Delayed mating in tortricid leafroller species: Simultaneously aging both sexes prior to mating is more detrimental to female reproductive potential than aging either sex alone

Abstract The effect of delayed mating on reproductive potential, longevity and oviposition period of female redbanded leafroller, Argyrotaenia velutinana (Walker) and Pandemis leafroller, Pandemis pyrusana Kearfott, was investigated in the laboratory. Virgin female or male moths of each species were held for 1, 2, 4, 6 or 10 days prior to pairing with one-day-old virgin conspecifics of the opposite sex. In addition, reproductive potential was assessed when both sexes of each species were aged for those periods prior to pairing. The expected reproduction of female A. velutinana was reduced by 34, 53, 71 and 81% for 2, 4, 6 and 10-day delays in female mating, respectively. For P. pyrusana, expected reproduction was reduced by 47, 74, 85 and 93% for 2, 4, 6 and 10-day delays in female mating, respectively. Increasing male age at mating in both species had a lesser effect on female reproductive output compared with increasing female age at mating. As male A. velutinana age at mating increased, the expected reproduction of female A. velutinana was reduced by 15, 45, 54 and 70% for 2, 4, 6 and 10-day delays, respectively. Comparing male P. pyrusana of various ages at mating, expected reproduction was reduced by 14, 42, 64 and 79% for 2, 4, 6 and 10-day delays in mating, respectively. The decrease in female reproduction when both sexes were aged prior to mating was higher than when either sex alone was aged prior to pairing with a one-day-old virgin of the opposite sex. The expected reproduction of female A. velutinana was reduced by 60, 83, 96 and 98% for 2, 4, 6 and 10-day delays in mating of both sexes, respectively. Only 7.5% of female eggs hatched when both sexes of A. velutinana were aged ten days prior to mating. When simultaneously aging both sexes of P. pyrusana prior to mating, expected reproduction was reduced by 71, 93, 96 and 99% for 2, 4, 6 and 10-day delays in mating, respectively. No P. pyrusana eggs hatched after a ten-day delay of mating for both sexes. For both species, female longevity increased and duration of oviposition period decreased with increasing female age at mating. Our results demonstrate that delayed mating in both females and males negatively affects female reproductive output in both species and that simultaneous aging of both sexes prior to mating has a greater effect than aging either sex alone. Our results suggest that laboratory studies that have paired aged females or aged males with conspecifics of optimal reproductive maturity have likely underestimated the effects of delayed mating on reproductive output

Reinecke (John) collection

MSS. 615. 1903-1987. 4 cubic feet. The collection consists of copies of entomological articles collected by Dr. Reinecke,a former adjunct professor of entomology at MSU, focusing on the boll weevil and pink boll-worm but also including other insects such as the sugar-cane borer and the tobacco budworm, their physiology, life-cycles, control, and rearing in the laboratory. The articles are drawn from a variety of scientific journals and other publications, mostly from the 1960s to the 1980s

The potential of Paranosema (Nosema) lucustae (Microsporidia: Nosematidae) and its combination with Metarhizium anisopliae var. acridum (Deuteromycotina: Hyphomycetes) for the control of locusts and grasshoppers in West Africa

[no abstract

Host plant finding by Acraea acerata Hew. (Lepidoptera: Nymphalidae), the sweet potato butterfly: implications for pest management

