Brinjal Shoot and Fruit Borer (BSFB)(Leucinodes orbonalis Guenee)

Introduction

Brinjal Shoot and Fruit Borer (BSFB) is a monophagous pest (feeds only on Brinjal). It is very important pest on brinjal owing to its feeding habit. By habit, it is an internal borer which damages the tender shoots and fruits. The normal reactive measures like spraying pesticides do not solve the problem. The usage of highly systemic poisons at a very high frequency that makes the vegetables poisonous, ecologically unsafe and economically unviable. This excessive pesticide usage threatens the health of farmers and consumers, besides making eggplant fruit more costly to consumers. In the meantime, the insect is becoming tolerant to the chemicals, making it more difficult to control. But if we understand the nature and behavior of each life stage of the cycle, it is easy to replace poisonous chemicals with knowledge, local resources and skills. Brinjal shoot and fruit borer (BSFB) (Leucinodes orbonalis Guenee) is a major insect pest of brinjal in Asia, which causes serious damage especially during the fruiting stage. The percent  fruit  infestation  caused  by  the  pest  reached  up  to  90.86%  (Rahman,  1997). Various insects  cause enormous losses to this vegetable throughout the  season in Bangladesh as well as in Indian sub- continent (Alam, 1969 and Dhankar, 1988), among them brinjal shoot and fruit borer (BSFB),  Leucinodes orbonalis Guenee, is the most serious and  destructive one. Due to the attack of this pest considerable damage is occurred each year affecting the quality and yield of the crop. Only the larvae of this pest cause 12-16 % damage to shoots and 20-60% to fruits (Alam, 1970; Maureal et al., 1982). The pest is very active during the rainy and summer season and often causes more than 90% damage (Ali et al., 1980; Kalloo, 1988). The yield loss has been estimated up to 86% (Ali et al., 1980) in Bangladesh and up to 95% (Naresh et al., 1986) in India.

Distribution

L. orbonalis is reported from regions of aubergine cultivation in Africa, south of the Sahara, and South-East Asia, including China and the Philippines. In South Asia it is widely spread in Bangladesh and India. A little presence in Nepal is found.

Host Range

Major hosts: Solanum melongena (aubergine), Solanum tuberosum (potato)

Minor hosts: Ipomoea batatas (sweet potato), Lycopersicon esculentum (tomato), Pisum sativum var. arvense (Austrian winter pea), Solanum indicum, Solanum myriacanthum, Solanum torvum (turkey berry)

Wild hosts: Solanum gilo (gilo), Solanum nigrum (black nightshade)

Morphology

Eggs - Creamy white egg

Larva - Pink in color

Pupa- Grayish boat shaped cocoon

Adults are white with a characteristic wing pattern. The wing span of the adult is 18-24 mm. Forewing is antemedian field brown, the median field with a large brown patch near the inner margin, reniform stigma brown. In the postmedian field, a black patch is present near the apex. A black patch is on the cross-vein of the cell in hind wing. Postmedian line diffuse, black with some black spots in the postmedian field.

Biology

Egg. Adult females lay eggs on the foliage (Figure 1). The number of eggs laid by an average female varies from 80 to 253. Oviposition takes place during the night and eggs are laid singly on the lower surface of the young leaves, green stems, flower buds, or calyces of the fruits. Eggs are flattened, elliptical, and 0.5 mm in diameter. They are creamy-white soon after they are laid, but change to red before hatching. Eggs hatch in 3 to 6 days. Prabhat Kumar and Johnsen (2000) found that adults were most active between 02.00 and 06.00 h. Most of the feeding, mating and egg laying occurred during this period, which lasted about 16 minutes. Eggs were laid in the early hours of the morning, singly or in batches on the ventral surface of the leaves.

