It is disheartening to sow the seeds of tomorrow’s success only for the victory to be snatched away after all the hard work done to reap it. More often that not, Indian farmers are victim to these situations as they along with their harvest, fall prey to pests. After successfully battling water scarcity, financial woes and the vagaries of climate, they finally succumb to the pest menace. By the time the researchers and farmers get to know a pest and ways to tackle them, there rises another, just like the Fall Armyworm – the new contender in the maize field.
Fall Armyworm (FAW), Spodoptera frugiperda (J. E. Smith)
Fall Armyworm (FAW) was discovered in Karnataka this July. The invasive pest is native of United States of America was observed by us in maize hybrids COH (M) 6, COH (M) 8 and fodder maize (African tall) sown during June and July at Eastern block and new area of TNAU, Coimbatore campus.
A major maize pest in North America, first reported in Africa in 2016 and it has threatened the continent’s maize crop, a staple which feeds 300 million people. The Karnataka finding is the first report of the pest in Asia. The discovery is more worrisome because the pest feeds on around 100 different crops, such as vegetables, rice and sugarcane. In Tamil Nadu the occurrence of this pest has also been reported from Anthiyur, Bhavani, Ammapettai, Bhavanisagar, Karur, Vagarai and Kallakurichi.
The life cycle is completed in about 30 days during the summer, but 60 days in the spring and autumn and 80 to 90 days during the winter.
Egg: The egg is dome shaped. The number of eggs per mass varies considerably but is often 100 to 200. The eggs are sometimes deposited in layers, but most eggs are spread over a single layer attached to foliage.
Larvae: There usually are six instars in fall armyworm Elevated spots occur dorsally on the body; they are usually dark in colour, and bear spines. The face of the mature larva is also marked with a white inverted “Y”.
Pupa: Pupation normally takes place in the soil, at a depth 2 to 8 cm. The larva constructs a loose cocoon, oval in shape and 20 to 30 mm in length, by tying together particles of soil with silk. Duration of the pupal stage is about eight to nine days during the summer, but reaches 20 to 30 days during the winter.
Adult: In the male moth, the forewing generally is shaded grey and brown, with triangular white spots at the tip and near the centre of the wing. The forewings of females are less distinctly marked, ranging from a uniform greyish brown to a fine mottling of grey and brown. Duration of adult life is estimated to average about 10 days, with a range of about seven to 21 days.
Characteristic marks on caterpillars
To differentiate this larva from other armyworm species or corn earworm one needs to look at the head of the insect. The fall armyworm’s head has a predominant white, inverted “Y”-shaped suture between the eyes and four dark spots forming a square on the second to last segment.
Young larvae – length 6-9 mm
Green or yellow in colours. These larvae are camouflage with green leaves and also confusion with other pests.
Mature larvae – length 30-36 mm
In the late stages of larvae is mostly brownish. Darker individuals appear when overcrowding occurs.
Field crops are frequently injured, including alfalfa, barley, Bermuda grass, buckwheat, cotton, clover, corn, oat, millet, peanut, rice, ryegrass, sorghum, sugar beet, Sudan grass, soybean, sugarcane, timothy, tobacco and wheat.
- Young larvae initially consume leaf tissue from one side, leaving the opposite epidermal layer intact.
- The second or third instar larvae begin to make holes in leaves and eat from the edge of the leaves inward.
- Feeding in the whorl of corn often produces a characteristic row of perforations in the leaves. (pin holes, small to medium elongated holes, parallel shot holes, and irregular shaped holes on leaves)
- Older larvae cause extensive defoliation, often leaving only the ribs and stalks of corn plants or a ragged, torn appearance.
- Presence of chewed up frass material and fecal pellets in the leaf whorl, drooping of leave portion above the feeding area, and feeding on tassel.
- Apply neem cake @ 250 kg/ to reduce the adult emergence from pupae
- Use light trap @ 1/ha during night hours to monitor the adult moth activity in and around maize fields.
- Since there is no label claim among the registered insecticides for frugiperda, the following botanical and synthetic insecticides recommended as per IRAC Modes of Action, for S. litura have been screened in the preliminary trials and they were effective.
Authors, Subash Chandra Bose and I. Rabeena are Ph.D. Scholars of AC&RI, Madurai.