Plant galls are formed from abnormal vegetative growth produced by a plant under the influence of an insect and some other organisms. Gall formation involves an intimate association between the plant host and gall maker. Galls are growing plant parts and require nutrients just like other plant parts steal vital plant food and adversely affect plant growth. This is most likely a problem when galls are numerous on very young plants. However, galls are rich in resins and tannic acid and have been used in the manufacture of permanent inks and astringent ointments, in dyeing, and in tanning. A high-quality ink has long been made from the Aleppo gall, found on oaks in the Middle EastMany galls are insect affected, modified plant products that provide nutrition for the maturing insect. In the Indian subcontinent, approximately 2000 different types of galls have been reported in gall flora.

Image: Galls of Gnetum scandens.

Nearly 90% of gall producing insects are host specific, displaying a high level of capability to particular species of plants. The gall insects are preferential not only in their choice of the plant species but also highly specific to the plant organs and tissues. On a global scale, the gall-inducing capability exists principally within Thysanoptera, Hemiptera, Diptera and Hymenoptera, whereas Lepidoptera and Coleoptera include relatively less number of gall-inducing species. Gall-inducing capability arose more than once in Agaonidae, Eulophidae, Eurytomidae, Pteromalidae, Tanaostigmatidae and Torymidae. The families of Chalcidoidea associated with plant galls in widely varying degrees of dependence are Aphelinidae, Encyrtidae, Trichogrammatidae, Eupelmidae, Mymaridae, Ormyridae, and Chalcididae.
Image: Galls of Lannea coromandelica.

In Bangladesh, Sixteen gall plants under ten diverse families, viz. Anacardiaceae, Apocynaceae, Combretaceae, Euphorbiaceae, Fabaceae, Gnetaceae, Lauraceae, Moraceae, Myrtaceae and Tiliaceae were recorded from different areas of Bangladesh. Three gall making insects are identified namely, Procontarinia matteina Kieffer & Cecconi (Diptera: Cecidomyiidae), Thrips sp. (Thysanoptera: Thripidae) and Blastophaga psenes (L.) (Hymenoptera: Agaonidae) which were reared from Mangifera indica, Erythrina variegata and Ficus racemosa as well as F. heterophylla respectively (Mazumdar et al. 2014; Table 1).


  Table 1 Gall plants and reared insects from plant galls 
Scientific name of
Gall plants
Economic importance of the host plant
The infected part of the host plant
Collection month
The scientific name of gall producing insects
(family name in parenthesis)
Lannea  coromandelica (Houtt.) Merr.

Softwood

Leaf

August

Insects not identified
Mangifera indica L.
Fruit & wood
Leaf
May
Procontarinia matteina (Diptera: Cecidomyiidae)
Alstonia scholaris. (L.) R. Br.
Medicinal  & Softwood
Leaf
May
Insects not identified
Terminalia arjuna (Roxb. ex DC.) Wight & Arn.
Medicinal & wood
Leaf
August
Insects not found
Bridelia retusa (L.) A. Juss
Firewood
Leaf
August
Insects not found
Bridelia stipularis (L.) Blume
Firewood
Leaf
August
Insects not found
Glochidion multilocularae (Rotller ex Wild) Voigt
Firewood
Stem, the auxiliary part
and leaf
August
Insects not found
Mallotus nudiflorus (L.) Kulju & Welzen
Softwood
Leaf
July
Insects not identified
Erythrina variegata L.
Wood, Hedge & Ornamental
Petiole
Aug.-Dec.
Thrips sp.
(Thysanoptera: Thripidae)
Pongamia pinnata (L.) Pierre
Medicinal  & Softwood
Fruit, Leaf, and Petiole
May-Dec.
Insects not found
Gnetumscandens Roxb.
Fiber
Leaf
June
Insects not identified
Cinnamomum   tamala (Buch.-Ham.) Nees & Eberm.
Spice & Wood
Leaf and Stem
June-Aug.
Insects not identified
Ficus heterophylla. L.f.
Medicinal  & Softwood
Leaf
June-July
Blastophaga psenes (♂)
(Hymenoptera: Agaonidae)
Ficus racemosa L.
Medicinal  & Softwood
Leaf
August
Blastophaga psenes (♂)
(Hymenoptera: Agaonidae)
Syzygium nervosum A. Cunn.ex DC.
Medicinal & wood
Leaf
July-Aug.
Insects not identified
Microcos paniculata L.
Softwood
Leaf
August
Insects not identified
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