Larva. Soon after hatching from eggs, young caterpillars search for and bore into tender shoots near the growing point, into flower buds, or into the fruits. Caterpillars prefer fruits over other plant parts. Larvae go through at least five instars (Atwal, 1976) and there are reports of the existence of six larval instars. Larval period lasts 12 to 15 days in the summer and up to 22 days in the winter. (Prabhat Kumar and Johnsen, 2000) A total of six larval instars have been recorded. Climatic conditions are important in the life cycle of the borer. As temperature increases and humidity decreases, fecundity increases and the duration of the life-cycle decreases. The larval period was the longest, followed by pupal and egg stages. Sandanayake and Edirisinghe (1992) studied the larval distribution on mature eggplant in Sri Lanka. They found first instars in flower buds and flowers, second instars in all susceptible plant parts, third and fourth instars in shoots and fruits, and fifth instars mostly in fruits. Larval feeding in fruit and shoot is responsible for the damage to eggplant crop. A full-grown larva measures 18 to 23 mm in length.

Pupa. Mature larvae come out of their feeding tunnels and pupate in tough silken cocoons among the fallen leaves and other plant debris on the soil surface near the base of eggplant plants. The color and texture of the cocoon matches the surroundings making it difficult to detect (Figure 1). Some studies indicate the presence of cocoons at soil depths of 1 to 3 cm. The pupal period lasts 6 to 17 days depending upon temperature.

Adult. Moths come out of pupal cocoons at night. Young adults are generally found on the lower leaf surfaces following emergence. EFSB females are slightly bigger than males. The abdomen of the female moth tends to be pointed and curl upwards, whereas the male moth possesses a blunt abdomen. The moth is white but has pale brown or black spots on the dorsum of thorax and abdomen. Wings are white with a pinkish or bluish tinge and are ringed with small hairs along the apical and anal margins. The forewings are ornamented with a number of black, pale, and light brown spots. The moth measures 20 to 22 mm across the spread of wings. Longevity of adults was 1.5 to 2.4 days for males and 2.0 to 3.9 days for females. The pre- Oviposition and Oviposition periods were 1.2 to 2.1 and 1.4 to 2.9 days, respectively (Mehto et al., 1983).

Baang and Corey (1991) reported six larval instars in the Philippines. The egg, larval and pupal periods were 6, 15 and 11.5 days, respectively; the average longevity of males and females was 4 and 7.5 days, respectively.

Mehto et al. (1983) reported that in India the egg, larval and pupal periods were 5.4, 17.5 and 9.8 days, respectively; the lifespan of adult males and females was 1.5-2.4 and 2.0-3.9 days, respectively. The number of eggs produced per female ranged from 84.5 in January to 253.5 in May.

In Ghana, the young larvae bore into young axillary shoots causing wilting. They enter the fruits and plug the small entrance holes with excreta. Fruits contain up to 20 larvae (Frempong, 1979).

Sandanayake et al. (1992a) determined the larval instars by measuring the size of the head capsules; they also studied larval distribution on aubergine in Sri Lanka. First-instars larvae were found in flower buds and flowers; second-instars larvae were present in all susceptible parts of the plant; larvae were confined to the shoots and fruits in the third and fourth instars; and fifth-instars larvae were found only in the fruits.

Nature of Damage

Bore Hole

Within one hour after hatching, EFSB larva bores into the nearest tender shoot, flower, or fruit. Soon after boring into shoots or fruits, they plug the entrance hole with excreta. In young plants, caterpillars are reported to bore inside petioles and midribs of large leaves. As a result, the affected leaves may drop off (Butani and Jotwani, 1984).

Presence of wilted shoots in an eggplant field is the surest sign of damage by this pest. The damaged shoots ultimately wither and drop off. This reduces plant growth, which in turn, reduces fruit number and size. New shoots can arise but this delays crop maturity and the newly formed shoots are also subject to larval damage.

Larval feeding in flowers—a relatively rare occurrence—results in failure to form fruit from damaged flowers. The feeding tunnels are often clogged with frass. This makes even slightly damaged fruit unfit for marketing. The yield loss varies from season to season and from location to location. Damage to the fruits in India, particularly in autumn, is very severe and the whole crop can be destroyed (Atwal, 1976). EFSB is active throughout the year at places having moderate climate but its activity is adversely affected by severe cold. EFSB is practically monophagous, feeding principally on eggplant; however, other plants belonging to family Solanaceae are reported to be hosts of this pest. They include tomato (Lycopersicon esculentum), potato (Solanum tuberosum), selected nightshades (S. nigrum and S. indicum), and turkey berry (S. torvum).

