Protective Fruit Wrapping

Ken Love                            Oct. 2002

 

For hundreds of years throughout most of Asia, farmers have been covering fruit with paper either to protect their appearance or to increase the time the fruit would be on the tree thus making it sweeter.

 

This practice first came to Hawaii with the early Japanese immigrants and in the 1920’s Ohau farmers employed school children to wrap figs.

 

Currently there are over 3000 types of bags manufactured in Japan alone. In addition to differences in size, the bags vary in the amount of light being transmitted to the fruit, color of paper, wax coatings  and chemicals impregnated in the paper. (.05% daiazinon is the most common). The bags all have a small wire imbedded at the top in order to facilitate the wrapping process. There are slits in the bottom so that any rain water can drain out. Some bags have or can be made with an open bottom.

 

 

The bags we used for this test were made in Niigata Japan. The company started manufacturing wax coated papers for umbrellas over 300 years ago. Currently the bags are sold throughout Japan, China, Taiwan, Malaysia, Korea, and Chile. They are used primarily on apples, asian pears, loquat, peaches, grapes and mango. Bags are  used to control ripening time, for desired coloration and for pest control. The company works directly with growers as well as wholesalers to find the best bag for a particular crop. The types of bags tested were recommended by the company after input from Hawaii growers and a tour of Big Island farms.

 

Hawaii Tropical Fruit Growers, West Hawaii chapter members participated in a number of bagging tests to determine the time to bag various fruit. The average was 7 minutes per 25  bags. There were some variables depending on the type of fruit and position of fruit to branch. In tests with 100 bags, bagging times ranged from 16 minutes to 30 minutes. There are bagging contests in Japan as part of some festivals where the average time per 100 bags is 8 minutes.

 

This report will touch on a number of fruit being tested with the bags.

The economics of using the bags, some of the horticultural practices

involved in bagging, problems encountered and the results.

 

Loquat

 

Although popular in many countries, the loquat has never found a following in the Hawaii or U.S. market with some notable exceptions in Calif. , Fla., and Southern Texas. This in part because of having to harvest the fruit early, before the birds and other pests get it. There seems to be a misconception that loquat is yellow when ripe. In Asia most varieties are orange when fully ripe and very sweet.  Using the bags prevents  the fruit fly and birds  from getting to the orange ripe fruit.  For the purposes of this test, we used 5000 bags on loquat growing at 3 locations ranging from 800 feet above sea level to 2000 feet. We practice  the Japanese type of production where flowers and young fruit are cut back so that there are only 3 or 4 fruit per cluster. In half the cases these clusters were bagged together. The rest of the fruit were bagged individually. Some fruit clusters were left unbagged on each tree at various heights. In no cases was unbagged  fruit able to ripen fully. Birds or stings damaged all fruit that had ripened to orange. “Almost ripe” yellow fruit was undamaged  30% of the time. this  fruit can be eaten but is somewhat sour. Often it is used for jelly, chutney or other products. The bagged  fruit had only one instance of damage from roaches.

 

Since there has been no market for loquat locally, we sent samples to a number of hotels as well as  sold some in local groceries. After a test shipment to one hotel, the chef called to say they would purchase all the loquat we could supply. Pricing as in Japan was based on sizing and fruit weight.  80 to 100 gram fruit was $3.50 per pound 50 to 80 gram at $3.00 and below 50 gram  at $2.00 from the 7800 fruit counted, the average weight was 60 grams. Most of the production coming from older varieties

such as Gold Nugget, Wolfe,Tanaka, Mammoth, Advance and a number of seedlings. The newer varieties from Japan; Obusa, Mizuho and Fusa hikari and others, have an average weight of 85 grams. These will be in full production within 4 years.

 

Counted totals:

7800 bagged  fruit

Insect damage: 3

 

2100 unbagged fruit

Bird damage: 747

Fruit fly stings : 984

Useable: 301

Other: 68

 

Types of bags tested:

White with light wax coating and 50% light transmission.

Red with light wax coating and 38% light transmission.

