Morphological Aspects of a New Emerging Leaf Eating Caterpillar, Trilocha varians on Ficus benjamina in Pakistan

Weeping fig (Ficus benjamina) is considered an important perennial plant with 10-20 meters height (Chuenban et al., 2017). The Ficus spp. like F. benjamina has some medicinal value (Sirisha et al., 2010; Lansky et al., 2008), cultivated as ornamental plant and for landscaping purposes alongside the roads in several regions especially Pakistan (Ramzan et al., 2019a). The plants can grow well at any either high or low temperature. To improve the aesthetic value, plants are trim and converted into the numerous shapes in various regions especially in Pakistan. It has been reported that Ficus plants attacked by whitefly and mealybug (Walton and Pringle, 2004; Avery et al., 2011). Among them, Trilocha varians is the most dangerous pest of ornamental plants in several countries like the Philippines, Pakistan and India (Navasero et al., 2013; Kedar et al., 2014; Singh and Brar, 2016; Ramzan et al., 2023) and caused 100% defoliation (Kedar et al., 2014; Basari et al., 2019), has negative impact on the aesthetic value of the country (Zolotuhin and Witt, 2009; Daimon et al., 2012; Navasero et al., 2013).

During the current study has been observed that the Ficus spp. especially F. benjamina which planted alongside the roads as ornamental plants for increasing the aesthetic value of country infested by leaf eating larvae. Mostly plants have been dried due to severe attacked of a moth, have negative impact on the country, Pakistan which identified as T. varians (Ramzan et al., 2020). It is needed to check the morphological parameters of all stages of this pests on F. benjamina, so the current study conducted.

The experimental study was carried out at MNS-University of Agriculture, Multan Pakistan. The country located at Latitude 30.2°N, Longitude 71.4°E and 123-meter-high above sea level.

The eggs, larvae and pupae were collected from different sites of study area and reared them in growth chamber. The procedure of Ramzan et al. (2019a) was followed for the rearing. Each specimen like larvae, pupa and eggs were separately placed in different plastic jars. The new fleshy leaves of F. Banjamina were supplied to larvae. After emergence of new moths from pupae, a pair of both male and female was placed into new plastic jar to check the mating behavior and eggs collection. The time of mating period was recorded and after mating, presence of eggs also recorded in each jar. The eggs were collected and place into new boxes for hatching. After hatching each larva was transferred into petri dishes. For this purpose, about 30 petri dishes were used, one larva was placed in each Petri dish and after one day the diet change and new fleshy leaves were placed into Petri dishes until they reached into pupal stage. All morphological aspects were recorded in this study.

Leaf eating caterpillar, T. varians is new emerged insect pest in Pakistan. The pests mostly found on the F. benjamina from the month of May-December (Singh and Brar, 2016). The complete metamorphosis (egg, larva, pupa and adult) was recorded in T. varians. The yellow in colour, while round, flat and cake shape eggs laid by female on the dorsal and ventral surface of leaves into cluster or layers. A female in her whole life period laid about 215±33.85 eggs in 2 to 6 layers on the surface of boxes as well as dorsal side of the leaves. The incubation period was lasted for 4 to 8 days on F. benjamina which may take long time on other hosts. Before hatching, eggs converted into dark colour.

About 0.91±0.03 mm and 0.92±0.50 mm was the average width and thickness of egg, respectively. The similar statement about eggs was recorded by (Daimon et al., 2012). The egg and larva last for 4-8 days and 11-15 days, while pupa and adult stage lasts for 3-17 and 5-16 days. The similar findings were reported by (Jia and Jinxin, 1997).

There were five instars of this pest. The colour of head, thorax and abdomen of newly emerge larvae was dark brown, which is similar to the observation of (Singh and Brar, 2016). The average body length of

Table 1: Head capsule length and width, body length of different instar larva of T. varians.

first, second, third, fourth, and fifth larval instar was 2.05±0.45, 4.01±0.50, 8.60±1.45, 14.17±3.01, and 23.01 ±4.99mm, respectively.

The head length of 1st, 2nd, 3th, 4th, and 5th instars was 0.30±0.05, 0.35±0.07, 0.93±0.08, 1.67±0.40, 2.09±0.09mm, respectively, while width of 1st to 5th larval instar was 0.28±0.02, 0.38±0.05, 0.89±0.06, 1.56±0.30, 2.00±0.07mm, respectively (Table 1).

The colour of first to fourth larval instars is brown and then after 24 hours change into greyish white, which is similar to the findings of another researcher (Daimon et al., 2012). The long caudal horn was present on the dorsal side of each larva, which is similar to other researcher findings as mentioned above.

Table 2: Length, width of male and female cocoon of T. varians.

Table 3: Description of male and female pupa and longevity of male and female adult.

The length of male pupa is less than female pupal length. The average length and width of male and female cocoon is given Table 2, while description of pupa is given in Table 3. The colour of cocoon is whitish yellow and pupation occur in boat shaped silky cocoon. The larvae spun into leaves and make cocoon. Our findings are similar to (Rajavel and Shanthi, 2007). The sex difference between male and female was observed under pupation on the presence and absence of suture present on the lateral side of pupa. The suture was present in female pupa while absent in male and larval stages. Our findings are similar with (Navesro and Navasero, 2014; Daimon et al., 2012; Ramzan et al., 2019b).

The forewings and hind wings of adults were recorded pale reddish brown and greyish brown, respectively. The length of male and female wingspan was 17.44 ± 1.56, 5.66 ± 0.49 mm, respectively, while body length of male and female was 8.84 ± 0.90mm, respectively. The length of male and female forewing and hind wing is given in Table 4. During the current study has been observed that female life period is long as compared to male. The same results have been reported by (Singh and Brar, 2016; Ramzan et al., 2021). It has been reported that climatic factors affect the morphology and biological aspects of insect pests, especially T. varians (Daimon et al., 2012; Lu et al., 2016; Sibly et al., 2016; Navasero and Navasero, 2014). It should be managed by using different strategies like monitoring and installing different traps (Murtaza et al., 2019).

This is serious pest of fig. this pest has complete metamorphosis. The larval stage is most damaging stage of the pest.

The authors are highly grateful to the MNS-University of Agriculture, Multan for facilitating the present research work.

Table 4: Dimensions (mm) of adult males and female.

This is the most dangerous pest of ornamental plants in the several countries of the globe. This is first morphological study which conducted on this pest. The current study results will be proved fruitful for further researchers and help in management of this pest.

MR conducted the study and write the manuscript. UNU and SS planned the study, while all other authors critically reviewed this manuscript.

The authors have declared no conflict of interest.