Fitness cost and reversion of resistance Leucoptera coffeella (Lepidoptera: Lyonetiidae) to chlorpyrifos.

A better understanding of fitness costs and insecticide resistance reversion has practical applications for improving resistance management approaches. The coffee leaf miner, Leucoptera coffeella, is one of the most important coffee pests worldwide. Chlorpyrifos is still used to control L. coffeella despite studies showing resistance in this pest. The current study investigated the fitness costs and reversion of resistance to chlorpyrifos in L. coffeella populations in coffee. The control failure of this insecticide was evaluated in 15 field populations. Selection of resistant and susceptible L. coffeella (G1-G10), with and without chlorpyrifos exposure, was evaluated. The following parameters were investigated: consumed leaf area, adult longevity, number of eggs per female, and egg viability. The present study showed control failures of chlorpyrifos and low (< 31-folds) to high levels (> 80-folds) of resistance in all field populations tested. The resistant population showed less fitness than the susceptible population. The fitness of the resistant population decreased significantly after 10 generations of chlorpyrifos selection. Specifically, the number of eggs per female, larvae hatched, and adult longevity were reduced by factors of 5, 2.3 and 3, respectively. Furthermore, the chlorpyrifos-resistant L. coffeella population consumed more than the susceptible population. Therefore, we concluded that non-exposing L. coffeella populations to chlorpyrifos insecticide leads to rapid reversion of resistance and susceptibility. In addition, resistant populations show reduced reproductive fitness and longevity, while consuming more, probably to meet greater metabolic demands.

Physico-chemical characteristics and productivity of tomato plants in function of nitrogen sources and doses / Características físico-químicas e produtividade do tomateiro em função de fontes e doses de nitrogênio

The objective of this study was to evaluate the effect of nitrogen sources and rates on the physicochemical characteristics and yield of tomato plants. Forty hybrids were cultivated at 100 and 400 kg ha-1of N, combined with four sources (urea, ammonium sulfate, ammonium nitrate and calcium), plus a treatment without N application in a randomized complete block design four replicates. Size, stem diameter, number of leaves, SPAD (Soil Plant Analysis Development), leaf nitrogen, number of fruits / plants, fruit firmness, bark thickness and average fruit size, ° BRIX, pH, calcium, potassium and sodium in fruits. There was an increase in SPAD index, Brix and longitudinal diameter of fruits as a function of the N dose. The use of ammonium nitrate and calcium provided stronger fruits. Urea and ammonium nitrate provided the highest pH value in tomato fruits. The application of the 100 kg ha-1 dose of N resulted in the highest potassium content in fruits. The highest productivity was obtained with the application of sources containing ammonium and the lowest in the control treatment. Sources and doses of nitrogen fertilizers influenced growth, productivity and parameters related to tomato quality.

Objetivou-se avaliar o efeito das fontes e doses de nitrogênio nas características físico-químicas e produtividade do tomateiro. Foi cultivado o híbrido Forty com doses de 100 e 400 kg ha-1 de N, combinadas com quatro fontes (ureia, sulfato de amônio, nitrato de amônio e de cálcio), mais um tratamento sem aplicação de N em delineamento em blocos casualizados com quatro repetições. Avaliou-se altura, diâmetro do caule, número de folhas, SPAD (Soil Plant Analysis Development), nitrogênio na folha, número de frutos/plantas, firmeza do fruto, espessura da casca e tamanho médio dos frutos, °BRIX, pH, cálcio, potássio e sódio nos frutos. Houve incremento do índice SPAD, ºBrix e diâmetro longitudinal dos frutos em função da dose de N. A utilização do nitrato de amônio e de cálcio proporcionou frutos mais firmes. A ureia e o nitrato de amônio propiciaram o maior valor de pH em frutos de tomate. A aplicação da dose de 100 kg ha-1 de N acarretou o maior teor de potássio nos frutos. A maior produtividade foi obtida com a aplicação de fontes que continham amônio e a menor no tratamento controle. As fontes e as doses de fertilizantes nitrogenados influenciaram o crescimento, produtividade e os parâmetros relacionados à qualidade do tomate.

Histopathological and cytotoxic changes induced by spinosad on midgut cells of the non-target predator Podisus nigrispinus Dallas (Heteroptera: Pentatomidae).

