Is rain good for fruit?

A lemon covered in raindrops
A lemon covered in raindrops

As a fruit grower, lying in bed listening to rain on the roof can bring up a wide range of emotions, both good and bad. In our typical dry summers most people welcome rain when it comes, so it never seems appropriate for us to express concern about the damage it can do to fruit. However, it hasn’t rained for a while, so this week we reflect on the question – “Is rain good for fruit?”

Like everything in farming, the answer is complicated, and depends on lots of different variables, so let’s break it down a bit.

1. Trees like rain better than irrigation waterup to a point! As a gardener, you’ve probably noticed how “perky” your garden looks just after rain. One of the reasons (apart from the leaves being cleaner) is because the rain carries dissolved nitrogen which is easily absorbed by the plants, giving them a nutritional boost. Too much rain, however, and the soil can become waterlogged, creating anaerobic conditions, which actually stops the plants’ roots being able to take up nitrogen! The other advantages of trees receiving their water from rainfall (rather than irrigation) are that the entire root system gets water (rather than just at the point of water delivery), and if you’ve been keeping your garden on rations due to dry conditions, they just love the opportunity to get their fill of water for a change!

A fungal disease outbreak on an apricot
A fungal disease outbreak on an apricot

2. Rain can trigger fungal disease. One of the biggest pest and disease risks in an organic farm (or garden) is fungal disease, and nearly all fungal diseases are triggered by wet conditions (at the right temperature). In general terms, the more rain, the more fungal disease. This risk is highest at the beginning of the season (i.e., at flowering time in spring), and then gradually decreases as the season progresses. During autumn, if the summer has been generally dry and there is not much fungal disease around, the risk of a new fungal outbreak is relatively low.

Cherries that have cracked in the rain
Cherries that have cracked in the rain

3. Rain can cause physical damage to fruit. This is very specific to the type (and even variety) of fruit. For example cherries are particularly vulnerable to splitting from the rain, and some varieties of apricots also split easily. Hardier fruit like apples and pears, however, rarely experience physical damage from rain.

An apricot with a severe crack caused by rain
An apricot with a severe crack caused by rain

4. “Hard” rain can damage all fruit. Storms that bring rain often also bring hail, and that can be completely devastating to all fruit. Hailstorms are very random and localised, so it”s pretty much the luck of the draw with this one, though if you live in a hail-prone area, netting can definitely be your saviour. All fruit are vulnerable to hail damage, including apples, pears, plums and quinces.

5. Rain is good for the landscape. When you’re trying to grow food in an arid landscape (as we are), the general impact of rain (as long as there’s not too much, or too quickly) is generally FABULOUS! It fills water storages, keeps the bush alive, helps to sustain our farming communities, and helps backyard fruit growers maintain their own food security. We love it….except…. when there’s too much! If rain becomes flooding and the soil becomes saturated for too long, it can lead to ALL sorts of problems! Anaerobic soil conditions, trees dying, waterborne soil disease, nutrient leaching, dams breaking their banks, and the list goes on. We’ve seen it before when the drought broke in 2010/11.

A rainy morning and green grass
A rainy morning and green grass

6. Rain is good for mental health. It’s a generalisation, of course, but very often rain can be a huge relief to farmers and others in the community, especially if it is relieving the pressures of trying to farm in a dry landscape, though as you can probably see from our list, it totally depends on the amount of rain, and the context!

Poppy lapping up a puddle
Poppy lapping up a puddle

Regardless of the timing of rain within the fruit season, it’s important to make sure your soil can act as a big “water storage tank” when it rains. As well as building really healthy soil (which is good for both water storage and drainage in your soil), techniques like swales and keyline (covered in this short course) can make a huge difference to how well your soil will store rainfall.

Four reasons for yellow leaves on fruit trees

Welcome to autumn! Though we’re having quite a warm summery week here in central Vic, we’ve had the first few cool, crisp mornings, and there’s a definite shift in the air.

Leaves on Angelina plum trees (on the LHS) starting to turn yellow in autumn
Leaves on Angelina plum trees (on the LHS) starting to turn yellow in autumn

Even if it still feels quite summery at your place, you can expect to start seeing some typical autumn features in your fruit trees soon.

