Bh. Subramanyam

Development and evaluation of sequential sampling plans for Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae) infesting farm-stored wheat

The development and evaluation of appropriate sampling plans are needed for cost-effective management of stored-product insects. Sequential sampling plans, which are based on a variable sample size, are generally more cost effective than plans based on a fixed sample size. For adults of the rusty grain beetle, Cryptolestes ferrugineus (Stephens), we developed sequential sampling plans based on complete counts and the presence/absence of insects in 0.5 kg grain samples removed with a trier from the top 1 m of wheat stored in farm bins. Insect count data were used to develop a sampling plan for estimating the density of C. ferrugineus with a fixed level of precision. The presence/absence data were used to develop a sampling plan for classifying the C. ferrugineus infestation level relative to an action threshold. The performance of these sampling plans was evaluated (validated) using independent data sets and an IBM-PC software program specifically designed to test the plans. This is the first paper illustrating the development and evaluation of sequential sampling plans for a stored-product insect.

Quantitative analysis of temperature, relative humidity, and diet influencing development of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)

Abstract Data from three published studies on the development of Prostephanus truncatus (Horn) reared at constant temperatures and relative humidities (RH) were reanalysed to provide new information and quantitative description needed for predicting developmental times or rates in different environments. Models fitted to the temperature‐dependent development data were used for comparing developmental times among insect stages, relative humidities, diets and studies. Development of the eggs and pupae was similar at 40%, 70%, 80%, and 90% RH. Significant differences were detected between studies in the egg hatch to adult development and larval development, attributable, in part, to differences in the degree of compaction of ground maize used for rearing insects. For all life stages the temperatures for minimum (Tmin) and maximum (Tmax) developmental rates, and degree‐days above Tmin required for completion of development, were estimated. The linear degree‐day and nonlinear models presented here could be use...

Effects of short-term feeding by adults of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on shelled maize

Abstract Laboratory tests were performed to determine the damage caused by adults of Prostephanus truncatus (Horn) feeding on shelled maize. Adults when fed at densities of 25, 50, or 100 on 200 maize kernels for 10–40 days did not preferentially feed on the endosperm or the germ and damaged both. Fifty or 100 adults of P. truncatus feeding on 100 g of maize for 10–40 days caused substantial damage resulting in decreased weight and kernel germination. Kernel damage, grain weight loss, and germination after 40 days of adult feeding was about 5–8, 6–8, and 68–72%, respectively. Adult survival during the 40-day period decreased linearly with time at the rate of 1.5 and 1.3% of adults/day at adult densities of 50 and 100, respectively. Fifty adults of P. truncatus when fed on 100 g of maize for 20 days at 75% r.h. caused significantly greater kernel damage and grain weight loss at 30°C than at 25 or 35°C. However, adult survival at the three temperatures was similar. Though P. truncatus develops less effectively on shelled maize than maize on the cob, our results suggest that a short period of adult feeding could result in substantial grain damage.

Moth control in stored grain and the role of Bacillus thuringiensis: An overview

Insects, among other biological agents like fungi, bacteria, and rodents, attack stored grains leading to losses in quantity and quality. On a worldwide basis 13 million tons of stored food grains are lost annually to insect deprations (Hall 1970). In the United States a USDA report (Anon. 1981) estimated annual storage losses of corn, wheat, barley, sorghum, and oats due to insects during 1950–1960 to be about 324.50 million bushels; the annual monetary loss during the same period being approximately

A new character for identifying larval instars of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)

454 million. Therefore, reduction of loss and deterioration of stored grains by insects is necessary for maximum utilization of the food commodity.

Effect of posttreatment temperature on the toxicity of five synthetic pyrethroids toTetranychus urticae Koch (Acari: Tetranychidae)

Abstract Three larval instars of Prostephanus truncatus (Horn) were recognized in rearings at 25°C and 75% r.h., based on the greatest distance between the ventrally sclerotized lateral structures of the frontoclypeus. This distance for the first, second and third instars averaged 0.135, 0.183 and 0.274 mm, respectively. Larvae can be measured under ethanol by this method; mounting on slides, a prerequisite for measuring head capsule width, is not required.