Broad-spectrum insecticides used in pest control are a risk for non-target insects. Their compatibility to the insecticide spinosad, used in agriculture and forestry as a biological control tool, needs to be evaluated. Podisus nigrispinus Dallas (Heteroptera: Pentatomidae) is a predatory bug used in the pest management of agricultural and forest systems where spinosad is also frequently applied. The aim of this study was to evaluate the toxicity, histopathology and cytotoxicity in midgut cells of P. nigrispinus exposed to spinosad. The toxicity test was performed to determine the lethal concentrations of spinosad after exposure by ingestion. The histopathology and cytotoxicity caused by spinosad were analyzed in the three midgut regions (anterior, middle and posterior) of P. nigrispinus during different exposure periods. Spinosad, at low concentrations, was toxic to P. nigrispinus [LC50 = 3.15 (3.02-3.26) µg.L-1]. Cell degeneration features such as cytoplasm vacuolization, chromatin condensation and release of cell fragments to the midgut lumen were observed in this organ. Cell death via apoptosis was found in the three midgut regions of this predator after exposure to the insecticide. Spinosad is toxic to P. nigrispinus, and causes histological and cytological damage followed by cell death in the midgut, suggesting a dangerous effect on a beneficial non-target insect.

Exposure to Insecticides Reduces Populations of Rhynchophorus palmarum in Oil Palm Plantations with Bud Rot Disease.

The South American palm weevil (SAPW), Rhynchophorus palmarum Linnaeus (Coleoptera: Curculionidae) is the main pest of Elaeis guineensis and damages palm trees with bud rot disease in the Americas. The effects of six neurotoxic insecticides (abamectin, carbaryl, deltamethrin, fipronil, imidacloprid and spinosad) were evaluated against SAPW for toxicity, survival, reproduction, and mortality. Abamectin (LC50 = 0.33 mg mL-1), Carbaryl (LC50 = 0.24 mg mL-1), deltamethrin (LC50 = 0.17 mg mL-1), and fipronil (LC50 = 0.42 mg mL-1) were the most toxic to SAPW. Adult survival was 95% without exposure to insecticides, decreasing to 78-65% in insects treated with the LC25 and 49-35% in insects exposed to LC50. Sublethal doses of carbaryl, fipronil and imidacloprid showed significant effect on the reproduction of this insect. Mortality of SAPW populations caused by insecticides had similar effects in the laboratory and field conditions. The results suggest that carbaryl, deltamethrin, fipronil, and imidacloprid caused significantly higher mortality as compared to the control in SAPW and may be used to control its populations in oil palm trees where bud rot appears as the key disease for SAPW attraction and infestation.

Chlorantraniliprole-mediated effects on survival, walking abilities, and respiration in the coffee berry borer, Hypothenemus hampei.

Hypothenemus hampei Ferrari (Coleoptera: Curculionidae) is the main pest of coffee crops, and effective methods for pest management are needed urgently. Bioassays were conducted to assess the effects of the insecticide chlorantraniliprole on H. hampei adults. Toxicity, survivorship, larval production, respiration rate, and behavioral responses to six concentrations of chlorantraniliprole were evaluated. Chlorantraniliprole was toxic to H. hampei (LD50 = 0.49 mg mL-1 and LD90 = 1.21 mg mL-1). Survivorship was 98% in adults not exposed to chlorantraniliprole, decreasing to 52% in insects exposed to LD50 and 2% in insects treated with LD90. H. hampei showed reduced mobility on insecticide-treated surfaces. The insecticide promoted a decrease in the respiration rate of H. hampei for up to 3 h after exposure, altering behavioral responses and locomotor activity. Chlorantraniliprole was shown to have lethal and sublethal effects on H. hampei and, thus, can be used rotationally in integrated pest management programs to control of this pest in coffee crops and retard of insect resistance.

Terpenoid constituents of cinnamon and clove essential oils cause toxic effects and behavior repellency response on granary weevil, Sitophilus granarius.

