The effect of laval diet on the growth and development of Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and Eldana saccharina Walker (Lepidoptera: PYralidae)

Sesamia calamistis Hampson and Eldana saccharina Walker larvae were reared at 25°C on pieces of stem from five indigenous African grasses. All five, Andropogon sp., Panicum maximum Jacq., Pennisetum polystachion (L.) Schult., P. purpureum L. and Sorghum arundinaceum (Desv.) Stapf. have been reported as host plants for one or both species. Larval survival, larval and pupal period and pupal weight were recorded and compared to values of these parameters for larvae reared on stems of maize and on artificial diet. S. calamistis larval survival was less than 10% on each grass species compared to 95% on artificial diet and 30% on maize stems. Larval period was similar on maize and the grasses, but was 50% faster on artificial diet. Pupal periods were similar for larvae reared on grasses, maize and artificial diet. Pupal weights were highest for larvae reared on artificial diet, followed by maize and then grasses. E. saccharina larval survival was less than 5% on each grass species compared to 60% on artificial diet and 19% on maize stem. Larval development was 25% faster on artificial diet than on maize or grasses. Larvae reared on grasses, maize and artificial diet had similar pupal periods. Pupal weights were lowest on grasses and highest on artificial diet

Habitat and plant specificity of Trichogramma egg parasitoids—underlying mechanisms and implications

Egg parasitoids of the genus Trichogramma are among the most important and best-studied natural enemies worldwide. Parasitism levels by Trichogramma vary greatly among different habitats, plants or plant structures on which the host eggs are located. Here we summarise the published evidence on mechanisms that may underlie the observed variation in parasitism rates. These mechanisms include plant spacing, plant structure, plant surface structure and chemistry, plant volatiles and plant colour. In addition, plants can affect parasitoid behaviour and activity by providing carbohydrate food sources such as nectar to the adult wasps, and by affecting the nutritional quality of the host eggs for progeny development. Knowledge of plant and habitat factors that affect Trichogramma spp. efficacy has important implications for biological control, and for assessing the risks that mass-released Trichogramma spp. may pose to non-target insects. [KEYWORDS: Biological control ; Conservation biological control ; Food ecology ; Multi-trophic interactions ; Non-target effects ; Plant volatiles ; Trichomes

Evaluation Of Pigeonpea Pod Borer And Pod Fly Tolerant Lines At Kabete And Kiboko In Kenya

