars at all concentrations, with treatment 6% causing 100% of mortality 72 hours after application. None of the treatments promoted contact action on fifth-instar caterpillars. In food tests with and without opportunity of choice, all treatments caused reductions in consumption, which classified all as phagodeterrent, with treatment 4% standing out as the least favorite. The presence of total polyphenols and flavonoids was found in the extract, presenting 58.75 ug/mL and 150.1 ug/mL, respectively. The A. curassavica extract proved promising in S. frugiperda control.

Insecticidal activity of essential oils in controlling fall armyworm, Spodoptera frugiperda

ABSTRACT: Fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) is one of the main pests in maize crop with developing resistance to chemical products and Bt technology. Therefore, alternative control methods such as essential oils are important steps in the implementation management strategies for this pest. This study aimed to evaluate the efficiency of essential oils (EOs) of Corymbia citriodora, Myrciaria dubia (Myrtaceae), Lippia microphylla (Verbenaceae) and Piper umbelattum (Piperaceae) in controlling S. frugiperda. The OEs were extracted and mortality tests were conducted with topic and volatile applications, in 30 second-instar caterpillars originated from insect rearing and artificial diet. As a control, we conducted tests with distilled water and acetone. EOs that provided mortality rates above 80% were submitted to chemical analysis for constituent identification. The efficient EOs were only those of C. citriodora and L. microphylla. For EO of C. citriodora, the LD80 was 7.06 ± 0.73 mg.g-1 in topical application and 5.85 ± 0.75 µL via volatile application. On the other hand, for EO of L. microphylla, DL80 was 9.95 ± 1.25 mg.g-1 in topical application and 18.56 ± 3.55 µL via volatile application. Chemical analysis showed that the main constituents were citronella for the EO of C. citriodora and (E)-caryophyllene and (E)-nerolidol to the EO of L. microphylla. EOs of C. citriodora and L. microphylla are promising for controlling S. frugiperda, with emphasis on the volatile effect of C. citriodora oil.

Leaf trichomes affect caterpillar feeding in an instar-specific manner

ABSTRACTLeaf trichomes play well-established roles in defense against insect herbivores, both as a physical barrier that impedes herbivore movement and by mediating chemical defenses. However, little work has examined how different trichome types influence herbivory by herbivores at different stages of development. We examined whether caterpillar instar and trichome type (glandular or non-glandular) affected the ability of the specialist herbivore caterpillar Manduca sexta to initiate feeding on 11 Solanaceous species exhibiting variation in the density and type of leaf trichomes. Our results suggest that non-glandular trichomes are far more effective than glandular trichomes in deterring the initiation of feeding by first- and second-instar caterpillars. Meanwhile, neither glandular nor non-glandular trichomes significantly affected the ability of third-instar caterpillars to commence feeding. These findings suggest that while non-glandular trichomes deter feeding initiation by early instar caterpillars, the contribution of both trichomes on later instars may depend on effects after feeding initiation.

Applying plant oils to control fall armyworm (Spodoptera frugiperda) in corn

Corn (Zea mays) is one of the world's main agricultural crops, and Spodoptera frugiperda (J. E. Smith) is its most important pest. In order to find natural controlling alternatives, this study aimed to determine the effect of plant oils on the feeding preference of first- and second-instar caterpillars. The experimental design was completely randomized in a 6 x 5 factorial combination (turmeric, clove, palmarosa, tea tree, common juniper, and neem oils) at five concentrations (0, 25, 50, 100, and 200 muL mL-1), plus a control consisting of acetone 100.0%, with five replicates per treatment. Twenty-five-day-old corn leaf sections received the corresponding treatments in addition to the control and were deposited along orthogonal axes in an arena arranged in Petri dishes. Ten 1st instar caterpillars were released at the center of the plates, and results were obtained after 8h and 24h from the release, based on the number of caterpillars found on each treatment. For 1st instar caterpillars, the best results were observed for clove and palmarosa, which negatively influenced caterpillar feeding activity in both evaluation periods, followed by turmeric oil, which showed the same effectiveness in the last period only. For second-instar caterpillars, the best effects were observed for neem, turmeric, palmarosa, and clove oil in the first evaluation period. Furthermore, the effectiveness of the first three oils was maintained in the second evaluation period. These results emphasize the potential capability of plant oils when used in management programs against this pest, in which the oils of turmeric, clove and palmarosa showing the best controlling potential of this pest from the lowest concentration corresponding to 25 muL mL-1.

