Experiment on pesticides Efficay on jassid insect in okra crop.
Introduction
Okra is a valuable vegetable crop available in tropical and sub-tropical regions of the world (Akinyele et al., 2006; Alam et al., 2008; Kumar et al., 2010; Wammanda et al., 2010). Okra is one of the most consumed vegetables grown in pakistan. It is also known as lady’s finger and is locally called bhindi. Okra is cultivated in pakistan in an area of about 15.081 thousand hectares with a total production of 114.657 thousand tonnes. Sindh contributes an area of 36.2 hectares with a production of 220 thousand tons. (Benchasri et al.,2012). Okra is cultivated on a small scale in kitchen gardening and on a large scale on the farm. Like pakistan okra is cultivated commercially in India, Turkey, Iran, Western Africa, Yugoslavia, Bangladesh, Afghanistan, Pakistan, Burma, Japan, Malaysia, Brazil, Ghana, Ethiopia, and the Southern United States. Okra is a very important vegetable that contains vitamins A, B, and C, fats, potassium, calcium, iron, and other minerals like magnesium, sodium, phosphorus, and carbohydrates needed for a balanced diet. (Randhawa et al., 1987; Masood et al., 2001). There are several insects that attack on okra vegetables like jassid, aphid, whitefly, leaf roller, and shoot and fruit borer. Among sucking insect pests jassid is one of the most sucking insects that causes severe infestation of okra. ( El-Tom et al., 1987; Singh et al., 1993; Dhandapani et al., 2003).Jassids or leafhoppers (Amrasca devastans Distant) (Hemiptera: Cicadellidae) are widely distributed in tropical, sub-tropical, and temperate regions. Jassid can be identified as a wedge-shaped body with a length of about 3mm and greenish yellow in color, Containing a black spot on the forewing and vertex. The female lays about 15 yellowish eggs underside of leaves. Eggs hatch in 4-11 days and give rise to nymphs. Nymphs suck cell sap underside of leaves and pass six stages of growth to become adults after 7-21 days. They live about 5-7 weeks and feed cell saps constantly. Jassid is a polyphagous pest of okra that cause heavy loss of okra. A high population of jassid sucks cell saps from the surface of leaves and injects saliva which is toxic in nature into plant tissues to turn leaves into yellowish color and curl upward. ( Singh et al., 2008). Jassid has piercing-sucking types of mouthparts. Both nymph and adult cause damage present underside of leaves. They suck cell sap from leaves as a result leaves curl upwards along the margins. The affected plant shows stunted growth. (Norman et al., 1992; Sharma et al., 1998).
• Materials and Methods
• Location of the experimental plot
• The experiment was conducted at the Department of Agriculture and Agribusiness Management, Karachi in 2019. The site is located in the field of agriculture and agribusiness management.
• Study Design
The study was conducted with four(pesticides) + one(water) treatment. The experiment was performed with a randomized basic method.
• Application of Pesticides
The comparative effectiveness of the following five treatments for okra Jassid was evaluated on the basis of the reduction of this pest
• T1 = Actara 25gms/acre
• T2 = Planum 100gms/acre
• T3 = Radient 80ml/acre
• T4 = Movento 125ml/acre
• T5 = Untreated control
All agricultural practices were maintained when required, the treatments were adjusted at par with the plot size, and insecticides were calibrated according to the plot size. Spraying was done at 5.00 pm to avoid evaporation of insecticides from direct contact with sunlight.
• Data collection
Data on infestation by okra Jassid under different treatments were recorded. For the pest counting pre-treatment observations were taken 24 hours before the application of insecticides and post-treatment observations were taken at 24hrs, 72 hrs, one week, and two weeks at the interval after the spray of insecticides.
