Several braconid and aphelinid parasitoids, midges, lacewings, and ladybird beetles are used to control aphids in greenhouses. Here, I review three topics as ecological bases for the biological ...control of aphids in a protected culture: the preliminary evaluation of biological control agents, natural enemy release strategies, and the effects of intraguild predation (IGP) on biological control. A comparison of several parasitoid species was conducted to select agents for the biological control of aphids; the intrinsic rate of natural increase was a useful criterion in the preliminary evaluation. To compare predators as biological control agents, the aphid‐killing rate must be considered as a critical criterion, rather than reproductive criteria. The banker plant system (open rearing system) is used as a release method for Aphidius colemani and other natural enemies of aphids. Continuous release of parasitoid adults, which is the important characteristic of this method, has a stabilizing effect on population fluctuation in the aphid–parasitoid system. Two species of natural enemies can be used to control aphids in greenhouses. When one parasitoid and one predator are used simultaneously in a greenhouse, IGP of the parasitoid by the predator can occur, but the effect of IGP is less important in greenhouses than in the field.
Oviposition by aphidophagous predators is triggered by semiochemicals emitted from aphids and host plants, such as volatile chemicals from host plants infested by aphids and from honeydew and aphid ...alarm pheromones.
Aphidoletes aphidimyza
(Rondani) (Diptera: Cecidomyiidae) is a common, widely distributed aphidophagous predator that is used as a biological agent to control aphids in greenhouses. Previous work showed that a volatile chemical emitted from honeydew produced by
Aphis gossypii
Glover (Hemiptera: Aphididae) on eggplants (
Solanum melongena
L.) attracted adult female
A
.
aphidimyza
, and identified it as phenylacetaldehyde. There are no known oviposition stimulants for
A
.
aphidimyza
females and the function of herbivory-induced plant volatiles (HIPVs) produced by eggplants infested by
A
.
gossypii
is not clear. Therefore, this study investigated the effects of HIPVs from eggplants induced by
A. gossypii
infestation and volatile chemicals in honeydew produced by
A
.
gossypii
on the oviposition of
A
.
aphidimyza
in bioassay cages. We found that HIPVs from
A
.
gossypii
-infested eggplants-induced oviposition. Moreover, using gas chromatography coupled with mass spectrometry, we identified 6-methyl-5-hepten-2-one, nonanal, and decanal as the HIPVs from eggplants. A mixture of these three compounds-induced oviposition of significantly more eggs than the control, but fewer eggs than the eggplant–aphid complex. Honeydew did not induce oviposition of significantly more eggs than the control. In conclusion, oviposition by
A
.
aphidimyza
females was induced by HIPVs from
A
.
gossypii
-infested eggplants. But the statistical difference in the number of oviposited eggs between the honeydew treatment and uninfested eggplant was not significant.
Zoophytophagous bugs feed on both arthropod pests and plants, and can survive or reproduce solely on particular plants. This characteristic ensures their survival when released as natural enemies ...when the density of target pests is low. When using zoophytophagous bugs, exotic species or strains should be avoided as biological control agents due to their ecological risks. This study reviews investigations of indigenous
Orius
species and indigenous strains of
N. tenuis
and their exploitations as biological control agents in Japan.
Orius strigicollis
, which can reproduce under short-day conditions, is recommended for augmentative biological control in greenhouses.
Orius sauteri
, the predominant and most abundant species in the field, is not recommended for releases in greenhouses because it enters diapause under short-day conditions. However, this species can be used for conservation biological control in the field, where the bug can be preserved through the use of selective pesticides or by conserving companion plants. Violet light illumination is a promising tool to manipulate the movement of this species in the field.
Nesidiocoris tenuis
occurs only in the southern region of Japan, and its density in the field is low. This bug can be used for augmentative biological control in greenhouses. It can reproduce on specific plants, including
Sesamum indicum
,
Cleome hassleriana
,
Verbena
×
hybrida
, and
Scaevola aemula
. These plants can be used as banker plants to improve the establishment and reproduction of
N
.
tenuis
in greenhouses. Indigenous
Orius
species and
Nesidiocoris tenuis
are promising biological control agents in Japan.