Light brown with  wax coating and 61% light transmission.

Recycled phone book paper with 33% light transmission.

Inner coated recycled phone book paper with 4% light transmission.

 

Fruit was bagged after it had been thinned and developed to about 20cm in length. In some cases top leaves were stripped back to facilitate the bagging.

 

We found few differences in bags during the previous years testing other than fruit exposed to direct morning sunlight would be susceptible to sunburn during the green to yellow stage of fruit development. When the fruit receives more sunlight, we found that using bags with less light transmission was desirable for better coloring and no damage. Larger bags (205mm x 300mm) were used to bag 3 or more fruit in a cluster and bags (102mm x 131mm) were used for individual fruit.

 

Less labor time to use one bag on three or more fruit rather than individual bags was somewhat offset by the differences in prices of the bags. Larger bags are priced at an average of 2.89 yen per bag in Japan.

Smaller ones at 1.09 yen per bag.

 

The use of bags on loquat is common in Japan, China, Spain, Israel, Algeria and other producing countries. For Hawaii it presents a unique opportunity for a new local market and a future possibility of export as our harvest time is different from other growing areas around the world.

 

 

 

 

 

Figs

 

Thought to be the first fruit wrapped in Hawaii, the practice of protecting figs from bird and insect damage was lost as itinerate labor moved on to steady jobs in the pineapple  and sugar fields of the 1930’s.

 

We tested 5 fig trees in 3 locations  from 600 foot to 1300 foot elevations. In previous years, in order to protect fruit from birds and fruit flies, we strung a number of cd roms from branches,  hung aluminum foil

and Christmas tinsel  as well as left a half dozen fruit fly traps around the tree. The main tree for this test is at the 1300 foot elevation in South Kona. This brown turkey variety produced an average of 250 figs per year for approximately 15 years. From that, only a handful ripened fully were without damage and edible. None were what I would call sellable. In an effort to secure a sellable crop, we started to use the cd roms to scare birds in 1998. In 1999 we added the fruit fly traps, more cd’s and tinsel.  This being an exceptionally good year for figs, we were able to harvest 268 that were in perfect condition, out of 331 counted. In 2000

we added some bags to the other pest management devices. After a heavy pruning at the end of the previous harvest season, we had  230 perfect figs out of 281. In 2001 we used 200 bags, 180 of which produced sellable fruit. Damage  to the other 20 figs was caused by insects on over ripe fruit which we did not harvest in time. This was true of fruit on the other trees we tested. Perhaps because of the additional heat inside the bag, the fruit tends to ripen much faster. In some cases with bags with less light transmission, the brown turkey figs,  will stay  green but ripen and become soft and sweet to the taste.  Kadota figs also ripened  faster inside the bags and have a light green color when ripe. Tests this year are inconclusive as we are in mid season. From the first 100 bagged figs,

 

undamaged  fruit  94

damaged 6

 

The damaged fruit was caused by what I believe were rats eating through the  paper. This occurred  on both uncoated and wax coated bags.

 

unbagged figs

86 were damaged from birds.

It was impossible to tell if the fruit was stung as the birds would leave only a small piece of skin or the stem of the fruit.

 

There are 300 bags currently on the fig trees and we should be testing close to 1000 figs in total this year.

 

We used 3 types of bags, all of which had a V cut in the top center of the bag to facilitate bagging the fruit close to the branch. In some cases we

would remove leaves  close to the fruit. Bagging takes place when the fruit is developed to about 30cm in length.

 

Types of bags tested:

Red with light wax coating and 38% light transmission.

Light brown with  wax coating and 61% light transmission.

Recycled phone book paper with 33% light transmission.

 

We also plan to test large white bags over the stems where 3 or 4 figs are clustered.

 

Fresh figs also represent a potential market. We’ve received a number of calls from wholesalers, hotels and West Coast distributors asking for quantities. Currently we sell some fresh figs in the local grocery  but most of them are processed into jam for two local shops and a shop in Japan.