Feeding by Adults of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on Shelled Maize: Influence of Damaged Grain, Adult Crowding and Grain Density

The synthetic pyrethroids bioallethrin,d-phenothrin, and fenvalerate, when tested by the slidedip technique, were more toxic to female two-spotted spider mites,Tetranychus urticae Koch, at 30°C than at 20°C. LC50 values differed by 1.7-, 3.8-, and 5.3-fold, respectively. Two other synthetic pyrethroids, flucythrinate and cyfluthrin, gave similar toxicity values at these two temperatures. The greater sensitivity ofT. urticae at a warmer temperature to the first three pyrethroids differs from insect toxicity studies, which often show negative temperature relationships.

Effectiveness of Insecto Applied to Shelled Maize Against Stored-Product Insect Larvae

In the laboratory, adults of Prostephanus truncatus (Horn) preferred artificially or naturally (insect) damaged maize kernels to sound kernels when adults were tested individually or in groups. Survival of P. truncatus was similar when I, 10, 40 or 80 adults were fed 100 g of shelled maize for 20 days; but more kernels were damaged at the highest adult density in comparison to the other densities of adults. Single P. truncatus adults on average damaged 9 maize kernels, but 10, 40, and 80 adults damaged approximately 15, 21 and 45 kernels, respectively, indicating that adults confined their feeding to only specific kernels. Survival of adults and number of kernels damaged were significantly affected when different quantities of shelled maize (25–500 g) were infested with 25 adults of P. truncatus. Adult survival at 25, 50, 100, and 200 g of maize/0.95–1 jar was similar (70.7–76.0%), but the number of kernels damaged increased significantly from approximately 15 at 25 g to 61 at 200 g. These results suggested that shelled maize grain compaction, which is influenced by the quantity of grain, may affect survival of and damage by adults of P. truncatus. Adults of P. truncatus successfully infested 25 g of shelled maize and damaged about 15 kernels, indicating that adults could temporarily survive on such small quantities of grain spilled in and around storages before infesting stored-maize.RésuméLes adultes de Prostephanus truncatus (Horn) ont nettement preféré les grains de maïs endommagés aux grains entiers, quand testés individuellement ou en groupes. La survie des adultes de P. truncatus s’est averée similaire quand 1, 10, 40 ou 80 adultes ont infesté 100 g de maïs pour une durée de 20 jours. Un nombre élevé de grains a subi des degats aux densités les plus elevées comparé aux autres densités. En moyenne, un seul adult de P. truncatus a endommagé 9 grains de maïs, maïs 10, 40 et 80 adultes ont infesté approximativement 15, 21 et 45 grains respectivement. Ceçi nous indique que l’attaque par les adultes a été reduite à des grains spécifiques. La survie des adultes et le nombre de grains endommagés ont été significativement affectés aux densités de grains suivantes: 25, 50, 100, 200, 300 et 500 g de maïs/0.951 jare, infestés par 25 P. truncatus adultes, pour une durée de 20 jours. La survie des adultes aux densités de 25, 50, 100 et 200 g de grain semblait similaire (70.7–76.0%), maïs s’est averée inferieure à celle aux densités de 300 et 500 g de grain (50.7–58.7%). Le nombre de grains endommagés s’est significativement élevé de 15.3 a 61.3 aux densités respectives de 25 et 200 g. Le nombre de grains endommagés n’a pas été significativement different aux densités de 200, 300 et 500 g de grain. Ces resultats suggèrent que la quantité de grain crée une compaction qui pourrait affecter la survie de P. truncatus. Les adultes ont succedé à infester 25 g de mais et à endommager 15 grains, indiquant que les adultes peuvent survivre sur de petites quantités de grains éparpillées aux alentours des lieux de stockage avant d’infester le maïs stocké.