Sugar preferences of western corn rootworm larvae in a feeding stimulant blend

Feeding behaviour, feeding intensity and staying behaviour of neonate western corn rootworm larvae (Diabrotica virgifera virgifera LeConte) were evaluated in response to synthetic feeding stimulant blends to determine larval preferences among the three maize root sugars (glucose, fructose and sucrose) in the active blend and to determine whether any single sugar can substitute for the 3-sugar combination in a feeding stimulant blend. These experiments demonstrated the strong affinity that western corn rootworm larvae have for the natural sugars found in maize roots and also showed that sucrose is the most preferred of the three primary maize root sugars. The blend containing sucrose at 30 mg/ml elicited feeding that was not significantly different than the natural glucose:fructose:sucrose blend. In subtraction bioassays, removal of sucrose from the blend resulted in significantly fewer larvae feeding. When the three-sugar blend was substituted with one of the number of various mono-, di-or trisaccharides, fewer larvae fed on all of the treatments compared to the blend with sucrose, except for the blend with maltose. In feeding choice tests, larvae preferred a blend containing sucrose over blends with either glucose or fructose, but larvae chose equally between a blend with sucrose and a blend containing the three-sugar mixture found in maize roots. Based on these results, a feeding stimulant blend with glucose (30 mg/ml), fructose (4 mg/ml) and sucrose (4 mg/ml) elicits the strongest feeding response, but sucrose alone, in amounts equivalent to the total maize root sugar concentration (30 mg/ml), could serve as a substitute for the 3-sugar mixture in a synthetic feeding stimulant blend

Repellent Effects of Methyl Anthranilate on Western Corn Rootworm Larvae (Coleoptera: Chrysomelidae) in Soil Bioassays

Methyl anthranilate (MA), a compound in maize roots that is repellent to western corn rootworm larvae (Diabrotica virgifera virgifera LeConte) was tested in behavioral bioassays in a soil environment. MA prevented larvae from locating roots of a maize seedling, and the repellency strengthened with increasing rates of MA. In a simple push– pull strategy between an MA-treated seedling and an untreated seedling, granules containing 0.1 mg/g MA pushed larvae to the untreated seedling. This push effect increased with dose, with 90% repellency observed for the highest dose tested (100 mg/g). Chemical analysis showed that MA concentrations remained high for 4 wk in dry, sterilized or unsterilized soil, but declined rapidly in moist soil. After 7 d, 50% less MA was recovered in moist, sterilized soil than in dry soil, and only a trace of MA remained in unsterilized moist soil, suggesting that both moisture and microbial activity contributed to the loss of MA. Various (MA) carrier granules were tested in bioassays after aging in moist soil. After 1 d, all of the MA granules were repellent at the 10 mg/g rate and clay granules were also effective at 1 mg/g. After 1 wk, only molecular sieve granules elicited repellency, but that activity disappeared after 2 wk. These results demonstrate that MA is repellent to western corn rootworm larvae in the soil environment and may have potential as a rootworm treatment if formulations can be developed that protect the material from decomposition in the soil

FIP200 claw domain binding to p62 promotes autophagosome formation at ubiquitin condensates

The autophagy cargo receptor p62 facilitates the condensation of misfolded, ubiquitin-positive proteins and their degradation by autophagy, but the molecular mechanism of p62 signaling to the core autophagy machinery is unclear. Here, we show that disordered residues 326-380 of p62 directly interact with the C-terminal region (CTR) of FIP200. Crystal structure determination shows that the FIP200 CTR contains a dimeric globular domain that we designated the "Claw" for its shape. The interaction of p62 with FIP200 is mediated by a positively charged pocket in the Claw, enhanced by p62 phosphorylation, mutually exclusive with the binding of p62 to LC3B, and it promotes degradation of ubiquitinated cargo by autophagy. Furthermore, the recruitment of the FIP200 CTR slows the phase separation of ubiquitinated proteins by p62 in a reconstituted system. Our data provide the molecular basis for a crosstalk between cargo condensation and autophagosome formation

Repellent Effects of Methyl Anthranilate on Western Corn Rootworm Larvae (Coleoptera: Chrysomelidae) in Soil Bioassays

Methyl anthranilate (MA), a compound in maize roots that is repellent to western corn rootworm larvae (Diabrotica virgifera virgifera LeConte) was tested in behavioral bioassays in a soil environment. MA prevented larvae from locating roots of a maize seedling, and the repellency strengthened with increasing rates of MA. In a simple push– pull strategy between an MA-treated seedling and an untreated seedling, granules containing 0.1 mg/g MA pushed larvae to the untreated seedling. This push effect increased with dose, with 90% repellency observed for the highest dose tested (100 mg/g). Chemical analysis showed that MA concentrations remained high for 4 wk in dry, sterilized or unsterilized soil, but declined rapidly in moist soil. After 7 d, 50% less MA was recovered in moist, sterilized soil than in dry soil, and only a trace of MA remained in unsterilized moist soil, suggesting that both moisture and microbial activity contributed to the loss of MA. Various (MA) carrier granules were tested in bioassays after aging in moist soil. After 1 d, all of the MA granules were repellent at the 10 mg/g rate and clay granules were also effective at 1 mg/g. After 1 wk, only molecular sieve granules elicited repellency, but that activity disappeared after 2 wk. These results demonstrate that MA is repellent to western corn rootworm larvae in the soil environment and may have potential as a rootworm treatment if formulations can be developed that protect the material from decomposition in the soil

