Ajai Mansingh’s research while affiliated with University of the West Indies and other places

The hydrolytic half lives of ethoprophos in distilled, river, brackish and open sea water were 25, 133, 65 and 81 days, respectively. Under laboratory conditions, volatilisation of the residues after 12 h was 1.4-3.6, 2.3-4.5 and 6.5-20.2% from a sandy loam soil with 1, 10 and 20% moisture levels, respectively. Photolysis in soil was significantly faster (P < 0.05) in direct sunlight (T1/2 of 4.7 days) than in the shade (T1/2 of 12.3 days). The microbial degradation of ethoprophos was more than two-fold faster in unsterile soil (T1/2 of 10.9 days) than in sterile soil (T1/2 of 28.8 days). The runoff of ethoprophos from unweeded plantation soil at 23 degrees slope was significantly (P = 0.015) less than at 38 degrees slope; the amounts lost after 9 weeks and 27.5 mm of rainfall were 89.4 and 91.2%, respectively, of the applied amount from the two respective slopes. In the weeded plots, 93.6 and 92.4% of the applied insecticide were lost from 23 degrees and 38 degrees slopes, respectively. Under laboratory conditions, between 67.0 and 85.1% of ethoprophos leached through the soil columns. Under field conditions, after 9 weeks and 25 mm of rainfall, only 2.8 and 2.0% residues were recovered at a depth of 10-15 cm from unweeded and weeded slopes, respectively at 23 degrees slope, and 2.2 and 1.9% from the two respective plots at 38 degrees slope.

A survey of 120 coffee farmers in the Portland watershed revealed that they lacked training in pesticide application, and had no concept of the transport of residues in the environment and their impact on non-target organisms. Residues of organochlorine (OC) and organophosphorous compounds (OP) were monitored monthly for over a year in plantation soil, and water, sediment and fauna of three rivers and coastal waters of Portland watershed by gas chromatography. OP residues were not detected in any sample while OC residues were below detection levels in Rio Grande. The mean concentration ± standard error of residues detected in water (μg L_1), sediment (ng g_1) and fauna (ng g_1 in wet weight) were: α-endosulfan 2.7 ± 1.29, 3.8 ± 0.15 and 15.9 ± 1.61, respectively, in Spanish River, 1.56 ± 0.43, 24.3 ± 16.44 and 9.0 ± 1.86, respectively, in Swift River; 0.40 ± 0.02, 1.77 ± 0.68 ± 12.63, respectively, in sea coast; β-endosulfan, 1.2 ± 0.48, 0 and 8.1 ± 1.99, respectively, in Spanish River, 1.9 ± 0.49, 0.75 ± 0.32 and 11. ± 4.32, respectively, in Swift River; 0, 5.1 ± 0.30 and 30.9 ± 15.96, respectively, in sea coast; endosulfan sulphate, 0.12 ± 0.12, 4.8 ± 1.62 and 10.0 ± 2.02, respectively, in Spanish River, 3.6 ± 0.95, 3.1 ± 0.56 and 7.9 ± 1.29, respectively, in Swift River and 0, 3.9 ± 2.17 and 24.0 ± 14.67, respectively, in sea coast. Dieldrin residues were detected only once in water (0.2 ± 0.03) and sediment (0.02 ± 0.003) of Spanish River, water (0.76 ± 0.09) of Swift River and sediment (0.1 ± 0.005) of sea coast; pp′ DDE was found twice in water (3.1 ± 1.53) and sediment (0.1 ± 0.007) of Swift River and water (0.8 ± 0.22) and sediment (6.14 ± 0.41) of sea coast. Arochlor was detected only twice (0.011 and 0.153) in water of Spanish River.

Topical application of crude ethanol extracts (CEs) of the leaves of 43 of 51 Jamaican plants produced varying degrees of multiple acaricidal effects on engorged Boophilns microplus Canst., including mortality (M), inhibition of oviposi tion (IO) and inhibition of embryogenesis (IE). Acaricidal indices (AI) ranged from 50 to 100 for the CEs of 29 plants, 38 to 47 for 9 plants and from 0 to < 25 for 13 plants. The most active CEs, in decreasing order of activity (AI values in parentheses) were those of: Siiiiaronba glmicn (100), Symphytiim officinale (99), Nicotiana tabacum (95), Hibiscus rosa-sinensis (93), Ervatmnin divaricala = Ricimis comimmis (82), Salvin serotina (80), Stachytarplietajamaicensis (79), BHghia snpida = Ocimum iiiicranthum (76), Spigeiia anthelmia (75), Cycloplis semicordata (74), Mormordica -. charnntin (71), Bontia daphnoidcs (69), Azadirachta indica (68), Capsicum annum = Calharanlus roseus = Pctiveria alliacca (66), Gliricida sepium (64), Lippin nlba (62), Cuscuta americana = Eryllirina cornllodendrum (61), Piper nmnlngo (60), Cannabis saliva = Cecropia peltnta (58), Dioscorea polygonoides (56), Arlocarpus altilis (53), Crolalaria retitsn (51), Citrus auranlium (50).

The most frequently detected residues in soils, well and spring water, and in water, sediment and fish/shrimp samples from rivers and sea coasts across Jamaica, are endosulfans > chlorpyrifos > diazinon > dieldrin; these often exceed LC50 values for many fish species. Mussels, sediment and water of Kingston Harbour had residues of eight organochlorines.

