Fresh from the Field: Staying Up To Date On Insect Checking/Bedikas Tolayim Part 1

Halachic issues of infestation in many of the fruits and vegetables that we consume are well known. Much has been written and said about these issues, albeit to various degrees of halachic stringency. This article will focus on the methods used to monitor this evolving industry. Doing so requires both monitoring of the various produce items, as well as keeping track of their sources on an ongoing basis. This is easier said than done! We will explore the challenges inherent in accomplishing these objectives and discuss some of the more recent items that have surfaced on the infestation radar screens.

The world of entomology is ever evolving. Chaza”l1 stress the importance of knowing the facts in each locale, as the variables that affect insects and infestation change constantly. It used to be that due to their short shelf-life, produce was mainly sourced locally. Knowing the infestation issues inherent in each location was somewhat easier to monitor. Nowadays, produce is sourced year-round from locations near and far – be it from North or South America, Europe, the Mid-East, or the Far East – and transported to our local markets.

An interesting side note is that in years past, before product globalization, when looking to recite Shehechiyanu on a new fruit one did not need to look too far. Today, it has become so much harder to find any fruits that are not available year-round. This has led to stores bringing in many exotic fruits almost unheard of in the past such as lychee nuts, kumquats, dragon fruit, etc., just so we Americans can recite a shehechiyanu.

While we clearly benefit from both the convenience and enjoyment of having any fruit we desire within easy reach, the new global fruit economy also presents us with the challenge of keeping track of new infestation issues that are only now becoming more well-known. The kashrus agencies are forced to try to keep one step ahead in becoming well versed in the intricacies of the entomological and agricultural sciences around the world.

Matzui or Not Matzui – That Is The Question

Let’s begin with a brief overview of the halacha. The prohibition of eating insects is one of the most severe in the Torah. Ingesting even one insect can mean transgressing as many as six Biblical prohibitions.2 We are, therefore, required to ensure that our food is free from any infestation concerns prior to consumption. This obviously applies only to foods in which infestation is prevalent.3 We also know that due to the severity the Torah ascribes to the prohibition of ingesting an insect, even produce that is not heavily infested still requires checking m’dirabonon if the infestation levels are within a certain threshold.4 Understanding how to determine this threshold is beyond the scope of this article. Generally, if there is a 10%5 or greater chance that a given food item6 will contain an insect, it is required to be checked prior to consumption. However, determining the precise or approximate infestation level7 for any given type of produce is extremely daunting. There are many variables that affect the infestation levels including temperature, wind, moisture level, humidity, altitude, proximity to other fields, roadways, wires running through a field (which prevent air-based pesticide application from being applied properly), railroad tracks, etc. These factors can all have significant impact on any given field, and taking them all into account is no easy feat. Insects thrive in warm, moist, oxygen rich environments. They are also not strong fliers and are easily transported by winds.

There are two extreme examples to bring out this point. Salinas, California is known as “The Salad Bowl of the World”. From April through November, most of our produce (in North America) comes from this region. This area is located in a valley off the Pacific coast. Known for its microclimates, the weather patterns fluctuate constantly and, many times, dramatically. From cool and dry to humid and hot, crossed by major highways and rail lines, scattered throughout with many organic fields,8 this area is extremely prone to insect pressure.9 On the other extreme is the Quito region in Ecuador. This is a location considered to be a prime source for growing kosher vegetables. Located approximately 7000+ ft. above sea level on the equator, the weather is consistently cool and dry year-round; oxygen levels are lower and, therefore, insect pressure is easier to control.

So, how do we determine the levels of infestation upon which we base our recommendations and procedures? STAR-K takes a three-pronged approach. First, we employ a team of mashgichim spread across many locales around the country who are constantly checking many different varieties of produce. Log books10 are kept in industrial facilities and restaurants which allow us to monitor seasonal insect pressure. We also have a team of mashgichim who work on special projects, gathering information on specific types of vegetables and their infestation levels.11 Items are checked consistently over long periods of time, and the findings are logged and reviewed. This gives us a very good idea of the actual levels of infestation year-round. When infestation claims are presented, the first step is to investigate to see if insects are, indeed, found in that item. We also look at sourcing and environment to see if the issue is local or more far reaching.