Pigeonpea lines which have shown tolerance to pod borer and pod fly damage at ICRISAT, Patancheru, India, were tested in the field at Kabete and Kiboko, Kenya, and compared with five local checks. There were sprayed and unsprayed plots for each line. Endosulfan 35 E.C. was applied at 0.07% active ingredient (a.i.) starting at flower bud expansion stage, at 50% flowering, early podding, and full podding stages. At crop maturity, all pods from three plants plot-1 were sampled and seed damage by different insect pests determined. The results showed that seeds from all lines were damaged by pod borers and pod sucking bugs. Pod fly incidence was greater at Kabete than at Kiboko, and damage was lower on test lines than on checks. Spraying reduced seed damage from 57.6% to 9.3% and from 59.9% to 4.5% on pod borer lines and pod fly lines, respectively, at Kiboko, and from 19.9% to 5.4% on pod fly lines at Kabete. At Kiboko seed damage in unsprayed pod borer (57.6%) and pod fly (59.9%) lines was similar. Seed damage on pod fly lines at Kiboko (59.9%) was significantly higher than at Kabete (19.9%). Positive significant correlations were observed between seed mass and pod fly damage at Kabete (r = 0.31*) and Kiboko (r = 0.30*). The results indicated that although some lines showed tolerance to pod borer and pod fly damage, they were highly susceptible to pod sucking bugs, suggesting that such tolerance does not hold against other insect groups.Des lign\ue9es de pois d'Angole qui se sont montr\ue9es tol\ue9rantes aux foreurs des gousses et aux mouches des gousses \ue0 l'ICRISAT-Patancheru, en Inde, ont fait l'objet des essais \ue0 Kabete et \ue0 Kiboko au Kenya et ont \ue9t\ue9 mises en comparaison avec cinq t\ue9moins locaux. Pour chaque lign\ue9e, il y a eu des parcelles pulv\ue9ris\ue9es et non pulv\ue9ris\ue9es. On a appliqu\ue9 l'endosulfan 35 E.C. \ue0 0,07% de mati\ue8re active d'abord \ue0 l'\ue9tape d'expansion des bourgeons florales, ensuite \ue0 50% de floraison, au d\ue9but et \ue0 la fin de la formation des gousses. Au stade de maturation, toutes les gousses pr\ue9lev\ue9es sur trois pieds par parcelle ont \ue9t\ue9 mises \ue0 l'\ue9chantillonnage afin de d\ue9terminer les d\ue9g\ue2ts caus\ue9s aux grains par des insectes ravageurs diff\ue9rents. Les r\ue9sultats ont r\ue9v\ue9l\ue9 que les grains de toutes les lign\ue9es ont \ue9t\ue9 atteints par des foreurs des gousses et des punaises suceuses de gousse. L'incidence des mouches des gousses a \ue9t\ue9 plus \ue9lev\ue9e \ue0 Kabete qu'\ue0 Kiboko. Les d\ue9g\ue2ts dus aux mouches des gousses ont \ue9t\ue9 plus faibles sur les lign\ue9es d'essais que sur les t\ue9moins. La pulv\ue9risation a permis de r\ue9duire les d\ue9g\ue2ts aux grains de 57,6% \ue0 9,3% chez des lign\ue9es tol\ue9rantes aux foreurs des gousses et de 59,9% \ue0 4,5% chez des lign\ue9es tol\ue9rantes aux mouches des gousses \ue0 Kiboko. A Kabete, la pulv\ue9risation a r\ue9duit les d\ue9g\ue2ts de 19,9% \ue0 5,4% chez des lign\ue9es tol\ue9rantes aux mouches des gousses. A Kiboko, les d\ue9g\ue2ts aux grains chez des lign\ue9es non pulv\ue9ris\ue9es tol\ue9rantes aux foreurs des gousses (57,6%) et aux mouches des gousses (59,9%) ont \ue9t\ue9 similaires. Les d\ue9g\ue2ts chez des lign\ue9es tol\ue9rantes aux mouches des gousses ont \ue9t\ue9 significativement plus \ue9lev\ue9s \ue0 Kiboko (59,9%) qu'\ue0 Kabete (19,9%). Des correlations significatives positives ont \ue9t\ue9 observ\ue9es entre le poids des grains et les d\ue9g\ue2ts dus aux mouches des gousses \ue0 Kabete (r = 0,31*) et \ue0 Kiboko (r = 0,30*). Les r\ue9sultats ont indiqu\ue9 que certaines lign\ue9es se sont montr\ue9es tol\ue9rantes aux d\ue9g\ue2ts dus aux foreurs des gousses et aux mouches des gousses. Cependant, elles ont \ue9t\ue9 tr\ue8s sensibles aux punaises suceuses de gousse, ce qui laisse sugg\ue9rer que de telle tol\ue9rance ne pourrait pas r\ue9sussir contre d'autres groupes d'insectes

Studies Of Pigeonpea Insect Pests And Their Management In Kenya, Malawi, Tanzania And Uganda

