Efficient Manipulation of Natural Enemies Through Increased Understanding Pest-Plant-Natural Enemy Interactions in Egyptian Crops. Collaborative Project with Dr. D. Bottrell (PI): P. Barbosa (Co-PI)

Traditionally, the major approaches to the biological control of insect pests have consisted of classical (importation) biological control, augmentation and conservation. Although the use of the first two approaches has been widespread and relatively successful, the use of biological control-enhancing genetically modified crops (BCEGMC) has been minimal. However, before such a strategy is implemented much more information is needed on between and within cultivar differences in attraction of natural enemies and, in particular, the aspects of plants that most affect natural enemy survival and effectiveness.

• Field Plot Evaluations
  
  Field plots of five major crops which may serve as model systems for the proposed research. The five systems evaluated have been soybeans, cole crops, tomatoes, peppers, and corn. Fifteen lines of corn also have been evaluated and are continuing to be evaluated under field conditions. Seven varieties of peppers are under greenhouse evaluation and we hope to do field evaluation in the near future. The names of the cultivars tested of each the latter crops are available on request. These evaluation have given some insights into the variable pest load on several different crops and the levels of activities by predators and parasitoids in several crops.



• Evaluations of Tri-Trophic Level Interactions
  
  The research in this domain has involved developing an understanding of the role of specific plant traits on natural enemies.
  
  Research has been conducted on the effects of plant morphological complexity on a predator of the pea aphid Coccinella septempunctata L.. This has been accomplished using isolines of peas (normal, tl, and aftl). Differences in morphology are such that morphological complexity of the near-isogenic lines can be ranked from low to high complexity. The near-isogenic lines exhibit two mutant genes af (afila) and tl (acacia) which alter the normal pea leaf considerably without exhibiting any other differences.
  
  Plant type and associated differences in leaf morphology were found to have no significant influence on aphid fecundity, intrinsic rate of increase, or pattern of distribution of aphids in the absence of predators. However, differences in the leaf morphology of the near-isogenic lines had a significant effect on the median residence time of the predator, when on leaves without aphids or with aphids. Beetles on the aftl leaf (the most complex leaf) had the longest residence time, whereas beetles on the Normal and tl leaves had the intermediate and the shortest residence times, respectively.
  
  Foraging times followed a pattern that was similar to that found for residence times. In the absence of aphids on leaves, leaf complexity had significant affects on foraging times. Beetles on the more complex leaf, aftl, had the longest foraging time compared to the Normal and tl. The frequency of falls from a leaf was not significantly associated with leaf morphological complexity. This was the case in both leaves with and without aphids. Leaf complexity had a significant effect on the search efficiency of the beetles with or without aphids. Search efficiency was significantly reduced on the more complex aftl leaves as compared to the Normal and tl leaves. Coccinellid area search efficiency was significantly increased on the tl vs the Normal leaves when aphids were present. The morphological complexity of the plant did not have a significant effect on the proportion of aphids consumed by C. septempunctata. While the predation efficacy of C. septempunctata was not affected by leaf morphology, plant complexity had a significant effect on the degree of prey disturbance by the predator. The location of surviving aphids was significantly different on each of the isolines.