Second, if infestation concerns are warranted we focus on developing or perfecting procedures to clean and/or check those items properly. Third, we present all of the above information to Rav Heinemann, shlit”a, and discuss the practicality of implementing these procedures in our certified facilities (as opposed to avoiding these items completely), as well as how to educate the kosher consumer with specific instructions. Sometimes, what is practical for a properly trained mashgiach may not be practical for home use. At other times, while we may offer a lenient approach for consumers, we may use more stringent options for the items we certify. Creating this balanced approach requires a rav hamachshir well versed in the facts of the fields, practicality of procedures, and halacha and daas Torah to decide how to balance disseminating the information in an accurate, clear, user friendly way.

Practically speaking, as we focus on procedures that are effective in worst case scenarios, there is less need-to-know precise infestation levels. Regardless of whether an item is infested 80% or 10% of the time, either way the item needs to be checked. In either case, the checking procedure is going to be the same. Generally, we recommend avoiding items that are highly infested to the levels of muchzuk, which means over 50% of the time they will be infested since the chances of actually getting these items clean can become very time-consuming and strenuous. Classic examples of items that are assumed to be infested to muchzak levels include many types of organic greens and berries. Generally, these items should be avoided. Then there are some items that may or may not be muchzuk; however, either way we have not found an effective means of checking them properly. Examples are artichokes, brussels sprouts,12 blackberries and raspberries. Therefore, we do not recommend that they be used at all – fresh or frozen – without a reliable hashgocha on the bag indicating that it is free of any infestation concerns. Lastly, there are some items that can be cleaned and checked only with great difficulty, i.e., broccoli and kale, which due to their structure of tight florets or extremely curly leaves are very difficult to clean and check. Proper cleaning and checking requires considerable force in agitating each head, and considerable physical strength is needed to perform this properly. We publish guidelines for these items specifying required checking procedures, as some might otherwise assume they do not require any checking at all. However, we encourage consumers to ensure they exercise proper techniques in this process. It is best to receive training or guidance from a professional mashgiach to ensure it is being done correctly.

The “Shmatte” Bedika – The Thrip Cloth Method

A very effective method for checking many common greens that was developed in Eretz Yisroel by leading experts is known as the Shmatte Bedika or “thrip cloth method”. The procedure: 1. agitate the greens vigorously in a bucket of soapy13 water, 2. pour the water through a 60 micron (or smaller) filter cloth, 3. inspect in good light.14 This method has been proven to be even more effective than checking lettuce or herbs leaf-by-leaf.15 However, we still do not recommend using organic products which will likely not pass inspection even after being washed well. However, if they do pass the “shmatte” inspection, they may be consumed without question.

Many have been skeptical about the effectiveness of this method, which does not physically look at each leaf. While this inspection demonstrates whether there are insects still present in the sample, why can we rely on this method to indicate that if no insects are found in the checked sample the remaining produce can be considered ‘clean’? The answer to this question is that the Torah doesn’t tell us how to check, it simply indicates the severity of the prohibition of eating insects. Therefore, we are required to check for them in our food and employ the best methods possible to avoid such a serious transgression. Moreover, extensive research has been conducted16 which showed conclusively the effectiveness of the thrip cloth method. Vegetables that had already ‘passed’ a leaf-by-leaf type of inspection, even by trained mashgichim, were found to contain insects when the thrip cloth method was subsequently performed. Further research showed that if the thrip cloth was clean, subsequent checks including leaf-by-leaf were also found to be clean, indicating conclusively that the thrip cloth method is the most effective inspection technique. Another benefit is that this method is much easier and faster, especially for larger quantities of produce. For the past five years, STAR-K has required the thrip cloth method for all our certified vegetable facilites and establishments. Many other agencies have also instituted this same procedure.

