Parasitoids
Parasitoids are a group of insects whose immature stages develop on or in the bodies of other host insects, which they eventually kill. Parasitoids of different pests are important beneficial insects present in nature. These parasitoids play a great role in minimizing several pests' populations and avoiding them to cross their economic damage levels.
In cashew, parasitoids have been recorded on several insect pests and the details are as follows.
Tea mosquito bug
Egg parasitoids
- There are three species of egg parasitoids which parasitize TMB eggs; among them Telenomus cuspis nov. (Hymenoptera: Platygastridae) is commonly recorded on the eggs of Helopeltis antonii in cashew plantations.
- Apart from this, Chaetostricha (Trichogrammatidae), Erythmeles helopeltidis (Mymaridae), Ufens sp. (Trichogrammatidae) and Gonatocerus sp. (Mymaridae) also parasitize the eggs of TMB.
- During certain months, 25-60 % parasitization of TMB eggs has been recorded. But mass culturing these egg paraistoids under laboratory conditions could not be achieved as they are host specific.
Nymphal parasitoid
A braconid parasitoid namely, Leiophron sp. is recorded as a nymphal parasitoid on Helopeltis antonii.
Parasitic mites and nematodes
Besides, a parasitic mite namely, Leptus sp. (Erythraeidae) and a mermetid nematode also occur on TMB adults, but recorded at very low intensity.
Leaf miner
The occurrence of three species of larval parasitoids namely, Chrysocharis sp., Closterocerus sp. and Aprostocetus sp. all belonging to Eulophidae were recorded on cashew leaf miner larvae at cashew plantations of ICAR-DCR, Puttur. Among these three parasitoids, Chrysocharis sp. was the dominant one (99.0 %).
Two larval parasitoids viz., Chelonus sp. and Sympiesis sp. were recorded on leaf miners in Kerala and Goa.
Cashew stem and root borer
The eggs of CSRB were recorded to be parasitized by Avetianella batocerae Ferriere (Encyrtidae: Hymenoptera) which, however is not commonly encountered.
The entomopathogenic nematodes belonging to Steinernema and Heterorhabditis are found to be effective in inducing mortality of the grubs under field conditions, which need to be further evaluated for field efficacy.
Shoot tip caterpillars
Four larval parasitoids, viz., Pristomerus sp. (Ichneumonidae), Apanteles sp. (Braconidae), Elasmus sp. (Elasmidae) and Sympiesis sp., (Eulophidae) have been recorded on shoot tip caterpillar causing parasitism.
Leaf and blossom webber
In east coast regions, leaf and blossom webber is parasitized by braconids (Apanteles spp.), elasmid (Elasmus sp., Elasmus johnstonii F.) and tachinid (Blepharella lateralis) in Andhra Pradesh and Odisha and maximum of 50 % parasitism was reported. While in Kerala, Apanteles sp., Avga choaspis (Nixon) (Braconidae) occur as parasitoid on leaf and blossom webber.
Hairy caterpillars
Braconids such as Aleiodes spp., Apanteles oblique, the chalcid, Brachymeria poithetrialis and the tachinid flies such as Blepharipa sp., Carcolia sp., Exorista sp. and Palexorista sp. are the parasitoids recorded on Lymantria ampla. While, Perilampus microgastri Ferr. (Perilampidae) is a parasitoid recorded on Metanastria hyrtaca Cram. Larvae of Euproctis scintillans is parasitized by Apenteles euproctisiphagus (Braconidae).
Mealy bugs
Apanteles sp. has been reported as a parasitoid on two tailed mealybug, Ferrisia virgata, besides Blepyrus insularis Cameron. In F. virgata, Aenasius advena Campere (Encyrtidae) has been reported to cause parasitism of 35 % in Kerala, up to 50 % in Karnataka.
Leaf folder
Cotesia sp. (Braconidae) and Chrysocharis sp. (Eulophidae) parasitize larvae of Caloptilia tiselia, a common tiny leaf folder defoliating cashew.
Tasar silk worm
Eggs of tropical tasar silkworm, Antheraea mylita (Drury) were found to be parasitized by a Chalcid parasitoid, Anastatus leithi (Walker) (Eupelmidae) for the first time at Puttur, Karnataka during August-September with 8 – 9 % parasitism.
Apple and nut borer
Three larval parasitoids viz., Panerotoma sp., (Braconidae) and Trathala flavorbitalis (Ichneumonidae) and one unidentified tiny dipteran fly occur on apple and nut borers and a maximum of 50 % parasitism has been recorded under field conditions.
