Major insect pests of Sorghum
06 January 2023, New Delhi: The three major pests of Sorghum are Shoot Fly, Stem Borer and Fall Army Worm.
- Management of Shoot fly in Sorghum
It is a major pest of sorghum and infestation occurs during the seedling stage for up to one month. Maggots cut the growing point and feed on the decaying tissues. The infestation results in withering and drying of the central leaf, giving a typical “dead-heart” symptom.
Control measures of Shoot Fly in Sorghum
It can be managed by early sowing within 7 to 10 days before the onset of monsoon and using a high seed rate @ 10 to 12 kg/ha in case of delayed sowing. Intercropping of sorghum + red gram in a 2:1 ratio should be followed. Seed treatment with Imidacloprid 70 WS @ 5ml/ kg or Thiamethoxam 70 WS @ 3 g/kg of seed may also be used. Soil application of Carbofuran 3G granules@ 20kg/ha in furrows at the time of sowing or spraying should be done at the seedlings stage.
- Management of Stem Borer in Sorghum
It attacks the crop from 2ndweek after germination until crop maturity. Irregular-shaped holes on the leaves are caused by the early instar larvae feeding in the whorl. Drying of the central shoot giving “dead-heart” is observed and extensive stem tunneling is also found. Peduncle tunneling leads to the breaking of the peduncle, which results in complete or partial chaffy panicles.
Control measures of Stem Borer in sorghum
Uproot and burn stubbles and chop off stems of the previous crop to prevent its carryover. Need-based whorl application of Carbofuran 3G @ 8-12 kg/ha inside the leaf-whorls of infested plants at 20 and 35 days after emergence reduce damage. Inter-cropping of sorghum with cowpea is also advised.
- Management of Fall armyworm in sorghum
Fall armyworm (FAW) is a polyphagous pest feeding on over 100 recorded plant species belonging to 27 families. However, it prefers plants from the Gramineae family including many economically important plants such as maize, sorghum, millets, sugarcane, paddy, wheat, etc.
The young larvae (Ist to IInd instar) scrape both sides of the leaves skeletonizing the upper epidermis and leaving a silvery transparent membrane. The IIIrd instar larvae, larvae enter the whorl and inflict ragged-edged oblong holes on leaf lamina presenting ragged-edged holes. Once the larvae reach the fifth instar it feeds voraciously causing extensive defoliation of the whorl. On average 1-2 larvae were found in each whorl.
Control measures for Fall Armyworm in Sorghum
Following are the management options suggested to manage the pest.
General management measures for Fall Armyworm in Sorghum
- Deep plowing of the field exposes the FAW larvae and pupae to sunlight and natural enemies
- For synchronous planting sow the crop within the sowing window so that a single stage of crop is available.
- Deploy pheromone traps @ 12 traps/ha for monitoring the FAW.
- Collect and destroy egg masses/ larvae during scouting
- Erect bird perches @ 25/ha. soon after sowing as it facilitates movement of insectivorous birds viz., black drongo and swallows which predate on flying moths as well as caterpillars.
Control of Fall Armyworm Early instars (I – II)
- Treat the millet seed with a mixture of Cyantraniliprole 19.8 % + Thiomethoxam 19.8% @ 4 ml/ kg of seed as it protects the crop for up to three weeks which in turn helps the crop to establish good initial plant vigor (Based-on results of Adhoc trials at IIMR, Hyderabad, Kharif, 2019)
- When incidence is low or at the early instar stage (7-30 days old crop), spray Azadirachtin 1500 ppm
@ 5ml/liter or 5% Neem seed Kernel extract (NSKE).
- Spray with fungal pathogen, Nomuraea rileyi (1 x 108 cfu@ 3 grams per liter of water
- In case of severe infestation (> 10% damage) as a last resort spray crop with Spinetoram 11.7 % SC @ 0.5 ml/l water or Chlorantraniliprole 18.5 @ 0.3 ml/lit of water or Thiamethoxam 12.6 % + Lambda cyhalothrin 9.5% ZC @ 0.25 ml/l of water. Alternate the chemical in subsequent sprays to avoid build-up of resistance in pest against insecticide.
Control of Fall Armyworm Mid instars (III – IV)
- Collect egg masses and larvae and destroy
- Apart from insecticides application of a mixture of sand (10kg) and lime 50 grams into the whorls, harms the larvae protecting the crop. This was observed at the farmers’ field.
- In case of severe infestation (10 – 20 % damaged plants) as a last resort spray crop with Spinetoram 11.7 % SC @ 0.5 ml/l water or Chlorantraniliprole 18.5 @ 0.3 ml/lit of water or Thiamethoxam 12.6 % + Lambda-cyhalothrin 9.5% ZC @ 0.25 ml/l of water. Alternate the chemical in subsequent sprays. Spray using a high-volume sprayer (Knapsack) preferably in the morning or evening with the nozzle directed towards the whorls is advised.
Control of Fall Armyworm Late instars (V- VI)
- The late instar larvae are very difficult to manage using chemicals. In case of the presence of late instar larvae poison baiting is suggested with a fermented mixture of rice bran.
Keep the mixture of 10 Kg rice bran + 2 Kg jaggery with 2-3 liters of water for 24 hours to ferment. Add 100 g Thiodicarb just half an hour before application in the field. The bait should be applied to the whorl of the plants.
- In case of severe infestation (> 20% damaged plants) as a last resort spray crop with Spinetoram 11.7 % SC @ 0.5 ml/l or Chlorantraniliprole 18.5 @ 0.3 ml/lit of water or Thiamethoxam 12.6% + Lambda cyhalothrin 9.5% ZC @ 0.25 ml/l of water.
- Spray using a high-volume sprayer, the nozzle directed towards the whorls for better control. The subsequent spray may be taken up after 10 -15 days depending on the intensity of the infestation avoiding the previously sprayed chemical.
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