|Published (Last):||28 July 2008|
|PDF File Size:||12.81 Mb|
|ePub File Size:||5.39 Mb|
|Price:||Free* [*Free Regsitration Required]|
Earias insulana enters the terminal bud of the vegetative shoot and channels downwards from the growing point, or directly penetrates the internode. Only soft growing tissue is attacked.
Extensive tunnelling results in wilting of the top leaves and the collapse of the apex of the main stem. The whole apex turns blackish-brown and dies. The result is bunched growth in young plants and death of the growing point in the mature plant. If only the apical bud is attacked, the damage may not be noticed until the main stem divides twinning when the axilliary buds take over growth Kashyap and Verma, ; Reed, As the buds and flowers appear they wither and are shed; they usually have a conspicuous hole where the larva has entered.
The shedding of minute buds is often blamed on mirids but may be caused by very young Earias Pearson, The bolls are also attacked, but only when they are unripe.
The larvae usually bore deeply, filling the tunnel opening with excrement. The tunnel often enters the bolls from below, at a slight angle to the peduncle Pearson Small bolls, up to 1 week old, turn brown, rot and drop.
Larger bolls, weeks old, may not drop, but open prematurely and may be so badly damaged they cannot be harvested. Bolls are vulnerable up to 6 weeks of age Butani, The larvae tend to move from boll to boll and the damage they cause may be disproportionate to their numbers.
Secondary invasion by fungi and bacteria may conceal the E. Earias spp. Young bolls or those without larval feeding holes rarely became infected. Okra is attacked in a similar way to cotton.
Initially, the terminal shoots are bored, with the attack moving to the flower buds and fruit as they appear. With severe tunnelling, the top leaves wilt and the whole apex of the plant droops, hampering further growth. Secondary branching may occasionally occur. When fruiting starts, larvae move to the flower buds, tiny fruits and eventually the mature pods. A severe attack causes the shedding of flower buds and reduced yield.
When attacking the fruit, the larvae feed on the milky seeds and other contents of the pod leaving excrement-filled tunnels. Cultural Control Much of the literature investigating cultural control of bollworms looks at mixed populations such as Pectinophora gossypiella.
In India, long duration cultivars of cotton supply a host for Earias from June or July until February, with okra providing an important carryover crop from one cotton season to the next.
Cotton plants not removed after the harvest also assist carryover because they sprout from the stump and continue to provide food for Earias.
Irrigated cotton in summer also provides extra food for the Earias population. Legislation in some countries requires farmers to uproot and destroy harvested plants to ensure an adequate close season, but this is seldom enforced.
However, in Cyprus, legislation requiring growers to destroy all okra plants before a fixed date was apparently ineffective in reducing damage, mainly because of the presence of wild malvaceous plants in the vicinity of the crop fields Melifronides et al. Eradication of alternative host plants has also been attempted, but is of doubtful benefit because many are valuable sources of food, feed or fibre and their removal may reduce the pool of natural enemies. Kashyap and Verma suggested that cotton should be inspected regularly and all wilted shoots removed, thus removing the larvae of Earias.
Some farmers allow livestock to graze cotton during the vegetative stage with the same effect. Nasr and Azab b also emphasize the importance of removing infested shoots and suggest that it be done when the egg-masses of Spodoptera littoralis are being collected and destroyed. The benefits of topping are controversial, although Nasr and Azab b claimed that the removal of the topmost few centimeters of the cotton plant at the beginning of the season reduced infestation and encouraged lateral branches, increasing the yield, without affecting the quality of the fibre.
Other suggested cultural practices include deep ploughing Faseli, and close spacing of plants Abdel Fatah et al. High doses of nitrogen fertilizers have been found to increase infestation Reed, Singh et al. Other studies have found that earlier sowings help reduce bollworm infestation Bishara, ; Ilango and Uthamasamy, ; Abdalla, Host-Plant Resistance Considerable resistance to Earias has been recorded in several wild species of Gossypium Anson et al.