Management

Cultural Method

Collection, destruction of dried shoot tips and bored fruits on campaign basis in an area is an efficient method because the larvae tend to pupate (transform into pupa and takes rest) in the plant residues itself. Burning of the infested parts and composting the crop remains is useful in preventing the buildup of the moth populations in a given area. After the final harvest, the old plants should be uprooted and burned promptly because they may harbor EFSB larvae which could become a source of future infestation. In West Bengal, India, Karmakar and Bhattacharya (2000) showed that the pest population can be maintained at well below the economic injury level (0-11.75 L. orbonalis Guen. /plot) using mechanical methods of control.

Crop rotation is beneficial as the insect survives only on brinjal. Avoid continuous cropping of brinjal crop. Intercropping brinjal with other crops like cowpea, maize, coriander should be done which improve the natural habitat for natural enemies (like spiders, lace wings, ladybirds etc) against the pest. Intercropping coriander with aubergine may be useful in IPM programmes against L. orbonalis by reducing fruit infestation and the amount of insecticide used by farmers (Khorsheduzzaman et al., 1997).

Erection of barrier around the field plot is one of the methods to control borer infestation. The net barrier is made 2-3 m height around the plot. This method restricts the movement of adult BSFB and eventually reduces the infestation. The use of the barrier along with sanitation reduces the shoot damage to an average of 62.7% compare to other without this practice (Alam et al., 2003).

Host-Plant Resistance

Several varieties of aubergine have been evaluated for resistance against infestation by L. orbonalis. Resistance in varieties SM 17-4, PBR 129-5 and Punjab Barsatiby was attributed to a large number of small fruits per plant with shorter inter/intracluster distance, late fruiting and a longer fruiting period (Dilbagh-Singh et al., 1991). Biochemical characters, such as total sugars and free amino acids, were positively correlated with fruit infestation, and polyphenol content was negatively correlated with attack (Darekar et al., 1991). Bajaj et al. (1989) suggested that the presence of glycoalkoids in association with phenolic compounds was responsible for the resistance in variety SM-17-4.

In Himachal Pradesh, India, Chaudhary and Sharma (2000) found that the aubergine variety Arka Kesav had a fruit borer incidence of 2.88 compared to 5.64 in variety SM 6-6.

The highly resistant aubergine variety, Sm-202, had tightly arranged seeds in the mesocarp (Lal, 1991). Mishra et al. (1988) attributed resistance in long-fruited varieties to thick fruit skin and closely packed vascular bundles in the pulp.

In Tamilnadu, India, Thangamani et al.( 2011) found that  the hybrid COBH-1 is the only hybrid with the highest marketable fruit yield per plant with the lowest fruit borer infestation. Two hybrids viz., COBH-1 and KBHL-3 of SAU’s and the three F1 hybrids evolved from ICAR institutes Viz., Pusa Hybrid-5, DBHL-14 and IVBHL-54 and the Private Institutes hybrids Viz., ARBH-785 and PK-123 possess higher marketable fruit yield per plant.

Hossain M. et al. (2002) reported that the brinjal shoot and fruit borer infestations for different varieties/lines were found in the following order of intensity: Nayankajal> BL095> BL085> BL098> BLO114> Khotkhotia-2> Berka> Laffa> lslampuri> BL045> Ohohazari-2> BL0101> Ohohazari-1> Khotkhotia-1> BL096> Sada ball> Singnath> Uttara> Baromashi> Jhumki.

Biological Control

Several parasitoids and predators of EFSB are prevalent in the eggplant fields in South and Southeast Asian countries. The most notable parasitoid is Trathala flavoorbitalis a tiny wasp that is harmless to humans. This wasp lays its eggs in EFSB larvae. The eggs hatch into wasp larvae that eat the EFSB larva they were laid into.