FIRST RECORD OF Xanthopastis timais IN AMARYLLIS AND EFFECT OF SOURSOP EXTRACT ON LARVAL MORTALITY

ABSTRACT The aim of this study was to report the occurrence of Xanthopastis timais (Cramer, 1780) (Lepidoptera: Noctuidae) in amaryllis (Hippeastrum hybridum Hort., Amaryllidaceae), as well as estimating lethal concentrations (LC50 and LC99) of soursop seed extract, Annona muricata L. (Annonaceae), against its larvae. The experiment was carried out at the Laboratory of Entomology of the Research Center for Agricultural Sciences, Federal University of Alagoas, in Rio Largo-AL, Brazil. First, we collected caterpillars from amaryllis plants that were reared until pupal and adult stages (parental generation). Next, part of the adults was used for species identification, and the rest were bred to produce next generation (F1), being after that applied in a laboratory bioassay. The lab trial was performed in a completely randomized design, with six treatments and five replications containing three second-instar caterpillars. These larvae were fed pieces of amaryllis leaf (4 x 4 cm), which were previously soaked in treatments for 30 seconds and, air -dried on absorbent papers for one hour. Each treatment consisted of one concentration of ethanol extract of soursop seeds (0.0, 1.0, 0.5, 0.25, 0.125 and 0.0625% w/ v) with distilled water and DMSO at 1% (v/ v), for solutions. We noted that the lethal concentrations LC50 and LC99 were 0.29% (w/ v) and 2.27% (w/ v), respectively. In view of our results, we can state that larval stage of X. timais were influenced by extract application in terms of survival, mortality, larvae weight and larval stage length. Besides of that, it was the first time this species was recorded in Alagoas state.

Exploration costs promote conservative collective foraging in the social caterpillar Malacosoma disstria

Collective choices of a food source are generally thought to arise from the amplification of individual preferences. However, costs associated with foraging can also influence food choice: animals faced with a poor-quality food source may either continue feeding on it (a conservative strategy), or search for a potentially more profitable one (a more risky strategy). Groups of nomadic, trail-following Malacosoma disstria caterpillars were offered a leaf of two different hosts, either side by side to determine preference, or at a distance to investigate how exploration costs affect food choice. Arenas with and without pheromone trails were used to distinguish between direct travel costs and unknown territory costs. When two leaves were side by side, groups of second-instar caterpillars showed clear preferences between host trees, whereas groups of fourth-instar larvae did not. When the two leaves were distant from each other, groups of second-instar caterpillars usually remained on the known source, irrespective of food preference or group size. These groups were more likely to relocate to a preferred food source when pheromone trails were present, suggesting that trails effectively decrease unknown territory costs. Groups of fourth-instar caterpillars were more likely to leave the known food source even when no trail was present, suggesting a developmental shift in costs associated with exploration. Our results show that collective choices reflect food preference when exploration costs are low (second-instar larvae with pheromone trails), but not when they are high (second-instar larvae without trails). Such a conservative foraging strategy can be adaptive if the exploration costs of leaving a known food source are greater than the potential benefits of discovering a better alternative, for example, in a homogenous environment like that of a tree.