This study evaluated toxic effects, repellency and respiration rate caused by terpenoid constituents of cinnamon and clove essential oils and against Sitophilus granarius L. (Coleoptera: Curculionidae). The lethal concentrations (LC50 and LC90), repellent effect, and behavior repellency response on adults of S. granarius after exposure to six concentrations of each essential oil and terpenoids were evaluated. The chemical composition of the cinnamon oil was also determined and primary compounds were eugenol (10.5%), trans-3-caren-2-ol (10.2%), benzyl benzoate (9.99%), caryophyllene (9.34%), eugenyl acetate (7.71%), α-phellandrene (7.41%), and α-pinene (7.14%). In clove essential oil, the primary compounds were eugenol (27.1%), caryophyllene (24.5%), caryophyllene oxide (18.3%), 2-propenoic acid (12.2%), α-humulene (10.8%), γ-cadinene (5.01%), and humulene oxide (4.84%). Cinnamon and clove essential oil was toxic to S. granarius. In toxic terpenoids compounds, eugenol has stronger contact toxicity in S. granarius than caryophyllene oxide, followed by α-pinene, α-humulene, and α-phellandrene. Insects reduced their respiratory rates after being exposed to essential oil terpenoids and avoided or reduced their mobility on terpenoid-treated surfaces. Cinnamon and clove essential oil, and their terpenoid constituents were toxic and repellent to adult S. granarius and, therefore, have the potential to prevent or retard the development of insecticide resistance.

Side-effects of pesticides on the generalist endoparasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae).

New plant protection strategies focus on minimizing chemical pesticide use and increasing their compatibility with biological control agents. The objective was to evaluate the side-effects of glyphosate, diflubenzuron, malathion, tebuconazole and triflumuron (at 720, 45, 400, 150 and 20 g ai ha-1, respectively), pesticides authorized for soybean crops in Brazil, on the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae) reared on Anticarsia gemmatalis (Lepidoptera: Noctuidae). The emergence and female numbers produced per P. elaeisis female were higher in A. gemmatalis pupae from caterpillars fed an artificial diet treated with glyphosate. However, emergence was lower than 50% when the caterpillars were fed on soybean leaves treated with glyphosate offered ad libitum (3-5 times). Palmistichus elaeisis died before parasiting A. gemmatalis pupae treated with malathion. Diflubenzuron reduced the P. elaesis sex ratio in the second generation. Tebuconazole and triflumuron did not cause side-effects on this parasitoid. A continuous exposure to glyphosate by the host may lead to side-effects on P. elaeisis emergence, but its moderate use is acceptable for this parasitoid. Diflubenzuron had severe transgenerational side-effects. Tebuconazole fungicide and triflumuron insecticide are compatible with P. elaeisis in sustainable integrated pest management (IPM) programs, while malathion can not be included in them.

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.

Can the Understory Affect the Hymenoptera Parasitoids in a Eucalyptus Plantation?

The understory in forest plantations can increase richness and diversity of natural enemies due to greater plant species richness. The objective of this study was to test the hypothesis that the presence of the understory and climatic season in the region (wet or dry) can increase the richness and abundance of Hymenoptera parasitoids in Eucalyptus plantations, in the municipality of Belo Oriente, Minas Gerais State, Brazil. In each eucalyptus cultivation (five areas of cultivation) ten Malaise traps were installed, five with the understory and five without it. A total of 9,639 individuals from 30 families of the Hymenoptera parasitoids were collected, with Mymaridae, Scelionidae, Encyrtidae and Braconidae being the most collected ones with 4,934, 1,212, 619 and 612 individuals, respectively. The eucalyptus stands with and without the understory showed percentage of individuals 45.65% and 54.35% collected, respectively. The understory did not represent a positive effect on the overall abundance of the individuals Hymenoptera in the E. grandis stands, but rather exerted a positive effect on the specific families of the parasitoids of this order.

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

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.

Ocorrência e distribuição espacial e temporal do coleóptero Naupactus curtus em cafeeiros de Minas Gerais, Brasil / Occurrence, spatial and temporal distribution of the coleopteran Naupactus curtus on coffee plants from Minas Gerais, Brazil

Não há registro de Naupactus curtus em Minas Gerais, e as poucas ocorrências em outros Estados brasileiros são escassas de informações acerca da sua distribuição espacial em cafeeiros. Assim, este trabalho tem por objetivos relatar a ocorrência dessa praga em Minas Gerais e estudar a sua distribuição espacial e temporal em quatro lavouras de Coffea arabica, em Ponte Nova e Jaboticatubas. Os insetos foram monitorados mensalmente. N. curtus foi encontrado nessas duas áreas e apresentou maiores densidades nas bordas das lavouras.

There were no reports of Naupactus curtus in Minas Gerais, and the few occurrences in other Brazilian States bring is little of information about its spatial distribution on coffee plants. This work aimed to report the occurrence of this potential in Minas Gerais and study its their spatial and temporal distribution dynamics on crops of Coffea arabica. The study was conducted in coffee plants in Ponte Nova and Jaboticatubas, with the evaluation of density being monthly. N. curtus was found in two areas in Minas Gerais, presenting higher densities at the edges of the crops.