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Plantwise Technical Factsheet

cabbage webworm (Hellula undalis)

Host plants / species affected
Brassica
Brassica oleracea var. botrytis (cauliflower)
Brassica oleracea var. capitata (cabbage)
Brassica oleracea var. gemmifera (Brussels sprouts)
Brassica oleracea var. italica (broccoli)
Brassica oleracea var. viridis (collards)
Brassica rapa subsp. pekinensis
Brassicaceae (cruciferous crops)
Nasturtium officinale (watercress)
Raphanus sativus (radish)
List of symptoms/signs
Growing point  -  external feeding
Inflorescence  -  wilt
Leaves  -  external feeding
Leaves  -  internal feeding
Leaves  -  webbing
Stems  -  internal feeding
Stems  -  internal feeding
Whole plant  -  dead heart
Whole plant  -  wilt
Symptoms
The young larvae mine leaves, bore stems and feed externally on the leaves; they then often penetrate the heart of the plant destroying the terminal bud, and prevent heading. While feeding they spin a silken tube. Plants wilt, and frass is exuded from the affected plant parts.
Prevention and control

Introduction

H. undalis frequently occurs in the same areas where the diamond back moth [Plutella xyolestella] is regarded as a major pest of Cruciferae. This complicates the control measures applied to H. undalis, since measures used to control P. xylostella may adversely affect measures used to control H. undalis (including H. undalis' natural enemies).

Biological Control

Dreyer (1987) found that weekly applications of simple neem products afforded good control in Togo.

Host-Plant Resistance

Srihari and Satyanarayana (1992) tested eight hybrids for resistance and found that TKCBN25 sustained the lowest H. undalis damage.

Lal et al. (1991) tested 64 cultivars of cauliflower in India. None was highly resistant, but the least infested variety was ES-9.

In Taiwan, it was found that variety B197 of Chinese cabbage was the least damaged by H. undalis (AVRDC, 1987). In 1979, research at the same centre found B159, B186, B488 and B501 to be the least affected by H. undalis.

Chemical Control

Diflubenzuron was found to be effective on the developmental stages of H. undalis in laboratory trials by Sumalatha et al. (1992).

In Turkey, Yabas and Zeren (1992) found that one or two applications of quinalphos, chlorpyrifos-ethyl [chlorpyrifos], Bacillus thuringiensis, trichlorfon and fenthion just after the appearance of H. undalis gave effective control.

An insecticide (malathion), an acaricide (dicofol), a fungicide (zineb) and a fertilizer (urea) were tested separately and in various combinations against pests and diseases of cabbage in Tamil Nadu, India, in 1981-82. Mixing malathion with the other compounds did not adversely affect its effectiveness against H. undalis (Krishnaia and Bhaskaran, 1988).

The chitin-synthesis inhibitor teflubenzuron was evaluated in the field in Singapore against Plutella xylostella and H. undalis on cabbage, broccoli and Brassica alboglabra, and its effectiveness was compared with that of triflumuron, the pyrethroid cypermethrin and the organophosphate profenofos. Teflubenzuron was highly effective against both pests and performed significantly better than the other compounds. Crop tolerance to teflubenzuron was good, but resistance of the pests to the compound was imminent (Ong and Ng, 1988).

The efficacy of various insecticides against H. undalis was assessed in Taiwan in 1985. The insecticides tested were teflubenzuron and chlorfluazuron (growth regulators), two strains of Bacillus thuringiensis (H3 and H7), Toarrow [B. t. subsp. kurstaki] and abamectin. Chlorfluazuron, abamectin and teflubenzuron were the most effective treatments, reducing infestation of H. undalis significantly compared with the untreated control from the beginning of the insecticide applications until harvest (AVDRC, 1987).

Field studies on the chemical control of H. undalis around Hyderabad in Andhra Pradesh, India, were carried out during 1974-75. Of the five chemicals, each of which was tested at three concentrations, carbaryl and quinalphos proved highly effective and were superior to malathion and fenthion.

Although the malathion and fenthion treatments resulted in less damage as compared with untreated plants, they were relatively ineffective in keeping down the numbers of H. undalis (Rao et al., 1979).

Sachan and Srivastava (1975) found in Jaipur, India that fortnightly sprays of carbaryl gave effective protection.

As cabbage heads mature at different times, 3-4 harvests are usually carried out over a period of 7-10 days. In order to protect the crop during this period, Sachan and Srivastava (1975) suggested that sprays of malathion should be applied immediately after each harvest.

Pheromonal Control

In Taiwan, AVRDC (1987) reported that sticky paper traps positioned at a height of 0.5 m attracted the greatest number of H. undalis moths.

Studies in Japan by Aria et al. (1982) showed that the sex pheromone of the pyralid H. undalis (an important pest of Brassica there) is (11E,13E)-11,13-hexadecadienal.

Impact
H. undalis is a serious pest of Brassicae and other crucifers in warm regions where it occurs. Without any control the yield loss in India amounts to 30% (Srihari and Satyanarayana, 1992).
Related treatment support
Plantwise Factsheets for Farmers
Kenya, Kengap Horticulture Ltd; CABI, 2012, English language
Cambodia, General Directorate of Agriculture; CABI, 2014, Cambodian language
Cambodia, General Directorate of Agriculture; CABI, 2014, English language
 
Pest Management Decision Guides
Cambodia, General Directorate of Agriculture; CABI, 2014, English language
Cambodia, General Directorate of Agriculture; CABI, 2014, Cambodian language
Badii, B. K.; Cudjoe, A.; CABI, 2016, English language
Badii, B. K.; Cudjoe, A.; CABI, 2016, English language
CABI; CABI, 2018, English language
 
External factsheets
Pestnet Fact Sheets, Pestnet, English language
Biovision Factsheets, Biovision Foundation, 2011, English language
Virginia Cooperative Extension - Agricultural Insects/Pests, Virginia Polytechnic Institute and State University, 2008, English language
TNAU Agritech Portal Crop Protection Factsheets, Tamil Nadu Agricultural University, English language
TNAU Agritech Portal Crop Protection Factsheets, Tamil Nadu Agricultural University, Tamil language
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