TOXICIDADE DE ÓLEO DE NIM PARA PUPAS E ADULTOS DE CHRYSOPERLA EXTERNA (HAGEN) (NEUROPTERA: CHRYSOPIDAE)

Susceptibility of Chrysoperla externa (Hagen, 1861) (Neuroptera: Crysopidae) to insecticides used in coffee crops

The coffee crop hosts pests such as mites, mealybugs, and aphids which serve as food for the predator Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae). The preservation of this chrysopid in coffee agroecosystem is very important to achieve sustainability of this agricultural sector, and can be obtained by applying low toxicity insecticides. The present study aimed to evaluate the susceptibility of C. externa to azadiracthin, chlorpyrifos, ethiprole and teflubenzuron. Predator eggs, third instar larvae, pupae and adults were exposed to insecticides by Potter tower spraying. When evaluating exposure of C. externa eggs we observed that chlorpyrifos, ethiprole and teflubenzuron reduced larvae hatching, while azadiracthin prolonged first instar duration. Meanwhile, the exposure of third instar larvae to chlorpyrifos and ethiprole caused mortality of all insects after 72 h, while azadiracthin prolonged the larval development time; we also observed that no compound allowed the formation of adults. After pupae were exposed to chlorpyrifos and teflubenzuron, it was observed a reduction on the emergence of adults, while the longevity of adults from these pupae and the evaluated reproductive parameters were reduced by all insecticides. For the bioassay with adults, chlorpyrifos, ethiprole and teflubenzuron reduced the longevity of insects, while the reproductive parameters evaluated were negatively affected after exposure to azadiracthin and teflubenzuron. It was concluded that all insecticides negatively affected at least one biological characteristic of the predator in at least one of the insect's developmental stages, requiring further research in semi-field and field conditions to prove its toxicity.

Lethal and Sublethal Toxicity of Insecticides to the Lacewing Ceraeochrysa Cubana

The lethal and sublethal effects of 11 insecticides on the predator Ceraeochrysa cubana (Hagen) were assessed under laboratory conditions. First-instar larvae and adults ≤ 48 h old were sprayed with the highest insecticides doses allowed to control Diaphorina citri Kuwayama in the citrus crop. The survival and duration rates of the different development stages, sex ratio, pre-oviposition period, fecundity, and fertility of the insects were evaluated. In the larval bioassay, chlorpyrifos and malathion had lethal effect which none larvae survived. Azadirachtin, lambda-cyhalothrin + chlorantraniliprole, lambda-cyhalothrin + thiamethoxam, and thiamethoxam had lethal and sublethal effects that did not allow to estimate the life table parameters because the low number of couples formed. Esfenvalerate, imidacloprid WG and SC, phosmet, and pyriproxyfen had sublethal effects which were reflected in the net reproductive rate and in the intrinsic rate of natural increase. In bioassay using adults, none of the individuals survived in the chlorpyrifos, lambda-cyhalothrin + chlorantraniliprole, lambda-cyhalothrin + thiamethoxam, malathion, or thiamethoxam treatments, and the azadirachtin, esfenvalerate, imidacloprid WG and SC, phosmet, and pyriproxyfen treatments were significantly lower compared to the control. None of the insecticides was harmless to first-instar larvae and adults of C. cubana under laboratory conditions showing their potential to reduce the efficiency of this predator.

Are the Pupae and Eggs of the Lacewing Ceraeochrysa cubana (Neuroptera: Chrysopidae) Tolerant to Insecticides?

The tolerance of Ceraeochrysa cubana (Hagen) pupae and eggs to 11 insecticides was evaluated under laboratory conditions, based on lethal and sublethal effects. Eggs at three ages (≤24-h-old, 48- to 72-h-old, and 96- to 120-h-old) and pupae at ≤48-h-old were used. All the insecticides were considered harmless when applied at the pupal stage. Phosmet and pyriproxyfen insecticides were considered harmless to eggs irrespective of the age. Esfenvalerate was harmless to eggs at the ages of ≤24-h-old and 48- to 72-h-old. Imidacloprid SC and azadirachtin were harmless to eggs at ages of 48- to 72-h-old and 96- to 120-h-old, and thiamethoxam was only harmless to eggs at 96- to 120-h-old of age. In contrast, chlorpyrifos and malathion were harmful to eggs at the age of 96- to 120-h-old, and imidacloprid WG was slightly harmful to the three egg ages evaluated. Lambda-cyhalothrin + chlorantraniliprole and lambda-cyhalothrin + thiamethoxam were slightly and/or moderately harmful to all egg ages evaluated. Based on the life table parameters, the insecticides thiamethoxam, imidacloprid SC, phosmet, pyriproxyfen, and azadirachtin did not affect the net rate of reproduction (Ro) of C. cubana. Lambda-cyhalothrin + chlorantraniliprole decreased the Ro and increased the population doubling time (Td) independently of the egg ages evaluated. Therefore, the insecticides pyriproxyfen and phosmet are compatible with eggs of the predator C. cubana, but other insecticides should be evaluated under field conditions to verify their effects on the predator.