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Background The successful rearing of predators or parasitoids is one of the most important elements in biological control programs. The dried fruit mite, Carpoglyphus lactis (L.), can be used as an alternative prey for the phytoseiid predatory mite, Amblyseius swirs0kii (Athias-Henriot). Main body This study aimed to evaluate the suitability of 3 different diets for C. lactis when rearing A. swirskii: brown sugar, baker’s yeast, and the mixture of brown sugar and baker’s yeast along with 3 initial predator:prey ratios (1:7, 1:12, and 1:20). After 30 days, both the baker’s yeast and the mixture of brown sugar + baker’s yeast diets resulted in the highest predator densities (40.5 times increase at an initial predator:prey ratio of 1:20, with the baker’s yeast diet), whereas the mixture diet produced the highest density of prey. The brown sugar resulted in the lowest number of predator and prey mites. This may be due to lower feeding and predation rates of the prey and the predator mites on the brown sugar medium since its relative moisture content and adhesiveness inhibits mite movement. The final predator:prey ratio was also highest on the baker’s yeast diet. Conclusions This study demonstrated that the population growth of A. swirskii was the highest when C. lactis was reared on baker’s yeast.

Because of their importance and abundance as predators of pest insects in agroecosystems around the world, eight species of lacewings from four genera (Apertochrysa, Chrysopa, Chrysoperla, and Dichochrysa) were investigated to evaluate their performance when reared on eggs of Ephestia kuehniella Zeller, a factitious prey commonly used in mass rearing systems. In particular, a comparative assessment of trash-carrying versus naked species (ones not carrying trash on their backs) was performed. We measured the developmental times and survival rates of the eight green lacewings and compared these characteristics between trash-carrying and naked lacewing species. Survival during immature development was higher (77–87%) for the two naked species (Chrysopa pallens (Rambur) and Chrysoperla suzukii (Okamoto)) than for the trash-carrying species D. alcestes (33%). Immature and larval developmental times were significantly longer among the trash-carrying species than the naked species. The rapid development of naked green lacewings may be a strategy to decrease predation risk by aphid guarding ants and intra-guild predators.

Pilophorus typicus (Distant) (Heteroptera: Miridae) is a predatory bug occurring in East, Southeast, and South Asia. Because the active stages of P. typicus prey on various agricultural pest insects and mites, this species is a candidate insect as an indigenous natural enemy for use in biological control programs. However, the mass releasing of introduced natural enemies into agricultural fields may incur the risk of affecting the genetic integrity of species through hybridization with a local population. To clarify the genetic characteristics of the Japanese populations of P. typicus two portions of the mitochondrial DNA, the cytochrome oxidase subunit I (COI) (534 bp) and the cytochrome B (cytB) (217 bp) genes, were sequenced for 64 individuals collected from 55 localities in a wide range of Japan. Totals of 18 and 10 haplotypes were identified for the COI and cytB sequences, respectively (25 haplotypes over regions). Phylogenetic analysis using the maximum likelihood method revealed the existence of two genetically distinct groups in P. typicus in Japan. These groups were distributed in different geographic ranges: one occurred mainly from the Pacific coastal areas of the Kii Peninsula, the Shikoku Island, and the Ryukyu Islands; whereas the other occurred from the northern Kyushu district to the Kanto and Hokuriku districts of mainland Japan. However, both haplotypes were found in a single locality of the southern coast of the Shikoku Island. COI phylogeny incorporating other Pilophorus species revealed that these groups were only recently differentiated. Therefore, use of a certain population of P. typicus across its distribution range should be done with caution because genetic hybridization may occur.

The harmful side effects of 11 pesticides, 5 acaricides, and 10 fungicides on nymphs and adults of the predatory mirid bug Pilophorus typicus Distant (Heteroptera: Miridae) were determined by dipping them into solutions of each chemical. Two insect growth regulators (IGRs), buprofezin and cyromazine, were not harmful to nymphal survival of P. typicus on the fifth day. Flufenoxuron, lufenuron, and novaluron (also IGRs) were seriously harmful to nymphal survival of P. typicus on the fifth day. IGRs that were deleterious to nymphal survival were probably harmful because they regulated molting. Three insecticides, buprofezin, cyromazine, and pyridalyl; one acaricide, bifenazate; and four fungicides, boscalid, captan, iprodione, and triadimefon, were found to be inert pesticides for nymphs and adults of P. typicus.

The functional response of the indigenous green lacewing Chrysoperla nipponensis (Okamoto) and the imported green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) feeding on seven different densities of the cotton aphid Aphis gossypii (Glover) (Homoptera: Aphididae) was studied under laboratory conditions at 20°C. C. nipponensis and C. carnea have shown a Type II functional response based on logistic regression analysis. The maximum number of prey eaten by C. carnea was higher than C. nipponensis. Handling time decreased at 24 h for both species, but was higher for C. nipponensis at 12 and 24 h than for C. carnea. The attack coefficient of C. nipponensis was slightly higher than C. carnea in second and third instars. These results indicate that C. carnea may eat more aphids at high prey densities; however, C. nipponensis could be considered a prospective candidate for use as a commercial biological control agent for aphids in Japan. C. nipponensis will become more important than C. carnea from the viewpoint of environmental safety because it is a native species adapted to the Japanese environment, and non-target effects can be avoided.

