How to identify and control the cotton bollworm and the tobacco budworm of the family Noctuidae?
The cotton bollworm and the tobacco budworm are two extremely similar insects that are very difficult to distinguish in production. Both belong to the order Lepidoptera, family Noctuidae, also known as the cotton bollworm moth and the tobacco budworm moth, and are widely distributed. So how do you identify the cotton bollworm and the tobacco budworm of the family Noctuidae? How should they be controlled? In daily life, the cotton bollworm damages many crops such as cherry tomatoes, okra, head lettuce, savoy cabbage, Brussels sprouts, melons, hyacinth beans, snow peas, sweet peas, sweet corn, vegetable soybeans, apples, pears, citrus, peaches, plums, grapes, figs, strawberries and cotton. The tobacco budworm damages tobacco, peppers, tomatoes, pumpkins, cotton, corn, sorghum, hemp, soybeans, peas, hyacinth beans and others.
How to identify them
The cotton bollworm, of the order Lepidoptera, family Noctuidae, is widely distributed in China and around the world, and occurs in all cotton regions and vegetable-growing regions of China. The Yellow River cotton region and the Yangtze River cotton region suffer the heaviest damage. In recent years, it has also occasionally occurred in the Xinjiang cotton region. Its host plants include more than 200 species in over 30 families. The cotton bollworm is an important boring pest during the cotton bud and boll stage, mainly boring into and feeding on buds, flowers and bolls, and also feeding on tender leaves,
The tobacco budworm, commonly known as the green worm and also called the tobacco noctuid, belongs to the order Lepidoptera, family Noctuidae. In the Northeast and North China it has 2 generations per year; in Henan, Shandong, northern Anhui and other places it has 3--4 generations per year; in the Northwest it has 4--5 generations per year, and in Central China 5 generations per year; in the Southwest it has 5--6 generations per year. In the Huang-Huai tobacco region, the pupa overwinters in soil at a depth of 7-13 cm, and the overwintering-generation adults appear from late May to early June, which is the peak egg-laying period; the peak egg-laying periods of generations 2-4 are respectively from early to mid-June to early to mid-July, from early July to early to mid-August, and from early August to early September. The first to third generations mainly damage spring and summer tobacco; the fourth generation damages the flowers and fruits of summer tobacco, among which the second and third generations cause the heaviest damage to tobacco.
1. Damage characteristics
Both bore into and feed on the flower buds, flowers, fruits and seed pods of plants with their larvae, and also bore into stems, fruit clusters, heads and so on, feeding on tender stems, tender leaves and tender shoots in the early stage.
2. Morphological characteristics
The adult cotton bollworm is 14-18 mm long with a wingspan of 30-38 mm, grayish brown to yellowish brown. The forewings have brown annular markings and kidney-shaped markings. On the costal vein in front of the kidney-shaped marking there are two brown lines, outside the kidney-shaped marking is a broad brown transverse band, and there are black dots between the veins in the terminal area. The hindwings are yellowish white to grayish brown, with the terminal area brown to black. The male moth has one small recurved hook at the tip of the aedeagus, and the small conical cornuti in the aedeagus are large and few (about 12 pairs). On the bursa appendage of the female moth's copulatory bursa, besides wrinkles, there are numerous small triangular spines. The egg is about 0.5 mm long, hemispherical, milky white, with a reticulate pattern; between the two longitudinal ridges there are 1-2 short longitudinal ridges, mostly in a two-forked or three-forked arrangement, with 25-30 longitudinal ridges in the middle, mostly 26-28, and the micropyle is not obvious. The mature larva is 30-42 mm long, with great variation in body color. From pale green, pale red to reddish brown and blackish purple, the green type and reddish brown type are common. The head is yellowish brown, the dorsal line, subdorsal line and spiracular line are dark longitudinal lines, the spiracles are white, and the crochets of the abdominal prolegs are in a biordinal mesoseries. The line connecting the two anterior thoracic lateral setae (L1, L2) is tangent to or intersects the lower end of the anterior thoracic spiracle. The body surface is covered with small spines whose bases are relatively large. The pupa is 17-21 mm long, yellowish brown. On the dorsal and ventral sides of abdominal segments 5 to 7 there are 7-8 rows of semicircular punctures, and the cremaster has 2 hooked spines.
The tobacco budworm is extremely similar to the cotton bollworm. The main differences are: the adult body color is more yellow, the lines on the forewings are clear, and on the inner side of the middle section of the brown-black broad band on the hindwing there is a brown-black line, with the outer side slightly concave. The male moth has no small hook at the tip of the aedeagus, and the long conical cornuti in the aedeagus are small and numerous (about 23 groups). On the bursa appendage of the female moth's copulatory bursa there are only wrinkles, with no small triangular spines. The egg is slightly flattened, pale yellow, with the longitudinal ridges in a biordinal arrangement, mainly one long and one short, with 21-26 longitudinal ridges in the middle, mostly 22-24, and the micropyle is obvious. The line connecting the two anterior thoracic lateral setae (L1, L2) of the larva is far from the lower end of the anterior thoracic spiracle, and the small spines on the body surface are shorter. The front part of the pupa body appears slightly thick and short. The spiracles are small and low, rarely protruding.
Control methods
The control methods for the cotton bollworm and the tobacco budworm are similar. After the tobacco budworm larva bores into the fruit at the third instar it no longer emerges, so chemical control must be carried out before boring.
(1) Plow the soil in winter and early spring to kill the pupae and reduce the overwintering pest sources in the field.
(2) Use blacklight lamps, high-pressure mercury lamps, poplar branch bundles or sex pheromone trap basins to trap and kill the adults.
(3) According to the cotton bollworm's selectivity for different hosts, deliberately plant trap strips of preferred host crops in the field to attract the cotton bollworm to lay eggs and reduce the damage to production vegetables.
(4) Combined with field management, remove egg-bearing leaves, fruits and tender shoots along with pruning and pinching, and during the pupal stage increase cultivation and irrigation to disrupt the normal pupation of the cotton bollworm.
(5) 3-4 days and 6-8 days after the egg peak, continuously spray Bacillus thuringiensis Bt emulsion or HD-1 powder, or cotton bollworm nuclear polyhedrosis virus. Before the second-instar larvae (before boring), choose 5% Nomolt emulsifiable concentrate at 3000-4000 times dilution, 10% Trebon suspension concentrate at 1500-2000 times dilution, 3% Mospilan emulsifiable concentrate at 1000-2000 times dilution, 5% Cascade emulsifiable concentrate at 1000-2000 times dilution, 52.25% Lorsban emulsifiable concentrate at 2500-3000 times dilution, 5.7% Betacyfluthrin emulsifiable concentrate at 3000-4000 times dilution, 12.5% Baofu suspension concentrate at 8000-10000 times dilution for spraying. After boring, it is best to spray in the morning or evening when the larvae emerge to move about.