Survey Collection and Study of the Mites Attacking Different Crops in Sind and Their Control

Abstract

The project entitled ‘Survey, Collection, and Study of the Mites Attacking Different Crops in Sindh and Their Control’ sponsored and graciously aided by Pakistan Science Foundation under its grant No. PSF/RES/S-TC/AGRI (18) MITES, was undertaken on February 15, 1975. It continued for three years and concluded on February 14, 1978. During the course of investigation, areas of TandoJam campus in particular and of Sindh in general were survedyed. The common occurring mites, both phytophagous and predacius ones, were collected and identifies to the specie level. Besides, chemical control experiments on a mite, Tetranychus urticae Koch were also carried out. 1. Nine species of phytophagous mites, belonging to the families, Tetranychidae, Tenuipalpidae and Tarsonemidae, were recorded. They were Tetranychus urticae Koch. Tetranychus cinnabarinus (Boisduval), Eutetranychus orientalis (McGregor) schizotetraanychus reticulatus n.sp., Oligonychus (Rookiella) pratensis (Banks), porcupinychus abutiloni Anwarullah, Brevipalpus karachiensis n. sp., Brevipalpus obovatus Donnadieu, and Tarsonemus latus Banks. The studies were made on their host range, distribution in Sindh, damage and symptoms, occurrence and incidence, population growth, and control. Brief details of these items for each mite have been given. 2. Sorghum rust mite O. (reckiella) pratensis. Seriously attacked sorghum crop causing red rust of leaves. In correlation studies made at the time of harvest of the crop, it was found that: a. Average no. of mites per leaf were positively and significantly corelated with the red rusted area of the leaf; b. The red rusted area of leaf was negatively correlated with the grain of yield; c. Average no. of mites per leaf was negatively correlated with the grain of yield; d. Average no. of mites per leaf was negatively (not so significant) correlated with stalk weight(fodder); e. The average no. of predictors was positively significant correlated with the average no. of mites per leaf; f. The average no. of predators was positively correlated with grain of yield;

3. Thick webbing produced by tetranychid mites, particularly T. urticae and T. cinnabarinus caused serious retardation in growth and stoppage of fruit formation 4. White papery mite, S. reticulatus produced papery capsules, equivalent to rice short grain, on upper surface of leaves of sugarcane and other host plant. 5. Among tetranychid mites, T. urticae occurring on Hibisous esculentus lin., E. orientalis on Ricinuscomunis lin., and O. pratensils on Sorghum vulgare preferred high temperature (average from 33.50C-34.60C) and low relative humidity (averagely from 32.5-34.7%) while B. karachiensis on Sesamum indicum lin. preferred comparatively low temp. (averagely 30.3-30.70C) and higher humidity (averagely from 56.3-67.0%) 6. Among natural enemies of phytophagous mites, five predacious mites were recorded. They were as a Agistemus impayidus n. sp., Phytoseius sp., Amblyseius sp. and cunoxid sp., the insect predators were Stethorus pauperculus wse., Brumus suturalis (F), Menochilus sexmaculatus (F), Coccinella septempunctata (L), Chilomenese sexamaculata (F), and Chrysopa sp. the observation made on their host, distribution occurrence and abundance, and predatory behaviour have been presented. 7. In studying predatory behaviour, two kinds of between Typhlodromus sp. (predator) and O. pratensis (prey) were observed in a single period of august 30 thru October 19. In the first kind of relationship during September 1 thru September 14, the predator was positively corelated with the prey; while in the second kind during September 14 thru October 19, the predator was negatively corelated with the prey. 8. Stethrou beetles were predictors of phytophagous mites, viz o. pratensis, T, urticea, E. esculentus etc. 9. Under natural field conditions, particulate when the rainfall occur during vegetative growth of the plant (H. esculentus), S. pauperculus was not so effective in controlling T. urticae. The rainfall seemed to have more adverse effect on the predator than the pest. 10. Chemical control experiment carried out in the year 1976 showed that almost all the eight pesticides were effective in controlling T. urticae on okra crop. However, among them chlordimeform, monocrotophos, discrotophos and dicofol were more effective than the other pesticides. Methyl dementon was the least in effect against the mite, followed by formothion. among all the pesticides formothion degenerate very quickly and lost its toxic effect one week after the application; while methyl demeton persisted for longer time. 11. In the experiment on pesticide doze levels, carried out in the year 1977, it was found that methidathion was very much effective at all the concentration as (0.12) low, o.25 (medium) and 0.5 (high) per cent level s in the controlling the mite, T. urticae. However, it should better result at high doze level (0.5%) this was followed by monocrotophos and dicofol at medium and high dose levels. Chlorobenzilate at almost all doze levels was least effective in controlling the mite. 12. Methidation was less persistent in toxic effect than monocrotophos. Therefore, for protection of vegetables such as okra, from mite attack application of methidathion at 0.25-0.5% is suggested.