• Results and Discussion
The application of different insecticides on okra crops for the reduction of the jassid population at different time intervals after the 1st, 2nd, and 3rd sprays are presented in the Table below. The overall result shows that both Spinetoram and Spirotetramat are more effective than Thiamethoxam. While pymetrozine shows moderate effectiveness. After 24 hours of application of 1st spray, Spinetoram was highly effective with a 55% reduction in the jassid population followed by Spirotetramat (54%), Pymetrozine (48%) and Thiamethoxam gave a 46% reduction in jassid population. After 72 and 168 hours Spintoram showed an increasing trend with a 58 and 59% reduction in the jassid population followed by Spirotetramet 58 and 19% and Pymetrozine 58 and 14% reduction. Thiamethoxam also performed well with 30 and 48% reduction at 72, and 168 hours post-application. A similar trend was observed after 2nd spray. Spintoram maintained its superiority over the rest of the insecticides with a rising trend with 55, 56, and 60% reductions in the jassid population after 24, 72, and 168 hours of 2nd spray. Although Spirotetramet and Thiamethoxam were effective with 41, 58, and 19% and 48, 62, and 38% reduction respectively. Pymetrozine was less effective as compared to 1st spray with 21, 15, and 12% insect mortality. Spintoram sustained its dominance with the increasing trend till 3rd spray reduced the jassid population by 60, 67, and 64%. Spirotetramet and Thiamethoxam gave similar results with a gradual increase in effectiveness as compared to previous treatments with 66, 87, 75, and 41% and 14, 75, and 52% insect mortality. Although Pymetrozine gave satisfactory results with a gradual increasing trend in effectiveness with 39, 62, and 35% reduction in the jassid population. After 240 hours of the 2nd and 3rd spray and 336 hours of the 3rd spray, all the insecticides decreased their effectiveness. After three consecutive sprays, the overall performance of all the insecticides (Table 2) represents that both Spinetoram and Spirotetramet were more effective than Thiamethoxam, while Pymetrozine was least effective.
Table: Percent reduction in jassid population on okra crop
First spray
Second spray
Third spray
Overall Percent Efficacy
The findings of the present study showed that spinetoram and spirotetramet followed by thiamethoxam performed best among the different insecticides against the jassid population. According to (Crouse et al. 2007). spinetoram is a good insecticide against sucking insects pest like thrips and psyllids. spirotetramate is a highly effective tool for the management of sucking pests in vegetable crops. It is recently registered in India for use and the field rate in okra and brinjal is 90 g a.i./ha against whitefly (Unpublished report). Although Plenum (a.i. pymetrozine) is reputed for its selectivity towards plant-sucking insects (Flückiger et al. 1992; Sechser et al. 2002), the present study demonstrates that parasitoid pre-imaginal development inside contaminated hosts (even at a sub-lethal concentration for the host) can be affected by this insecticide. Laboratory and field experiments have shown pymetrozine alone (Sechser et al. 2002) to be harmless to several insect species belonging to the orders of Coleoptera, Neuroptera, Heteroptera, Diptera, and Hymenoptera. Misra (2002) found that imidacloprid, as well as thiamethoxam, proved significantly superior in controlling aphids and jassids. Sharaf et al. (2003) reported that confidor and Best also induced the highest initial activity in the immature stages of whitefly. Confidor and Best induced the highest initial and residual activity in mature stages. Razaq et al. (2003) illustrated that thiamethoxam as well as imidacloprid were effective against jassids (Amrasca biguttula Ishida) at 72, 168, and 240 h after spraying. Khattak et al. (2004) found that thiamethoxam (Actara), as well as imidacloprid (confidor), reduced the mean percent population of whiteflies even 240 h after spraying. Aslam et al. (2004) mentioned that confidor (imidacloprid) was the most effective on jassids, and was effective up to 7 days on thrips. Asi et al. (2008) found that imidacloprid was effective against whiteflies and jassids up to 168 h after spraying. Dhawan et al. (2008) mentioned that thiamethoxam was the most effective against cotton aphids under screen house conditions. Also, El-Zahi and Aref (2011) found that thiamethoxam and imidacloprid were the most effective against cotton aphids under field conditions. In contrast to our findings, Zidan et al. (2008) found that thiamethoxam was effective against whitefly (adults) for 15 days after treatment. El-Zahi (2005) reported that imidacloprid proved to be the most effective against aphids causing a 98.17% reduction as the general mean of the effect. El-Dewy (2006) mentioned that imidacloprid (confidor) proved to be a superior compound against aphids, jassids, and whitefly (adult). This is in accordance with the findings of Anitha (2007) who found that thiamethoxam was superior in controlling leafhoppers in okra. Sujay Anand et al. (2013) reported that thiamethoxam and acetamiprid resulted in the effective management of leaf hopper in okra followed by buprofezin and pymetrozine.
Conclusions
It is concluded that Spinetoram, Spirotetramet, and Thiamethoxam, being synthetic insecticides, could be the potential tool for controlling jassids on okra crops. However, their impact on beneficial insects, particularly on pollinators needs to be studied.