Luis Carlos Martínez

Ultrastructure and cytochemistry of salivary glands of the predator Podisus nigrispinus (Hemiptera: Pentatomidae.

Podisus nigrispinus Dallas (Hemiptera: Pentatomidae) is a zoophytophagous insect with a potential for use as a biological control agent in agriculture because nymphs and adults actively prey on various insects by inserting mouthparts and regurgitating the contents of the salivary glands inside the prey, causing rapid paralysis and death. However, the substances found in saliva of P. nigrispinus that causes the death of the prey are unknown. As a first step to identify the component of the saliva of P. nigrispinus, this study evaluated the ultrastructure and cytochemistry of the salivary glands of P. nigrispinus. The salivary system of P. nigrispinus has a pair of principal salivary glands, which are bilobed with a short anterior lobe and a long posterior lobe, and a pair of tubular accessory glands. The principal gland epithelium is composed of a single layer of cells enclosing a large lumen. Epithelial cells of the principal salivary gland vary from cubic to columnar shape, with one or two spherical and well-developed nuclei. Cells of the anterior lobe of the principal salivary gland have an apical surface with narrow, short, and irregular plasma membrane foldings; apical and perinuclear cytoplasm rich in rough endoplasmic reticulum; and mitochondria with tubular cristae. The basal portion of the secretory cells has mitochondria associated with many basal plasma membrane infoldings that are short but form large extracellular canals. Secretory granules with electron-dense core and electron-transparent peripheral are dispersed throughout the cytoplasm. Cells of the posterior lobe of the principal salivary gland are similar to those of the anterior lobe, except for the presence of mitochondria with transverse cristae. The accessory salivary gland cells are columnar with apical microvilli, have well-developed nucleus and cytoplasm rich in rough endoplasmic reticulum, and have secretory granules. Cytochemical tests showed positive reactions for carbohydrate, protein, and acid phosphatase in different regions of the glandular system. The principal salivary glands of P. nigrispinus do not have muscle cells attached to its wall, suggesting that saliva-releasing mechanism may occurs with the participation of some thorax muscles. The cytochemical and ultrastructural features suggest that the principal and accessory salivary glands play a role in protein synthesis of the saliva.

Toxic effects of the neem oil (Azadirachta indica) formulation on the stink bug predator, Podisus nigrispinus (Heteroptera: Pentatomidae).

This research investigated the effects of neem oil on mortality, survival and malformations of the non-target stink bug predator, Podisus nigrispinus. Neurotoxic and growth inhibitor insecticides were used to compare the lethal and sublethal effects from neem oil on this predator. Six concentrations of neem oil were topically applied onto nymphs and adults of this predator. The mortality rates of third, fourth, and fifth instar nymphs increased with increasing neem oil concentrations, suggesting low toxicity to P. nigrispinus nymphs. Mortality of adults was low, but with sublethal effects of neem products on this predator. The developmental rate of P. nigrispinus decreased with increasing neem oil concentrations. Longevity of fourth instar nymphs varied from 3.74 to 3.05 d, fifth instar from 5.94 to 4.07 d and adult from 16.5 and 15.7 d with 0.5 and 50% neem doses. Podisus nigrispinus presented malformations and increase with neem oil concentrations. The main malformations occur in wings, scutellum and legs of this predator. The neem oil at high and sub lethal doses cause mortality, inhibits growth and survival and results in anomalies on wings and legs of the non-traget predator P. nigrispinus indicating that its use associated with biological control should be carefully evaluated.

Bioactivity of six plant extracts on adults of Demotispa neivai (Coleoptera: Chrysomelidae).

ABSTRACT. Demotispa neivai Bondar (Coleoptera: Chrysomelidae) damage oil palm fruits, which makes it necessary to develop products to control this insect. The mortality, repellency, and antifeeding effects on adults of D. neivai of six plant extracts of Azadirachta indica A. Juss. (Sapindales: Meliaceae), Ricinus communis (L.) (Malpighiaes: Euphorbiaceae), Citrus sinensis Oesbek (Sapindales: Rutaceae), Nicotiana tabacum (L.) (Slanales: Solanaceae), Capsicum annuum (L.) (Solanales: Solanaceae), and Artemisia absinthium (L.) (Asterales: Asteraceae) were determined: 1) the lethal concentration LC50–90, lethal time of D. neivai was evaluated after spraying the fruits of oil palm; 2) repellent effects of each ingredient were evaluated by calculating the index of repellency; 3) antifeeding effects with the rate of inhibition calculated between doses of 20 and 24 g/liter. The mortality of D. neivai was higher with the extracts Ci. sinensis, R. communis, N. tabacum, and Ca. annuum. The mortality of D. neivai increased in the first 72 hr in all treatments. The extracts of N. tabacum, Ca. annuum, and A. indica were more repellent to D. neivai that those of Ci. sinensis, Ar. Absinthium, and R. communis. Antifeeding effect was higher with Ci. sinensis and R. communis. The increased mortality of D. neivai by Ci. sinensis can be explained by the effect of this compound on the respiratory system of insects. Extracts of Ci. sinensis, R. communis, N. tabacum, and Ca. annuum repelled and caused mortality of D. neivai and, thus, can be used in integrate pest management programs of this pest in oil palm plantations.