Phytophagous insects such as Lepidopteran species utilise both olfactory and visual cues to locate their host-plants used as mating or oviposition sites, shelter or food. Larvae of Acraea aceratafeed on sweet potato plant leaves causing more that 50 % loss of sweet potato tuber yield in some East African countries. Attempting to elaborate a management strategy to control A. aceratasuitable to a tropical resource- poor farming system, it was essential to investigate how the butterfly finds its host- plants. The results of a wind tunnel bioassay using glass-screened, muslin-screened and non-screened sweet potato plants suggested that sweet potato plant volatiles play an important role in attracting A. aceratato its host-plant. This was supported by both the distance moved by female A. aceratatowards muslin-screened plants (olfactory cues) and the percentage of butterflies which landed on the screen. Visual stimuli seemed to have a negative effect. The attractiveness of sweet potato plant volatiles to A. aceratawas later confirmed by the use of volatiles collected by headspace entrainment from sweet potato plantsThe main components of sweet potato plant volatiles were tentatively identified by GC-MS (Gas Chromatography coupled with Mass Spectrometry) analysis and electrophysiological responses were recorded for some of them. Compared to ethylbenzene, 3-carene and (-) trans-caryophyllene, 3-hexen-l-ol,(Z), a general green leaf alcohol, elicited far more substantial EAG (electroantennogram) responses in A.acerata.This result suggested that A. aceratamight well respond to a specific blend of volatiles made up of the different chemical components of sweet potato plant volatiles instead of one or two specific chemical components.Considering the important role of sweet potato plant volatiles in attracting A. acerata,a number of plants reported to be repellent to herbivorous insects were mixed with sweet potato plants and screened for repelling/disorienting of female A. aceratain olfactometer and wind tunnel bioassays. Two plant mixtures with opposite effects on the response of A. aceratato their volatiles were identified: sweet potato + Desmodiumplant volatiles were found to be more attractive to the butterfly than sweet potato plant volatiles alone, and sweet potato + onion plant volatiles which reduced considerably the attractiveness of sweet potato plant volatiles to A. acerata.As the trichomes of Desmodiumplants were reported to trap insects, a ‘push-pull’ management strategy for A. aceratainvolving the two intercrops was suggested: the intercrop sweet potato + onion plants would ‘push’ away ovipositing A. aceratawhereas the intercrop sweet potato + Desmodiumplants would attract the butterflies which would be trapped by Desmodiumtrichomes. The results of a preliminary field experiment carried out in Uganda suggested that the intercrop sweet potato + onion plants had a negative effect on the number of egg batches laid by A. acerataon sweet potato plants. There is, therefore, a need for comprehensive field experimentation of the whole strategy to validate these laboratory and field experimental findings

Habitat management using stimulo-deterrent diversion techniques to decrease infestation of sugarcane by Eldana saccarina Walker (Lepidoptera: Pyralidae)

Despite research focused on the control of E. saccharina Walker (Lepidoptera: Pyralidae), it remains the most destructive pest of sugarcane in South Africa and therefore a shift in the approach to the control of this insect was required. Habitat management techniques were employed through trials to understand the mechanisms used by insect pests in their host plant oviposition behaviour. Indigenous and beneficial non-crop plants, which could be used to attract insect pests away from sugarcane were identified and tested. An African grass, Melinis minutiflora, shown to be repellent to lepidopteran stemboring pests, was used in field trials in sugarcane. Eldana saccharina was shown to be fairly indiscrimate in choosing host plant species. Oviposition trials showed that females made no choice for host plants oviposition based on the volatiles released by those plants. Females showed no preference for males over test plants. But did consistently move and make a plant choice more often than male moths. Moths were not attracted by the volatile stimuli of a host plant and the availability of cryptic sites might be a factor that influenced ovipositing females to choose a host plant. Field trials tested the repellent action of Melinis minutiflora against E. saccharina and were shown to be more effective over a big field with space for M. minutiflora to establish thick undergrowth alongside a field plot. The other field sites showed no significant effect from M. minutiflora intercropped into treatment plots, or a slight negative effect. Later sugarcane planting times in relation to the grass planting time was a possible reason for the positive result in only two field sites allowing the grass to grow and establish before the sugarcane competed with the grass for sunlight. A cost benefit analysis of planting a hectare of sugarcane with M. minutiflora showed an economic benefit linked to reduction in E. saccharina infestation. Field sites with low population pressure from E. saccharina would not yield the economic benefit of planting this grass. There was no significant loss in the height, density or sucrose yield (ERC% cane) between control and treatment plots in the field plots due to the presence of M. minutiflora. Comparison of weed biomass between treatment and control plots showed a significant reduction in the treatment plot where M. minutiflora out-competed the weeds already present. This grass was advantageous in the sugarcane field as it sometimes reduced moth infestation but did not significantly compete with sugarcane and showed weed suppressing potential