Numerous trials have tested the resistance of various cultivars and reduced susceptibility has been found in many of them. Those with high levels of tannin and gossypol Sharma and Agarwal, ; Mohan et al. Hirsute varieties Agarwal and Katiyar, and glandless varieties Brader, have been found to be more susceptible.
Conversely, dwarf varieties with early flowering habits have been found to escape the damage of spotted bollworm Wankhede and Sadaphal, Khambete and Desai found some okra varieties had a certain amount of resistance.
Nerkar discusses the possibility that resistance might be found in wild relatives of okra such as Abelmoschus spp. Biological Control A number of studies have investigated the potential of various parasitoids against Earias spp.
The failure of the cotton crop in the Punjab in , owing to infestation with Earias, was attributed to the absence of Bracon greeni, which at the time was considered to be so efficient as a biological control that it was specially transported from Delhi to Lyallpur now Pakistan Lefroy, Ahmad and Ullah suggested that the rains, by lowering the temperature and enhancing relative humidity, benefited B.
Khan and Verma reported a very high population of B. There have been several field trials involving parasitoid release. Trichogramma australicum and B.
Releases of T. In another study, T. It was concluded that the use of natural enemies could be incorporated into an integrated control programme for cotton pests Pawar and Prasad, ; Prasad et al. Although parasitoids can control Earias, it appears that large numbers are necessary and the evidence suggests that these high levels have to be artificially maintained.
Stam and Elmosa found that parasitoids were relatively unimportant in controlling lepidopterous pests in cotton in Syria, but that the use of pesticides reduced the numbers of predators, resulting in a reduction in seed cotton yields. There are fewer studies on other types of biological control.
Bacillus thuringiensis has been used with some success. Glazer et al. Li et al. Croizier et al. Atger also mentions undefined viruses attacking E. Cork et al. A series of trials in Pakistan, using a slow release 'twist-tie' formulation, containing the major components of E. Nakache et al. Kehat and Dunkelblum tested various traps and dispensers for pheromone control in Israel. Chemical Control Due to the variable regulations around de- registration of pesticides, we are for the moment not including any specific chemical control recommendations.
The importance of Earias species varies considerably and, in some countries, has changed over the years. There appears to be some confusion concerning the impact of the pest. Often the literature does not distinguish between Earias spp and other bollworms when estimates of damage are given. In addition, the results of studies carried out in research farms are apparently not comparable to the losses in farmers' fields Reed, Sufficiently long periods in which conditions are naturally unfavourable appear to be adequate for reasonable control of the pest.
Earias insulana used to be a major pest of cotton in Egypt, but changing farming practices and the invasion of the pink bollworm, Pectinophora gossypiella, upset the food supply sufficiently to reduce E. The cold winter in northern Iran also effectively keeps populations of E.
Pearson suggests that even in areas with ideal conditions, cotton may not be the first choice of host for E. It is most common in the Punjab, becoming less common further south. However, field tests carried out in the Indian Punjab in to investigate the damage to different cotton varieties caused by several bollworms, including E.
Damage by E. Faseli reported that in the south Khorrasan region of Iran, E. Stam and Elmosa report that E. Khajuria, A. Pest Management Decision Guides English. External factsheets English. External factsheets Tamil.
Cookies on Plantwise Knowledge Bank. Close Find out more. Species Page. On this page:. Related treatment support. Prevention and control.
EPPO Global Database
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report. Abdalla EF, Effect of sowing date and certain chemical control programs against the cotton bollworms Pectinophora gossypiella Saund. The spacing and density of cotton plants as factors affecting populations of the bollworms, Earias insulana Boisd.
Taxonomic placing : Insecta, Holometabola , Lepidoptera , Noctuidae. Geographical distribution : The pest occurs around the Mediterranean and in Africa. CIE map Host plants : The spiny bollworm is oligophagous on Malvaceae , including cotton and okra Hibiscus esculentus Linnaeus. Morphology : The forewings of the adult moth are yellow-green or sometimes brown, with a diagonal green stripe. The hindwings are dull white with a brown subterminal line. The larva is initially grey, later grey-blue with yellow spots, its dorsum with small tubercles bearing short hairs.
List of symptoms / signs