Leucothyreus femoratus (Coleoptera: Scarabaeidae): Feeding and Behavioral Activities as an Oil Palm Defoliator

ABSTRACT Leucothyreus femoratus Burmeister (Coleoptera: Scarabaeidae) is an important insect pest of oil palm plantations, because larvae and adults feed on plant roots and leaves, respectively. This suggests the necessity of comprehending the pests feeding and behavioral habits for pest management. Food consumption and injury to leaves of Elaeis guineensis Jacq. (Arecales: Arecaceae, African oil palm) by adults of L. femoratus in Colombia were studied. Locomotion of adults was evaluated with respect to 6 behaviors, i.e., emergence, hiding in the ground, walking, flying, feeding, and mating. In addition, larvae were collected from the roots of other plants found in the oil palm plantation in order to determine possible alternative hosts. Leaf consumption per adult L. femoratus was 13 mm2/day/insect (&khgr;2 = 19.33, P < 0.0001). Leaf injury was in the form of squares or rectangles and cumulative defoliation reached 15.5% in 60 days. The insect showed predominantly nocturnal feeding and mating (&khgr;2 = 95.53, P < 0.05; &khgr;2 = 207.01, P < 0.05, respectively). Larvae of L. femoratus were found in abundance on the roots of Croton trinitatis Millsp. (Euphorbiaceae, road side croton) and Imperata cilindrica (L.) P. Beauv. (Poaceae, cogon grass). The feeding habits of larvae and adults of this insect may be main factors in their adaptation to oil palm plantations. The understanding of the feeding habits and behaviors of L. femoratus are important to define strategies for the management of their populations in oil palm plantations.

Insecticidal activity of garlic essential oil and their constituents against the mealworm beetle, Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae)

This study evaluated the insecticidal activity of garlic, Allium sativum Linnaeus (Amaryllidaceae) essential oil and their principal constituents on Tenebrio molitor. Garlic essential oil, diallyl disulfide, and diallyl sulfide oil were used to compare the lethal and repellent effects on larvae, pupae and adults of T. molitor. Six concentrations of garlic essential oil and their principal constituents were topically applied onto larvae, pupae and adults of this insect. Repellent effect and respiration rate of each constituent was evaluated. The chemical composition of garlic essential oil was also determined and primary compounds were dimethyl trisulfide (19.86%), diallyl disulfide (18.62%), diallyl sulfide (12.67%), diallyl tetrasulfide (11.34%), and 3-vinyl-[4H]-1,2-dithiin (10.11%). Garlic essential oil was toxic to T. molitor larva, followed by pupa and adult. In toxic compounds, diallyl disulfide was the most toxic than diallyl sulfide for pupa > larva > adult respectively and showing lethal effects at different time points. Garlic essential oil, diallyl disulfide and diallyl sulfide induced symptoms of intoxication and necrosis in larva, pupa, and adult of T. molitor between 20–40 h after exposure. Garlic essential oil and their compounds caused lethal and sublethal effects on T. molitor and, therefore, have the potential for pest control.

Juvenile hormone downregulates vitellogenin production in Ectatomma tuberculatum (Hymenoptera: Formicidae) sterile workers

ABSTRACT In the ant Ectatomma tuberculatum (Olivier 1792), workers have active ovaries and lay trophic eggs that are eaten by the queen and larvae. Vitellogenins are the main proteins found in the eggs of insects and are the source of nutrients for the embryo in the fertilized eggs and for adults in the trophic eggs. In social insects, vitellogenin titres vary between castes and affect reproductive social status, nursing, foraging, longevity, somatic maintenance, and immunity. In most insects, vitellogenin synthesis is mainly regulated by juvenile hormone. However, in non-reproductive worker ants, this relationship is poorly characterized. This study determined the effects of juvenile hormone on vitellogenin synthesis in non-reproductive E. tuberculatum workers. Juvenile hormone was topically applied onto workers, and the effect on vitellogenin synthesis in the fat body and vitellogenin titres in the haemolymph were analysed by ELISA and qPCR. Juvenile hormone downregulated protein synthesis and reduced vitellogenin titres in the haemolymph, suggesting that in workers of E. tuberculatum, juvenile hormone loses its gonadotrophic function. Summary: Juvenile hormone downregulates vitellogenin synthesis in worker ants producing trophic eggs.

Ultrastructure of the Salivary Glands of the Stink Bug Predator Podisus distinctus.

