With the price of food rising rapidly over the last year and the awareness of the benefits of healthy eating growing.  We'll take a look at which organic foods offer you the most benefit.
In other words, which fruits and vegetables absorb the most pesticides for it to be worthwhile paying that little extra for an organic alternative.

The Environmental Working Group, is a nonprofit research organization.
They've produced a list which is an aid to strategic shopping when buying organic fruits and vegetables.

For example onions, mangoes, asparagus, broccoli and eggplant are all low in pestcide residues when grown using conventional farming methods.

While peaches, strawberries, sweet bell peppers (capsicums), celery and lettuce are foods that typically have high levels of pesticide residue.

Data provided by Environmental Working Group (EWG)

Why Should You Care About Pesticides?

There is growing consensus in the scientific community that small doses of pesticides and other chemicals can adversely affect people, especially during vulnerable periods of fetal development and childhood when exposures can have long lasting effects. Because the toxic effects of pesticides are worrisome, not well understood, or in some cases completely unstudied, shoppers are wise to minimize exposure to pesticides whenever possible.

Will Washing and Peeling Help?

Nearly all of the data used to create these lists already considers how people typically wash and prepare produce (for example, apples are washed before testing, bananas are peeled). While washing and rinsing fresh produce may reduce levels of some pesticides, it does not eliminate them. Peeling also reduces exposures, but valuable nutrients often go down the drain with the peel. The best option is to eat a varied diet, wash all produce, and choose organic when possible to reduce exposure to potentially harmful chemicals.

How This Guide Was Developed

The produce ranking was developed by analysts at the not-for-profit Environmental Working Group (EWG) based on the results of nearly 43,000 tests for pesticides on produce collected by the U.S. Department of Agriculture and the U.S. Food and Drug Administration between 2000 and 2004.

Most Contaminated: THE DIRTY DOZEN

Consistent with two previous EWG investigations, fruits topped the list of the consistently most contaminated fruits and vegetables, with seven of the 12 most contaminated foods. Among the top six were four fruits, with peaches leading the list, then apples, nectarines and strawberries. Cherries, imported grapes, and pears, were the other three fruits in the top 12. Among these seven fruits:

• Nectarines had the highest percentage of samples test positive for pesticides (97.3 percent), followed by peaches (96.6 percent) and apples (93.6 percent).
• Peaches had the highest likelihood of multiple pesticides on a single sample — 86.6 percent had two or more pesticide residues — followed by nectarines (85.3 percent) and apples (82.3 percent).
• Peaches and apples had the most pesticides detected on a single sample with nine pesticides on a single sample, followed by strawberries where eight pesticides were found on a single sample.
• Apples had the most pesticides overall with some combination of up to 50 pesticides found on the samples tested, followed by peaches with 42 pesticides strawberries with 38.

Sweet bell peppers, celery, lettuce, spinach, and potatoes are the vegetables most likely to expose consumers to pesticides. Among these five vegetables:

• Celery had the highest of percentage of samples test positive for pesticides (94.1 percent), followed by sweet bell peppers (81.5 percent) and potatoes (81.0 percent).
• Celery also had the highest likelihood of multiple pesticides on a single vegetable (79.8 percent of samples), followed by sweet bell peppers (62.2 percent) and lettuce (44.2 percent).
• Sweet bell peppers was the vegetable with the most pesticides detected on a single sample (11 found on one sample), followed by celery and lettuce (both with nine).
• Sweet bell peppers were the vegetable with the most pesticides overall with 64, followed by lettuce at 57 and celery with 30.

Least Contaminated: CONSISTENTLY CLEAN

The vegetables least likely to have pesticides on them are onions, sweet corn, asparagus, sweet peas, cabbage, broccoli, and eggplant.

• Nearly three-quarters of the eggplant (76.6 percent), broccoli (71.9 percent), sweet pea (77.1 percent), and cabbage (82.1 percent) samples had no detectable pesticides. Among the other three vegetables on the least-contaminated list, there were no detectable residues on 90 percent or more of the samples.
• Multiple pesticide residues are extremely rare on any of these least contaminated vegetables. Eggplant had the highest likelihood, with a 6.9 percent chance of more than one pesticide when ready to eat. Onions and corn both had the lowest chance with zero samples containing more than one pesticide when eaten.
• The greatest number of pesticides detected on a single sample of any of these low-pesticide vegetables was four as compared to 11 found on sweet bell peppers, the most contaminated crop with the most residues.
• Broccoli and asparagus both had the most pesticides found on a single vegetable crop at up to 19 pesticides but far fewer than the most contaminated vegetable, sweet bell peppers, on which 64 were found.

The five fruits least likely to have pesticide residues on them are avocados, pineapples, mangoes, kiwi, and bananas.

• Fewer than 10 percent of pineapple, mango, and avocado samples had detectable pesticides on them and fewer than one percent of samples had more than one pesticide residue.
• Though 59 percent of bananas had detectable pesticides, multiple residues are rare with only 2 percent of samples containing more than one residue. Kiwi had residues on 15.3 percent of samples, and just 3.4 percent had multiple pesticide residues.