Preference and performance of the gypsy moth cater­pillars on sweet chestnut and some oak species

In the establishment of mixed plantations, it is necessary to examine previously the relations of the principal and the admixed species and the most significant pests. This paper presents the results of the study of the gypsy moth caterpillar preference and performance on sweet chestnut and four oak species. Preference index is the highest for Hungarian oak (0.83) and Turkey oak (0.77), for sessile oak it is significantly lower (0.33), and for common oak it is equal to 0. In combination with sweet chestnut, the gypsy moth second-instar caterpillars prefer Hungarian oak, i.e. Turkey oak leaves. In combination with sessile oak or common oak, the gypsy moth caterpillars prefer sweet chestnut leaves. The analyzed parameters which characterise the performance of the gypsy moth fourth-instar caterpillars are lower for all study oak species compared to sweet chestnut, except in the case of Turkey oak. Based on the study results and the adopted principle that the mixture should be composed of the most favourable species, which will serve as the 'trap plant' during the gypsy moth outbreak, it can be concluded that Turkey oak is more favourable for the mixture with sweet chestnut than the other analyzed oak species.

Consistent individual differences in the foraging behaviour of forest tent caterpillars (Malacosoma disstria)

Outbreaking insects are often considered identical units despite recent work in behavioural ecology that shows repeatable differences can exist between individuals and can have important implications for individual fitness and population processes. However, although entomologists have neglected the hypothesis that differences between individuals can play an important role in the ecology of a species, it is not new. Wellington (1957. Can. J. Zool. 35: 293–323) suggested that consistent individual differences in behaviour may play a role in the population dynamics of Malacosoma (Hübner, 1820) species (Lepidoptera: Lasiocampidae). We used a novel approach to determine if individual larval Malacosoma disstria Hübner, 1820 exhibit distinct and repeatable behavioural traits. Second-instar caterpillars were placed on individual arenas for 1 h on 4 consecutive days, and the proportion of time spent walking, searching, quiescent, and eating was documented. Active and sluggish behavioural types were distinguished and stable differences in individual activity were observed. Activity was positively correlated with growth during the 4 days of the experiment, but no significant relationship was detected between behaviour during the experiment and overall larval performance in the laboratory setting. These findings demonstrate consistent variation in the foraging behaviour of forest tent caterpillars and lay the basis for further investigatison of its role in colony function and population dynamics.

Flower vs. Leaf Feeding by Pieris brassicae: Glucosinolate-Rich Flower Tissues are Preferred and Sustain Higher Growth Rate

Interactions between butterflies and caterpillars in the genus Pieris and plants in the family Brassicaceae are among the best explored in the field of insect–plant biology. However, we report here for the first time that Pieris brassicae, commonly assumed to be a typical folivore, actually prefers to feed on flowers of three Brassica nigra genotypes rather than on their leaves. First- and second-instar caterpillars were observed to feed primarily on leaves, whereas late second and early third instars migrated via the small leaves of the flower branches to the flower buds and flowers. Once flower feeding began, no further leaf feeding was observed. We investigated growth rates of caterpillars having access exclusively to either leaves of flowering plants or flowers. In addition, we analyzed glucosinolate concentrations in leaves and flowers. Late-second- and early-third-instar P. brassicae caterpillars moved upward into the inflorescences of B. nigra and fed on buds and flowers until the end of the final (fifth) instar, after which they entered into the wandering stage, leaving the plant in search of a pupation site. Flower feeding sustained a significantly higher growth rate than leaf feeding. Flowers contained levels of glucosinolates up to five times higher than those of leaves. Five glucosinolates were identified: the aliphatic sinigrin, the aromatic phenyethylglucosinolate, and three indole glucosinolates: glucobrassicin, 4-methoxyglucobrassicin, and 4-hydroxyglucobrassicin. Tissue type and genotype were the most important factors affecting levels of identified glucosinolates. Sinigrin was by far the most abundant compound in all three genotypes. Sinigrin, 4-hydroxyglucobrassicin, and phenylethylglucosinolate were present at significantly higher levels in flowers than in leaves. In response to caterpillar feeding, sinigrin levels in both leaves and flowers were significantly higher than in undamaged plants, whereas 4-hydroxyglucobrassicin leaf levels were lower. Our results show that feeding on flower tissues, containing higher concentrations of glucosinolates, provides P. brassicae with a nutritional benefit in terms of higher growth rate. This preference appears to be in contrast to published negative effects of volatile glucosinolate breakdown products on the closely related Pieris rapae.

