Induction of inherited sterility and sex ratio distribution due to exposure to substerilising doses of gamma radiation in cotton bollworm Earias vittella fabricius. Substerilising doses of gamma radiation induced inherited sterility and sex ratio distortion in the cotton bollworm Earias vittella fabricius. Adults irradiated with 75 Gy and self-crossed, provided sterile F 1 adults, suitable for direct use in sterile insect technique SIT. With 25 Gy, a sex ratio distortion was recorded in F 1 1 male: 2. Backcrossing of the F 1 female produced F 2 progeny with a sex ratio of
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The symptoms of attack are similar for all Earias species and are often described in general terms rather than for individual species in much of the literature. Cotton infestation generally starts with shoot boring in the young crop. Only soft growing tissue is attacked. Extensive tunnelling will result in the wilting of the top leaves and the collapse of the apex of the main stem. The whole apex turns blackish-brown and is generally killed.
The result is bunched growth in young plants and killing of the growing point in the mature plant. If only the apical bud is attacked, damage may not be noticed until the mainstem divides 'twinning' as the axilliary buds take over Pearson, ; Kashyap and Verma, Attack moves to buds and flowers as they appear, which wither and are shed. There is usually a conspicuous hole. Pearson commented that the shedding of minute buds, often blamed on mirids, might be due to very young Earias larvae, although he was not specifically referring to E.
The bolls are also attacked, but only when unripe. The larvae usually bore deeply, filling the tunnel opening with excrement.
The tunnel often enters bolls from below, entering at a slight angle to the peduncle Pearson, Small bolls up to 1 week old turn brown, rot and drop, whereas bigger bolls of weeks may not drop but open prematurely and be so badly damaged as to be unharvestable.
Bolls of up to 6 weeks of age are vulnerable Butani, ; Sidhu and Sandhu, The larvae tend to move from boll to boll and damage may be disproportionate to their numbers. The tendency for secondary invasion by fungi and bacteria may conceal the infestation.
Borker et al. The attack of okra follows a similar pattern to that of cotton. Terminal shoots are bored initially, with attack moving to flower buds and fruit as they appear. Singh and Bichoo found that Earias attack was visible when the okra crop was 3 weeks old, when larvae bored into shoots.
In 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 flower buds, tiny fruits, and eventually the mature pods. 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 and Sanitary Methods E. This may be provided by crops interspersed with other suitable hosts. In India, long duration cultivars of cotton alternated with okra supply E. Irrigated cotton in summer also supports the Earias population Reed, If cotton plants are not removed after the harvest, they sprout from the stump.
Lower pest incidence was found in fields where stumps were removed after harvest Sawhney and Nadkarny, Legislation in some countries requires farmers to uproot and destroy harvested plants, but this is apparently poorly enforced Pearson, Removal of possible alternative host plants was recommended by Christidies and Harrison This is now thought to be of dubious benefit as many are useful to man and removal may reduce the pool of natural enemies Reed, Kashyap and Verma suggested that cotton should be inspected regularly and all wilted shoots removed, thus removing larvae.
Some farmers allow livestock to graze cotton during the vegetative stage with much the same effect. The benefits of such 'topping' are apparently controversial. Dash et al. The timing of sowing may also help reduce infestation. In India, it was found that earlier sowings were beneficial Ilango and Uthamasamy, In China, Meng et al. Reduced damage by Earias spp. Kumar and Urs b found a positive correlation between nitrogen uptake by the plants and infestation of okra by E. Butani also noted this, but concluded that with chemical control the increased yields of cotton after application of nitrogen fertilizers outweighed the disadvantages.
Potassium uptake was negatively correlated with infestation. Because there is evidence to suggest that E. 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. Singh et al. Conversely, dwarf varieties with early flowering habit have been found to escape the damage of spotted bollworm Wankhede and Sadaphal, Khambete and Desai investigated okra varieties and found some had a certain amount of resistance.
Kadam and Khaire observed that sticky secretions released by okra when bitten by larvae could act as traps, killing E. Nerkar discusses the possibility that resistance might be found in wild relatives Abelmoschus spp.
Biological Control A large number of parasitoids have been recorded preying on E. Kashyap and Verma compiled a list of natural enemies for the Indian subcontinent. Far fewer predators have been recorded, probably due to the inherent difficulties in observation.
Information on the numbers and effects of natural enemies on E. Failure of the cotton crop in the Punjab in because of Earias infestation was attributed to the absence of Bracon greeni which at the time was considered so efficient that it was specially transported from Delhi to Lyallpur now in Pakistan Lefroy, Ahmad and Ghulamullah suggested that the rains, by lowering the temperature and enhancing relative humidity benefitted B.
Khan and Verma reported a very high population of B. However, subsequently Trichogramma australicum and B. Sangwan et al. Some years later, T. There was a significant reduction in damage to cotton, and it was concluded that the use of natural enemies could be incorporated in an integrated control programme for cotton pests Pawar and Prasad, ; Prasad et al.
A subsequent trial using T. Pawar et al. Subsequent surveys suggested that the parasite was becoming established and overwintering was observed. Surulivelu also reported reduced numbers of E. Kamath reported that B.
However, subsequent surveys showed that the parasite failed to establish itself. Krishnamoorthy and Mani investigated the use of the egg parasitoid T. Pheromone Use The components of the female sex pheromones of E. Subsequent synthetic formulations have shown promise in Pakistan, disrupting mating and achieving season-long control Critchley et al. 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 impact of E. Often the literature does not distinguish the losses due to E. Reed commented that the results of studies carried out in research farms are often not comparable to the losses in farmers' fields. Hiremath and Thontadarya studied the damage to cotton plants by known numbers of E. Bourgeois reported that farmers in Cambodia were starting to give up growing cotton, partly because of infestation by E.
Kamath reported that E. Srinivasan and Krishnakumar reported E. Singh and Bichoo found little information other than sketchy reports on the nature and extent of damage. Damage and excrement-filled tunnels in surviving fruit result in a low market price. Pest Management Decision Guides English. Khajuria, A. External factsheets English. External factsheets Tamil. Cookies on Plantwise Knowledge Bank. Close Find out more. Species Page. On this page:.
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