Bitter gourd (Momordicacharantia L.) known also as bitter apple or Bitter melon or Balsam pear, is a tropical vine belonging to the order Cucurbitales, family Cucubitaceae and genus Momordica. The plant is cultivated as medicinal as well as vegetable crop widely in India, China and South East Asia ([5]). Even though whole plant is palatable in nature, Bitter gourd is mainly grown for its fruit part. Fruits, flowers and young shoots are used as flavouring agents in various Asian dishes. Fruits are cooked with other vegetables especially in soups for the slight bitter taste. However, in Indian cuisines, fruits are mainly used after blanching or par boiling or soaking in salt water to reduce bitterness ([19]). Fruits can also be canned or pickled or dehydrated in addition to cooking or deep frying. It is considered widely as a folklore medicine against diabetes amongst the indigenous population of Asia, South America, India and East Africa ([12]). Apart from fruits, the roots, leaves and vines are used as a suppressant for tooth ache, diarrhoea and furuncle. Various products of Bitter gourd like Bitter gourd tea, which is known as gohyah or herbal tea made from dried slices of bitter gourd, are gaining popularity as herbal medicine ([11]).

Researchers have proved that Bitter gourd contains an insulin like principle which is often being designated as plant insulin, which has positive effects in lowering the blood and urine glucose content ([10]). It has also been shown to have anti-cholesterol ([19]), anti-cancer ([4]), anti-dementia ([13]), anti-bacterial & anti-fungal ([16]), antioxidant and anti-inflammatory ([6]) activities. All part of the plants mainly the fruits and seeds, contain more than 60 phyto-medicines active against more than 30 diseases including cancer and diabetes ([15]).

Cucurbit fruit fly (Bactroceracucurbitae) is one of the serious pests that limits the production of cucumber. It is also known as melon fly and melon fruit fly. The extents of damage due to cucurbit fruit fly vary between 30% to 100% depending upon the season and susceptibility of the crop’s species and varieties ([8]).

When the temperatures fall below 32˚C, and the relative humidity ranges between 60% to 70%, Cucurbit fruit fly’s (Bactroceracucurbitae) abundance increases ([8]).

Chemical pesticides are generally used to control the cucurbit fruit fly. But chemical pesticides are very harmful to our environment as well as for living beings. Alternatively, bio-pesticides are plant extracts, which are less hazardous to environment. On the other hand, one kind of botanical may be effective against only one kind of insect or pest, and combination of two or more botanicals may help to control all kinds of insect in crop field. Chemical pesticides are costly in the market but bio pesticides from plant extract are cheaper and even farmers may be able to make it at their home. Botanicals are easily prepared and their use in controlling cucurbit fruit fly from local plants is sustainable ([2]).

Therefore, the present study was conducted to examine some botanicals having insecticidal activity against cucurbit fruit fly and to identify the effect of botanical extracts on growth and yield of bitter gourd.

Botanicals are traditional and non-synthetic protectants derived from plants. Traditionally, different types of plant parts are used for the protection of agricultural produce; these plants are available in many developing countries and contain several active ingredients and act in different ways under different circumstances ([9]). Botanicals break down rapidly to harmless metabolites and appear less likely to build up genetic resistance to targeted species. They are also less harmful to mammals and other beneficial organisms ([17]).

This experiment was carried out to evaluate the effects of 13 plant extracts on fruit fly infestation. Aqueous extracts of botanicals may act as effective insecticides against cucurbit fruit fly (Bactroceracucurbitae) of Bitter gourd.

Table 2 shows the effect of botanicals on number of fruits per plant and fruit fly infestation in first experiment. The highest number of fruits per plant (30.67 ± 2.08a) was observed in pesticide treatment. The extract of 10% Custard apple leaves treatment showed 2^nd highest (26.33 ± 4.16ab) number of fruits per plant. The 10% Custard apple leaves treatment kept about 2.26 times better performance than that of control treatment (Table 2).

The number of fruits infested by cucurbit fruit fly was regularly monitored during this study. Table 2 shows the effect of botanicals on numbers of fruits infested by cucurbit fruit fly. The highest percentage (71.43%) of fruits infested (8.33 ± 4.16bcd) by cucurbit fruit fly was found in control treatment. The lowest percentage (14.13%) infestation (4.33 ± 1.53d) of cucurbit fruit fly was found in Pesticide treatment. Among the botanicals lowest percentage (41.67%) infestation (6.67 ± 0.58cd) of cucurbit fruit fly was found in 10% Ginger treatment. In 10% Custard apple leaves treatment the percentage of fruits infestation (11.33 ± 3.21abc) was 43.04%.

Table 2.Fruits per plant and fruits infested by cucurbit fruit fly (1^st Experiment).

[22] found a less number of Cucurbit fruit fly attack on cucumber in 10% Ginger treatment. Only 7.06% fruits were infested by Cucurbit fruit fly. The Ginger treatment reduced 14.17 times Cucurbit fruit fly infestation compared to control.

Zingiberene, shogaol, and gingerol are the active components of ginger that give Ginger its potent biopescidal qualities ([21]).

Custard apple extract with methanol solvent were found effective to toxic and residual effects against pulse beetle ([1]).