FITNESS RELATED DIET-MIXING BY INTRASPECIFIC HOST-PLANT-SWITCHING OF SPECIALIST INSECT HERBIVORES

Generalist insect herbivores may profit by feeding on a mixture of plant species that differ in nutritional quality. Herbivore performance can also be affected by intraspecific host plant variation. However, it is unknown whether conspecific plant individuals differ sufficiently to promote diet-mixing behavior in specialist herbivores. We experimentally tested this "specialist diet-mixing hypothesis" for specialist caterpillars (Chrysopsyche imparilis, Lasiocampidae) in a West African savanna. The caterpillars switched regularly between host tree individuals (Combretum fragrans, Combretaceae). To examine whether switching benefited caterpillar performance via diet-mixing, the caterpillars were reared either on leaves from several plant individuals (mixed diet) or on leaves from a single plant. The strongest effect of diet-mixing was found for fecundity, with females reared on a mixed diet laying significantly more eggs than sisters receiving a single-plant diet. In addition, a mixed diet decreased variability in egg size and increased the growth of second-instar caterpillars. Supplementary food choice experiments were conducted to assess a potential influence of lowered host quality (induced by herbivory) on caterpillar behavior; no such effect was found. By linking intraspecific host-switching behavior and herbivore performance, this study provides new information on the relevance of intraspecific plant variation for herbivorous insects.

Laboratory Measurement of Predation by Podisus maculiventris and P. sagitta (Hemiptera: Pentatomidae) on Beet Armyworm (Lepidoptera: Noctuidae)

Predation rates for nymphs and adults of the predatory stink bugs, Podisus Maculiventris (Say) and Podisus sagitta (F.), on the different developmental stages of the beet armyworm, Spodoptera exigua (Hubner), were measured in the laboratory. Development and survival of predator nymphs also were monitored to evaluate prey suitability. The predators displayed high predation rates against different stages of the beet armyworm. However, eggs, first- and second-instar caterpillars, and adults of S. exigua proved to be less suitable prey for late instars and adults of both pentatomids. Predation rates of P. maculiventris were similar to or slightly higher than those of the smaller-sized P. sagitta. Results are discussed in relation to experimental conditions (searching arena, temperature) and quality of laboratory-reared predators.

Life of Acrobasis rubrifasciella (Lepidoptera: Phycitidae), Its Main Parasite, Agathis calcarata (Hymenoptera: Braconidae), and Three Hyperparasites (Chalcidoidea)

In northeastern Minnesota, the young caterpillar of Acrobasis rubrifasciella (Packard) resumes life in May in the wintered leaf-buds of Alnus . As it grows, mostly in June, it constructs a silken growth tube with an external layer of its fecal pellets, from which shelter it feeds until full-grown. As pupation approaches, it enlarges the end portion of the tube to form a pupal chamber that eventually is bulbous and sealed, separated from the tube by a plug, but with an escape hatch left near the base of the chamber for emergence of the moth. From 1 to 9 caterpillars, each in its own tube, may occur in a single nest, obscured in plant parts bound with gray silk. The pupal and adult stages appeared from June 22 to August 9; apparently the small larvae overwinter. Four instars of Agathis calcarata (Cresson) are described. The first instar was found in host larvae from mid-May to July. Diapause usually ends when the host seals its pupal chamber preparatory to transformation, and the second to fourth instars of Agathis develop in a few days, destroying the host before it can pupate. A cellophane-like cocoon is spun in the host chamber, and the red-and-black adult emerges about 15 days later, through the hatch prepared by the caterpillar. Although actual parasitization and the egg were not observed, the first-instar Agathis apparently winters in first- or, possibly, second-instar caterpillars. Both Acrobasis and Agathis are univoltine. The cocoon phase of this Agathis is subject to attack by 3 chalcid hyperparasites, Perilampus tristis Mayr, Habrocytus sp., and Eupelmella vesicularis (Retzius).