Predators
Campyloneura sp (a bug), Cheilomenes sexmaculata (a ladybird beetle), Coccinella septempunctata (seven spotted ladybird beetle), Brumoides suturalis (three striped ladybird)

Parasitoids
Pseudoperichaeta sp, Phanerotoma sp, Itamoplex sp, Eriborus argenteopilosus, Diadegma apostata

Entomopathogens
Fungus (Bipolaris tetramera), Baculovirus, Nuclear polyhedrosis virus

Spray Bacillus thuriengiensis var kurstaki @ 1500 ml/ ha (750 lit of spray fluid)

Release egg parasitoid: Trichogramma chilonis @ 50,000/ ha, four times from 30 DAT

Chemical Control

Insecticides are currently the main method of control for L. orbonalis. Contact insecticides are the most commonly used and show varying degrees of efficacy against the pest. Deltamethrin and endosulfan were the most effective insecticides used in South Asia (Thanki and Patel, 1991).

In field experiments conducted in Andra Pradesh, India, triazophos and methomyl were applied when >20% of aubergine fruits were infested; highest fruit yields and return were obtained with triazophos (Radhika et al., 1997).

From the survey done in Orissa, India (Babu et al.,2002) it is found that the most commonly used insecticide in the field was carbaryl, followed by endosulfan, carbofuran and cypermethrin. In the nursery, however, majority of the farmers (81.4%) did not follow any control measures, and only 13.00% of the farmers used carbaryl spray. Majority of the farmers (41.7%) followed a 7- to 8-day spraying, and nearly 30% followed a 9- to 12-day spraying.

Spray endosulfan 35 EC @ 2 ml/lit + neem oil 2ml/lit, Quinalphos 25 EC @ 1ml/lit + neem oil 2ml/lit, Neem seed kernel extract (NSKE) 5 %

Sharma and Chhibber (1999) tested deltamethrin, endosulfan and neem oil against L. orbonalis in India. Six sprays of Deltamethrin was the most economical treatment and neem oil treatment was the least economical. Kumar and Babu (1998) compared two commercial neem formulations against each other and against endosulfan. A 5% Azadirachtin treatment showed more ovipositional deterrent effects than a 1% formulation of endosulfan. However, endosulfan was superior with respect to ovicidal effects.

A combination of cypermethrin/deltamethrin and triazophos/endosulfan sometimes combined with cartap hydrochloride and diflubenzuron gave higher yields than non-treated plots; cypermethrin/deltamethrin mixtures were most effective Kumar et al., 2000, 2001; Biradar et al., 2001).

(Latif M.A. et al., 2006) A field experiment at Bangladesh revealed  that  spraying  of  flubendiamide  at  2%  shoot  +  2%  fruit infestation  against  the  brinjal  shoot  and  fruit  infestation  reduced  the  shoot  and  fruit infestation,  increased  the  marketable  healthy  fruit  yield  of  brinjal.  On  the  other  hand, flubendiamide  spray  at 5%  fruit  infestation gave  the similar  results  for yield of brinjal but reduced the number of insecticide application and increased about 2.5 times higher BCR. This would have positive  impact on environment,  reduce  toxic  residue  load on brinjal fruits and finally  the  cost  of  control measure would  be minimized  significantly. Therefore,  5%  fruit infestation  may  be  considered  as  the  best  threshold  for  application  of  flubendiamide  in managing the brinjal shoot and fruit borer of brinjal.

Pheremonal Control

Sex pheromones can be used to trap male EFSB moths. A 2-3 mg pheromone sample contained in porous plastic tube, when baited in a suitable trap and placed in the field, can attract male moths continuously for up to 6 weeks.

It is the smell of the pheromone seeping from the lure tube that attracts male EFSB moths. They enter the trap, fly around the lure, and fall into the soapy water and die. It is important that the soapy water inside the trap is replenished often to make sure the trap is never dry, or else the moths will not be killed. This trap can last at least one season.

No matter what type of pheromone trap is used, the lure tube should always be kept closed. Pheromone chemical seeps slowly and uniformly from this tube. Traps should be erected in the field starting 3-4 weeks after transplanting until the last harvest. A distance of 10-15 m should be maintained between traps in the field. The traps are hanged in such a way that the lure is just above the plant canopy. This will require that the traps be moved higher as plants grow taller.