In order to establish the optimal thermal conditions for mass rearing of the predatory mirid bug Pilophorus typicus, we investigated the effect of temperature on the development and fecundity of this bug at 6 constant temperatures (17.5, 20.0, 22.5, 25.0, 27.5, and 30.0°C) under a 16L8D photoperiod. The developmental period of P. typicus from egg to adult at different temperatures was not affected by sex. The developmental zero (T0) and thermal constant (K) of females from egg to adult were 12.0°C and 357.1 day-degrees, respectively. The corresponding values for males were 12.1°C and 357.1 day-degrees, respectively. The mean generation time (T) of P. typicus decreased with an increase in temperature from 17.5°C to 30.0°C. Among the temperatures investigated, the net reproductive rate (R0) was highest at 25.0°C, whereas the highest intrinsic rate of natural increase (rm) occurred at 27.5°C. These results indicate that the optimal temperature for the mass rearing of P. typicus is between 25.0°C and 27.5°C.

To elucidate the defensive functions of the trash-package of the green lacewing Mallada desjardinsi larva against the ladybird Harmonia axyridis, the contact frequency, attack rate, and capture rate of ladybirds were compared between the ‘with trash’ or ‘naked’ treatments of the green lacewing. The contact frequency until the ladybird captured the green lacewing was significantly more in the ‘with trash’ treatment (median: four times) than in the ‘naked’ treatment (median: one time), which indicates that the trash-package of the green lacewing offers protection from predation by ladybirds. The attack rate of the ladybirds on the ‘with trash’ green lacewing larvae (55%) was significantly lower than that on the ‘naked’ ones (90%). After the ladybirds first attacked, their capture rate of the ‘with trash’ green lacewing larvae (18%) was significantly lower than that of the ‘naked’ ones (83%). Thus, the trash-package of the green lacewing affords prevention against recognition (primary defense) and subjugation (secondary defense) from the ladybird.

To search for a useful biological control agent and to determine the optimal rearing conditions for the green lacewings Mallada desjardinsi and Chrysoperla nipponensis, thermal effects on development, survival, and adult body size were examined at seven constant temperatures (15.0, 17.5, 20.0, 22.5, 25.0, 27.5, and 30.0°C) with a photoperiod regime of 16L : 8D (h). The developmental zero of M. desjardinsi larvae was higher than that of C. nipponensis larvae. The developmental zeros of C. carnea and C. nipponensis in earlier reports were similar to that of C. nipponensis in the present study. On the other hand, that of M. desjardinsi in earlier studies was somewhat higher than that of M. desjardinsi in the present study. A lower survival rate of C. nipponensis was observed in the cocoon stage at 15.0°C. On the other hand, lower survival rates of M. desjardinsi were observed in the egg stage at 30.0°C and in the cocoon stage at 15.0, 27.5 and 30.0°C. The body size of both green lacewings was affected by temperature throughout the range tested. Smaller body sizes of M. desjardinsi and C. nipponensis adults were observed at 15.0, 27.5 and 30.0°C. These results indicate that C. nipponensis has a wider optimum range of temperature for immature development than M. desjardinsi.

The predatory mirid Pilophorus typicus (Heteroptera: Miridae) is a potential biological control agent against Bemisia tabaci (Hemiptera: Aleyrodidae), but the sucking for host plant is unknown. To investi­ gate collaboration use of P. typicus and nicotinoid granules and to confirm the sucking for pepper plant, resid­ ual harmful toxicity of 4 nicotinoids: acetamiprid; imidacloprid; nitempyram; and thiamethoxam on P. typi- cus adult were investigated at 7, 14 21, 28 and 35 d after treatment of the nicotinoid granules. The sys­ temic toxicity of these nicotinoids was found to be moderately or seriously harmful. The residual toxicity was persistent for 35 d after application at the growing points of the pepper plant. The mortality of P. typicus due to the 4 nicotinoids was significantly higher than that due to the control treatment, which indicated that P. typicus sucked the active ingredient of the nicotinoid granules along the nutrition and/or water from the growing point of pepper plant. For this reason, P. typicus will be one of zoophytophagous mirids.

The developmental and reproductive characteristics of a mealybug, Phenacoccus solani, were investigated at 20, 25, and 30°C and a photoperiod of 16L : 8D. The total developmental periods of the immature stages and the pre-reproductive period of adults decreased significantly with increased temperatures. Survival rates of immature stages were high at all temperatures. The number of offspring produced per female was significantly lower at 30°C than at other temperatures. Adults lived significantly longer at 20°C than at other temperatures. Generation time was longest at 20°C. The net reproductive rate and the intrinsic rate of natural increase were highest at 25°C.