Pentatomid stinkbugs are important predators of defoliating caterpillars in agricultural and forestry systems, and knowledge of the impact of insecticides on natural enemies is important information for integrated pest management (IPM) programs. Thus, we assessed the toxicity and behavioral sublethal response of the predators Podisus nigrispinus and Supputius cincticeps exposed to deltamethrin, methamidophos, spinosad and chlorantraniliprole, insecticides commonly used to control the velvetbean caterpillar (Anticarsia gemmatalis) in soybean crops. With the exception of deltamethrin for S. cincticeps, all insecticides showed higher acute toxicity to the prey than to these natural enemies providing effective control of A. gemmatalis. The recommended field concentration of deltamethrin, methamidophos and spinosad for controlling A. gemmatalis caused 100% mortality of P. nigrispinus and S. cincticeps nymphs. Chlorantraniliprole was the less toxic and the most selective insecticide to these predators resulting in mortalities of less than 10% when exposed to 10× the recommended field concentration for a period of 72 h. Behavioral pattern changes in predators were found for all insecticides, especially methamidophos and spinosad, which exhibited irritability (i.e., avoidance after contact) to both predator species. However, insecticide repellence (i.e., avoidance without contact) was not observed in any of the insects tested. The lethal and sublethal effects of pesticides on natural enemies is of great importance for IPM, and our results indicate that substitution of pyrethroid and organophosphate insecticides at their field rates by chlorantraniliprole may be a key factor for the success of IPM programs of A. gemmatalis in soybeans.
Feeding behavior can explain how predaceous Pentatomidae use different food sources as a result of ecological and evolutionary changes. This study describes the salivary glands of adults of the predator Supputius cincticeps (Stål) (Heteroptera: Pentatomidae) to assist in understand the feeding habits of this natural enemy. A pair of principal and accessory glands in the prothorax form the salivary system of S. cincticeps. The principal glands are bilobed with a spherical anterior lobe and are smaller than the posterior lobe, which has a prolonged sack form. The accessory glands are present in a long and tubular form that arises from the terminal portion of the curved accessory duct. The salivary system of S. cincticeps presents the same morphological pattern of other Asopinae predators.
Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) is a common natural predator of defoliating caterpillars in agricultural and forest systems. Insecticides acting as growth regulators of insect pests can indirectly affect their predators through consumption of contaminated prey. We examined the reproductive performance of P. nigrispinus fed on caterpillars of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae) reared on soybean leaves exposed to the chitin synthesis inhibitor, diflubenzuron. Caterpillars of A. gemmatalis were fed for 12 h with treated soybean leaves and offered to adults of the predator P. nigrispinus over five consecutive days. The fertility of P. nigrispinus was reduced when feeding on diflubenzuron treated caterpillars, especially at the beginning of the reproductive period, but recovered 3 weeks later. The effects of diflubenzuron ingestion on the life table parameters of P. nigrispinus included an increase in the period taken to double the population size, and reductions in the intrinsic rate of population increase, generation duration, and net reproductive rate. Diflubenzuron therefore had an indirect negative effect on the reproduction and the population dynamics of the non-target predator P. nigrispinus. Clearly, its use in integrated pest management requires further evaluation.
The development and survival of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) nymphs fed on larvae of Chlosyne lacinia saundersii Doubleday & Hewitson (Lepidoptera: Nymphalidae) was studied at 25 ± 1ºC, 68 ± 10% relative humidity and 12 h photo phase. P. nigrispinus developed until the adult stage when fed on C. lacinia saundersii caterpillars. However, the survival rate of P. nigrispinus during early instars allowed this predator to complement its diet with other preys and to maintain its populations in areas with the sunflower culture
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