P.C. Annis

Fumigant Toxicity of Essential Oils and Monoterpenes Against the Red Flour Beetle, Tribolium castaneum Herbst

Abstract Toxicity of various essential oils and their volatile components against the red flour beetle, Tribolium castaneum (Herbst) was determined. The most potent fumigant toxicity was found in essential oil from rosemary (LD 50 = 7.8 μl/l air) followed by the oils of lemon (LD 50 = 16.2 μl/l air), basil (LD 50 = 17.8 μl/l air), lime (LD 50 = 17.9 μl/l air), and peppermint (LD 50 = 25.8 μl/l air). 1,8-Cineole was the most toxic fumigant compound found in rosemary essential oil (LD 50 = 7.4 μl/l air) followed by menthone (LD 50 = 8.5 μl/l air) and p -cymene (LD 50 = 11.4 μl/l air). 1,8-Cineole exhibited similar fumigant toxicity against a PH3-resistant T. castaneum relative to the susceptible insects. Therefore, 1,8-cineole and rosemary essential oil could be a safer fumigant to control stored-product insect pests than those currently used.

Laboratory determination of the requirements for control of Trogoderma variabile (Coleoptera: Dermestidae) by heat.

The use of heat to disinfest storage structures (the bake-out technique) is enjoying a resurgence of interest because it represents a possible replacement for whole structure fumigation with methyl bromide. This technique uses moderately elevated temperatures typically in the range 50‐608C, over a period of hours to days. The objective of this work was to determine the basic requirements to controlTrogodermavariabile using heat so that e!ective bake-out procedures could be developed. The most heat-tolerant stage of T.variabilewas shown to be the full-grown larva and it requires 36.48C-min above the threshold of 49.48C to achieve 99% mortality. Thus the temperatures used in a practical bake-out should be as high as the other constraints will allow, and maintained somewhat longer than data for other species would suggest. In so doing, a control procedure aimed atT.variabilewould be expected to control all other species present. #2001 Published by Elsevier Science Ltd.

The acute mortality effects of carbon dioxide on various life stages of Sitophilus oryzae.

Abstract Raised levels of carbon dioxide (CO2) are known to be toxic to many insect species. Sitophilus oryzae had previously been shown to be one of the more tolerant species to this treatment. Cohorts of known age S. oryzae were treated at 25 °C and 60% r.h. with CO2 concentrations in the range of 15 to 100% with air as the balance. The nature of the mortality data obtained precluded the use of conventional probit analysis. Fitting the logit of response against a cubic polynomial of time gave a satisfactory fit for most data. Confidence intervals were estimated using a series of best cubic fits around tentative values of LTx. It was not possible to define a single mortality response surface taking into consideration concentration and time. Therefore, individual LTxs and confidence intervals were calculated for each concentration and age cohort. At higher CO2 concentrations pupae were the most tolerant (LT99 = 6.9 d in 65% CO2) and adults (LT99 = 1.5 d in 65% CO2) the most susceptible stages. At lower concentrations eggs were most susceptible (LT99 = 8.5 d in 20% CO2) with all other stages having an LT99 of longer than 45 d.

Fumigant toxicity ofEucalyptus blakelyi andMelaleuca fulgens essential oils and 1,8-cineole against different development stages of the rice weevilSitophilus oryzae

Essential oils extracted fromEucalyptus blakelyi (1,8-cineole, 77.5%),Melaleuca fulgens (1,8-cineole, 56.9%) and 1,8-cineole were shown to have fumigant toxicity against different development stages ofSitophilus oryzae. The eggs ofS. oryzae were the most tolerant, followed by pupae, larvae and adults in that order.M. fulgens oil,E. blakelyi oil and 1,8-cineole at 100 µl per liter of air gave, respectively, LT50 values of 16.2, 17.4 and 9.1 h for adults, 31.1, 19.3 and 17.5 h for larvae, 55.6, 75.2 and 39.7 h for pupae, and required >7 days for eggs. Only 1,8-cineole (200 µl−1 air) gave a significant egg kill by 7 days and the LT95 was 134.5 h. 1,8-Cineole could be a useful new fumigant.

Wind forces and their influence on gas loss from grain storage structures

Abstract The wind-generated pressure coefficients likely to be encountered in a free standing cylindrical grain storage with a conical roof are presented as measured from model experiments in a wind tunnel. These take into account the turbulent flow and vertical wind velocity profile likely to be found around such structures. The influence of pulsating wind flows is discussed theoretically and the practical consequences of wind-generated gas losses are detailed for fumigation or controlled atmosphere storage of grain.

The production and accumulation of carbon monoxide in stored dry grain

Abstract Carbon monoxide was identified as a common constituent of head space atmospheres in storage containing dry grain (

Quality changes in maize stored in sealed bag stacks.

Abstract White maize was stored for 9 months in four 228 t bag stacks, either sealed and treated with an initial dose of carbon dioxide for disinfestation, or left unsealed in air, but fumigated and sprayed. The quality of the maize stored in sealed enclosures was well maintained with minimal changes in insect damage at the completion of the storage trial. Better quality retention was observed in the sealed than in the unsealed stacks as judged by counts of insects (total insects and primary insect pests), percentage weight loss, moisture content, fat acidity values and colour; but not as judged by counts of discoloured grains. Increases in counts of insects and the related quality parameter, percentage weight loss, were markedly lower in the sealed stacks, indicating the efficacy of this treatment in retarding insect infestation and associated quality loss. Changes in insect counts were highly correlated with changes in percentage weight loss in unsealed stacks. There was an overall weight loss of 3.3% in the unsealed stacks. The use of sealed bag stacks shows significant advantages over conventional bag stacks for long-term storage of white maize in the humid tropics.