Systematic surveys were conducted in farmers' fields in Kenya, Malawi, Tanzania, and Uganda to determine the incidence, distribution and damage levels due to insect pests of pigeonpea seeds. Three surveys were conducted in eastern Kenya, one in 1992 and two in 1995. Two surveys, one per country per year - were conducted in Malawi, Tanzania, and Uganda in 1995 and 1996. Key insect pests were pod sucking bugs (dominated by Clavigralla tomentosicollis St\ue5l), pod and seed boring Lepidoptera (Helicoverpa armigera H\ufcbner, Maruca vitrata (= testulalis) Geyer, Etiella zinkenella Treitschke), and pod fly (Melanagromyza chalcosoma Spencer). Seed damage due to insect pests were 22, 15, 14, and 16% in Kenya, Malawi, Tanzania, and Uganda, respectively. Damage levels indicated that pod sucking bugs were more damaging in Malawi (caused 69% of total seed damage) and Kenya (43%), while pod borers caused more damage in Tanzania (50%) and Uganda (54%). Pod fly caused more damage in Kenya than in the other countries. Pod borer damage was high in early maturing crops and pod fly in late maturing crops, while pod sucking bugs damage was high regardless of crop maturity period. Greater variations in seed damage were observed between locations in Kenya, Malawi, and Tanzania than in Uganda. Warm and dry locations had less seed damage than warm and humid, cool and dry, or cool and humid locations in Kenya, Malawi and Tanzania. None of the farmers visited in Malawi, Tanzania, and Uganda used conventional pesticides on pigeonpea in the field. Over 80% of these farmers used traditional methods in storage pest management. In contrast, 35 and 53% of farmers in Kenya had used conventional pesticides on long-duration pigeonpea genotypes in their fields.On a conduit une s\ue9rie d'enqu\ueates en champs paysans au Kenya, au Malawi, en Tanzanie, et en Ouganda afin de d\ue9terminer l'incidence et la r\ue9partition des ravageurs de pois d'Angole ainsi que les taux de d\ue9g\ue2ts aux grains dus \ue0 ces ravageurs. Trois enqu\ueates ont \ue9t\ue9 men\ue9es dans l'est du Kenya, une en 1992 et deux en 1995. Chacun des trois pays - Malawi, Tanzanie et Ouganda - ont fait l'objet d'enqu\ueates une fois en 1995 et une autre fois en 1996. Les ravageurs importants ont compris des punaises suceuses de gousse (surtout Clavigralla tomentosicollis Stal), des foreurs des gousses et des grains (Helicoverpa armigera Hubner, Maruca vitrata (=testulalis) Geyer, Etiella zinkenella Treitschke), ainsi que des mouches des gousses (Melanagromyza chalcosoma Spencer). En milieu r\ue9el, les d\ue9g\ue2ts aux grains dus aux ravageurs ont \ue9t\ue9 22% au Kenya, 15% au Malawi, 14% en Tanzanie, et 16% en Ouganda. Les taux de d\ue9g\ue2ts ont indiqu\ue9 que les punaises suceuses de gousse ont \ue9t\ue9 les plus graves au Malawi (69% des d\ue9g\ue2ts totaux aux grains) et au Kenya (43%), tandis que les foreurs des gousses ont occasion\ue9 plus d'atteintes en Tanzanie (50%) et en Ouganda (54%). Les mouches des gousses ont caus\ue9 plus de d\ue9g\ue2ts au Kenya que dans d ' autres pays. Les foreurs des gousses ont provoqu\ue9 des d\ue9g\ue2ts importants chez les cultures pr\ue9coces et les mouches des gousses chez les cultures tardives. Les punaises suceuses de gousse ont caus\ue9 des atteintes graves sur tous les cycles de maturation. Il y a eu plus de variations dans les taux de d\ue9g\ue2ts parmi les localit\ue9s au Kenya, au Malawi et en Tanzanie qu'en Ouganda. Les localit\ue9s chaudes et s\ue8ches ont eu moins de d\ue9g\ue2ts que les localit\ue9s chaudes et humides, fra\ueeches et s\ue8ches, ou fra\ueeches et humides au Kenya, au Malawi et en Tanzanie. Les paysans qu'on a rencontr\ue9s au cours des enqu\ueates au Malawi, en Tanzanie et en Ouganda n'ont pas appliqu\ue9 de pesticides conventionnels sur le pois d'Angole aux champs. Plus de 80% de ces paysans emploient des m\ue9thodes de lutte traditionnelles contre les insectes des denr\ue9es. Par contre, 35% des paysans rencontr\ue9s au Kenya en juillet 1995 et 53% en ao\ufbt 1995 ont appliqu\ue9 des pesticides conventionnels sur les g\ue9notypes de pois d'Angole tardifs dans leurs champs