Infochemical-tritrophic Interactions of Soybean Aphids-host Plants-natural Enemies and Their Practical Applications in Pest Management

The soybean aphid, Aphis glycines Matsumura, is a newly invasive insect species that seriously threatens U.S. soybean production. This aphid pest has kept haunting many soybean growers by developing large colonies on soybeans in North America since 2000. Since its first appearance inWisconsin, it has spread to over half of US states and southern provinces in Canada. The heavy infestation of this pest whittles soybean growers’ profits and causes hundreds of million dollar losses. The present chapter will mainly describe efforts in studying aphid chemical ecology and sensory physiology for understanding how male aphids find their mates and host plants. It will also cover research efforts to understand host plant associated volatiles being used as cues for overwintering host plant location. In addition, findings on how soybean plant defensive system works against aphid infestation, as well as how those induced plant volatiles are used by aphid’s natural enemies for prey location will be presented. Finally, the use the basic understandings for developing useful tools for soybean aphid practical control will be discussed

Effects of hydroxycinnamic acid esters on sweetpotato weevil feeding and oviposition and interactions with Bacillus thuringiensis proteins

Sweetpotato weevil (SPW) pest management is challenging because the pest target is sub-terranean, so the application of pesticides is impractical and usually ineffective. Host plant resistance and the genetic transformation of sweetpotatoes to produce entomotoxic Bt proteins offer potential for environmentally benign pest control. Resistance can be conferred by naturally occurring hydroxycinnamic acids which protect against oviposition by adults, but these compounds are restricted to the root surface so do not protect against the cortex bound larvae where the greatest damage occurs. Resistance could be enhanced if combined with expression of Bt proteins in transformed plants but interactions between hydroxycinnamic acids and Bt proteins remain unknown. Here the bioactivity of Cry7Aa1 protein and hydroxycinnamic acid esters was evaluated individually and in combination against SPW larvae and mortality determined. Low and high concentrations of hydroxycinnamic acid esters alone caused significantly higher mortality of both weevil species in all experiments compared to the control. SPW larval mortality was greater when tested as a combination of hydroxycinnamic acid esters and Bt protein but this effect was additive not synergistic. Although we report no evidence of antagonistic interactions the antifeedant effects of the plant compounds conferring host plant resistance could have reduced consumption of the Bt protein in our assays leading to a lower efficacy when combined. Further work is required to determine if the toxic effects of Bt proteins function alongside host plant resistance in sweetpotato under field conditions

In-ground post maturity storability of five local sweetpotato varieties

Two experiments are described in which prolonged post maturity storability of sweetpotato (lpomoea batatas L.) was studied between 1990 and 1992 at Namulonge Agricultural and Animal Production Research Institute (NAARI). Five commonly grown local varieties Tanzania (TZ), Tororo I (TOR l), Tororo 3 (TOR 3), Kawogo (KA} and Kyebandula (KY) were harvested at 4, 5, 6, 7, 8, 9 and 10 months after planting (MAP). The harvest date (HD) for optimum storage root yieldsfor for varieties TZ, TOR I, KA and TOR 3 were at 8 MAP while that for KY was 9 MAP. Varieties KA and KY attained their optimum fresh root yield at 10 MAP while varieties TOR 3, TOH I and TZ attained theirs at 7, 8 and 8 MAP, respectively. Storage root quality varied among varieties and deteriorated with time for all varieties. The magnitude of weevil damage increased with increase in in-ground storage period, but remained relatively stable after 9 MAP. The different varieties correlated differently but not significantly with the level of weevil damage except TZ ( r= -0.88*). The dry matter content percent (DMC %) varied among varieties and was negatively but non significantly correlated with rainfall. In-ground post maturity period had no significant effect on root cooking quality, taste and texture. However, the optimum HD is crucial if optimum economic yield is to be achieved.Key words: Harvest date, in-ground storage, lpomoea batatas. yield, quality, weevil