Wheat Stem Borer and Red Pumpkin Beetle Pest Management
Wheat Stem Borer (S. inferens)
Systematic Position
- Class: Insecta
- Order: Lepidoptera
- Family: Noctuidae
Habits
The wheat stem borer is a nocturnal insect, living for 10–15 days. Eggs are laid on the inner surface of the host plant’s leaf sheath. Caterpillars bore into the stems of the wheat plant to feed. The caterpillar prefers moist weather to infest new shoots.
Damage
The caterpillars attack and destroy young shoots of the wheat crop, causing uneven growth. The central shoot is damaged completely, resulting in deadhearts. This significantly reduces the yield.
Life Cycle and Control of S. inferens
The life cycle of the wheat stem borer is completed in 30–45 days, involving the following stages:
(i) Eggs
The adult female moth lays about 300 eggs in 2–3 rows on the inner surface of the leaf sheath. The eggs are rounded with flattened poles.
(ii) Caterpillar
After an incubation period of 6–7 days, tiny caterpillars emerge. They are pink to violet on the upper surface and whitish on the undersurface, about 10 mm in length. The caterpillar bores into the wheat stem to feed and never feeds in an exposed position. During growth, the caterpillar burrows up and down, moving from one shoot to another. The caterpillar becomes full-grown after 6–7 months, reaching a length of about 3–5 cm.
(iii) Pupa
The caterpillar pupates in a rough cocoon made of silk and debris, either within the shoot or outside under a dry leaf sheath. It is dark brown in color with a purple head and is about 20 mm in length. The pupation period lasts from a couple of days to more than 14 days.
(iv) Adult
After a pupation period of 6–10 days, the young adult emerges from the stem through pores made by the larvae before pupation. The adult moth has a stout body of dark straw or light brown color and is nocturnal.
Control Measures
The following measures are used to control wheat stem borers:
- Affected shoots should be removed and destroyed to kill the borers they contain.
- Grassy weeds should be removed, buried, or burnt to kill eggs and larvae.
- Crop rotation should be practiced.
- 35% endosulfan should be sprayed at the rate of 1.1 liters per hectare.
- 5% BHC or DDT at the rate of 7–8 kg per acre should be applied as dust.
Red Pumpkin Beetle (Aulacophora foveicollis)
Systematic Position
- Class: Insecta
- Order: Coleoptera
- Family: Chrysomelidae
Habits
The adult beetles attack vegetables in April and May. They possess biting and chewing mouthparts. Adults hibernate from November to February under grasses, weeds, and bushes.
Life Cycle
The life cycle is completed in 25–40 days, with five broods occurring in a year.
(i) Eggs
A mature female lays 60–300 oval, yellow eggs on moist soil near the host plant, laid singly or in batches.
(ii) Grubs
Grubs hatch in 1–2 weeks. They are creamy colored with a brown head and prothorax. They feed on underground parts of the host plant, such as roots, and fruits lying on the soil. The larval life lasts for 13–23 days, during which grubs undergo four moults.
(iii) Pupa
Pupation occurs in the soil within oval, thick-walled earthen chambers. This stage lasts for 7–17 days, after which adults emerge.
(iv) Adults
Adults are oval, about 6 mm long, with a bright orange-red body and a black undersurface. Adults may live for 60–85 days.
Damage
Grubs bore into roots and stems, causing plants, particularly seedlings, to wither and die. Adults feed on leaves, flowers, and fruits, leading to growth retardation or plant death. Their attack makes fruits unfit for consumption. There may be a 10–20% loss of the crop.
Control
The following measures are taken for control:
- Deep ploughing should be done to kill the insects and pupae.
- Early varieties of these vegetables should be sown.
- Younger plants should be dusted with ash.
- Beetles may be collected by nets and killed.
- Pyrethrum (5%) should be dusted.
- Lindane 1% at the rate of 250 liters per acre should be sprayed.