Cork et al. (2001) optimized different blends of the female sex pheromone in West Bengal, India. Blends containing 1 and 10% E11-16/OH caught more male L.orbonalis than E11-16Ac alone. Different trap structures were evaluated in the study.

Chatterjee H. (2009) developed module with three components i.e. pheromone trap, timely mechanical control and application of azadex (neem based insecticides), which was found most effective in reduction of shoot damage (76.59%) followed by the farmer's practice (i.e. twenty times application of insecticides) (76.36%).

IPM

Islam et al. (1999) investigated the management of L. orbonalis using insecticides applied at 10% action threshold level (ATL) and at the peak of adult emergence (POAE), and by applying mechanical control which resulted in the reduced applications (4-7) compared to scheduled sprays (16) and reduce the fruit damages. The benefit cost ratio (BCR) (12-15) was about three times lower than in the ATL and POAE treated plots (28-38). A hymenopterous parasitoid wasp of L. orbonalis was less affected in the IPM intervention plots than in the scheduled spray plots.

Sasikala et al. (1999) compared the efficacy of ecologically friendly methods of control in Bapatla, India. Treatments included neem seed kernel extract, neem oil, Bacillus thuringiensis var. kurstaki, lufenuron, carbaryl, combination treatments, mechanical removal and the destruction of infested shoots and fruits, and release of the egg parasitoid, Trichogramma japonicum. Mechanical destruction of infested shoots and fruits, neem oil and the release of T. japonicum gave good control of L. orbonalis compared to the control. Plots treated with neem oil, neem oil + Bt, neem oil+ lufenuron, and neem oil + carbaryl gave higher fruit yield than the untreated control plots.

Chakraborti (2001) assessed the effectiveness of a biorational integrated approach for the management of aubergine Pusa Purple Cluster L. orbonalis using the application of fresh neem cake in the nursery at land preparation, every 30 days after transplanting, foliar application of neem seed kernel extracts at 7-day intervals beginning 30 days after transplanting, root zone application of benzene once every 30 days after transplanting, clipping and destruction of infested plant parts, and a single application of carbofuran 30 days after transplanting. A low mean shoot and fruit infestation (4.92 and 5.32%, respectively) was recorded with this treatment whereas the chemical method, failed to afford adequate protection and recorded 20.42 and 25.24% mean shoot and fruit infestation, respectively.

Sudhakar et al. (1998) studied the influence of fertilizers and insecticides on the damage potential of L. orbonalis. A higher dose of potash along with the chemical treatments carbaryl + dicofol, malathion and bifenthrin were effective against L. orbonalis; the percentage of aubergines damaged on a weight basis was also low in these treatments. A lower dose of potash resulted in higher shoot (14.4%) and fruit (44.3%) infestation, on a par with the control. The highest marketable fruit yields, 7.7 and 6.7 t/ha, were recorded with bifenthrin and the higher dose of potash, respectively. Lowest marketable fruit yields, 1.6 and 2.1 t/ha, were obtained in plots treated with neem cake and vermicompost.

Naitam and Mali (2001) used combinations of insecticide mixtures and natural enemies in the field. The highest cost benefit ratio (1:9.95) was recorded in a treatment of B. thuringiensis var. kurstaki + monocrotophos. Rabinda and Prasad (2001) found significant suppression of L. orbonalis when aubergine was grown in association with either marigold (Tagetus erecta) or okra (Abelmosschus esculentus) in Bihar, India.

Removal and destruction of twigs/fallen leaves twice in a week + Bt @ 0.5 kg/ha showed minimum infestation of shoot (1.23 and 1.13%) and fruits (1.10 and 0.90%) and produced maximum healthy fruits over rest of the treatments in managing the shoot and fruit borer infestation is followed by neem gold @ 2 mill + mechanical removal (T1). Cypermethrin @ 0.016% and imidacloprid @ 0.015% were found next effective treatment in order of efficacy (Ghanand T., 2002).