The pea leafminer, Chromatomyia horticola (Goureau) (Diptera: Agromyzidae) is a polyphagous and serious pest of peas. In India, this pest is attacked by many parasitoids and among them Diglyphus horticola Khan (Hymenoptera: Eulophidae) is an important one, however, demographics and pest-kill potential of this parasitoid has not been studied so far. This study presents the first report on its demographics and pest-kill potential on C. horticola. The parasitoid showed three modes of host-killing behaviour viz. host-feeding, parasitism and host-stinging. The parasitoid females killed more number of hosts by parasitism than host-feeding or host-stinging. The pre-adult survival, net reproductive rate, intrinsic rate of increase (rm) and finite rate of increase (λ) were higher on the 5-days old host larvae than those reared on the 3-days old larvae. Demographics and pest-kill parameters of D. horticola were also better on 5-days old host larvae than on 3-days old host larvae. Based on the study, D. horticola appeared to be a promising biocontrol agent for the suppression of C. horticola in peas and could be promoted through conservation biological control. Further studies are required to standardize the mass production protocol and release rates to use the parasitoid by augmentation.

In spite of the fact that since the end of the eighties, the horse chestnut leafminer, Cameraria ohridella, has established itself throughout Europe, native predators such as ants and birds are not attuned to this neozoic species. In contrast, several parasitic wasp species already started to exploit the invasive horse chestnut leafminer, but until now parasitation rates are quite low, mainly because of asynchrony in the lifecycles of parasitoids and host. Only the removal of leaf litter, in which pupae hibernate, is at the moment a strategy to reduce the infestation level in the next year. Unfortunately, not only hibernating horse chestnut leafminers but also parasitoids are removed, and important resources for biocontrol are unused. In the current study, we investigated the potential efficiency of the horse chestnut leafminer parasitoid complex extracted from leaf litter in defined environments. Parasitoids were released at different densities to investigate density dependence in parasitation rates.

Although seven different species were released in our experiments, only Pnigalio agraules turned out to be responsible for biocontrol of C. ohridella. We recorded parasitation rates of up to 35%. Overall, parasitation rates were independent of the leafminer density but increased fourfold if ten times more parasitoid individuals were released. Unfortunately, none of the parasitoid species could be established in the experimental units in the long run. Results are compared to other parasitoid-leafminer systems, and promotion of horse chestnut leafminer parasitoids to support natural selection and biological control of the horse chestnut leafminer is discussed.

Parasitoid fitness depends largely on the capability to locate a host in an ecosystem. A parasitoid of a polyphagous host might not be able to find or to access the host in all its feeding niches. This study evaluated the niche selection of Hyssopus pallidus (Askew), a larval parasitoid of Cydia pomonella (Linnaeus), at the plant level with the goal of assessing its potential for biological control on different fruit crops throughout the plant cycle. Parasitoid behaviour during host location and reproduction rate were investigated on host caterpillars actively feeding on apple, pear, apricot or plum, and on caterpillars diapausing under the bark. Under laboratory conditions, the host searching behaviour of H. pallidus varied depending on the fruit species offered and the infestation of the fruits. Parasitoid females searched longer on apples than on other fruit species, and they searched longer on infested than on uninfested apples. Female wasps were able to locate and parasitize host caterpillars under the tree bark, and their behaviour did not vary with host accessibility. The numbers of caterpillars attacked by H. pallidus depended on the fruit species. The highest numbers of caterpillars were parasitized in apples and apricots. Their accessibility (i.e. position) within the fruit or on the branch did not influence parasitism success. Although hosts were parasitized throughout the season, the best results were achieved with early and late releases. Therefore, the host niche selection behaviour of H. pallidus most likely co-evolved with the host C. pomonella on apples, which renders H. pallidus a valuable biocontrol agent for successful release at different times of the season into apple orchards.

Aleurolobus barodensis (Maskell) was more abundant than Neomaskellia andropogonis Corbett on sugar-cane in Pakistan. Azotus delhiensis Lal, Eretmocerus sp., Prospaltella flava Shafee, Amitus sp. and Tetrastichus sp. parasitized nymphs and pupae of A. barodensis and E. serius Silvestri those of N. andropogonis. Chrysopa carnea Steph., Brumoides suturalis (F.), Catana parcesetosa (Sic.), Oenopia sauzeti Muls., Scymnus sp. and S. nubilus Muls. preyed on the immatures of the aleurodids.

In Peshawar valley where the crop is aerially sprayed twice a year to control Chilo infuscatellus Sn., Tryporyza nivella F., A. barodensis and Pyrilla spp., the rate of parasitism on A. barodensis was very low and its density was very high, being 330 immatures/leaf at Charsadda and 425 at Mardan in November 1979. At Sialkot (Punjab) where the crop is not sprayed, the rate of parasitism, mainly by A. delhiensis and Amitus sp., at this time was 22% and the density of A. barodensis was 70.4 immatures/leaf. The maximum rate of parasitism was 71% in January. The abundance of A. barodensis in Peshawar valley seems to be due to the mortality of natural enemies because of aerial spraying, therefore, judicious use of insecticides and redistribution of natural enemies in these areas is recommended.