For example you might start to see the leaves on your fruit trees start to turn yellow (if they haven’t already), especially if you’ve already picked the crop. The typical pattern is that the leaves will stay green and continue doing their job as long as the tree is bearing fruit, but once the fruit is off, it will quickly start go into senescence, or winter dormancy.

Close-up of yellowing leaves on plum tree
Close-up of yellowing leaves on plum tree

At that time, the tree starts to withdraw all the useful nutrients from the leaves back into the buds and bark — the first sign of this happening is the leaves changing colour. This type of yellowing is completely normal, and you see it every year.

Another reason for yellowing leaves that is of more concern is caused by lack of water, as you can see on this cherry tree.

A cherry tree that has turned yellow from lack of water
A cherry tree that has turned yellow from lack of water

It’s all too easy for this to happen when you have an automatic irrigation system, because drippers can easily block up, and unless you’re checking them regularly (which is a really good idea), you might not realise you have a problem until the tree starts telling you loud and clear by the leaves turning unseasonally yellow (you can see all the other trees nearby are still green).

Another common reason for leaves to turn yellow is from nutritional deficiencies.

Iron deficiency (chlorosis) on peach leaves
Iron deficiency (chlorosis) on peach leaves

A number of nutritional deficiencies can cause yellow leaves as one of their symptoms, including iron (as you can see above), manganese and zinc.

The fourth reason for yellow leaves is because of a virus disease, such as apple mosaic virus as you can see in this leaf.

Apple mosaic virus on leaf
Apple mosaic virus on leaf

Viral diseases are not good news, but unfortunately are not really treatable, so the best bet is to look after the tree as well as you can, and try to avoid the virus spreading by not planting other trees of the same type nearby.

So if the leaves on your fruit tree are turning yellow it’s probably a perfectly normal seasonal response, but your tree might also be trying to tell you something! If you feel like you need more detailed help diagnosing what your fruit tree is trying to tell you, please download a copy of Keep Your Fruit Trees Free From Disease short course.

Apricot leaves showing beautiful autumn yellow and orange colours
Apricot leaves showing beautiful autumn yellow and orange colours

Noticed any brown rot this summer?

Nectarine with brown rot infection
Nectarine showing signs of Brown rot

One of the diseases it’s important to monitor at this time of the year is Brown rot. In our part of the world (in southern Australia), our typically hot, dry conditions have not favoured the disease much this year, but we’ve still noticed an occasional piece of fruit with it, as you can see.

If you’ve had a rainy fruit season, you’re at a much higher risk of a Brown rot outbreak. It particularly loves warm, wet weather.

It’s important to pick any fruit that show symptoms, and dispose of it well away from the tree – put in the compost, feed to animals, or cook (after you cut off the bad bits, of course!).

Peaches with brown rot ready to be cut up and cooked

The infection can quickly spread (especially in rainy weather), so monitoring your trees once a week, and removing infected fruit, gives the remaining fruit the best chance of staying healthy. 

Brown rot spreading from one piece of fruit to another in a bunch of president plums

Even in organic gardens and farms, it’s possible to take preventive action to minimise the risk of diseases like Brown rot.

Hygiene (e.g. removing fruit as described above) is one of the most important, but you should also aim to keep a ‘cover’ spray of one of the safe organic fungicides on your trees at all times.

If you only have a few trees to manage, you can quickly and simply do this job with a simple sprayer, as Hugh is demonstrating here. With more trees to manage, you may want a more mechanised set-up.

There are so many spray systems to suit every size of garden or farm, but it can be really hard to figure out which spray system will suit you best, and what’s the best balance between budget and value.

It’s not worth spending hundreds (or thousands) of dollars on a system that’s too big and sophisticated for your needs. On the other hand, you may be able to save yourself many, many hours (and therefore $$) by investing in a system that will do the job you need quickly and efficiently.

It depends on a few things — how many trees you have, your topography (i.e. how steep your block is), what equipment you have available, and your goals for your fruit trees. If you’re hoping to sell some of your fruit, for example, you really need to make sure you can spray quickly, and easily, as often as you need to. We’ve demystified the whole topic in our short online course Choose the Right Spray Gear.