Podisus distinctus (Hemiptera: Pentatomidae) is a zoophytophagous insect with significant potential for use as a biological control agent in agriculture and forestry because their nymphs and adults actively prey on diverse insect species. The saliva of this insect possesses active substances that cause paralysis and death of the prey. As the first step in identifying compounds of P. distinctus saliva, this study describes the ultrastructure of the salivary glands of this predator. The salivary system of P. distinctus possesses a pair of main salivary glands with a short anterior lobe, a long posterior lobe, and a pair of tubular accessory glands. The main salivary gland of P. distinctus has no associated muscles, suggesting that the saliva-release mechanism occurs with the help of certain thorax muscles. The main salivary gland epithelium has a single layer of cells (varying from cubical to columnar) with cytoplasm rich in rough endoplasmic reticulum, spherical granules of different sizes, a nucleus with a predominance of decondensed chromatin, and nucleolus. The apical cell region has a few short microvilli and the basal region has plasma membrane infoldings. The epithelium of the accessory salivary glands possesses a single-layered epithelium of cubic cells delimiting a narrow lumen. The apical cell region has a high density of microvilli and pleomorphic mitochondria, whereas the central cell region is rich in rough endoplasmic reticulum with a well-developed nucleus and decondensed chromatin. The basal cell region is characterized by the presence of several basal plasma membrane infoldings associated with mitochondria and numerous openings to the hemocoel forming large channels. The ultrastructural characteristics suggest that the main salivary glands and accessory salivary glands play a vital role in protein synthesis for saliva production and that the accessory glands are involved in transport of materials of the hemolymph.

Interactions Between the Bud Rot Disease of Oil Palm and Rhynchophorus palmarum (Coleoptera: Curculionidae).

Abstract Rhynchophorus palmarum (L.) causes great losses to the oil palm plantations, and therefore, the spatial and temporal distribution of this insect should be studied, to manage its populations. Insect sampling was done for 2 yr in an oil palm plantation from Colombia. In total, 60 pheromone traps were used in healthy palm trees and infected ones with the Bud Rot disease. On the other hand, developmental stages of this insect were quantified on healthy and diseased palms for two consecutive years. Number of adult R. palmarum per sampling was higher in the plantation with diseased palm trees, 3.85 and 74.7 insects per trap, than in those with healthy ones, 1.91 and 9.48 insects per trap, in the first and second years, respectively. After the integration of pheromone traps, there was a significant increase in the infestation level at all stages of development of the insect. For the first time, the presence of R. palmarum attracted to diseased palms is reported. The association between R. palmarum and the Bud Rot disease is a cause of death and great loss to the oil palm plantations.

Lepidoptera vectors of Pestalotiopsis fungal disease: first record in oil palm plantations from Colombia.

Pestalotiopsis is a disease that causes damage to the leaves of Elaeis guineensis Jacquin and defoliation in commercial plantations. Lepidoptera larvae are the main insects that spread the disease. The aim of this paper is to report for the first time the insects found in oil palm plantations in Colombia. Lepidoptera larvae were collected from cultures in the presence of Pestalotiopsis and were identified to species level. Severity and duration of the symptoms of Pestalotiopsis were evaluated from the damage caused by the insects of each species. Eighteen species of the families Dalceridae (one), Elachistidae (four), Limacodidae (eight), Megalopygidae (two), Nymphalidae (one), Psychidae (one) and Saturniidae (one) confirmed assistance and disease transmission. Increased severity of Pestalotiopsis damage was induced by Acharia hyperoche, Acraga ochracea, Durrantia arcanella, Euclea diversa, Euprosterna elaeasa and Stenoma impressella. The development of Pestalotiopsis on the leaves of E. guineensis and its symptoms were observed between 16.8 and 72.9 days. The damage caused by these insects on the leaves of E. guineensis was the main entrance of the virulent fungal spores. The results of this study contribute to the knowledge of Lepidoptera that attend and spread the Pestalotiopsis fungus on leaves in oil palm plantations. To our knowledge, no previous records of this disease on the plant are found in Colombia.

Squamocin induce histological and ultrastructural changes in the midgut cells of Anticarsia gemmatalis (Lepidoptera: Noctuidae)

Annonaceous acetogenins (Annona squamosa Linnaeus) comprises of a series of natural products which are extracted from Annonaceae species, squamocin proved to be highly efficient among those agents. Squamocin is mostly referred as a lethal agent for midgut cells of different insects, with toxic effects when tested against larva of some insects. In present study, LC50 and LC90 of squamocin for A. gemmatalis Hübner (Lepidoptera: Noctuidae) were calculated using probit analysis. Morphological changes in midgut cells were analyzed under light, fluorescence and transmission electron microscopes when larvae were treated with LC50 and LC90 of squamocin for 24, 48 and 72 h. Results revealed that the maximum damage to midgut cells was found under LC90 where it showed digestive cells with enlarged basal labyrinth, highly vacuolated cytoplasm, damaged apical surface, cell protrusions to the gut lumen, autophagy and cell death. The midgut goblet cells showed a strong disorganization of their microvilli. Likewise, in insects treated with squamocin, mitochondria were not marked with Mitotracker fluorescent probe, suggesting some molecular damage in these organelles, which was reinforced by decrease in the respiration rate in these insects. These results demonstrate that squamocin has potential to induce enough morphological changes in midgut through epithelial cell damage in A. gemmatalis.