Marigold as a Trap Crop Against Tomato Fruit Borer(Lepidoptera:Noctuidae)

MATERIALS AND METHODS

A field experiment was conducted at Division of Entomology, SKUAST-K, farm during kharif 2003 and 2004 to evaluate different planting combinations of tomato hybrid (Arka Vishali) with marigold in a Randomized Block Design with three replications. Twenty days old tomato hybrid and forty day old marigold seedlings were simultaneously transplanted in the field. For tomato hybrid the row-to-row distance was 75 cm and plant-to-plant distance was maintained 50 cm. Whereas, marigold seedlings were planted 25 cm apart. No insecticidal spray was used during the period of experiment and the recommended cultural practices of SKUAST-K were adopted for raising good crops of both tomato and marigold.

During the present studies the six treatments were used as detailed below:

Observation on population of tomato fruit borer plant^-1 was recorded from the selected plants of both tomato and marigold at 35, 65 and 80 Days After Transplanting (DAT).

The percentage of fruit damage was also calculated at 35, 65 and 80 days after transplanting. The fruit damage percentage was calculated by the percentage formula:

RESULTS

The data on the effect of marigold which act as a trap crop along with various combinations of tomato showed differential response to fruit borer and the resulted fruit damage by this pest was also found variable at 35, 65 and 80 days after transplanting during 2003 and 2004 at p = 0.05. At 50 days after transplanting there was a significant difference in percent fruit damage in treatments when compared with sole crop (control) at p = 0.05 during both years. However, fruit damage decreased significantly with the passage of time at 65 and 80 days after transplanting in all combinations except in case of sole tomato where it increased at different dates after transplanting.

It is quite evident from the data that average fruit damage ranged from 5.59 to 18.76% and 4.95 to 17.83% during 2003 and 2004, respectively. The lowest fruit damage was observed in 3:1 combination which recorded 5.59 and 4.95% during first year and second year as depicted in Table 1 and sole crop recorded highest fruit damage of 18.76 and 17.83 during first and second year. Observations recorded at different dates after transplanting revealed that average fruit damage in various combinations were in order of sole tomato >15:1>12:1>9:1>6:1>3:1 during both the years.

Population of larvae plant^-1 on tomato plants revealed that there was a marked difference between sole crop and intercropped tomato with trap crop at different dates of transplanting at p = 0.05 (Table 2). 3:1 combination significantly recorded lowest population than other treatment combinations but sole crop recorded the highest population which act as a control. All the treatment combinations reduced the population on tomato plants which ranged from 81.0 to 61.0 and 88.89 to 54.70% during 2003 and 2004. Treatment combination, 3:1 gave maximum reduction (81.0 and 88.89%) followed by 6:1, 9:1, 12:1 and 15:1 combination (Table 2).

Population count of larvae plant^-1 on marigold plants ranged from 0.30 to 0.86 in different treatments as compared to sole crop which trapped 1.00 larvae plant^-1 (Table 3). Trapping of larvae plant^-1 was highest in 3:1 (0.86) among the intercropped tomato during 2003 on marigold. During 2004, population of larvae plant^-1 ranged from 0.28 to 0.91 in different treatment combinations. Trapping of larvae plant^-1 was highest in 3:1 (0.91) among the intercropped tomato which was significant to sole crop and other treatments at p = 0.05.

Table 1:	Effect of marigold on the infestation of tomato fruit borer on tomato during 2003 and 2004
* DAT = Days after transplanting

Table 2:	Impact of marigold on incidence of Helicoverpa armigera on tomato during 2003 and 2004
* Larval population, ** Days after transplanting, Figures in parenthesis are percent reduction

Table 3:	Trapping of Helicoverpa armigera on marigold as a trap crop
* Larval population, ** Days after transplanting

So the trapping of larvae plant^-1 was in order of 3:1>6:1>9:1>12:1>15:1 combinations during both the years in different treatment combinations when marigold plants were used as a trap row.

DISCUSSION

Successful use of marigold as a trap crop for management of tomato fruit borer on tomato is on record (Srinivasan et al., 1994). Continuous presence of marigold, which produces abundant flowers was maintained in order to facilitate feeding for tomato fruit borer throughout tomato cropping season in different row combination because the larvae readily feed on flowers and have no tendency to migrate to tomato crop/row. In the present investigation it was observed that fruit damage was less in all combinations where tomato was intercropped with marigold and in different combination treatments where the marigold plants were too away, the level of infestation on the main crop was higher. Further, fruit damage decreased in both years as tomato plant becomes more hardly at advanced growth stages and therefore the infestation was low at 65 and 85 days after transplanting. These findings draw their support from the works of Srinivasan and Moorthy (1991), Srinivasan et al. (1994) and Virk et al. (2004).

Population of tomato fruit borer (larvae) was also significantly reduced in various treatment combinations on both tomato and marigold plants. Larval population on tomato plants decreased at latter stages because the larvae were trapped on marigold plants and have no tendency to migrate on tomato plant rows. However, the larval population on marigold plants increased at latter stages because of the quick appearance of marigold flowers. These observations draw their support from the findings of Sridhar et al. (2001), Srinivasan et al. (1994) and Torres-Villa et al. (2003). Moreover, larval population in early crop stages was surely higher on both marigold and tomato plants because larvae had a convenient environment in terms of abundance of flowers, fresh leaves and green fruits which promoted better larval performance (Shelton and Perez-Badenes, 2005).

In recent years, interest in trap cropping has increased considerably and become a vital component for pest management. Inherent characteristics of a trap crop may include not only differential attractiveness for feeding but also other attributes that enable the trap crop plants to serve as a sink for insects. Marigold used as a trap against tomato fruit borer gave maximum reduction in fruit damage as well as larvae on tomato plants because it does flower synchronously with the tomato with marigold in a 3:1 combination could be adopted for the management of tomato fruit borer.