Insect pests of cultivated and wild olives, and some of their natural enemies, in the Eastern Cape, South Africa

This thesis has two focuses. The first problem facing the olive industry in the Eastern Cape is the growers’ perceptions of both what the industry will provide them and what a pest management program might entail. The second focus is the biology of olive pests in the Eastern Cape in terms of understanding their populations and their natural enemies on private farms, with future hopes of understanding how Integrated Pest Management strategies can be developed for this crop. Eastern Cape private farmers, small-scale farmers and workers from agricultural training institutions were interviewed regarding the history and cultivation of the local olive crop. Only one commercially viable olive grove was identified; other groves were small, experimental pilot ventures. The introduction of olives to small-scale farmers and agricultural training schools was generally a top-down initiative that led to a lack of sense of ownership and the trees being neglected. Other problems included poor human capital; poor financial capital; lack of adequate support; lack of knowledge transfer and stability; lack of communication and evaluation procedures of the project; miscommunication; and finally, olive pests. Apart from hesitancy to plant at a commercial scale, the main problem facing private farmers (Varnam Farm, Hewlands Farm and Springvale Farm) was pests. Therefore an investigation of pests from private farms was conducted ranging from collection of cultivated and wild olive fruit and flea beetle larvae for parasitism, trapping systems both for fruit flies and olive flea beetle adults. A survey of olive fruits yielded larval fruit flies of the families Tephritidae (Bactrocera oleae (Rossi), B. biguttula (Bezzi) and Ceratitis capitata (Wiedemann)) and Drosophilidae (Drosophila melanogaster (Meigen)) from wild olives (O. europaea cuspidata (Wall. ex G. Don) Cif.) but none from cultivated olives (O. e. europaea L.). Braconid wasps (Opiinae and Braconinae) were reared only from fruits containing B. oleae and B. biguttula. This suggests that B. oleae is not of economic significance in the Eastern Cape, perhaps because it is controlled to a significant level by natural enemies, but B. biguttula may be a potential economic pest. A survey of adult fruit flies using ChamP traps baited with ammonium bicarbonate and spiroketal capsules and Sensus trap baited with methyl eugenol and Questlure confirmed the relative importance of B. biguttula over B. oleae. ChamP traps were over 50 times better than Sensus traps for mass trapping of B. biguttula but both were ineffective for trapping B. oleae and C. capitata. Six indigenous flea beetles of the genus Argopistes Motschulsky (Chrysomelidae: Alticinae) were found, three described by Bryant in 1922 and 1944 and three new species. Their morphology was investigated by scanning electron microscopy and mutivariate morphometric analysis. The leaf-mining larvae are pests of wild and cultivated olives in South Africa and threaten the local olive industry. At Springvale Farm, A. oleae Bryant and A. sexvittatus Bryant preferred the upper parts of trees, near new leaves. Pseudophanomeris inopinatus (Blkb.) (Braconidae) was reared from 23 Argopistes larvae. The beetle larvae might not be controlled to a significant level by natural enemies because the rate of parasitism was low. The olive flea beetles showed no attraction to traps containing various volatile compounds as baits. The lace bug, Plerochila australis Distant (Tingidae), was sometimes a pest. It showed a preference for the underside of leaves on the lower parts of the trees. A moth, Palpita unionalis Hübner (Crambidae), was reared in very low numbers and without parasitoids. A twig-boring beetle larva, chalcidoid parasitoids and seed wasps of the families Eurytomidae, Ormyridae and Eupelmidae were also recorded