Sugar preferences of western corn rootworm larvae in a feeding stimulant blend

Feeding behaviour, feeding intensity and staying behaviour of neonate western corn rootworm larvae (Diabrotica virgifera virgifera LeConte) were evaluated in response to synthetic feeding stimulant blends to determine larval preferences among the three maize root sugars (glucose, fructose and sucrose) in the active blend and to determine whether any single sugar can substitute for the 3-sugar combination in a feeding stimulant blend. These experiments demonstrated the strong affinity that western corn rootworm larvae have for the natural sugars found in maize roots and also showed that sucrose is the most preferred of the three primary maize root sugars. The blend containing sucrose at 30 mg/ml elicited feeding that was not significantly different than the natural glucose:fructose:sucrose blend. In subtraction bioassays, removal of sucrose from the blend resulted in significantly fewer larvae feeding. When the three-sugar blend was substituted with one of the number of various mono-, di-or trisaccharides, fewer larvae fed on all of the treatments compared to the blend with sucrose, except for the blend with maltose. In feeding choice tests, larvae preferred a blend containing sucrose over blends with either glucose or fructose, but larvae chose equally between a blend with sucrose and a blend containing the three-sugar mixture found in maize roots. Based on these results, a feeding stimulant blend with glucose (30 mg/ml), fructose (4 mg/ml) and sucrose (4 mg/ml) elicits the strongest feeding response, but sucrose alone, in amounts equivalent to the total maize root sugar concentration (30 mg/ml), could serve as a substitute for the 3-sugar mixture in a synthetic feeding stimulant blend

« Identification des groupes techniques à partir d'exemples du XVe siècle »

The susceptibility of western corn rootworm, Diabrotica virgifera virgifera LeConte, larvae to nine insecticides from five different classes and to Bt proteins eCry3.1Ab and mCry3A in the presence or absence of feeding stimulants, was estimated in filter paper and diet toxicity assays, respectively. The use of a synthetic feeding stimulant blend of the sugars glucose, sucrose, and fructose plus linoleic acid at a ratio of 30:4:4:0.3 mg/ml of distilled water was evaluated to determine whether they increase the efficacy of insecticides and Bt proteins. The efficacy of thiamethoxam diluted in solutions with feeding stimulants was significantly increased when compared to thiamethoxam dilutions in water (\u3e60-fold). Differences in the efficacy of the other insecticide classes when diluted in feeding stimulant solutions were no greater than fivefold when compared to the insecticides diluted in water. The presence of corn root juice as a natural feeding stimulant diminished toxicity of the insecticides, except for thiamethoxam, even though larval fresh weight was higher when fed on root juice compared to feeding stimulant or water. The use of feeding stimulants in diet toxicity assays did not enhance efficacy of eCry3.1Ab nor mCry3A proteins. Feeding stimulants can be recommended in combination with thiamethoxam to increase larval mortality. These results are discussed in terms of applicability of feeding stimulants to improve susceptibility of western corn rootworm larvae to pesticides in general

Comportamento de larvas de Diabrotica speciosa (Coleoptera: Chrysomelidae) em resposta ao CO2 e a plântulas de espécies cultivadas Behavioral responses of Diabrotica speciosa (Coleoptera: Chrysomelidae) larvae to CO2 and seedlings of host plants

As respostas de larvas de Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) ao CO2 e o comportamento destas larvas quando expostas a plantas hospedeiras e não hospedeiras foram estudadas em laboratório. Larvas de primeiro ínstar de D. speciosa foram utilizadas. Num primeiro bioensaio, as larvas preferiram o tratamento com CO2, que foi gerado a partir da reação de bicarbonato de potássio com ácido acético em oposição a água destilada. Quando se observou o comportamento das larvas em relação a plantas hospedeiras, verificou-se que ocorreu um número significativamente maior de "mudanças de direção" em milho e milho pipoca do que em feijão, soja, trigo e sorgo. Este parâmetro foi inferior no sorgo em relação a todos os outros tratamentos. Valores similares foram verificados em milho pipoca e milho (26,2 e 24,2, respectivamente). Em relação a distância percorrida, foram verificadas maiores distâncias na aveia em comparação com milho pipoca, milho, feijão e sorgo. Após o contato das larvas com sorgo, elas não apresentaram comportamento de busca, pois a larva caía da plântula ou não se movia .<br>Responses of Diabrotica speciosa (Germar) (Coleoptera: Chrysomelidae) larvae to CO2 and their behavior when exposed to host and non host plants were studied in the laboratory. First instar larvae of D. speciosa were used. In a first bioassay, larvae preferred the treatment with CO2, from the reaction of the potassium bicarbonate and acetic acid, in opposition to distillated water. When the behavior of the larvae was observed in response to host plants, a significant higher number of turns was found in corn and popcorn than in common beans, soybean, wheat and sorghum. Sorghum differed from all other treatments with a lower number of turns. Similar values were found in popcorn and corn. The greater distances ranged were found on oats in comparison to pop corn, corn, common beans and sorghum. After contact with sorghum seedlings larvae did not present searching behavior because they fell from the seedling or no movements were saw seen