Guava Growers

‘Dear Dr. Kris,
I have pests attacking my guava tree that has been growing for several years. I have noticed that last year it produced less fruit than in previous years, and some sort of pest seems to be getting in there. The leaves and stems have a white sticky substance all over them and I have noticed leaves in the bushier parts are being eaten. The plant has heaps of foliage but it seems to be very dry almost shrivelled. Is this from the pests because the tree gets plenty of water? How can I negate the damage?
Thanks in advance.
Roger

Instead of trying to treat the fungus and pests, heavy pruning is the way to go. A guava tree or nearly any plant for that matter will always benefit from a trim as long as it is done at the right time. For a fruiting tree such as yours the best time to cut would be immediately after the fruiting period, that way you will achieve maximum growth before the next fruiting cycle.

From your description it sounds like your plant could do with an extensive going over. Fruit trees that become heavily overgrown or too bushy will start to become a haven for many types of pests and diseases, then throw humid weather into the mix and you will have the perfect storm for pest production. The problem is twofold, because overgrown foliage will provide pests shelter from predators and the elements, whilst the lack of airflow through the tree will encourage fungal growth which is the white sticky substance that you notice accumulating. Pests eating the leaves combined with fungus attack leads to the result which you now have, a stressed and tired dry looking tree. The tree is putting all of its energy into just trying to produce more foliage as it struggles against pests and disease, meaning less energy put into fruit production, setting the tree off on a cycle of slow decay of decreasing yields whereby it is struggling just to stay alive.

The first place to start is to cut off the branches affected by the fungus. This may mean that you will have to trim the tree back to the main truck with just a few limbs remaining. Always keep in mind the shape of your tree and do your best to leave it looking balanced. Rather than just cutting it all in one go, trim a bit stand back observe, then plan which limb to cut off next to maintain the balance. Don’t worry if it’s not perfect it will grow back and you can re-trim it into shape if it’s not perfect. Pruning is one of those things that you learn by doing, so the more you do it the better you will get at it, so just get in there and give it a go. You will be surprised at how quickly it will regenerate, even if you trim it back to almost nothing. You should get a bigger crop off the new season growth as it regrows. Passionfruit is another plant to cut back every year to allow for air circulation, new growth and increased fruit production.

Pruning tips – You may need a handsaw and some sharp secateurs. Make sure that you make clean cuts. Start by cutting branches back to the trunk or where they fork. Do not leave branch stubs or uneven surfaces. Don’t cut half a branch off leaving a piece of dead wood poking out, not only is it dangerous but it would likely attract disease to invade the internal parts of the tree. You need to make sharp cuts with clean tools. Once you have removed fungus affected foliage dispose of it immediately being careful to make sure that it doesn’t come into contact with any other plants.

Fungus will survive on dead branches and leaves so prune off all affected areas. Diseased twigs, leaves, and fruits which fall to the ground, are a potential source of infection so collect and dispose of them in the rubbish, not the compost. One infected twig lying in the soil for months is enough to spark an outbreak later on. Also try to keep the base area around the plant as weed free as possible, and clear of infected debris. Make sure the tree is pruned in such a way to allow air to circulate through the tree, avoid watering overhead, deliver water directly to the soil otherwise you are inviting the fungus back. If you are cutting back healthy foliage keep it and make tea from the leaves, guava leaf tea is reputed to be good for diabetics and many other health conditions, the fruit itself is packed full vitamins, very high in Vitamin C and a good source of Vitamin A, Folate, Potassium, Copper and Manganese.

To get your tree going again use a complete fertiliser developed specifically for fruit trees, with correct ratios of nitrogen (N), phosphorous (P) and potassium (K). Fertilise with a product that has a higher (P) and (K) ratio. Look for a ratio formulation, such as 16-16-16 or 10-20-20 N-P-K on the label. The influence of K on fruit quality is greater than any other plant nutrient. Too much nitrogen will also damage flowers. It is best to keep fruit trees away from lawn area. If grass grows up to the tree trunk, cut it back and replace it with a ground cover or mulch.

A well drained soil will promote good flower formation. Increase watering through the development stage of the fruit. Depressions or gullies are poorly drained and planting on these sites should be avoided. Provide these basic steps of care to your guava trees, healthy vigorous plants are less likely to encounter disease problems in the future.