 

 

Abiu

 

The growing popularity of this fruit in local and mainland markets warrants growers giving it much more space in their fields. Currently

with 5 prolific producing trees we cannot supply enough for 1 customer. The attractive yellow color makes it a target for consumers as well as  for birds, fruit flies and hosts of other  pests.  With an approved treatment for irradiation, the abiu has a promising future for Hawaiian growers. In our test marketing at the Kona Pacific Farmers Cooperative (KPFC), we’ve had no negative comments on the fruit, even when visitors

got a little latex on their lips.

 

We bagged abiu at 2 Kona locations ranging from 900 to 1500 foot elevations.  Previous testing taught us that bags with a V cut in the  center top and an extended wire, cut bagging time considerably. When we bagged fruit in previous years, we found some green fruit with and apparent fruit fly stings and some with a sunburn. This year we bagged younger fruit, about 6cm in length. In some cases, perhaps because of our dryer area, rough handling during the bagging caused the fruit to fall from the branch. Greater care and more time had to be taken with individual fruit. In other cases, fruiting  and flowering occurred at the same time and flowers close to the fruit were removed during the bagging.

 

This year we are using a light brown bag with  wax coating and 61% light transmission.

 

Current tests are still underway. So far we have bagged 500 fruit and harvested 78. There has been no visible damage. Two of the harvested fruit had some blemishes. One of those had mealy bugs close to the stem end. The fruit was able to ripen fully on the tree. We harvested 38 unbagged fruit, all of which was stung or had bird and rat damage. In no cases could the fruit reach full ripeness without significant damage. In 5 cases with

almost ripe fruit, there was little visible damage but when the fruit was opened, sting damage was evident and in 2 cases, larva  was visible.

 

In previous years, we have been able to get few fruit to market that had not been bagged. Our conclusion is that bagging abiu is the only way to make it marketable in West Hawaii.

 

 

Mango

 

Although a poor season for mango in Kona, we were able to perform a few tests on the varieties:  Kensington, Kurashige, Pirie, Peach and an unnamed Australian variety. Mangos are being bagged successfully in Japan and other Asian growing locations but it is unclear if these locations  have the same problems with fruit fly, seed weevils, mites, thrips, anthracnose and stem rot and the other problems that plague Hawaiian growers. Closed bottom bags are  used in Japan where mangos are grown inside and in the Ogasawara islands.

 

We tested both closed and open bottom bags in a variety of colors and light transmission capabilities. Although coloring is affected slightly, we could find not significant difference in bags with 33% to 73% light transmission. More research is indicated in order to determine the best coloration for individual varieties.

 

We found that with open bottom bags some mango were free of infestation. With all closed bottom bags there was some infestation

from either roaches or borers. In some cases cane spiders or geckos

made a home inside the bags. For some reason this only happened

on mango.

 

The trees we tested  were at 800 and 900 foot elevations. With these limited tests of only 120 bagged  fruit, the only notable difference was on the Kensington. The bags seem to promote a more even coloring and were more blemish free than the unbagged fruit. There were no stings on the bagged fruit whereas all the unbagged fruit had some sting damage.

 

Fifty bagged Kensington were marketable.

Fifty unbagged fruit, were not marketable but 20 were edible and

good for home use or for processed products.

 

The 25 bagged Kurashige seemed to suffer from stem rot, anthracnose or thrips both in and out of the bag although this could be because of the time at which we bagged the fruit. 

 

The Australian variety had a much lighter coloration when bagged

than the unbagged  fruit even with 73% light transmission. Coloring

was uneven in both bagged and unbagged fruit. The 20 bagged mango

were free from infestations with the exception of roaches on both

open and closed bottom bags. Unbagged fruit fell from the tree much faster than the bagged fruit although the bagged fruit seemed to ripen faster.

 

Our conclusion is that much more research is needed to determine the types bags to use for different mango varieties and the best time to bag them.

