Jack fruit is the largest tree-borne tropical fruit species found in high rainfall, coastal and humid areas of the world (Sturrock, 1959). In India, about 39 species of insects are known to attack jack fruit (Butani, 1979). Among them, the shoot and fruit borer Diaphania caesalis (Walker) is a major (Soumya et al., 2015; Soumya et al., 2019). Though ample studies have been conducted on its biology (Manjunatha et al., 2014; Soumya et al., 2019), the literature available on its management through IPM is scanty. Although pesticides generally are used to kill a particular target pest, several other non-target pests and beneficial organisms also will be killed in the process (Patil and Bheemanna, 2015). In tree crops, especially with a large canopy, like jack fruit tree application of insecticides is more difficult, and aerial sprays are found effective (Hill, 2008). However, the application of pesticides by aerial spray method can cause adverse effects on different crops, livestock, waterways and environment. Hence, IPM is a more ecofriendly approach, especially in jack fruit, where insecticide sprays on huge canopy will be a difficult task. Although IPM represents a key strategy for the control of jack fruit pests, it has not been attempted. Therefore, this study to evaluate IPM modules against D. caesalis.

Experiments were conducted in the laboratory and in the jack fruit orchards of the Indian Council of Agricultural Research- Indian Institute of Horticultural Research (ICAR- IIHR), Bengaluru (12 8’N; 77 35’E) during May 2014- December 2016. Trees selected for the study were of medium height (2.00 - 2.50 m), aged between 12 and 20 years and being pruned once in a year. Recommended agronomic practices (i.e. weeding, pruning, fertilization with minerals and organic nutrients) were followed, except pesticides. Laboratory assay was conducted with the treatments viz, neem soap (5 gm/ l), pongamia soap (5 gm/ l), N. riley WP (1.0x 10 ⁹conidia/ ml @ 10 gm/ l), B. bassiana WP (1.0x 10⁹ conidia/ ml @ 10 gm/ l), and M. anisopliae oil formulation (1.0 ×10 ⁹conidia/ml @ 0.5 ml/ l). Fresh shoots with 2 - 3 leaves were kept individually in small transparent plastic trays (12x 12x 2 cm) and were sprayed with fungal pathogens and botanicals using a hand sprayer. Different larval instars of D. caesalis were allowed to feed on treated leaves. Five replications were maintained for each treatment. Each replication consisted of 10 larvae of first, second, third, fourth and fifth larval instars. The efficacy of treatments against larval instars was evaluated in the laboratory. The mortality of larval instars was observed daily up to seven days after treatments.

Field trials were conducted in a randomized complete block design (RCBD) with different treatments in ten replications, each consisting of one tree. All treatments were imposed simultaneously once a week. Foliar sprays (5 l/ tree) of botanicals i.e. neem soap and Pongamia soap, microbial agents i.e. N. rileyi, B. bassiana and M. anisopliae and organic insecticides i.e. Dipel (Bacillus thuringiensis) and One Up (spinosad) were applied to the crop in the morning (9.00- 10.00 hr) using knapsack sprayer (Lotus knapsack sprayer, 16l). The effect of canopy shape on D. caesalis infestation was evaluated. The jack fruit trees were grouped into four categories as open type (T1), oval type (T2), round type (T3) and spreading type (T4) based on their canopy shape. Fruit bagging and hooking experiments were conducted to evaluate their effect on D. caesalis infestation. Fruits were bagged using polyethene bags (55x 85cm) after fruit set. Tiny holes were made at the bottom of the polyethene bag for aeration and escape of transpiration water/ rainwater. Hooking was done using a small sharp forceps (10x 12x 2 cm). Wax was applied on the hooked portion to prevent water from entering into the damaged fruit, which causes fruit rotting. Data on fruit infestation and fruit weight was recorded both from bagging and hooking experiments.

Light traps (white light) were installed within the field on a pole (9 m) and were secured firmly on the ground. In order to rear T. chilonis and A. stantoni in the laboratory, rice moth, C. cephalonica was cultured following the methods of Kumar and Murthy (2000) and Nathan et al. (2006). Rearing of A. stantoni was carried out from the field-collected parasitoid cocoons as well as from parasitised D. caesalis larvae. The mated females of A. stantoni were released in the field during evening hours @ 450 adults/acre/week as followed by Mitchell et al.(1997) for Cotesia (=Apanteles) plutellae. Different IPM modules evaluated- Module I (Nomuraea rileyi (WP)@10 gm/ l, pongamia soap 5 gm/ l, T. chilonis@ 45,000 adults/ ha and Apanteles stantoni@ 450 adults/ ha); Module II (Beauveria bassiana @10 gm/ l, neem soap 5 gm/ l and Apanteles stantoni @450 adults/ ha); Module III (Beauveria bassiana @10 gm/ l, T. chilonis @ 45,000 adults/ ha and Apanteles stantoni @450 adults/ ha); Module IV (Nomuraea rileyi WP @10 gm/ l, Apanteles stantoni @ 450 adults/ ha) and Module V (T. chilonis @ 45,000 adults/ ha and Apanteles stantoni @ 450 adults/ ha). Observations were recorded for assessing the suppression level of D. caesalis and population of natural enemies. From each selected plant, 30 buds were selected randomly from the upper, middle and lower canopies to record the pest population. Infestation level was recorded before and after treatments. Incidences of pests and natural enemies were assessed one day before treatment as a pretreatment observation and on the 7^th day after treatment as post-treatment observation. The data on D. caesalis damage in different canopy-types jack fruit trees, mean mortality of D. caesalis in the laboratory and in the field was subjected to one-way ANOVA followed by Tukey’s Honest Significant Difference (HSD) multiple range test (p=0.05) to find the significant difference. Student ‘t’- test was used to compare the % fruit damaged by D. caesalis in hooking and bagging experiments.

