Secondary pest outbreak is a counterintuitive ecological backlash of pesticide use in agriculture that takes place with the increase in abundance of a non-targeted pest species after pesticide application against a targeted pest species. Although the phenomenon was well recognized, its alternative causes are seldom considered. Outbreaks of the southern red mite Oligonychus ilicis are frequently reported in Brazilian coffee farms after the application of pyrethroid insecticides against the coffee leaf miner Leucoptera coffeella. Selectivity favoring the red mite against its main predatory mites is generally assumed as the outbreak cause, but this theory has never been tested. Here, we assessed the toxicity (and thus the selectivity) of deltamethrin against both mite species: the southern red mite and its phytoseid predator Amblyseius herbicolus. Additionally, behavioral avoidance and deltamethrin-induced hormesis were also tested as potential causes of red mite outbreak using free-choice behavioral walking bioassays with the predatory mite and life-table experiments with both mite species, respectively. Lethal toxicity bioassays indicated that the predatory mite was slightly more susceptible than its prey (1.5×), but in more robust demographic bioassays, the predator was three times more tolerant to deltamethrin than its prey, indicating that predator susceptibility to deltamethrin is not a cause of the reported outbreaks. The predator did not exhibit behavioral avoidance to deltamethrin; however insecticide-induced hormesis in the red mite led to its high population increase under low doses, which was not observed for the predatory mite. Therefore, deltamethrin-induced hormesis is a likely cause of the reported red mite outbreaks.

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Lethal concentration (LC) has been widely used to estimate pesticide toxicity. However, it does not consider the sub-lethal effects. Therefore we included the instantaneous rate of increase in association with LC to estimate population-level effects of the acaricides fenbutatin oxide and sulfur on the predator Iphiseiodes zuluagai and its prey, the phytophagous southern red mite, Oligonychus ilicis. The predator was 32.84x and 17.20x more tolerant to fenbutatin oxide and sulfur, respectively, than its prey, based on LC50 estimates obtained from acute concentration-mortality bioassays. The instantaneous rate of population growth in both mite species decreased with increasing acaricide concentration. Both acaricides provided effective control of O. ilicis at their recommended concentrations, but sulfur drastically compromised the predator populations quickly leading them to extinction due to the low reproductive potential of this species compared with its prey.

A produção integrada é um sistema agrícola que objetiva produzir alimentos de boa qualidade de acordo com os requerimentos de sustentabilidade ambiental, segurança alimentar e viabilidade econômica. Apesar de ainda não existirem projetos de produção integrada de morango, técnicas de controle biológico e de resposta induzida a herbivoria poderiam ser utilizadas no controle de ácaros fitófagos do morangueiro. Nesta revisão, serão discutidas estas técnicas de manejo de ácaros dentro do contexto da produção integrada de morango.

The predatory mite Phytoseiulus macropilis is a potential biological control agent of the two-spotted spider mite (TSSM) Tetranychus urticae on strawberry plants. Its ability to control TSSM was recently assessed under laboratory conditions, but its ability to locate and control TSSM under greenhouse conditions has not been tested so far. We evaluated whether P. macropilis is able to control TSSM on strawberry plants and to locate strawberry plants infested with TSSM under greenhouse conditions. Additionally, we tested, in an olfactometer, whether odours play a role in prey-finding by P. macropilis. The predatory mite P. macropilis required about 20 days to achive reduction of the TSSM population on strawberry plants initially infested with 100 TSSM females per plant. TSSM-infested plants attract an average of 27.5 ± 1.0% of the predators recaptured per plant and uninfested plants attracted only 5.8 ± 1.0% per plant. The predatory mites were able to suppress TSSM populations on a single strawberry plant and were able to use odours from TSSM-infested strawberry plants to locate prey in both olfactometer and arena experiments. Hence, it is concluded that P. macropilis can locate and reduce TSSM population on strawberry plants under greenhouse conditions.

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-Plants of strawberry Fragaria x ananassa may present mechanisms of direct and indirect defenses against herbivores. Such defenses may influence behaviour and development of phythophagous mites and their natural enemies, thereby reducing herbivory rate. We tested the effect of pre-infestation of strawberry plants by Tetranychus urticae Koch on the development and reproduction of the mite species. Strawberry plants (cultivar IAC Campinas) were divided into two groups: plants without and plants with pre-infestation of T. urticae. The length of immature phases, the number of eggs per female and the survival of mites were not altered by the pre-infestation. These results may be associated to either the absence or low level of induced resistance of the cultivar IAC Campinas or perhaps the pre-infestation was insufficient to induce defenses. The reported resistance of this cultivar to T. urticae could be related to indirect defenses.KEY WORDS: Fragaria x ananassa, two spotted spider mite, induced resistance RESUMO -Plantas de morangueiro Fragaria x ananassa podem apresentar mecanismos de defesa direta e indireta contra herbívoros. Tais defesas podem alterar o comportamento e o desenvolvimento dos ácaros fitófagos e seus inimigos naturais, reduzindo a taxa de herbivoria. Testou-se o efeito da pré-infestação de plantas de morangueiro por Tetranychus urticae Koch sobre o seu desenvolvimento e reprodução. Plantas de morangueiro cultivar IAC Campinas foram divididas em dois grupos: plantas limpas e plantas pré-infestadas por T. urticae. A infestação prévia de plantas de morangueiro por T. urticae não alterou a duração das fases imaturas, a fecundidade e a sobrevivência das fêmeas do ácaro. Tais resultados podem estar associados à inexistência ou baixo nível de resistência induzida da cultivar IAC Campinas, ou ainda, ao fato de a pré-infestação ter sido insuficiente para induzir defesa. Assim, a resistência relatada na cultivar IAC Campinas a T. urticae pode estar relacionada às defesas indiretas.

The spined soldier bug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) is a generalist predator that can alternatively feed on plant tissue to survive under prey scarcity. This research aimed to evaluate the effects of plant feeding forced by a shortage of prey on the survival and reproduction of P. nigrispinus on Eucalyptus urophylla S.T. Blake (Myrtaceae) plants in the field. Podisus nigrispinus adults were enclosed on branches of eucalyptus by using gauze bags. These adults were fed daily with Tenebrio molitor pupae (T1) or after 5 (T2), 10 (T3) or 15 (T4) days from mating to simulate prey shortage. The pre-oviposition period, number of egg masses, number and viability of eggs and longevity of females were evaluated. Females of P. nigrispinus had a longer pre-oviposition period and produced lower number of egg masses as the period of prey shortage increased. However, the average number of eggs per egg mass, emergence of nymphs and longevity of P. nigrispinus females were not affected by prey shortage. Females of P. nigrispinus can survive 15 days without prey by feeding on eucalyptus leaves and if it finds prey afterwards can still reproduce. This shows that plant feeding is a successful incidental strategy to survive periods of food scarcity (and thus increase the efficiency) of this predator as a biological control agent.