Obviously, this procedure has certain caveats and details for specific types of produce, and its effectiveness depends on the type of produce being checked. Such details are beyond the scope of this article, and more information can be found on our website,

Current Events

As previously mentioned, we have dedicated many resources and personnel to ensuring we stay as up-to-date as possible with our recommendations. With the encouragement of Rav Heinemann, shlit”a, and as our motto indicates, we place great emphasis on educating and sharing the knowledge we obtain with other kashrus agencies and consumers. As Sy Syms so famously used to say, “An Educated Consumer is the Best Customer”. Indeed, it is imperative that the kosher consumer be as informed as possible. It is also important that the facts remain reported as facts. Each agency or consumer can then take these facts and ask their own shailos regarding what their hanhaga should be. I would like to briefly highlight some of the facts we have seen regarding some recent issues.


Although we said we will avoid talking about the ‘same ole’ issues, no article can avoid the most basic yet challenging leafy green (i.e., romaine and iceberg). At the forefront of so many menus and events, there are significant challenges involved with certifying lettuces on a grand scale. The following is a brief17 synopsis of the methods used for washing, cleaning, and inspection.

Our certification requirements begin with finding a washing facility that includes systems equipped with adequate agitation to effectively clean the lettuce. Experience has shown that it is not worthwhile trying to certify a company unless there is an effective wash system in place. A key component of an effective wash is also the filtration system. Since it is cost- prohibitive to use fresh water all day long, wash water is recycled through the machine. Without an effective filter (50 micron or smaller) on the return water, insects that had been washed off will simply circle around and around in the water, which can negate any effectiveness that the wash may have had.

Next, the mashgiach will take a pre-wash sample of each lot being attempted for kosher. This check will decide which lots are cleaner and will be more likely to pass the final, post-wash inspections. The more infested lots are rejected outright.18

The final determination is made by the mashgiach checking the product post-wash, as it comes off the wash line, prior to packing.19 Large samples20 are taken throughout the production to ensure the finished product is truly naki m’chashash tolayim. Even one insect found at any time during the production will cause the entire production to be rejected.

Quinoa, Brown Rice and Other Dried Goods

There has recently been much discussion concerning the discovery of insects in quinoa, brown rice and other dried good items. It is well known that all types of dried goods21 can often contain microscopic eggs. If left to incubate, they will hatch and can result in a seemingly sudden infestation. Improper storage conditions include warm, moist environments (e.g., over the stove or on top of fridge) and direct sunlight. These insects are known in the world of entomology and food safety as ‘pantry pests’, since they will often be found in a pantry containing food that has been stored there for too long. All food manufacturers, from commercial to retail bakeries, spice companies, pasta companies, grain manufacturers and mills, etc., are all aware of this issue and should have proper quality control measures in place to prevent the occurrence of infestations. Dry, cool storage rooms are common in the industry where dried goods can be stored for longer periods of time. Standard protocols in distribution also require (usually by law) ‘First-In-First-Out’ (FIFO) in order to prevent any product from sitting around for too long.

However, periodically somewhere along the distribution chain, a particular lot of product can be left improperly stored [in a warehouse]. When it hits the market, people may find insects and pandemonium can ensue. It is important to note that these types of infestations are usually going to be specific to a storage issue and generally do not indicate a global issue with that particular product. In the most recent example of the red quinoa and brown rice, not only was it a specific type and lot of quinoa and rice, it was even isolated to a specific distributor in a certain region. It was not even found in every place where those lots were sold.

It should be clear that overall dried goods, including quinoa and flour (at least in the U.S.A and Canada), do NOT require any checking unless a specific storage problem is suspected. STAR-K recommends that all dried goods be stored in cool dry conditions, avoiding the above mentioned types of warm moist areas. If you do want to stock up (e.g., for Yoshon), research22 has proven that holding the product in a freezer (below freezing) for 96 hours will kill any eggs that are present. Subsequently, as long as the product is kept sealed properly no other issues should develop.
If you are going on vacation for the summer, ensure that your kitchen temperature will not rise above 80o F for a long period of time or you could end up having an issue.


