Monitoring is the first step in managing pests and preventing fruit damage. Here’s advice on how this should be done.
For fruit farming to be successful, you need to know as soon as a pest appears in your orchards, so that something can be done before it is too late.
Insects and mites multiply very quickly, especially when it is warm. It is easy to get rid of pests when there are only a few. But when there are many, it can be impossible to get rid of them before serious damage is done.
- Insects can cause damage to fruit and various parts of the trees.
- Damaged trees cannot produce a good yield or good-quality fruit.
- Trees could die if the damage is serious enough.
- Damaged fruit cannot be marketed, which leads to less income earned.
- Buyers also reject fruit if there are insects on or in them.
Fungicides can be applied regularly to prevent diseases from infecting the trees, but insect and mite pests cannot be controlled with such preventative spray programmes; control measures for them only work once the pests are present. Monitoring of orchards should therefore be a vital part of the pest management programme on any farm.
Not all insects and mites found in orchards are pests. Many of them do a good job by pollinating fruit or eating harmful insects and mites.
The scout, the person who inspects the fruit trees regularly for the presence of pests, should be able to distinguish and identify the most important pests and beneficial (good) insects and mites, so that money is not wasted to control an insect or mite that does no harm.
Good eyesight is important, because many insects and mites are very small and difficult to see. Scouts need the right tools for the job. These include a pocket-sized notebook or a clipboard with an orchard plan, pencil, magnifying glass, and a pocket knife. A guide or pamphlet providing photographs to help identify pests and their damage is also useful.
- If you have 25 or fewer fruit trees, inspect every tree.
- In a 1 ha orchard you need to inspect at least 12 trees.
- On larger farms, orchards are divided into blocks of about 2 ha each.
- Select and mark 25 trees evenly spaced throughout each 2 ha block, using a marker so the scout can easily identify these trees.
- Inspect the same trees every 2 weeks throughout the growing season.
- All parts of the tree – stem, branches, leaves and fruit – should be inspected.
Shoot tip inspection:
- Inspect 5 shoot tips on each tree marked for monitoring and note any insect damage or pests found on them.
- Remember to record how many of the 5 shoots from each tree were damaged and how many were undamaged.
As soon as the blossoms lose their petals and the small fruit begin to form, inspect 5 fruit clusters per marked tree every 2 weeks and note any insect damage or pests found.
- Examine both sides of 2 leaves on every marked tree – 1 leaf from the inside and 1 from the outside of the tree – every 2 weeks and look if mites are absent or present.
- Because mites are very small, a magnifying glass with at least 10 times magnification is needed to inspect them properly.
Leaf axil inspection:
Inspect the leaf axils (where the leaf joins the stem) of half of each marked tree every 2 weeks for the presence of woolly apple aphid colonies.
- Just before thinning, the fruit from 5 fruit clusters of each marked tree should be counted and examined.
- Make a note of any insect damage on each fruit.
- Count how many fruit are inspected in total, so that the percentage fruit damage can be calculated.
- Just before harvest, count and inspect all the fruit in 5 clusters on each marked tree.
- Note all fruit damage.
- Cut through the core of 1 fruit from each cluster and note any insects in the calyx.
- Some insects, especially flying insects such as moths and fruit flies, are more easily monitored if you use traps.
- These traps come with bait or a lure that attracts a particular insect and a sticky surface to which the insects cling (almost like sticky fly paper).
- 1 trap should be hung in the middle of each 2 ha block, about 1.5 m to 2 m above the ground. Make sure that the open sides are not covered by leaves or branches.
- The scout should every 2 weeks, record the number of insects caught on the sticky bottom of the trap.
- Some crawling insects, like banded fruit weevil, can be monitored by tying a corrugated cardboard band around the stems of the marked trees.
- Weevils don’t like light and shelter under the band during the day.
- When the band is loosened, the number of weevils hiding inside can be counted and recorded.
- Keeping an honest, accurate record of inspection results is very important.
- Each marked tree and trap should be numbered.
- These numbers are used to record the result of the inspection on the record sheet.
- Mark the outer tree of the row in which traps or marked trees are found.
- This will make the scout’s work easier and ensure that traps or trees are not missed.
- The fortnightly notes the scouts or monitors make are used to decide if it’s necessary to control a pest.
- Monitoring records should be kept for the entire season, because doing so will help the farmer identify problem areas (also called hotspots).
- These are the areas where special attention should be paid to monitoring and control in the coming season.
- This article was written by Elleunorah Allsopp and Muriel Knipe and first appeared in Farming SA.