 

 

White Sapote

 

A fruit that thrives at higher elevations in Kona, the sensitivity of the skin as well as the fruit seems to prevent successful marketing. However, at the KPFC test market, those trying the fruit for the first time have always asked for seconds or purchased a number of the fruit. The tree also has a reputation for aborting small fruit and dropping others in strong winds. We looked at bagging the fruit as a way to keep the fruit attached to the tree with the help of the wire in the bag. This practice is common for greenhouse grown mango in Japan. Pest control and even coloration were also helped by bagging. The white sapote which seems to suffer from a number of viruses as well as insect damage and we found the bags seemed to promote consistency in ripe fruit.

 

Types of bags tested:

Red with light wax coating and 38% light transmission.

Light brown with  wax coating and 61% light transmission.

Recycled phone book paper with 33% light transmission.

White with light wax coating and 73% light transmission.

 

Although there were some differences in fruit color with the various bags, we could discern no other differences with the limited testing.

 

200 bags were used on trees in 4 locations. In a few cases the fruit did fall inside the bag and various beetles would chew through the bag to get at the fruit. All the bags that fell had some infestation. From the 184 fruit harvested, the color was more even and the skin undamaged. Fruit that was bagged at a later stage of development still had some skin discoloration but this did not affect the flesh or taste of the fruit. There was no insect damage in any of the bagged fruit.

 

Out of 184 unbagged fruit randomly chosen for comparison, 103 had some insect damage that would make the fruit unmarketable. In 32 cases, the fruit had split which made it more appealing to other insects. The remainder of the fruit was intact but uneven in coloration.

 

White sapote will ripen after harvest and the use of the bags along with taste tests at the KPFC test market showed that there is a potential for this fruit in todays marketplace.

 

 

 

 

 

Lychee

 

Perhaps the most extensive testing we performed this year was on lychee. Trees at five locations ranging from 900 to 1600 foot elevations were used. Varieties tested included Kaimana, Pot po hung, Brewster, Groff, Kwai mi and a number of seedlings.  

 

Preliminary previous years testing dictated that we use open bottom

bags in order to prevent some  mealy bug or roach infestation. The white bags available were 254 mm x 340 mm.  Based on this years test we would recommend a length of 450 mm and a wire that extended an additional 30 mm from the top of the bag. In years with a heavy fruit set, the width could be extended to 300 mm. The additional length would help protect against the fruit fly stings that occurred on the bottom fruit in bagged  clusters. The extra wire would facilitate the bagging process in tightly grouped clusters and while bagging from a ladder.

 

Overall we used 7000 bags at 6 locations at trees from about 700 to 1500 foot elevations. 4000 of these bags were given to West Hawaii chapter members.

 

The translucent white bags with 50% light transmission helped to promote more even ripening on the lychee. There were  few cases of the side facing the sun being red and the back side still green. With the  bags, we could keep the fruit on the tree up to 3 weeks longer allowing it to ripen to it’s  fullest and enabled us to have fruit to sell after the season was over for other growers. The coloration on Kaimana was perfect and we could command a higher price for the perfect fruit.

 

We bagged the lychee after the main fruit set. This being a mediocre

year for lychee in Kona, the bags insured a greater number of marketable fruit. In some cases, with smaller clusters of fruit that were next to each other, we stripped some of the leaves and bagged 2 of the clusters together. With a longer bag, this leaf stripping might not be necessary.

 

We found some differences between the varieties bagged although most of our efforts went into Kaimana. With Pot po hung, there were greater incidents of mealy bugs than on other cultivars. The Brewster seemed more resistant to stings and birds.

 

In some cases the crop from whole trees was bagged while other trees were left unbagged. In other cases trees were left half unbagged. We could tell no difference in percentages of good fruit versus damaged fruit. Of high number of stings or infestation on bagged fruit,1004 cases, 998 occurred on the fruit at the bottom of the bags. 

 

With labor, we found it easier to find part time help at the time of bagging

for $10 to $12 per hour than  during harvest  time at $12 to $15 per hour.

 

One of the biggest differences we found was in the time to cull harvested  fruit. The average time to harvest and prepare an order was less than half with the bagged fruit. Overall we are looking forward to next season when we don’t have to count all the fruit!