The pest control potential demonstrated by various extracts and compounds isolated from the kernels and leaves of the neem plant (Azadirachta indica) A. Juss. (Meliaceae) seem to be of tremendous importance for agriculture in developing countries. Laboratory and field trial data have revealed that neem extracts are toxic to over 400 species of insect pests some of which have developed resistance to conventional pesticides, e.g. sweet potato whitefly (Bemisia tabaci Genn. Diptera: Aleyrodidae), the diamond back moth (Plutella xylostella L. Lepidoptera: Plutellidae) and cattle ticks (Amblyomma cajennense F. Acarina: Ixodidae andBoophilus microplus Canestrini. Acarina: Ixodidae). The compounds isolated from the neem plant manifest their effects on the test organisms in many ways, e.g. as antifeedants, growth regulators, repellents, toxicants and chemosterilants. This review strives to assess critically the pest control potential of neem extracts and compounds for their use in the tropics. This assessment is based on the information available on the wide range of pests against which neem extracts and compounds have proven to be toxic, toxicity to non-target organisms, e.g. parasitoids, pollinators, mammals and fish, formulations, stability and phytotoxicity.

Kingston Harbour, a 50 km2 bay connected to the Caribbean sea only through a 3.5 km channel, is contaminated with residues of at least seven insecticides, which are introduced by the Rio Cobre. Weekly sampling of the Harbour for a month in July 1992 revealed the following maximum and mean residue levels in water (μg l−1) and sediments (ng g−1; data in parentheses), respectively: α-endosulphan, 8.56 and 2.18 (1 and 0.52); β-endosulphan, 15.7 and 7.86 (0.76 and 0.4); endosulphan sulphate, 0.0003 and 0.0003 (0); p,p′-DDT, 7 and 7 (0.04 and 0.35); dieldrin, 3.75 and 1.88 (0.001 and 0.001); aldrin, 0 (36.7 and 9.2); endrin, 0.93 and 0.26 (0.006 and 0.006); lindane, 0 (0.8 and 0.5); and diazinon, 0.1 and 0.05 (0.007 and 0.045). Oysters and fish were also contaminated with α-endosulphan, diazinon and aldrin.

Crude ethanol extracts (CE) of leaves of 60 plant species belonging to 32 families and 52 genera were bioassayed for toxicity to adult Tribolium confusum by spraying a 10% (w/v) concentrate under a Potter's tower. CE of eight plants had none and three had some bioactivity; 36 CE killed from 13 to 40% of the beetles. Thirteen plant extracts inflicted between 53 and 100% mortality in the following order: Azadirachta indica (53%) < Eupatorium odorantum = Gliricida sepium = Mimosa pudica (60%) < Annona reticulata = Hibiscus rosa sinensis (67%) < Cycloptis semicordata < Artocarpus altilis < Capsicum annum (90–97%) < Bontia daphnoides = Cuscuta americana = Dioscorea polygonoides = Nkotina tabacum (100%).RésuméDes extraits bruts d'éthanol provenant de feuilles de 60 espèces de plantes appartenant à 32 families et à 52 genres ont été soumises à des analyses biologiques destinées à déterminer leur toxicité à des Tribolium confusum adultes au moyen de pulvérisations sous tour potters d'un concentré de 10% (poids sur volume).Les extraits de 8 plantes n'ont montré aucune bioactivité, alors que 3 ont montré activité; 36 extraits ont tué de 13 à 40% des scarabées. 13 extraits ont infligé une mortalité de 53 à 100 %. L'orde des plantes bioactives est le suivant: Azadirachta indica (53%) < Eupatorium odorantum = Gliricida sepium = Mimosa pudica (60%) < Annona reticulata = Hibiscus rosasinensis (67%) < Cycloptis semicordata < Artocarpus altilis < Capsicum annum (90–97%) < Bontia daphnoides = Cuscuta americana = Dioscorea polygonoides = Nicotina tabacum (100%).

Kinetic studies on the degradation of three commonly used pesticides in Jamaica, dieldrin{(1R,4S,5S,8R)-1,2,3,4,10,10-hexachloro-6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-endo,exo-1,4:5,8-dimethanonaphthalene} and alpha- and beta-endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide), were carried out under laboratory conditions that simulated those of tropical agroecosystems. Studies included measurements of rates of volatilization, hydrolysis, and photolysis. Volatility from EC formulations on glass surfaces at 30-degrees-C was in the order alpha-endosulfan > dieldrin > beta-endosulfan. Kinetic data provided first-order plots of 1n F vs t with correlation coefficients ranging from 0.99 to 0.85 (F is the volatilization flux expressed as mu-g cm-2 day-1 and t is the time in days) and t1/2 values ranging from 2 to 7 days. Hydrolytic degradation rates of both alpha- and beta-endosulfan at 30-degrees-C decreased with pH in the sequence pH 9.5 (t1/2 = 0.04 days) > pH 7.0 (t1/2 = 25 days) > 4.5 (t1/2 = 90 days) for a first-order model. Hydrolysis of dieldrin (t1/2 = 95 days) was insensitive to pH over the same range. Photolytic degradation followed a first-order model and the half-lives were in the order dieldrin (2.5 h) < beta-endosulfan (3.5 h) < alpha-endosulfan (20 h) in hexane solution and dieldrin (1.7 h) < beta-endosulfan (33 h) < alpha-endosulfan (48 h) in aqueous solution. Photolysis rates in sunlight were in the same order, but half-lives were between 20 and 40 days in bulk hexane solution, while the average t1/2 was 15 h for each compound in a thin layer of hexane solution.