A laboratory study was conducted on the deterrent effect of different aqueous plant extracts against pulse beetle, Callosobruchusmaculatus (Fabricius) (Coleoptera: Bruchidae) in stored seeds of cowpea, Vigna unguiculata(L.). Among different aqueous extracts of plants materials, maximum percentage of oviposition deterrence was observed in custard apple seed extract (67.19%), custard apple leaf extract (65.95%). The maximum adult emergence reduction was seen in custard apple seed extract (78.45%), custard apple leaf extract (77.14%) ([7]).

Custard apple extract showed the highest efficiency (80% and 76%) reduction against the aphid and the mite in hydroponic cucumber cultivated under greenhouse conditions ([20]). The crude oils from seeds of custard apple at 2.5 and 5 percent concentrations significantly reduced leaf damage caused by S.litura larvae ([3]).

[14] isolated two insecticidal compounds from the seeds of Annona squamosa. One was identified as annonin (squamocin) and the other was characterized as a novel dihydroxy-bistetrahydrofuran fatty acid lactone (acetogenin) with 35 carbons. These two compounds were toxic to eggs, larvae and adults of the fruit fly.

These observations are similar with the present findings.

Table 3 shows the effect of botanicals on average fruit size of Bitter gourd (cm). The Pesticide treatment showed the best performance on average fruit size (14.23 ± 0.95a) of Bitter gourd and the extract of Custard apple leaves treatment showed 2^nd best fruit size (14.00 ± 0.61ab) whereas the lowest fruit size (9.53 ± 0.67g) was found in Banana leaves treatment.

Table 3 shows the effect of botanicals on total yield of Bitter gourd (gm). The Pesticide treatment showed the best performance on yield (2621.50 ± 130.37a) of Bitter gourd. The 2^nd best yield (1472.33 ± 153.01b) was found in Custard Apple leaves treatment. The Custard Apple leaves treatment kept about 5.33 times better performance on Bitter gourd yield than that of control treatment (Table 3).

Table 3. Effect of botanicals on Bitter gourd fruit size and yield (1^st Experiment).

Further 2^nd experiment was carried out, which was dose dependent, (10% and 20%) of three best botanicals which ranked up to 2^nd position among the botanicals in 1^st experiment in respect of low fruit fly infestation (Ginger and Custard Apple) and higher fruit size (Custard Apple and onion) and yield (Custard Apple and onion) to confirm the efficacy of these botanicals (Table 4).

Table 4.Description of treatments of 2^nd experiment.

In second experiment highest number of fruits per plant (32.33 ± 2.08a) was observed in pesticide treatment. The extract of Custard apple leaves 20% solution treatment showed 2^nd highest (28.00 ± 1.00b) number of fruits per plant. Here the Custard apple leaves treatment kept about 3.36 times better performance than that of control treatment (Table 5).

Table 5.Fruits per plant and fruits infested by cucurbit fruit fly (2^nd Experiment).

Table 6.Effect of botanicals on Bitter gourd fruit size and yield (2^nd Experiment).

The highest percentage (68.00%) of fruits infested (5.67 ± 2.08c) by cucurbit fruit fly was found in control treatment. The lowest percentage (13.40%) infestation (4.33 ± 1.53c) of cucurbit fruit fly was in pesticide treatment. The 2^nd lowest percentage (38.30%) of fruits infestation (6.00 ± 1.00c) was found in Ginger 20% solution. Custard apple leaves 20% solution treatment showed 41.67% fruits infestation (11.67 ± 2.08a) (Table 5).

Table 6 shows the effect of botanicals on average fruit size (cm) and yield (g) of Bitter gourd. The Pesticide treatment showed the best performance on average fruit size (14.50 ± 0.50a) of Bitter gourd and the extract of onion 20% solution treatment showed 2^nd best fruit size (14.33 ± 0.76a).

Table 6 also shows the effect of botanicals on total yield of Bitter gourd (gm). The Pesticide treatment showed the best performance on yield (2844.73 ± 261.91a) of Bitter gourd. The 2^nd best yield (1618.17 ± 102.00b) was found in 20% Custard Apple leaves solution treatment. The 20% Custard Apple leaves treatment kept about 7.50 times better performance on Bitter gourd yield than that of control treatment (Table 6). [18] found that the application 20% solution of Annona squamosa (Custard Apple) leaves enhance the growth, increased production and suppressed insect pest attack on jute in experimental field.

The present study revealed that Cucurbit fruit fly infestation was significantly reduced by some botanical extracts. Out of thirteen botanicals, Ginger (Zingiber officinale) 20% solution treatment showed best performance for the control of cucurbit fruit fly infestation in experimental Bitter gourd field.

A low fruit fly infestation was also found in the Custard apple (Annona squamosa) leaves 20% solution treatment. This treatment also produced the highest production of Bitter gourd among the tested botanicals.

Therefore, Ginger rhizome and Custard apple leaves 20% solution can be used as bio-pesticides in Bitter gourd field to manage the cucurbit fruit fly infestation in eco-friendly way.

This research was conducted self-funded by the authors.

Md. Kaysar Ikbal: carried out the field experiment, data collection, data analysis and writing; Tashfia Tashnim Dia: helped in monitoring pest infestation; Mst. Samia Sultana: helped in data analysis and Md. Abul Kalam Azad: conceptual design of research work, supervision and review and editing of manuscript.