Jump to content
Sign in to follow this  
Janet Macunovich

Deformed raspberries, Japanese beetles

Recommended Posts

M.E. asked recently:

I have had a raspberry patch for about 5 years.  My starter plants were given to me as suckers from a friend who said they were "Heritage" variety everbearing from the MSU extension.


Starting with one row, I have gradually dug up suckers that have grown up where I didn't want them, and made new rows. They have produced beautifully, one large crop in July, and then a smaller crop with bigger berries in September.  This year the newest row planted is producing some normal looking berries, but lots of very small black colored ones.  I'm just interested from a botany point of view what is going on.  Can you explain?


We replied:

There are numerous reasons for odd raspberries, from poor pollination to fungus infection (infection that can be weather related; last year was definitely a year for WEATHER...) It's also possible your raspberries have a virus infection, pretty common in raspberries and the reason many growers routinely grub out whole patches and start over with new  plants that have been virus-indexed as clean of the crumbles virus.


Sucking insects carry this virus from wild plants and infected cultivated plants, to others. So commercial growers also tend to spray insecticides regularly and burn out wild raspberries nearby, all to keep the leafhopper numbers down.


You can read about raspberry fruit problems in Extension bulletins linked below. Keep in mind as you look at images that technical writers usually show advanced stage disease photos because they are more definitive, just as a human medical book may show problems like rickets in its deformed-legs stage but not show the earlier, less distinct symptoms.







Raspberry fruit showing some developmental problems -- note the deformed and missing segments on the back, right fruit (arrow). The virus causes the fruit to be dry, fewer segments to form (sometimes there will be only two or three dark, dry segments per fruit.



Where there are fungal infections and water problems, fruit tissues usually rot and die. Note the discolored segments, which on inspection turn out to be moist.


Starting a season by identifying and looking into the problems of the previous year will give you time to do something different this year, whether that's do nothing because it was mainly a weather issue, or do some insect control (floating row cover is another, pesticide-free way to reduce leafhopper feeding) or replace your plants.


Thanks for your okay to post this exchange at our Forum so we  can see if others can add to the discussion.


What say you-all: Did you see unusual problems with raspberries in 2015, or problems you haven't identified yet?

Share this post

Link to post
Share on other sites

M.E. continued:

I do have some wild raspberries near my cultivated patch, and will consider getting rid of them.  Otherwise, I think I'll adopt a "wait and see" approach to see what happens this year. 


I have had quite a few Japanese beetles on them the last couple of years, but haven't worried about them, as they seem to eat only the leaves, and not the berries.  Could they have a long term negative affect on my crop, and if so, what would you recommend?


The first summer, I was so disgusted with them that most mornings I went out with a bucket of soapy water and hand picked them off the leaves into the water, but I felt I was fighting a losing battle, and didn't do that last year.  


I think I read that they winter under the soil and that some control can be gained by digging between the rows each spring, but that seems a rather arduous task unless I know I'm really accomplishing something worthwhile.


I've posted this exchange at our Forum, with photos. You can read and continue it here.


The beetles do not do lasting damage and don't transmit this virus. (Sucking insects draw fluids from one plant and then inject them with their saliva into living cells on other plants, infecting them. Chewing insects like beetles devour tissue.)  If they eat enough of the leaves they can reduce the raspberry plant's energy level to the point where it produces smaller, fewer fruits. And if the beetles are there in large enough numbers you can end up harvesting beetles along with fruit. Yuck.


Excluding the beetles helps. e same non-chemical control that helps beat leafhoppers can help a lot-- cover the raspberries with floating row cover.



Floating row cover is bed warmer as well as plant protector. It's fabric that's light enough that plants are not crushed, and it allows light and rain to enter while it bars insects and holds in some heat. This bed is covered against frost. (You get the idea, I hope. We've covered lots of things against insects over the years -- roses, raspberries, peonies, grapes -- but it appears we didn't take photos of those.)


It does require a large piece of row cloth to cover raspberries but that's why the manufacturers make it in such big sizes. Tent it then pull all edges down to the ground and use metal staples (like tent stakes) to hold them in place, or lay scrap lumber on the edge to secure it.


The beetles will still smell the raspberries, one of their favorite food plants, but they will be crawling on the fabric when you come out each morning to brush them down into your soapy water. Yes, every day, and best in the morning when the beetles have just arrived and are still slow in the cooler air. Don't neglect the daily patrol as if the row cover can do the whole job. It can't: some beetles will eventually bumble through gaps along the bottom or sides, and end up underneath.


The saving grace is that you only need to patrol for about a week, maybe 10 days. After that, the local beetle population is congregated elsewhere.



That's why Japanese beetle control is most effective IF YOU BEGIN AS SOON AS THE FIRST WAVE ARRIVES. That's in late  June as the white snowball hydrangea flowers begin to turn white. All the Japanese beetles in an area emerge from their underground grub-metamorphosing-to-adult state at about the same time. That's just a few day period. Then, the first ones to find good food begin releasing pheromones that call beetles within 1/4 mile. Once more beetles arrive and they begin to mate, sex pheromones are added to the chemical call and the crowds really swarm to that word. If you catch and kill the first wave, the local beetle population will all end up elsewhere, orgy-ing together.


Japanese beetles are grubs in the ground from late summer until very early spring, then they enter a non-eating resting state to change into beetles, which dig up and emerge in late June (or by the Fourth of July; the emergence is variable based on accumulated heat for the year. So better than watching the calendar is to watch the plants like hydrangea that are following those same cues.)


After feeding and mating, these beetles lay their eggs at the base of grasses, since the grubs must eat grass roots. If your rows between the raspberries are free of weed grasses you are probably not harboring the grubs. Nearby lawns are, however, as are gardens with ornamental grass and weed grass.


The beetles are most easily killed while young. As with most living things, it takes a lower dose of poison or fewer predatory nematodes to kill a baby than it does to kill a teenager or near adult. Resting-state insects that are not eating, are immune to stomach poisons but still susceptible to becoming nematode prey. So if you apply a grub killer or predatory nematodes please soak it into the lawn or grassy area when it will have the most effect, in late summer or in September.


Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

  • Create New...