Recently, there was much discussion regarding finding insects inside onions. Our research team investigated onions from various locations, both fresh from the fields and in stores. While we did find insects in some onions, overall our findings did not indicate an infestation level that would be considered matzui. As such, STAR-K policy does not require that onions be checked.23 Unfortunately, (like any natural product) there can be bad batches which become infested. It is unfortunate when this happens, especially when the bad lots end up in kosher markets. However, looking at the bigger picture these findings are clearly the exception and not the rule. Thus, our policy has remained that all types of onions (excluding scallions) do not require any checking.
[Bez”H, the second half of this article will appear in the next issue of Kashrus Kurrents.]

יעוין פרי חדש יו ב”ק כ”ד ס”ד סי’ פ” . 1
2. There are three types of שרץ המים ( 1 .שרצים , which is four שרץ הארץ ( 2 ;לאווין , which is five שרץ העוף ( 3 ;לאווין , which is six לאווין . The איסורים are listed in ויקרא פרק י”א and .דברים פרק י”ד
3. The inference of this being ‘ מדאו is only in regards to items which are מוחזק , meaning there is over a 50% chance of finding an insect in any given serving. .ואכמ”ל
יו”ד סי’ פ”ד סע’ ח’ . 4
יעוין משכנות יעקב סי’ י”ח . 5 . However, the exact number doesn’t really matter, as we shall soon see.
6. Rav Heinemann, שליט”א , follows the opinion of the חת”ס יו”ד סי’ ע”ז that it is determined by serving size. This means we look at the percent or chance per serving.
7. See KK It is also important to note that any research statistics need to be from post-washed product that is technically ready to eat. .יע’ שם
8. Which use less pesticides or other effective controls, they are generally highly infested, and also affect surrounding fields.
9. Industry term for infestation levels
10. Mashgichim record the type and source of each produce item, as well as pass/fail and how infested it actually was.
11. Recent projects include corn, strawberries (again!), raisins, blueberries, oranges and orange juice, pineapples and pineapple juice, other dried fruit, onions, chives and many others that we hope to address in future issues. In the meantime, our guidelines on our website,, are kept completely up-to-date with our policies, based on our research.
12. They can be checked by taking them apart like a cabbage, but that is not how people like to eat them. It is recently becoming more popular to buy shredded brussels sprouts, which can be checked much more easily using the thrip cloth method.
13. We have found that adding a non-toxic dishwasher soap (not regular dish soap) to the water greatly improves the accuracy of the checking. Soap acts as a surfactant to kill the insects so they release their grip; and it also helps to physically remove the insects. This is opposed to plain water or even most veggie washes which do not accomplish this. However, the original research did not require soap in the checking water.
14. For a video demonstration, see
15. We found that even trained mashgichim may miss insects when checking leaf-by-leaf, especially large quantities. This is not saying that the leaf-by-leaf method is invalid, rather that the thrip cloth is just better and more accurate.
16. By experts in E”Y, as well as our own research. Interestingly, a very similar method is used by entomologists when they conduct research.
17. For more details, please see and also
18. They are obviously not disposed of, rather they are used by for the non-kosher customers.
19. An important note on this last point is the requirement to check BEFORE the product is packed and labeled (which happens simultaneously) as kosher. If the product would be checked as it is being packed, then in the event infestation is found, all the packed and certified product would need to be discarded or re-worked, which can be a costly prospect.
20. For more details on this, see
21. Including cereal, beans, rice, pasta, popcorn, beans, oatmeal, dried fruit, etc.
22. Feel free to google it on your own; there is plenty of research on this.
23. This does NOT include scallions, which definitely need to be checked. See our guide for details.