To develop an augmentative biological control programme for
Bemisia tabaci
(Gennadius) (Hemiptera: Aleyrodidae) and
Thrips palmi
Karny (Thysanoptera: Thripidae) using
Nesidiocoris tenuis
(Reuter) ...(Hemiptera: Miridae), we studied the life history traits of a Japanese strain of
N. tenuis
reared on
B. tabaci
and
T. palmi
in controlled environments. The lower developmental threshold during the nymphal period was far higher than those estimated for Spanish, Moroccan, and Iranian strains, indicating that the Japanese strain is better adapted to higher temperatures than the other three strains tested. The intrinsic rate of increase
r
m
was highest at 30 °C and lowest at 20 °C. The
r
m
value for individuals reared on
T. palmi
at 25 °C was lower than that for individuals reared on
B. tabaci
at the same temperature. Implications of these results for the biological control of
B. tabaci
and
T. palmi
in greenhouses are discussed.
Many natural enemies of insects use honeydew as a volatile cue to locate hosts or prey, as an oviposition stimulant, and as an arrestant for foraging. The aphidophagous gall midge Aphidoletes ...aphidimyza (Rondani) (Diptera: Cecidomyiidae) has predacious larval stages and can be used to control aphid populations, especially in greenhouses. Previous studies have shown that the honeydew, excreted by the aphid Myzus persicae, attracts A. aphidimyza, but the crucial attractants have not been identified. Using an olfactometer, we studied behavioral responses of female A. aphidimyza to volatiles emitted from honeydew excreted by the aphid Aphis gossypii on eggplants. The volatiles attracted female midges and induced oviposition. Moreover, using gas chromatography coupled with mass spectrometry (GC/MS), we identified phenylacetaldehyde as the attractant compound in the honeydew, although it did not induce oviposition in olfactometer experiments.
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•Aphidoletes aphidimyza adults feed on aphid honeydew.•We analyzed the sugar compositions of aphid honeydews.•Sucrose caused the greatest increase in the longevity of A. ...aphidimyza.•Additional sucrose increased the fecundity of A. aphidimyza even when aphid honeydew was available.
The predatory gall midge Aphidoletes aphidimyza, which is used for augmentative biological control of aphids in greenhouses, uses aphid honeydew as an energy source. Currently, Rhopalosiphum padi on barley plants and Melanaphis sacchari on sorghum plants are used as the banker plant systems for A. aphidimyza to control Aphis gossypii on eggplant in Japan. We analyzed the sugar components of the honeydew of these three species by HPLC. The major components of honeydew were sucrose, fructose, and melezitose for A. gossypii; glucose and fructose for R. padi; and glucose, fructose, and melezitose for M. sacchari. Maltose and trehalose were minor components of the honeydew of these species. We investigated the influence of sugars, including three artificial aphid honeydews, six sugar components, and distilled water, on the longevity of unmated A. aphidimyza. Both females and males attained the greatest longevity on sucrose and artificial honeydew of A. gossypii. Mean longevities of both females and males were shortest when they were provided only with water. We conducted another experiment in which a mated female was released in a cage with an eggplant seedling infested with A. gossypii and fed with sucrose or only water. Females fed with sucrose lived significantly longer and had higher lifetime fecundity than those fed only water.
Crypsis can be either defensive or aggressive in function, and the first evidence that crypsis reduces the probability of being detected by a predator was collected almost a century ago. Crypsis in ...mantids may reduce the probability that a mantid will be detected by its prey, but no experiments have been carried out to test this idea. We tested the hypothesis that the approach strategy of the mantid Tenodera aridifolia (Stoll) toward prey when the wind is blowing is adaptive. Significantly less time elapsed between the discovery of the prey by the predator and capture action under windy conditions than under windless conditions. Approach behaviors (walking and body swaying) were observed more frequently under windy than under windless conditions. When the wind stopped, mantids became still, and they changed their behavior in response to alternately changing wind conditions. Moreover, the discovery rate of the predator mantids by conspecific prey mantids was significantly lower on swaying leaves than on fixed leaves. The capturing rate of the prey by the mantid was significantly higher under windy conditions than under windless conditions. We suggest that the strategy of approaching prey quickly when the wind blowing is adaptive for reducing the risk of discovery and escape by the prey.
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