- Author: Ben Faber
Last May/June during a hot period and soon after fruit set, avocado growers and PCAs in the Oxnard/Camarillo area were calling in about young fruit about he size of a quarter showing up with white spots. Cutting into the fruit there might only be a small black spot just below the injury. Because that's what it is, a wound response on the part of the fruit to a physical damage. This occurred on several orchards also in the San Luis Obispo area and it seemed to happen in orchards that had recently been sprayed for avocado thrips. No piercing-sucking insects were found at any of these sites. Insects that would feed by feeding on the fruit and causing damage and malformed fruit. Insects that could typically make probing inspections of fruit prior to laying eggs. No eggs or larvae were found in the fruit. Nothing like lygus bug, BMSB, Bagrada bug or other stink bugs was found.
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=15198
Did it have anything to do with the spray? With the hot weather? With the hot weather and the spray? With the hot weather and the insects that came with it? Did it have anything to do with the hot weather? Did it have anything to do with insects?
And then late June, the calls stopped. No more damaged fruit was being found. And then a lone call from Cayucos. Damage was found on young and older fruit. New damage seemed to be occurring on the fruit that normally sets later in that northern area. The grower walked the orchard and didn't find any bugs. The PCA swept the grove for insects. A yellow sticky card was put out.
So far, no insect has been found on the fruit. So what caused and "is" causing the damage to the fruit? It's not clear. Fruit that was damaged in Oxnard back in late May was tagged to see if it recovered. Ten fruit were flagged and two months later, those tagged fruit were still on the trees. So either the fruit that was attacked fell off with the initial damage or the fruit observed later had healed itself. Fruit have this capacity when they are actively growing to cover over damage. Often it is malformed. In most of cases with this fruit, the damage was very superficial. Occasionally, there deeper pits, but we didn't see any burrowing or tunneling.
If anyone else saw similar damage and has more to offer about this happening, I would be glad to hear about it.
Photos: Damaged fruit that was flagged and observed 2 months later.
- Author: Ben Faber
What this means is that there is different feeding behavior on different scion varieties that is unaffected by the rootstocks used in this study. This does not mean "a" rootstock can not have an effect, just that the ones used in this trial did not.
EFFECT OF DIFFERENT CITRUS SCION AND ROOTSTOCKS
COMBINATION ON FEEDING OF Diaphorina citri
Alves GA1, Beloti VH1, Carvalho SA2 & Yamamoto PT1
1Escola Superior de Agricultura ‘Luiz de Queiroz'/
Universidade de São Paulo, Piracicaba, SP, Brazil; 2Instituto
Agronômico (IAC), Centro de Citricultura, Cordeirópolis, SP,
Brazil; e-mail: gralves@usp.br
The Asian citrus psyllid (ACP) is the vector of bacteria associated to the huanglongbing and has a host range of more than 50 species of the Rutaceae family. The knowledge about the feeding behavior in different hosts can show useful aspects for future studies of plant resistance and ACP management. Therefore, was evaluated the effect of different combinations of scion and rootstock of citrus in the feeding of ACP adults. For this, we tested Valencia, Pera and Hamlin sweet orange, Ponkan mandarin and Sicilian lemon grafted on Rangpur lime and Sunki mandarin rootstocks.
The flushes were individualized with cages made of transparent plastic cup and “voile” tissue. To collect the honeydew, discs of filter paper were placed at the base of each flush. The adults fed for a period of 72 h. After this, the discs were removed and immersed on the ninhydrin solution. After 24 h, the drops area of honeydew was determined using the Quant software. The feeding was more intense on sweet orange varieties, with a highest value observed to Valencia (0.902 cm2) and the smaller area to Ponkan mandarin(0.269 cm2). Unlike observed for scion varieties, when different rootstocks for the same scion variety were tested, no difference was observed in the consumption of ACP.
Rootstocks can have a tremendous effect, but not in this case with the rootstocks used