The extent of D. caessalis infestation among different canopy types of jackfruit trees was significantly different (F = 304.49.8, df = 3, 36; P < 0.05). In open and oval type of canopies, the number of damaged buds significantly less and ranged between 0.00-0.45 and 0.45 - 1.10 damaged buds/tree respectively. The pest incidence was relatively higher (6.42 - 11.00 damaged buds/tree) in trees with round canopy when compared to open and oval types. The spreading type canopy was most susceptible to the attack of the pest, which showed 10.87 - 14.40 damaged buds and significantly higher when compared to the other three canopy types. The results regarding the influence of canopy on D. caesalis infestation was similar to that of Singh and Verma (2013) who reported the greater outbreak of mango leaf webber Orthaga euadrusalis Hampson (Pyralidae: Lepidoptera) in mango orchards with a dense canopy. Greater infestation of D. caesalis in spreading type canopy could be due to the availability of more fresh shoots in these trees. The percentage of D. caesalis infestation in treated and control fruits was significantly different in both bagging (t (38) = 24.63; p < 0.05) and hooking (t (38) = 16.74; p < 0.05) experiments. The fruit damage in covered fruits was 0.5% while it was 31.65% in control. However, average fruit weight was 6.90 kg in bagging and 7.00 kg in control, which was not significantly different. The fruit infestation in hooked fruits was 5.50% while it was 39.5% fruits in control. Colour of the covered fruits was bright greenish-yellow and appearance was better than that of control fruits. The infestation of D. caesalis was lesser in bagged jack fruit as reported by Abbasi et al. (2014) in bagged guava fruits which were less infested with Bactrocera dorsalis Hendel (Tephritidae: Diptera).

The effect of biopesticides and botanicals screened against D. caesalis in the laboratory is given in Table 1. The effectiveness of N. rileyi, B. bassiana, neem soap and Pongamia soap on larvae was more in all larval instars of D. caesalis except in fifth. The mortality in fifth instar larvae was highest with pongamia soap, neem soap and B. bassiana treatments when compared to neem soap N. rileyi and M. anisopliae; mortality of D. caesalis was highest in pongamia soap (87.33%) followed by N. rileyi (80.03%), B. bassiana (79.57%), neem soap (70.81%) and M. anisopliae (27.14%) (Table 1). The present result with N. rileyi is similar to Burges (1998) and Ramanujan et al. (2003) who reported greater efficacy of N. rileyi formulation, against lepidopteran pests. Yi and Qui (1999) reported that Bt insecticide was effective in controlling D. indica. The effectiveness of T. chilonis in controlling D. caesalis was similar to that reported by Jalali and Singh (1992), Singh et al. (2004). Krishnamoorthy (2012) and Sardana et al. (2005), who reported that the inundative release of T. chilonis reduced the incidence of several lepidopteran pests. The mortality of D. caesalis was more in all the five modules of IPM. The bud damage by D. caesalis on the seventh day after treatment was significantly lesser in M- I (3.43%) followed by M- II (10.10 %), M- III (11.50 %) and M- IV (16.75 %) and M- V (17.50 %). The fruit damage in different IPM modules remained significantly lowest in M-I (5.50%) %) followed by MII (10.50%), M- III (10.59%), M- IV (11.50%) and M- V (12.50%) as compared to control (35.40 %) (Table 2).

The natural enemy (reduviids, spiders, coccinellids and A. stantoni) population did not significantly differ with IPM modules evaluated. However the parasitization by the larval parasitoid A. stantoni expressed as percentage differed significantly among the modules (Table 2). Dipel and B. bassiana has been widely used for the control of different economically important lepidopteran pests, i.e. Helicoverpa armigera (Hubner) (Noctuidae: Lepidoptera) and S. litura (Chandrakar et al., 1999; Mohammed et al., 2005). The results regarding the effect of neem in controlling D. caesalis was similar to that of Gowda (2000) who reported that neem seed kernel extract (NSKE) and neem oil and pungam (Pongamia pinnata) seed extract were effective in controlling D. pulvernlentalis in mulberry crop.

Values in parentheses square root-transformed. Means in columns followed by different alphabets significantly different (Tukey’s HSD test, p < 0.05, ANOVA).

Means in columns followed by different alphabets significantly different (p < 0.05,‘t’ test). BT- Before treatment, AT- After treatment.

References