A Survey of Five Stem-Feeding Insect Pests of Wheat in the Northern Great Plains
The wheat stem sawfly, Cephas cinctus Norton, the wheat stem maggot, Meromyza americana Fitch, the Hessian fly, Mayetiola destructor (Say), the wheat jointworm, Tetramesa tritici (Fitch), and the wheat strawworm, Tetramesa grandis (Riley), have long been considered wheat pests in the northern Great Plains. This paper reports results of surveys for these pests conducted over 3 yrs in parts of Montana (10 counties), North Dakota (14 counties), South Dakota (1 county), Nebraska (4 counties) and Wyoming (1 county). Fields were randomly selected and a mean of 191 stems were sampled from each field. The percentage of stems infested with each pest was recorded. The percentage of parasitized wheat stem sawfly larvae also was noted. The wheat stem sawfly, wheat stem maggot, and Hessian fly were the most commonly encountered pests, recorded in nearly every county. Wheat stem sawfly density was twice that of wheat stem maggot (7% vs 3.2%) in infested fields. Wheat stem sawfly densities exceeded 10% in 4 counties: Da...
Biology of the galling wasp Tetramesa romana, a biological control agent of giant reed
The biology of the gall-forming wasp Tetramesa romana Walker (Hymenoptera: Eurytomidae) from southern France and Spain was studied to determine its suitability as a biological control agent of giant reed (Arundo donax L.), an exotic and invasive riparian weed in the US and Mexico. Females produced eggs parthenogenetically and deposited them into shoot tips. Eggs were 1.26 mm long and hatched within 5 days of oviposition. The larvae completed three instars within 23–27 days, with the first and second instars lasting 5 days each at 27 C and the third instar lasting 12 days. Larvae increased in length from 0.9 mm to 4.1 mm between the first and last instars. The total generation time averaged 33 days. Adults were 6.8 mm long with antennae and lived 3.7 days. Spanish wasps lived 1.3 days longer than French wasps. Most (80%) parthenogenetic reproduction involved wasps that were less than 5 days old. A total of 36% of French wasps tested and 65% of Spanish wasps produced offspring. Individual Spanish wasps produced an average of 26 (up to 66) progeny, displaying an intrinsic capacity for increase of 0.081 and a population doubling time of 9.2 days. Over 90% of exit holes made by emerging wasps were located within two nodes of the shoot tip. Reproductive wasps made 2.5-fold more probes than did wasps that failed to gall stems, and probing behavior was 13% more prevalent in the afternoon than in the morning. The Spanish genotypes of T. romana are particularly suitable for mass production to support field releases.
The Performance of Insecticides – A Critical Review
As part of minimizing the risk of crop losses due to herbivorous arthropods (here, mainly referring to insects and mites), most of the World’s commercial food production systems are subjected to several applications of pesticides before being harvested. Some crops are sprayed 10-20 times, while most field crops are sprayed 1-5 times during the growing sea‐ son. In the US alone, the average number of insecticide applications ranges from 1-3 for most of the major field crops, and the total annual costs of pesticide applications exceed $1.3 billion ([1], U.S. Department of Agriculture agricultural statistics services: www.nass.us‐ da.gov/). Several large ag-producing countries publish extensive details on insecticide use, including Australia, and the data presented below were collected from a public website (http://usda01.library.cornell.edu/usda/nass/AgriChemUsFruits//2000s/2008/AgriChemUs‐ Fruits-05-21-2008.pdf) on pesticide applications in the US in 2006. A somewhat extreme but also important example is the fresh sweet maize production in the US, which was grown on about 85,000 ha. Based on data from 14 US states, 20 different active ingredients of herbi‐ cides were applied an average 1.04 times to fresh sweet maize and amounted to about 2.6 kg of active ingredients of herbicides per ha. The same data suggested that about 3.5 kg of 23 different active ingredients of insecticides were applied on average 2.10 times per ha. Simi‐ larly, tomato fields (grown on about 42,000 ha in the US in 2006) were treated with 12 differ‐ ent active ingredients of herbicides, which were applied, on average, 1.14 times and the equivalent of about 0.7 kg of active ingredients per ha. Regarding insecticides, the same to‐ mato fields were treated with 32 different active ingredients, which were applied an average of 3.6 times and equal to about 4.9 kg of active ingredients per ha. While tomatoes and sweet corn may be close to the top of the list of growing crops receiving pesticide treatments, cau‐ liflower, celery, and many other horticultural crops and fruits are also subjected to intensive pesticide spraying regimes. Thus, farmers acknowledge that weeds and arthropods can po‐ tentially cause significant economic losses, and total pesticide application costs are low