 

Lychee numbers

 

Bagged fruit

 

total harvest  5997

 

           marketable fruit  4768

 

           damaged fruit  1229

                       split   60

                       bird    9

                       sting or infestation  1004

                       immature  159

 

unbagged fruit

 

total harvest 10,739

 

           marketable fruit   4379

 

           damaged fruit   6360

                       split    114

                       bird     2373

                       sting or infestation   1825

                       immature   2048

 

Average bag cost 7 cents per bag

 

Time

 

Average time to bag fruit = 7 minutes for 25 bags

Average number of fruit in bag: 23

Average number of fruit per pound: 25

 

Average time to harvest 

75 fruit = 9 minutes - unbagged

75 fruit = 8 minutes - bagged

 

Average time to cull fruit

2163 fruit in 219 minutes - unbagged

238 bagged  fruit - 7 minutes to unbag and cull

 

external labor cost

Average cost per hour for pre season labor $10. to $12.

Average cost per hour for peak season labor $12. to $15.

 

We believe that the increase in labor cost and the cost of the bag is more than offset by the greater number of fruit that is marketable and by the

time saved during the culling process.

 

Per 1000 Lychee

Bagged = 32 pounds at an average price of $3.50 per pound.

Unbagged =16 pounds at an average price of $2.75 per pound.

 

Overall labor time was less with the bags because of the

dramatic decrease in time to cull harvested fruit.

 

Per 1000 lychee we could achieve an additional profit of $75.00.

 

Other tests

 

All of our results clearly show the need for more testing as well as the advantage of using bags for fruit quality as well as quantity. How the bags made for climates in Asia and Chile affect the crops in Hawaii is unknown.

How the colors and materials ( wax coatings etc.) of the bags affect the flavor of the fruit can only be guessed at without further testing.

 

Preliminary tests on tomato, white pineapple, cucumber and guava

are encouraging.  

 

 

Q&A

 

Why use some types of bags over other types?

 

In Asia bags are used as much for coloration and to control ripening times as for pest control. Some farmers in Japan will choose bags for peaches

based on the color they want. Wax coating helps during the rain season

and may help prevent some types of pests from attacking the fruit. Further tests are indicated as to color of some bags on Hawaiian tropical fruit.

 

At what stage should the fruit be bagged?

 

Usually after fruit set although this is not as crucial on open bottom bags.

With loquat, bagging needs to take place while in the early green stage in order to prevent sunburn. This may be true with some abiu as well.

 

Should we strip leaves close to the fruit?

 

Although a common practice in some parts of Asia, leaf stripping  or counting the number of leaves per fruit is not practiced in Japan. I’ve found that in some cases such as with loquat, this helps to improve fruit size and facilitate the bagging procedure. With lychee, stripping some of the leaves also helps the bagging procedure and makes harvesting easier and faster.

 

 

How can you tell when fruit is ready to pick?

 

The bags tend to promote a more even ripening time. Random checks will tell if it’s time to harvest. With some fruit a gentle squeeze will let you know it’s time. In other cases you can tell from the color through the bag.

It depends on the color of the bag and fruit type. In very few cases was it

necessary to open the bag to determine harvest time.

 

Doesn’t it cost too much to bag the fruit?

 

No, the cost of the bags and time to bag fruit is more than offset by the time saved in culling bad fruit, the increased numbers of marketable fruit and the higher price fruit can be marketed for because of the better color.

 

How much do the bags cost?

 

From 3 cents to 10 cents are average prices. It depends on the quantity ordered as well as  bag type.

 

The bags will be available through the :

Kona Pacific Farmers Cooperative

tel: 808-328-2411

fax: 808-328-2414

 

Acknowledgements

University of Hawaii

Dr. Dick Bowen

Dr. Kent Fleming

Virginia Easton Smith

Dr. Robert Paull

Marc Meisner

Dr. Francis Zee

WSARE

George & Margaret Schattauer

Ader Takaki

Kona Pacific Farmers Cooperative

The Members of HTFG - West Hawaii